Here's to Ted…

Fearless Fathauer has left the building.

It's official, Ted has retired:

Ted helped me get my first job in Alaska and I've learned a lot from him in the past 25 years. He was the last of the old school meteorologists here, who cut their teeth in the weather forecasting biz before computer models largely replaced the need for actual physical understanding. Ted's surface and upper air analyzes are a pleasure work with, painting the weather story of the day.

 Good Luck Ted!!

Unstable Temperatures

Here is a plot of hourly temperatures Sunday at a handful of sites in greater Fairbanks-land.

The low lying areas such has Goldstream Creek (GCSA2) and Woodsmoke PWS (WODA2) have been unable to pop the inversion due to the clearing that followed the occlusion, while high elevations, Clearly Summit (CLRA2) and Keystone Ridge (KERA2) have been breezy and in the warm air for a couple days now. At both valley and higher elevations temperatures have been fairly stable.

But look what's happening right near the Tanana River: Eielson AFB (PAEI) was cold, then gusty southeast winds broke through and temperatures have been very mild since mid morning. This is quite common at Eielson. Both Fairbanks Airport (PAFA) and Nenana Airport (PANN) have had big temperature swings during the day as the differing airmasses waffle back and both across these specific points. The Alaska Fish and Game Alaska Division of Geological & Geophysical Surveys* PWS on College Road (C6400)) has not had the swings in temperature as the airport but is a milder version of Goldstream Creek.

Note: There is a chance the Fairbanks Airport temperature swings are not real but represents intermittent sensor failure. However, given the overall situation, the reported temperature variations are probably real.

*Thanks to Chris S. for pointing out my incorrect attribution of the operator of this PWS. 

Denali Heat Wave

Temperatures Sunday morning have boomed into the 40s in Denali Park area with pretty decent chinook underway. Peak winds so far include 58 mph at Antler Creek RWIS (between Healy and Glitter Gulch), 49 mph at Healy (at the DOT camp) and 43 mph at the Otto Lake PWS. The NOAA-18 infrared image from just before 6am AST Sunday shows the occlusion in an arc across the central Interior. Note the mountain wave clouds just to the south of the high cloud edge.

Courtesy of NWS Alaska Region

Temperatures at 8am (ish) Sunday on the east side of the Park include:
Healy: 46F
Denali Park Airstrip: 45F
Antler Creek RWIS: 45F
Otto Lake PWS: 44F
Denali Park HQ: 41F

The high temperature of 42F at Denali Park HQ Coop is not a record for Dec 30th. That is still 48F set in 2000.

West of the Toklat River it's warm too:

Stampede Airstrip:42F
Wonder Lake: 44F
Kantishna: 44F

Delta Differences

Courtesy of the Weather Underground

For those familiar with the Delta Junction area, the plot at the left from the Weather Underground nicely illustrates the competing airmass regimes. From Fort Greely northward the Tanana Valley jet is blowing, draining the cold pool still sitting over the upper Tanana Valley. Just to the south, along the Delta River. chinook warmed airmass is in place. If/when the southerly flow breaks through look for temperatures to jump 20F or more in a few minutes at Fort Greely and the immediate Delta Junction area.

Clarification: This is data from about 10am AST Saturday

It has Began…

The big warm-up the numerical models have been advertizing for a week is here. The upper air sounding from early Saturday morning already had the temperature at freezing 900 meters up, 42F warmer than the surface. 

Temperatures have continued to rise since then; some 9am AST Saturday temperatures include:

• Eielson AFB: 8F
• Woodsmoke PWS: 8F (near North Pole)
• Goldstream Creek: 8F
• Fort Wainwright: 10F
• Fairbanks Airport: 11F
• UAF West Ridge: 16F
• College Hills: 26F
• Keystone Ridge: 31F
• Skyline Ridge: 34F

Temperatures near the Alaska Range Saturday morning are way up above freezing, including 9am temperatures of 38F at Healy and 41F at Bolio Lake south of Fort Greely.

The 9am GOES infrared image shows the fractured occlusion over the central Interior, and the next wound-up storm plowing northward through the Gulf of Alaska:

Courtesy of NWS Alaska Region

This will ensure warm winter weather in Fairbanks-land into the New Year.

Seasonal Inversion

As we await the Great 2012-13 Mid-Winter Warm-up, here's a quick and easy way of assessing  daily inversion strength in Fairbanks-land over a seasonal basis. This is simply the difference in mean daily between the Fairbanks Airport and Keystone Ridge. Just a reminder: Fairbanks Airport elevation is 440' MSL and  Keystone Ridge, 14 miles northwest of the Airport is at 1600' MSL. Importantly, the climate day is the same, so this is a straight apples-to-apples comparison.

Until the snow cover was established in mid-October, the Airport was generally warmer than the Ridge. Since November 1st, the median "inversion strength" has been 15F. Only the snow of earlier this month was enough to completely disrupt the inversion. The strongest daily inversion was on December 22nd, when the Airport had a daily mean temperature of -39F and Keystone Ridge had a daily mean of -4F.

Christmas Weather in Fairbanks

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
145 PM AKST TUE DEC 25 2012

...CHRISTMAS DAY IN FAIRBANKS...

CHRISTMAS DAY 2012 IN FAIRBANKS WAS NOTABLE FOR THE BREAK IN THE
COLD SNAP THE GRIPPED THE AREA SINCE THE BIG SNOWS OF DEC 11TH TO
13TH. 

OVER THE PAST 108 YEARS...CHRISTMAS DAY HAS BROUGHT TEMPERATURES
AS LOW AS 56 BELOW IN 1961 AND AS WARM AS 34 ABOVE IN 1985.

THE SNOWIEST CHRISTMAS WAS IN 1999...WHEN 3.8 INCHES OF SNOW FELL. 
AN INCH OR MORE OF SNOW HAS OCCURRED ON CHRISTMAS DAY JUST 13
TIMES SINCE 1904.

FAIRBANKS ALMOST ALWAYS HAS A WHITE CHRISTMAS...AND THIS YEAR WAS
NO EXCEPTION....WITH A 17 INCH BLANKET OF SNOW. THE DEEPEST SNOW PACK
ON CHRISTMAS DAY WAS 39 INCHES IN 1970. ONLY ONCE HAS FAIRBANKS
NOT HAD A WHITE CHRISTMAS. IN 1934...THE GREATEST WINTER CHINOOK
IN FAIRBANKS WEATHER HISTORY EARLY THAT DECEMBER BROUGHT FIVE
DAYS IN A ROW WITH HIGHS IN THE 50S AND COMPLETELY MELTED THE THIN
SNOW PACK THAT HAD BEEN PRESENT. AFTER THE CHINOOK ENDED THERE WAS
ONLY MEAGER AMOUNTS OF SNOW UNTIL THE 26TH. AS A RESULT...CHRISTMAS
DAY 1934 HAD JUST A TRACE OF SNOW ON THE GROUND. EVERY OTHER
CHRISTMAS FOR WHICH THERE IS A RECORD HAD AT LEAST FOUR INCHES OF
SNOW COVER.

$$
RT DEC 12

Cold Snap Gone But Not Forgotten

Temperatures popped above zero early Christmas morning in the Fairbanks bowl, with no return to the deep cold anytime soon. Here's an update of daily mean temperature anomaly plot.  Since October 15th just under half of the days (33 of 69) have had a daily mean temperature 1.0 or more standard deviation below normal, which is a pretty healthy run of persistent below normal temperatures. The average temperature during that time is -8.3F. So far, ten days this winter have had a low temperature of 40 below or lower, which is about the average number for the whole winter. However, the numerical guidance is now in pretty good agreement that sustained above normal temperatures will be with us for the next couple weeks at least. This close to winter solstice, in valleys at least, a warm overall pattern will be tempered by strong inversions developing any time skies clear for any length of time. But no more 40 below in the foreseeable future.

Warming Up, But Still Cold

Courtesy of NWS Alaska Region

Winds aloft are now southerly over most of Interior Alaska. This is both warming the airmass and brought some areas of clouds that had been over the YT into region. The NOAA-18 Polar Orbiter infrared image from 619am AST Monday tells the tale. Clouds were mostly confined to areas north of 67N, after bringing somewhat "less cold" temperatures places that had been very cold, with highs Sunday of -22F at Eagle and -30F at Tok.

The warming in valleys that don't get any wind will be slow and limited because at this point there is no deep cloud layer likely to survival crossing the Chugach and Alaska Ranges over the next few days. Any place that does get wind though will see much warmer temperatures: compare the 9am AST Monday temperature of +1F at Nenana and -29F at Fairbanks International.

So what does this mean for the cold December in Fairbanks? The average temperature (at the Airport) for the first 23 days of the month is -23.0F, and this is about the bottom. I expect the final eight days of the month will finish up averaging a bit below normal (today and Christmas Day significantly so). At this point there does not seem to be a path for December 2012 to be in the top five coldest Decembers, even just considering the Weather Bureau/NWS era (since 1929), though this will very likely be the coldest December since 1980, when the monthly mean was -24.0F. This is yet another case (like, e.g. January 2006) where the lack of extremely low temperatures is keeping the mean temperature from being super low. No calendar day this month has had a high temperature in the -40s, and the monthly minimum of -48F is pretty underwhelming by historic standards. While urban effects/ice fog are playing some role, it can't be the whole story: December 2012 minimum temperatures of -58F at Tok and Chicken, -54F at Eagle Co-op, -55F at the Fort Yukon AWOS are all historically way off the mark.

Record Low Temperatures in Tok

SXAK79 PAFG 230543
RERAFG

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FAIRBANKS AK
843 PM AKST SAT DEC 22 2012

...RECORD LOW TEMPERATURES IN TOK

THE LOW TEMPERATURE AT TOK AS REPORTED BY THE NATIONAL WEATHER
SERVICE COOPERATIVE OBSERVER ON SATURDAY WAS 57 BELOW. THIS TIES
THE RECORD LOW FOR DECEMBER 22 PREVIOUSLY SET IN 1961.

THE HIGH TEMPERATURE SATURDAY IN TOK WAS 48 BELOW. THIS IS THE
LOWEST MAXIMUM TEMPERATURE OF RECORD FOR DECEMBER 22 IN
TOK...BREAKING THE PREVIOUS RECORD OF 45 BELOW SET IN 1957.

WEATHER OBSERVATIONS HAVE BEEN MADE IN TOK...THOUGH WITH GAPS IN
THE RECORD...SINCE 1954.

RT DEC 12

The Cold Goes On

Courtesy NWS Alaska Region

Here's a very nice NOAA-18 infrared image from 542am AST Saturday. Except for some clouds over the southern Yukon Territory and cirrus wisps over the Beaufort Sea, this is a clear sky image. The cold pooled in many valleys, the dramatically warmer hills. Tanana Valley jet other drainage wind regimes blowing over the flats on the north side of the Alaska.  The comparatively mild North Slope. You could do a seminar on Interior Alaska winter weather just from this image.

Some lows reported through 9am in Fairbanks-land Saturday include:

Woodsmoke PWS: -47F (near North Pole)
Goldstream Creek: -44F
Eielson AFB: -44F 
Fairbanks Airport: -43F
Fort Wainwright: -43F
UAF West Ridge: -37F
College Hills PWS: -21F
Skyline Drive PWS: -10F
Keystone Ridge: -6F
Cleary Summit RWIS: -3F

In the eastern Interior…

Eagle co-op: -54F
Fort Yukon Airport: -54F
Fort Yukon co-op: -53F
Coal Creek RAWS: -53F
Northway -50F

And we await the Chicken report…The Chicken RAWS up on the hills is -53F, a couple degrees colder than Friday. Do I hear a -60F?

Updated: Nope, we don't have a -60F at Chicken co-op: low of -57F.

Solstice Low Temperature Summary

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
339 PM AKST FRI DEC 21 2012

...A COLD WINTER SOLSTICE IN INTERIOR ALASKA...

TEMPERATURES IN CENTRAL AND EASTERN INTERIOR ALASKAN VALLEYS
AGAIN DIPPED INTO THE 40S AND 50S BELOW...MAKING FOR A MIGHTY
CHILLY WINTER SOLSTICE. HOWEVER...AS BRISK AS IT IS...NO LONG
TERM OBSERVING LOCATION SET A NEW RECORD LOW FOR DECEMBER 20TH. 

AT FAIRBANKS INTERNATIONAL AIRPORT...THE LOW SINCE MIDNIGHT HAS
BEEN 46 BELOW...MAKING THIS THE EIGHTH DAY THIS MONTH WITH A LOW
OF 40 BELOW OR LOWER. THE LAST TIME DECEMBER HAD THIS MANY
40 BELOW DAYS WAS BACK IN 1980.

OTHER VALLEY LOW TEMPERATURES FRIDAY IN THE FAIRBANKS AREA
INCLUDED...

WOODSMOKE...................51 BELOW (NEAR NORTH POLE)
BADGER AND RAPP ROAD........49 BELOW (NEAR NORTH POLE)
FORT WAINWRIGHT.............48 BELOW 
GOLDSTREAM CREEK............47 BELOW 
EIELSON AFB.................46 BELOW

ELSEWHERE IN INTERIOR ALASKA LOWS INCLUDE...

CHICKEN.....................58 BELOW
TOK.........................56 BELOW
FORTYMILE RIVER.............54 BELOW
EAGLE.......................52 BELOW 
FORT YUKON..................52 BELOW
NORTHWAY....................51 BELOW 
SALCHA RIVER MILE 25........51 BELOW
NENANA......................47 BELOW
CENTRAL.....................46 BELOW 
DENALI PARK TRAIN STATION...42 BELOW 
FORT GREELY.................41 BELOW 
DENALI PARK HQ..............31 BELOW

$$
RT DEC 12

Inversion Nirvana

Here's a plot of hourly temperatures in the past 24 hours for Goldstream Creek, College Hills and Keystone Ridge, representing low, middle and high elevations. At 10am Friday the inversion now exceeds 40 degrees between the cold spots in the Fairbanks Bowl to locations above  2000' MSL. Typically inversions this strong happen just a few times a winter.


9 to 10am temperatures:

Fort Wainwright: -44F
Fairbanks Airport : -41F
College Hills: -23F
Skyline Drive: -13F
Keystone Ridge: -6F
Cleary Summit: -2F
Wickersham Dome -1F

Still Cold…but No Silliness

Thursday evening I was amused by various Facebook posts with someone somewhere forecasting a low of 60 below for this morning at Fort Wainwright. Not only would such a temperature be extremely unusual, even a cursory look at the meteorology would have suggested that was highly unlikely: the air mass was already warming, as evidence by the gradually rising temperatures at higher elevations. This morning's sounding shows  moderate surface based inversion (by Fairbanks standards) with the air 500 meters up about 20C (36F) warmer than at the surface.

As I wrote about last winter, at 65 degrees north latitude there is no appreciable solar heating in the weeks around winter solstice, which means there is no change in solar heating that would cause one to think the temperature would drop overnight. The lack of auto traffic overnight can result in thinning of ice fog (though that's not a hard and fast rule), which can allow for surface cooling if the ice fog thins enough. In general though, with a gradually warming airmass, no clouds and no wind, Interior Alaska valley temperatures in late December should be nearly steady, eventually rising a bit. 

Courtesy of IARC

The 2-day plot of the 2-meter temperatures from the sensor near Smith Lake on the UAF Campus shows all this nicely: there is no sign of any afternoon solar related temperature increase and since about 4pm Thursday there is has been minimal temperature variaiton.





Low temperatures since Thursday afternoon include:

North Pole: -51 (thru 11pm Thursday)
Woodsmoke PWS: -49F (near North Pole)
Fort Wainwright: -48F
Fairbanks Airport: -47F
Golstream Creek: -47F
Eielson AFB: -46F 
UAF West Ridge: -38F
College Hills: -30F

Cold…But Not as Cold as It Used to Be

It's another brittle morning in Fairbanks-land, with temperatures in the 30s and 40s below in the valleys, and even most hill sites near or below 20 below. At the Fairbanks Airport the temperature did nick down to 40 below just before midnight Wednesday evening, so today, Thursday, with a low so far of 44 below makes this the sixth day in a row with a low of 40 below or lower.  The last time there was a six day streak of 40 below lows wholly in December was 1975 (but several asterisks for recent  as long or longer streaks partly in December: Nov 29 through Dec 04 1990, Dec 28, 1999 through Jan 05, 2000 and Dec 28, 2008 through Jan 11, 2009).

Here's a plot of temperatures in the lowest 1000 meters from the Thursday morning sounding. This morning's comparison though is to one of the great cold snaps in modern times. The blue line is the sounding from the afternoon of December 27, 1961.

Notice that surface temperature on the ice foggy afternoon was about 4C colder than this morning. But look at the temperatures above the valley floor: there was no surface-based inversion at all (deep, prolonged ice fog). Temperatures 200 meters up were about 18C colder that afternoon than this morning, and the temperature was colder than -40F through almost the entire lowest kilometer.. At the peak of the 1961 cold snap, the UAF West Ridge coop site (the observation site at the time was near what is now the Jack Townshend Point near the Museum of the North) recorded a low of -66F, by far the lowest of record there. Fairbanks Airport recorded a low of 62 below on December 29, 1961, the all-time record low for December.

Updated Temperature Anomaly Plots

Here are daily mean temperatures and associated anomaly plots for Fairbanks for 2012. Recall that the shaded area on the top plot is one standard deviation from the mean, so temperatures inside the shaded area can be considerable "close to normal". Sunday, with a standardized departure of -2.63 was the most anomalous day since Dec 4, 2012, which had a standardized departure of  +2.73. 

A Tanana Valley Jet and other Exicting Developments

Valley temperatures have moderated a bit around Fairbanks, though hill temperatures have leveled out. To the left is a plot of the temperature in the lowest kilometer from the past three soundings (nominal times 3AM Monday, 3PM Monday and 3AM Tuesday). The warming as continued on the valleys since early this morning. Almost everywhere is now up to -30F or warmer.

The core of the cold air has moved into the eastern Interior, with lows this morning of 51 below at Northway and 48 below (thru 8am) at Chicken. Meanwhile, our friends in the Delta Junction are being buffeted by 15 to 40 mph and temperatures in the teens below in a classic "Tanana Valley Jet". This happens when cold air in the Upper Tanana Valley moves downriver (in response to lower pressure to the west) and is squeezed through the constriction in the valley near Cathedral Rapids. Since air is a fluid, the velocity has to increase to move through the constriction. The result: strong down-valley winds from about Dot Lake westward across the Delta Junction area and the Tanana Flats south of Fairbanks. On occasion the jet makes it all the way to Nenana, which it did in this case (temperatures was still -41F at 11pm but has been as around 6 below for some hours down with a gusty east wind).

The NOAA-18 1km resolution infrared image from 630am Tuesday shows this in detail.

The cold air pooled in the Upper Tanana is evident (along with the cold valleys of the Fortymile County and the Yukon Flats). The Tanana Valley Jet shows up as the streaky looking of darker color (warmer temperatures) west of the Tetlin Flats.  

Still Warm…Aloft at Least

Fairbanks-land inversions continue to grow early Monday evening: at 6pm, it was above zero in the warmest higher elevations and still in the 40s below on the valley bottoms

Warming Aloft

Temperatures have started to rise above the valley floor in Fairbanks-land. On the right are plots of the temperature in the lowest 1000 meters from Sunday morning and Monday morning soundings. Above about 25 meters above the ground the sounding is warm Monday morning than Sunday morning, with the most dramatic warming between 200 and 400 meters AGL. Since then temperatures have continued to rise: at 10am temperatures are up to 11 below on Cleary Summit, 14 below at Wickersham Dome and 16 below on Keystone Ridge.

Coldest December Temperature

View from UAF West Ridge Sunday, Dec 16, 2012

Updated:

Through 8am Monday the low temperature at Fairbanks Airport has been 48 below. This is not only not a record low for December 17th (52 below in 1917), but on only two days in December (the 1st and 2nd) would 48 below be cold enough for a new record.

That said, this is the coldest December temperature since 1999, when the temperature fell to 53 below on New Years Eve (and the dense ice fog caused cancellation of the big fireworks planned to celebrate the end of the millennium). Even more notably, this is the lowest pre-Christmas temperature in Fairbanks since 1977, when it dipped to 52 below on December 13th.

Updated:
Specific low temperatures Monday include:

Fairbanks Airport: -48F
Fort Wainwright: -48F
Woodsmoke PWS: -48F (near North Pole)
Salcha River 25 Mile: -47F
Goldstream Creek: -46F
Eielson AFB: -44F
UAF West Ridge: -41F
College Hills: -30F
Keystone Ridge: -25F

Noon Twilight at Arctic Village

Courtesy of the FAA

Here's the FAA webcam photo from Arctic Village Saturday afternoon about 1235 pm AST, which is almost exactly solar noon. As you can see, no noon sun six days before the solstice at 68.1 degrees North. Just a lovely twilight, and, oh yeah, 44 below and some thin ice fog.

Back in the Drink

Courtesy of Alaska Climate Research Center

A cold airmass and only variable low cloud cover have allowed temperatures to again plunge in Fairbanks-land. Low temperatures through 10am include:

Fairbanks Airport: -41F
Goldstream  Creek: -38F
Fort Wainwright: -36F
Eielson AFB: -34F
UAF West Ridge: -32F
Keystone Ridge: -26F
Cleary Summit: -20F

Big Cooling

Just a quick post showing the dramatic cooling during the day Thursday in Fairbanks, with the 3am vs. the 3pm upper air soundings. That's a lot of cooling in the lowest 1000 meters in just 12 hours. Here on the hill, the high today was 26F, about 3am, and as of 5pm it was -1F.

The Big Snows

Keystone Ridge Weather Station Thursday afternoon

Looks like Fairbanks Airport is going to finish up with a two day snow total of 11.9 inches,
9.5" on Wednesday and 2.4" Thursday (through 3pm).  That's a lot of snow in one storm for Fairbanks. So how often does that happen?

Well, turns out that there are only 24 calendar days in the entire 108 years of Fairbanks weather records with more than 9.5" of snow in a calendar day. Since 1930, the Weather Bureau/NWS era, calendar snowfalls of 9.5" or greater have occurred in just 20 of 83 years. The frequency of a foot of snow in two days is almost identical. So, snowfall like this is something like a one in four year event, though the last occurrence was the freak storm of February 2011.

 Here's the 3am AST Thursday 500mb analysis from Environment Canada: a pattern similar to this, with deep southwest winds aloft  is how we get this kind of heavy precipitation into Fairbanks-land, winter or summer: wrap  oceanic moisture around the Alaska Range.   

Courtesy of Environment Canada

This was not especially close to more than daily record snow. The 24 hour snowfall record for December is 14.7" set in 1968. The all-time 24 hour snowfall record is 20.1" in Febraury1966.

Snow Amounts

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1112 AM AKST THU DEC 13 2012

...HEAVY SNOW BLANKETS THE FAIRBANKS AREA...
 

A VERY MOIST WEATHER SYSTEM MOVING ACROSS INTERIOR ALASKA HAS
BROUGHT SIGNIFICANT SNOWFALL TO THE FAIRBANKS AREA. SINCE THE
SNOW BEGAN EARLY TUESDAY MORNING...SNOWFALL TOTALS AROUND TOWN
HAVE RANGED BETWEEN 9 AND 14 INCHES WITH THE HEAVIEST AMOUNTS
NORTH OF FAIRBANKS. SNOW SHOWERS WILL CONTINUE TO MOVE THROUGH
THE AREA TODAY WITH AN ADDITIONAL 1 TO 2 INCHES POSSIBLE BEFORE
THE SNOW TAPERS OFF TONIGHT.

THE FAIRBANKS AIRPORT REPORTED 9.5 INCHES OF SNOW YESTERDAY...AND
THIS BREAKS THE DAILY SNOWFALL RECORD FOR DEC 12TH. THE PREVIOUS
RECORD WAS 5.7 INCHES WHICH WAS SET IN 1972.

STORM TOTAL SNOWFALL THROUGH THURSDAY MORNING:

BIRCH HILL.......................13.5 INCHES (THROUGH 9AM)
COLLEGE HILLS....................12.8 INCHES (THROUGH 6AM)
KEYSTONE RIDGE (MURPHY DOME).....12.3 INCHES (THROUGH 6AM)
ESTER............................11.9 INCHES (THROUGH 9AM)
17 MILE CHENA HOT SPRING RD......11.5 INCHES (THROUGH 9AM)
UAF WEST RIDGE...................11.1 INCHES (THROUGH 9AM)
TWO RIVERS.......................10.8 INCHES (THROUGH 6AM)
AURORA...........................10.1 INCHES (THROUGH 6AM)
EIELSON AFB......................10.0 INCHES (THROUGH 9AM)
BADGER ELEMENTARY................9.7 INCHES (THROUGH 6AM)
NORTH POLE (BADGER AND REPP RD)..9.5 INCHES (THROUGH 6AM)
NORTH POLE (WOODSMOKE SUBD)......9.5 INCHES (THROUGH 6AM)

It's Heavy and It's Snow

I'll have a more extensive post after I do some shoveling, but 9.5" at Fairbanks Airport on Wednesday smashes the daily record for Dec 12th of 5.7 set in 1972. It is also the biggest December snow since Dec 28, 1990, when 10.9" of snow fell.

This snow is pretty wet and heavy by Fairbanks standards; 0.72" of liquid for the 12th is also the most precip any December since 1990. 

Here on the hill, 12.3" storm total as of 6am, and 17.8" since Sunday.

More to follow.

Heavy Snow Miscellanea

As of early afternoon, the College Hills spotter had 6.5" new snow and by the time I got home from work, late afternoon, 6.9" here on Keystone Ridge. Fairbanks Airport had 5.0" through about 3pm and should reach the heavy snow criteria (and set a new record snowfall for Dec 12).

Very well defined warm front set up  just south of Fairbanks-land, with highs of 31F at Healy and 34F at McGrath. The high temperature of 20F at Fairbanks Airport (through 3pm) makes this warmest day since November 10th.

Heavy Snow in Fairbanks

With "heavy snow" in the news for Fairbanks-land, I thought it might be useful to look at how often such a thing happens in the Golden Heart City. As usual with this kind of question, it's a simple question that is actually hard to answer.

First, what do we mean by "heavy snow"? A long used Weather Service definition in Fairbanks has been "heavy snow" mean six inches or more in 24 hours. The snow might be heavy and wet (for you old-timers, think September 1992), or  it might be dry powder, like this past March. That does not figure in the equation. Just, is the snowfall 6" or more in any 24 hour period?  So, now that we have a definition of "heavy snow", we can readily answer the question, yes?

No.

Why is it hard to answer? Historically, snowfall as been recorded for some 24 hour period (since the late 1930s in Fairbanks on a midnight to midnight standard time schedule) AND the maximum 24 hour snowfall in each calendar month is recorded, but the maximum 24 hour amounts per storm have never been systematically archived. What can we derive from the data we have?

First, since 1930 there have been 84 calendar days with 6" or more of snow, just about one per year, on average. However, this would miss a "heavy snow event" such as the following hypothetical example:  snow starts at at 6pm, with four inches of snow by midnight, then it keeps snowing til noon with another four inches. That's 8" of snow in 18 hours, a very healthy snow event for Fairbanks, but neither calendar meets the criteria.

If we calculate the snowfall totals for every two days (so that for, say, the value for Dec 11 is the snowfall on the 10 plus the snowfall on the 11th), this would capture the hypothetical example. If we do this, we find that since 1930 there have been 250 days when the two-day total snowfall is 6" or more, an average of three per year.

However, this must overestimate the number of heavy snow events, because every calendar day that has six inches or more will get counted twice. To see this, image that December 9th has no snow, December 10th as 7" of snow, and December 11th has no snow. When we do the two-day totals, the two-day total for the 10th is 7" (0+7), and the total on the 11th is also 7" (7+0).

So if we subtract out the 84 calendar days days with 6" from the 250 days with a two day total of 6" or more, we're left with 166 "unique" days with six inches or more of snow in two days. Now this must still overestimate the number of times that six inches of snow falls in 24 hours. Sometimes that six inches or more will fall over a period longer than 24 hours (up to 48 hours), and there will be a few events when close to, but not quite six inches of snow fell AND measurable snow fell on the day before and the day after that will result in an overcount.

It would be possible to whittle this down further by going through and manually checking the 166 days and removing all days in months when we know that the 24 hour snowfall was less than 6 inches, but that will have to be a task for another day.  What we have here does not quite correspond with the NWS traditional definition (this has more events), but we are probably in the ball park (I'd guess this is probably still over counting by something like 25%). 

Of course, some winters have multiple heavy snow events and others none at all. Here is the histogram showing the distribution:

Notice that more than 20 percent of years have no days when the two-day snow total exceeds six inches, and more than 45% of years have just one or two. A handful of years have significantly more days with "heavy snow".

Inversions: Not Just for the Interior

At 10am Monday, the Imnaviat Creek SNOTEL, near Mile 286 Dalton Highway reports a temperature of 0F. I've been known to refer to Innaviat as "the Healy of the North". The Sag River platform, near Mile 320 Dalton Highway, which amazingly enough is still sending data, reports a temperature of -40F. Other temperatures range from 42 below at Nuiqsut and 38 below at Umiat to 2 above at the Killik Pass RAWS, west of Anaktuvuk Pass and 4 below on top of Atigun Pass at Mile 245 Dalton Highway.

Courtesy of NWS Alaska Region

To the left is the NOAA-18 Polar Orbiter infrared image from 615am. The cold (white) surface temperatures on the North Slope, but notice the darker (warmer) Brooks Range. Also pretty clear over the Beaufort and Chukchi Seas, with good views of the sea ice. More subtly,  surface temperatures are somewhat milder north of 71N north, near Barrow, and sure enough, Barrow's a pleasant 16 below with light east winds Monday morning.

The Longest Subzero Stretches in Fairbanks

The high temperature at the Fairbanks Airport was at 0F or lower from November 24th through Dec 9th, 15 straight days, and I asked what is the longest such streak. Readers Dana TM and Richard both opined the record was about a month.

The correct answer is…it depends: either 30 or 43 days is the longest streak,

Since the winter of 1929-30, when the Weather Bureau, and then later the Weather Service have been responsible for weather and climate observations for what we call "Fairbanks". For temperatures, this has been the midnight to midnight calendar day since then. During this time, the longest streak for the temperature remaining zero or lower is 30 days, from January 9th through February 7, 1953. So a month is an excellent guess.

However...there is an even longer steak in the pre-Weather Bureau era of Fairbanks climate records.

The first weather observations were made in the new town of Fairbanks in September 1904 by staff of the Episcopal Church — the very first monthly form is signed the Rev. Hudson Stuck, well known at the time as the "mushing Bishop" and even better known today as one of the leaders of the first successful submitting of Denali. In the summer of 1911 the observation program was transferred to the Agricultural Experimental Station, which at the time was in the boondocks five miles west of Fairbanks but is now on the UAF campus, where daily weather observations are still made. 

In general, I'm pretty critical of the general state of the observations during this period; the quality of the observations was dependent in large part on the interest of the person charged with doing the observations.

In December of 1917, the Agricultural Experimental Station reported a high temperature the entire month of -11F. This is much lower than any other other monthly maximum temperature (the next lowest is +5F in January 1966). Is this another example of bad observations? Almost certainly not.

Here is the narrative summary published in "Climatological Data" for December 1917. The author, Melvin Summers, was the Meteorologist-in-Charge at Juneau, which was the only "full" Weather Bureau station in Alaska at this time. Mr. Summers notes that every station in the "Yukon Valley", what today we would call the Interior, had a high below zero (though there were no higher elevation stations in operation at the time). Mr. Summers also noted that the temperatures were more notable for the consistency of the cold rather than being especially extreme. This puts the high of -11F at the Experiment Station in context. It is consistent with other observations in a way that, say, the reputed high of 99F in July 1919 is not. 

In fact, the Experiment Station reported high temperatures of zero or below every day between November 23, 1917 and January 3, 1918, 43 straight days, and I'd say that this is valid.

The Way The Cold Ends

Well, that didn't take long: the miracle of clouds and snow. Temperatures have come up about 10 degrees at higher elevations, and 35 degrees on the valley floor. As a reminder, GSCA2 is Goldstream Creek, PAFA is Fairbanks Airport, CLGA2 is College Hills, and KERA2 is Keystone Ridge.

Big Ridge Revealed

Courtesy of ESRL

Reader Gary asked about the persistent ridge impacting the region. Here's the NCEP reanalysis showing the mean 500mb height anomalies Nov 10 through Dec 05. If's that too much jargon, the yellows and reds show unusually high pressure at mid levels of the atmosphere, the blues unusually low pressure. That is a huge positive anomaly through the Bering Strait for an almost four week period.

Anomolies and Other Chilly Questions

With the end of this cold snap in sight, here is an update of the standardized daily temperature anomalies plot through Friday. Every day since Nov 10th has been below normal and yes indeed, Monday was the most anomalously cold day of the year; the mean temperature of -35F was 2.29 standard deviations (SD) below normal, just edging out May 2nd, which was 2.26 SD below normal. The warmest day relative to normal was September 21st; at 2.13 SD above normal, it's the only day this year to be more  than two SDs above normal. A cold snap trivia question: Friday was the 14th consecutive day with a maximum daily temperature 0F or lower. What's the longest consecutive streak of days a maximum daily temperature 0F or lower in Fairbanks?

Low Snow

Four weeks ago today, Saturday, November 10th, the last significant snow fell in Fairbanks. Since then, just 0.1 inches of snow has fallen (the slight dusting  early Wednesday morning ). For comparison, the 1981-2010 normal snowfall for this four week period is 11.2 inches. Given that autumn is the snowiest time of winter, how unusual is this? As I discuss below, being below normal is not unusual at all (in fact, being below normal is "normal"), but 0.1" of snow is the lowest of record in Fairbanks for this period. In fact, only one other time (1953), has there been less than an inch of snow in Fairbanks between Nov 10 and Dec 08.

To put this in a more complete context, here is a histogram of total snowfall for the four weeks November 10 through December 08 for the Weather Bureau/NWS era in Fairbanks (begins December 1929).

Notice that the distribution in the histogram is not normal. i.e. does not have a "bell-shaped curve". This is typical of precipitation and other climatological statistics that have a natural lower bound (can't have less than zero snow, wind speed, etc), but have an effectively unbounded upper end AND the lower bound is close to observed values (for you stat geeks, this is a Weibull distribution). This is reflected in the difference in the 83 year median and mean values, with the mean snowfall 25% higher than the median (recall, the median is the value that half the sample is above and half below). Unfortunately, and this is a pet-peeve of mine, NCDC uses the mean snowfall (and precipitation) as "normal". But, because of the skewed distribution, most of the time snowfall (and precipitation) will be below "normal". For example during 1981-2010 climate normals period, the snowfall Nov 10-Dec 08 was below normal 60 percent of the time. Happily, snow is on the way for Fairbanks-land, which will reduce the current dry spell to a statistical memory—at least until frozen pipes start being reported in February.

Daytime High Temperatures

Weather the past several weeks over Interior Alaska has been dominated by surface high pressure, with clear skies much of the time. Also, during the past couple weeks winds have not been able to break through the inversion. As a result, temperatures have remained strong elevationally stratified. Here is a plot of daytime (7am-7pm) daily high temperatures (based on hourly data) since Thanksgiving Day at eight weather stations in the greater Fairbanks area. The stations are:

WODA2=Woodsmoke PWS (near North Pole), elevation 500' MSL
GCSA2=Goldstream Creek CWOP elevation 577' MSL
PAFA= Fairbanks Airport, elevation 435' MSL
FAOA2=UAF West Ridge, elevation 597' MSL
CLGA2=College Hills PWS (near the top of Baline Hill) elevation 751' MSL
NHPA2=Nenana Hills RWIS (Parks Highway between Fairbanks and Nenana), elevation 1398' MSL
KERA2= Keystone Ridge, elevation 1600' MSL
WICA2=Wickersham Dome, elevation 2230' MSL

The comparative gap in the middle is a function of the narrow elevational band that is intermediate between "valley" and "hill" and there happens to be few weather stations in that band (there is at least one other PWS, that is in the intermediate band at 1100' MSL, CW6333, but it has reported only a few days in the past two weeks). That is too bad because many of the residences in the "hills" are only a few hundred feet above the valley floor. 

End of Cold, Start of Snow

I usually try to avoid talking about short term weather forecasts here (too much like work),  but occasionally sometimes it seems worthwhile.

Courtesy of the European Centre for Medium-Range Weather Forecasts

So, the end of the cold snap is in sight. The numerical models came into line on Tuesday with a pattern change, with the cold air that's been entrenched for six weeks being first overrun and then rooted out by increasing southwest flow aloft. To the left is this morning's ECMWF forecast of 500mb heights and 850mb temperatures valid next Wednesday morning (I've added an * to roughly locate Fairbanks).

This is a completely classic upper air pattern for heavy snow in Fairbanks-land: ridge in the Gulf of Alaska with deep west southwest mid-atmospheric flow into the Interior. Temperatures would be something like 0 to 20F above with this kind of pattern.

Cold start…but Not Unprecedented

I've heard that the current cold snap over Alaska has been labeled by some media outlets as "historic" or "unprecedented". I'm not interested in surfing the net to find such quotes, but here's the fact: across much of central and eastern Interior Alaska, this is the coldest late November to early December since 1948. To the left is a plot of mean daily temperatures at Fairbanks comparing the two years. On the whole, 1948 was considerably colder, and that's the case for other places (e.g. Northway, Delta Junction). So, a claim that this is the coldest "early winter" in 65 years would be true, but it has been colder this early in the season before.

Never too Cold to Snow

Courtesy of the FAA

Clouds and light snow have moved into the Upper Tanana Valley from the east. As of 11am, -49F and snowing lightly at Tok.

Not So Normal Temperatures

Here's an update of daily temperature anomalies for Fairbanks through Sunday. At the top is a plot of the actual daily mean temperatures. The gray shading represents one standard deviation from the 1981-2010 normal, so temperatures outside of the shading are "unusually" warm/cold for the date.
The bottom plot is my usual daily standardized anomaly plot, which is simply the departure from normal divided by the standard deviation of the normal temperature for that date. Sunday, at 2.2 standard deviations below normal was not quite the most anomalous day of the year (May 2 was 2.3 SD below normal), but with an apparent high temperature Monday of 32 below, Monday will likely claim that title at midnight.

40s Below in Fairbanks-land

Monday morning brought the first 40s below temperatures to the colder areas around Fairbanks. However, a moderate pressure gradient produced some wind at higher elevations, keeping temps considerably warmer.

Low temperatures reported so far include:
Woodsmoke PWS: -45F (near North Pole)
UAF Smith Lake: 43 below
Eielson AFB: 42 below
Fort Wainwright: 41 below
Goldstream Creek: 40 below
Fairbanks Airprot: 38 below

The inversion was not especially sharp: with lower hillside low temps including:

UAF West Ridge: 37 below
College Hills PWS: -34F (near top of Baline Hill)
Gilmore Creek CRN: -27F

Meanwhile, at higher elevation, overnight lows include:

Keystone Ridge: -9F
Cleary Summt: -11F
Wickersham Dome: -13F

The downward trend in temps the past week is nicely illustrated by this 7 day plot of 2-meter temperatures from the UAF Smith Lake site:

Courtesy IARC at UAF

Nippy Sunday

Courtesy of Alaska Climate Research Center

December's off to a cold start, though the inversion is not especially strong this morning.  The 1025am AST sunrise photo from the Alaska Climate Research Center on UAF West Ridge shows only minimal ice fog over the west side of town.









 Low temperatures through 9am Sunday include:


Woodsmoke PWS: 41 below (near North Pole)
UAF Smith Lake: 39 below
Fort Wainwright: 37 below
Eielson AFB: 36 below
Goldstream Creek: 36 below
Fairbanks Airport: 35 below
UAF West Ridge: 33 below
College Hills: 27 below
Keystone Ridge: 23 below
Nenana Hills RWIS: 21 below
Wickersham Dome: 14 below
Cleary Summit: 13 below

Following the Bouncing Inversion

Here's a plot of the daily high temperatures in November for Fairbanks Airport and Keystone Ridge (about 1150' elevation difference). Notice the dramatic and sustained increase in inversion strength following Thanksgiving.

Fairbanks November Wx Summary

NOAK49 PAFG 011807
PNSAFG
AKZ222-020445-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
727 AM AKST SAT DEC 1 2012

...MONTHLY WEATHER SUMMARY FOR FAIRBANKS ALASKA...

NOVEMBER 2012 IN FAIRBANKS WAS EXCEPTIONALLY COLD WITH UNUSUALLY
LOW SNOWFALL.

COLD WEATHER WAS PERSISTENT BUT NOT EXTREME IN NOVEMBER 2012.
IN NOVEMBER 2012 THERE WERE NO RECORD TEMPERATURES ESTABLISHED...AND
ONLY THREE DAYS ALL MONTH HAD AN AVERAGE DAILY TEMPERATURE ABOVE
NORMAL. THIS DIFFERS FROM NOVEMBER 2011 WHEN SIX DAILY RECORD LOWS
WERE TIED OR SET. FIVE DAYS THIS NOVEMBER WERE 20 DEGREES OR MORE
BELOW NORMAL...AND 17 DAYS HAD A LOW TEMPERATURE OF 20 BELOW OR
COLDER WITH ONLY NOVEMBER 1975 HAVING MORE SUCH DAYS.


OVERALL...AT THE FAIRBANKS INTERNATIONAL AIRPORT THE AVERAGE HIGH
TEMPERATURE IN NOVEMBER WAS 0.4 DEGREES ABOVE ZERO AND THE AVERAGE
LOW WAS 17.9 DEGREES BELOW ZERO. THE AVERAGE FOR THE MONTH OF 8.7
DEGREES BELOW ZERO WAS 11.3 DEGREES COLDER THAN NORMAL AND MADE THIS
THE 6TH COLDEST NOVEMBER IN MORE THAN A CENTURY OF WEATHER
OBSERVATIONS. THE HIGHEST TEMPERATURE FOR THE MONTH AT THE AIRPORT
WAS 22 DEGREES ON THE 10TH...WHILE THE LOWEST WAS 31 BELOW ZERO ON
THE 30TH. THE TEMPERATURE DIPPED INTO 40S BELOW IN A FEW OF THE
NORMALLY COLDER LOW LYING AREAS DURING THE LAST TWO DAYS OF THE
MONTH. IN CONTRAST...TEMPERATURES AT SOME HIGHER ELEVATIONS DID
NOT DROP COLDER THAN 10 BELOW ANYTIME DURING NOVEMBER.

SNOWFALL WAS QUITE LIGHT IN NOVEMBER...AND ALL THE ACCUMULATING
SNOW FELL DURING THE FIRST TEN DAYS OF THE MONTH. THE MOST SNOW IN
ONE DAY AT THE AIRPORT WAS JUST 2.6 INCHES ON THE 10TH...AND THE
MONTHLY TOTAL WAS A MERE 4.2 INCHES. THIS IS ABOUT A THIRD OF
NORMAL. HOWEVER...THREE NOVEMBERS IN THE PAST 12 YEARS HAVE HAD
LOWER SNOWFALL. THUS FAR THIS WINTER ONLY 11.3 INCHES OF SNOW HAS
FALLEN...WHICH IS LESS THAN HALF OF NORMAL. SNOW DEPTH HAS BEEN
STEADY AT SIX INCHES SINCE MID-MONTH. THE LONG TERM AVERAGE SNOW
DEPTH AT THE END OF NOVEMBER IS ABOUT 11 INCHES.

SKIES WERE FREQUENTLY CLEAR AND WIND SPEEDS MUCH OF THE MONTH WERE
CHARACTERISTICALLY LOW...RESULTING IN EXTENDED PERIODS WITH VERY
STRONG INVERSIONS AND LOCALLY POOR AIR QUALITY IN THE FAIRBANKS
AND NORTH POLE AREAS. HOWEVER...WINDS GUSTED TO 20 MPH OR MORE
FROM THE 17TH THROUGH THE 19TH...WHICH HELPED CLEAR THE AIR AT
THAT TIME. THE FREQUENT CLEAR SKIES AT NIGHT ALLOWED FOR VIEWING
OF SEVERAL NICE AURORA DISPLAYS.

LOOKING AHEAD TO DECEMBER...AVERAGE TEMPERATURES SLOWLY FALL
DURING THIS DARKEST MONTH OF THE YEAR. THE NORMAL HIGH TEMPERATURE
FALLS FROM 7 ABOVE ON THE FIRST TO 2 ABOVE ON NEW YEARS EVE. THE
AVERAGE LOW FALLS FROM 11 BELOW ON THE FIRST TO 16 BELOW ON THE
31ST. IN THE PAST 107 YEARS...DECEMBER TEMPERATURES HAVE VARIED BY
120 DEGREES IN FAIRBANKS...FROM A HIGH OF 58 ABOVE IN 1934 TO A
LOW OF 62 BELOW IN 1961. AVERAGE SNOWFALL IS 12 INCHES...BUT HAS
BEEN AS MUCH AS 50.7 INCHES IN 1984 TO AS LITTLE AS A TRACE IN
1969. POSSIBLE DAILY SUNSHINE FALLS TO THE ANNUAL MINIMUM OF 3
HOURS AND 42 MINUTES ON THE SOLSTICE BEFORE STARTING THE LONG
CLIMB BACK TOWARD THE MIDNIGHT SUN OF JUNE.