Soundings from Fairbanks Sunday show the extreme warmth:



High temperatures Sunday include:

Woodsmoke PWS: 40F (near North Pole)
Eielson AFB: 39F
Fairbanks Airport: 37F
UAF West Ridge: 37F
Keystone Ridge: 33F
Cleary Summit: 33F

Another Hot Sunday in Fairbanks

A deep storm west of Kodiak Island has brought another Sunday Chinook to Interior Alaska. Here's the 3AM AST Sunday surface analysis from NWS Anchorage:



Temperatures in the valleys rose sharply after midnight, erasing the strong inversion from yesterday and are now near or above freezing at most low elevation sites.

The 340am AST Sunday NOAA-19 Polar Orbiter infrared image shows a classic cyclone structure:



High temperatures through 10am AST include:

Eielson AFB: 39F
Woodsmoke PWS: 38F (near North Pole)
Two River PWS: 38F
UAF West Ridge: 35F
Fairbanks Airport: 34F
Keystone Ridge: 32F
Goldstream Creek: 28F

Inverion Holds

Here's an updated plot of the inversion, with the Saturday afternoon sounding plotted along with the morning data.

Barrow near the Solstice

Winter solstice this year is at 830pm AST Wednesday. Here's a photo at Barrow from the Sea Ice webcam at 1235pm Saturday. This is about 40 minutes before solar noon.

Strong Inversion

Mostly clear skies the past day or so have allowed a typically strong inversion to develop in Fairbanks. Here's the temperature in the lowest kilometer of the atmosphere from the 3am AST Saturday sounding.

Low temperatures on the ground through 10am Saturday morning reflect this:

Fairbanks Airport: -10F
Chena Hot Springs: -10F
Woodsmoke PWS: -9F (near North Pole)
Goldstream Creek: -9F
College Road: -7 (NRCS SNOTEL near Fairgrounds)
UAF West Ridge: +2F
Two River PWS: 7F
Keystone Ridge: 18F
Cleary Summit: 22F

Second Warmest first half of December at Fairbanks

from my colleague Corey:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1251 AM AKST FRI DEC 16 2011

...2ND WARMEST FIRST HALF OF DECEMBER ON RECORD AT FAIRBANKS...

THROUGH YESTERDAY THE 15TH THE AVERAGE TEMPERATURE AT THE
FAIRBANKS INTERNATIONAL AIRPORT WAS 14.1 DEGREES...WHICH WAS
17.9 DEGREES ABOVE AVERAGE. IT WAS THE 2ND WARMEST FIRST HALF OF
DECEMBER ON RECORD AT FAIRBANKS. ONLY 1934 WAS ANY WARMER...AND THIS
WAS DUE TO AN INCREDIBLE CHINOOK EARLY IN THE MONTH THAT SENT
TEMPERATURES INTO THE 50S ON 5 CONSECUTIVE DAYS...AND LED TO THE
ONLY CHRISTMAS ON RECORD WITH NO MEASURABLE SNOW ON THE GROUND AT
FAIRBANKS. IN 1934...TEMPERATURES TURNED SHARPLY COLDER THE
SECOND HALF OF THE MONTH...AND BY THE END OF MONTH IT DID NOT EVEN
END UP AS ONE OF THE TOP TEN COLDEST DECEMBERS ON RECORD. THE
WARMEST DECEMBER ON RECORD OCCURRED IN 1914 WITH AN AVERAGE
MONTHLY TEMPERATURE OF 10.2 DEGREES. TEMPERATURES ARE EXPECTED TO
REMAIN ABOVE NORMAL FOR NEXT WEEK...INCREASING THE CHANCES THAT
THIS DECEMBER WILL GO DOWN IN THE RECORD BOOKS AS ONE OF THE
WARMEST ON RECORD.

$$

CB DEC 11

Deep Storm

Here's the 3am AST Thursday GOES-15 image showing an intense cyclone over the eastern Aleutians. The minimum Sea Level Pressure at Dutch Harbor was 945.8mb at 2AM AST. Dutch had a peak wind from this storm of 76KT late Monday afternoon.

Solar Noon at Prudhoe Bay

Here's a photo, looking south from Prudhoe Bay (thanks to the FAA webcam) from just after solar noon on Wednesday.

Let it Snow

Snowfall during mid-winter in Interior Alaska often does not show much of valley to ridge difference. After all, precipitation is almost always snow, and the elevations where people live vary by perhaps 2000 feet (say, Nenana to Ester Dome), trivial compared to, say the vertical change over similar distances in the Rockies.

That has most definitely not been the case so far month. Here is a chart of the daily snowfall thus far this month at Fairbanks International Airport and Keystone Ridge.



There was similar, though less extreme difference last month, when the Airport measured 9.2 inches of snow and Keystone Ridge 20.7 inches.

Below is a plot the difference in total December snowfall since 1996 between the Airport and Keystone Ridge. Monthly differences have not exceeded six inches, and the difference has not been more than 50% of the total at Fairbanks: thus far this month, the difference of 14.0 inches is a stunning 241% of the Fairbanks total.



Of course, with more than two weeks left in December this difference will likely narrow, but given the usual minimal differences is unlikely to dramatically change.

Messy Image

This 430pm AST Monday GOES-15 image shows lots of (disorganized) clouds across eastern mainland Alaska, while a tight cyclone is impacting the central Aleutians.

The Anchorage area received 6-12 inches of snow in town and up to two feet of new snow on the upper hillside. Amounts in Fairbanks-land have been mostly an inch or two, but with enough southwest wind to blow the snow around in town, always a notable event. However, it remains very mild, with temperatures so far stuck in the teens and 20s.

The Sea Level Pressure at Adak at 5pm AST Monday was 959mb with the low center just to their east.

Updated: The minimum pressure in this storm at Adak was 951.2mb at 1016pm AST Monday.

Another Seward Pen Blizzard

Here's the FAA webcam shot from Nome at 1pm AST Saturday. Nome's been reporting blizzard conditions since before 10am, with winds gusting to nearly 50 mph. Similar at Golovin.




The 9am AST Saturday surface analysis from NWS Anchorage shows a complex low in the western Bering Sea.

Snowfall Friday

Nice little snowfall in Fairbanks-land Friday.

Some totals include:
Fairbanks Airport: 2.9 inches (most any day so far this winter)
Fairbanks Mid-town: 2.5"
UAF West Ridge: 2.4"
Goldstream Creek: 2.1"
Keystone Ridge: 5.4"

The much higher amount here on the ridge was probably an elevation effect: low level west winds lifted a 1000' up from the Minto Flats, with the atmosphere unstable enough for that lift to enhance snow crystal production. Just a guess of course. However, on my home from work late Friday evening the snow amounts did not look to increase much until I started up the hill.

Solar Noon at Arctic Village

From the FAA, this photo from Arctic Village Friday 1240pm, is close to solar noon.

Clocks Don't Matter

Classic December Day: High temperature at 1am, low temperature in the middle of the afternoon…

CDAK49 PAFG 090937
CLIFAI

CLIMATE REPORT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1237 AM AKST FRI DEC 9 2011

...................................

...THE FAIRBANKS AK CLIMATE SUMMARY FOR DECEMBER 8 2011...

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1904 TO 2011


WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST
VALUE (LST) VALUE VALUE FROM YEAR
NORMAL
..................................................................
TEMPERATURE (F)
YESTERDAY
MAXIMUM 22 1258 AM 55 1934 6 16 -16
MINIMUM 0 340 PM -53 1935 -10 10 -28
AVERAGE 11 -3 14 -22

Winds

Fairbanks Airport reported a peak wind of 51 mph at 1021AM Monday. Gust data is only available at Fairbanks since the mid-1980s, but since then this is the highest gust of record for December. The previous record was just 38 mph on Christmas Eve 1985.

Here is a plot of winds from the NRCS SNOTEL up on Eagle Summit at Mile 107 Steese Highway (elevation 3750' MSL). Winds between an ASOS/AWOS and SNOTEL are not directly comparable, but you get the idea. The anemometer often ices up on Eagle Summit, but evidently not today.



It's been a really windy day up there! The highest gust has been 55 mph, and a quick look shows nothing that high in the past couple winters (50 mph was the highest reported in the storms last February)

Storm Aftermath

Here's the 3am Monday Surface Analysis from Environment Canada. The 975mb low near Banks Island is responsible for the re-surge of winds across the area this morning.

Impacts:
Fairbanks North Star Borough Schools and State Offices are closed today (Monday) due to poor road conditions. FNSB Borough Offices and UAF are open. Fort Wainwright has "late arrival" policy in place.

Weather:

Record High Temps for December set Sunday:

North Pole: 49F (old record 47F on Dec 29 1982)
Eielson AFB: 48F (old record 47F on Dec 24 1985)
UAF West Ridge: 45F (old record 44F Dec 24 1985)

The high of 47F at Fairbanks International is the highest temperature of record in December except for Dec 4-8, 1934, when every day had a high in the 50s.

There were some big snow amounts:
Bettles: 14.3 inches Sunday
Ruby 14NE: 13.5 inches (cooperative station upriver from Ruby)
Galena: 8.0 inches

Rain

Rain in Fairbanks Sunday afternoon evidently did not amount to much (trace to a couple hundredths), though this time of year any is a problem for roads, walkways, etc. Much higher amounts though occurred near Denali National Park, with 0.20" reported from Park Headquarters this morning and 0.30" at Healy. Nenana also received almost a tenth of an inch of rain Sunday afternoon before it changed over to snow.

Big Chinook

It appears that the temperature spiked to 47F at 1119am at the Fairbanks Airport right as the front came through, mixing out the weak inversion that was present. If this is correct, this is the highest temperature of record in December EXCEPT for the five days from December 4-8 1934, when the temperature got to 50F or higher each day. More on this to follow.

Here's the plot of temperatures from the 3am and 3pm RAOBs from Fairbanks.



That's a lot of cooling!

Record High Temperatures

Here's the METAR plot from 10am Sunday observations: a wind shift just came through Fairbanks: the surgace front is probably lagging a bit behind.



For climate sites that do not have records going back to the great December 1934 Chinook appear to have set or tied new December high temperatures. The following are all preliminary and subject to revision:

Eielson AFB: 48F (47F on Dec 24 1985)
UAF West Ridge: 45F (44F on Dec 24 1985)
North Pole current record for December is 47F

other daily records:
Fort Greely/Big Delta: 51F

Other high temperatures:
Rex Brige RWIS: 49F (Mile 276 Parks Hwy)
Mile 42 Steese Hwy: 47F
Nenana Hills RWIS 44F (at FNSB Borough Boundary on Parks Hwy)

Also of note:
Antler Creek RWIS (south of Healy) peak wind 81 mph at 505pm Saturday Dec 03

Extreme Heat in the Central Interior

3AM Sunday surface analysis from NWS Anchorage:



7-8am Sunday Temperatures around the central Interior

Kantishna SNOTEL: 51F
Chena Hot Springs: 50F
Nenana: 50F
Woodsmoke PWS: 49F
Eielsion AFB: 48F
Birch Lake RWIS: 48F
Denali Park AWOS: 45F
Cleary Summit: 41F
Keystone Ridge: 40F
Fairbanks Airport: 36F
Eagle Summit SNOTEL: 36F

Much more to come after I've had some coffee…

Surface Analysis

Here's the 3pm AST Saturday surface analysis from NOAA's Ocean Prediction Center. The deep southerly flow, at least a breeze and thick cloud cover has boasted temperatures across area, resulting in frosty roads.




6pm Saturday…

Two Rivers PWS: 30F
Keystone Ridge: 30F
Clearly Summit: 29F
Fairbanks Airport 28F
Woodsmoke PWS: 28F
Eielson AFB: 25F
Goldstream Creek: 22F

Warming Up

Here's the 3pm Saturday RAOB from Fairbanks. I've plotted temperatures on the left and wind speed of the right for the lowest 1500 meters of the atmosphere. Temperatures vary between -1 and -5C and winds speeds are on the way. Free air wind speeds are nearly always higher than that reported from surface stations at similar elevation (excepting ridge top locations, e.g. like Mt Washington, New Hampshire).

Thermometer Yoyo

Here's a plot of temperatures over the past few days here at Keystone Ridge. The sharp dip there on the morning of December 1st is accurate: the inversion very briefly sloshed up before retreating down the hillside.

And the swings of the yoyo will increase over the next 36 hours.

Early December Storm

Here's the 850mb temperature forecast for Fairbanks from the 12Z Saturday GFS. It is quite similar to yesterday's run; warm in the morning (no chance of record though as this is the anniversary of the great 1934 chinook); the cold front is a smidge faster, coming through during the afternoon followed, by about 12 hours of snow and 24 hours of gusty west to southwest winds. It's not out of the realm of reasonablity that there could be a little freezing rain right at the start, but it would not last more than minutes before changing to snow.

No Rest for the Weary

Another big storm is on the way for northern Alaska. Here are forecasts from the GFS for 3am and 3pm AST Sunday. What does this mean for Fairbanks-land?



First, Saturday night into Sunday morning, big chinook. It is very likely that it will get significantly above freezing throughout the area. Then, about as strong a cold front as ever is seen in Interior Alaska comes blasting through late Sunday afternoon or evening. Here's the forecast for the 850mb temperatures (about 4500' MSL, a decent guide to the temperature of the low level airmass).



Yes, that's plotted correctly: the model is forecasting an almost 9C fall between 3pm and 6pm Sunday. There will be snow and lots of southwest wind as the cold air returns. Above tree-line on the highways north of Fairbanks it's really going to howl. The southwest winds will break through in town too; I would not be surprised to see Fairbanks Airport report blowing snow at some point Sunday night/Monday morning.

November Weather Summary

November Summary for Fairbanks...

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1155 AM AKST THU DEC 1 2011

...MONTHLY WEATHER SUMMARY FOR FAIRBANKS ALASKA...
...OUTSTANDING COLD SNAP MID-MONTH...

NOVEMBER 2011 WILL LONG BE REMEMBERED FOR THE MID-WINTER-LIKE COLD
SNAP WHICH SETTLED IN THE WEEK BEFORE THANKSGIVING. THE WEEK OF
NOVEMBER 15TH TO 21ST...WITH AN AVERAGE TEMPERATURE OF
30.1 BELOW...IS THE COLDEST WEEK EVER RECORDED IN FAIRBANKS BEFORE
THANKSGIVING DAY. SIX DAILY RECORD LOWS WERE SET DURING THIS
TIME...WHICH IS TRULY OUTSTANDING FOR A LOCATION WITH MORE THAN A
CENTURY OF UNBROKEN WEATHER OBSERVATIONS.

THE FIRST HALF OF NOVEMBER...WITH AN AVERAGE TEMPERATURE OF 3.0
DEGREES ABOVE ZERO WAS ONLY A BIT COOLER THAN NORMAL.
HOWEVER...THE SECOND HALF OF THE MONTH...WITH AN AVERAGE
TEMPERATURE OF MINUS 19.2 DEGREES WAS THE COLDEST SECOND HALF OF
NOVEMBER SINCE 1963.

FOR THE MONTH AS A WHOLE...AT THE AIRPORT THE AVERAGE HIGH
TEMPERATURE WAS ZERO AND THE AVERAGE LOW 17 BELOW. THE AVERAGE
TEMPERATURE LAST MONTH OF 8.2 BELOW MADE THIS THE SIXTH COLDEST
NOVEMBER OF RECORD. DURING THE PAST 50 YEARS...THE ONLY COLDER
NOVEMBER WAS IN 2006...WHEN THE AVERAGE TEMPERATURE WAS 9.9 BELOW.
THE COLDEST NOVEMBER OF RECORD WAS IN 1927...WHEN THE AVERAGE
TEMPERATURE WAS MINUS 11.2 DEGREES.

THE HIGH FOR THE MONTH WAS 25 DEGREES ON THE 4TH. THE LOWEST
TEMPERATURE AT THE AIRPORT WAS 41 BELOW ON THE 17TH...AND IS THE
FIRST TIME THE TEMPERATURE HAS FALLEN PAST 40 BELOW IN NOVEMBER
SINCE 1994. SEVEN DAYS HAD LOW TEMPERATURES OF 30 BELOW OR
LOWER...THE MOST IN A NOVEMBER SINCE 1963. SOMEWHAT LOWER
TEMPERATURES WERE RECORDED IN THE NORMALLY COLDER SPOTS...INCLUDING
49 BELOW IN NORTH POLE ON THE 17TH.

SNOWFALL WAS GENERALLY A BIT BELOW NORMAL IN THE IMMEDIATE FAIRBANKS
AREA...AND NEARLY ALL OF IT FELL DURING THE FIRST TWO WEEKS OF THE
MONTH. THE TOTAL AT THE AIRPORT OF 9.2 INCHES WAS ABOUT 4 INCHES
BELOW NORMAL. THIS MELTED DOWN TO 0.46 INCHES OF WATER...WHICH IS
ABOUT TWO-THIRDS OF NORMAL. SNOW DEPTHS INCREASED FROM 3 INCHES ON
THE FIRST TO A STEADY 7 INCHES THE LAST TWO WEEKS OF THE MONTH.

HIGHER SNOWFALL AMOUNTS WERE OBSERVED NORTH OF TOWN. FOR NOVEMBER
12.0 INCHES OF SNOW WAS MEASURED AT MILE 42 STEESE HIGHWAY. THE
KEYSTONE RIDGE COOPERATIVE STATION...NEAR MURPHY DOME...REPORTED
20.7 INCHES OF SNOW FOR THE MONTH.

WINDS WERE CHARACTERISTICALLY LIGHT IN NOVEMBER...ESPECIALLY
DURING THE COLDEST WEATHER. AVERAGE DAILY WIND SPEEDS WERE LESS
THAN TWO MPH EVERY DAY AFTER THE 13TH. ICE FOG DURING THE COLDEST
WEATHER WAS NOT ESPECIALLY DENSE.

LOOKING AHEAD TO DECEMBER...NORMAL TEMPERATURES SLOWLY DECLINE...
FROM 2 BELOW ON THE FIRST TO 7 BELOW ON NEW YEARS EVE. OVER THE
PAST 106 YEARS...DECEMBER TEMPERATURES HAVE RANGED FROM A HIGH OF
58 DEGREES IN 1934 TO 62 BELOW IN 1961. ON AVERAGE A FOOT OF NEW
SNOW FALLS DURING THE MONTH...BUT HAS RANGED FROM 50.7 INCHES IN
1984 TO JUST A TRACE IN 1969. POSSIBLE SUNSHINE DECREASES FROM 4
HOUR 42 MINUTES ON THE FIRST TO 3 HOURS 42 MINUTES FOR A FEW DAYS
AROUND THE WINTER SOLSTICE...AND THEN INCREASES THEREAFTER.

$$
RT DEC 11

Winter Sunshine

Noontime sun and 13 below at Central. Photo courtesy of the FAA.

Dramatic Temperature Swings

Interesting temperature variation the past day in Fairbanks-land. Here is a plot of hourly temperatures from a number of locations.

The max temperatures early in the morning make a useful case study: Eielson reach their max temperature when the southeast winds broke through ahead of the trough, so are hour or so earlier than the other valley locations (in spite of Eielson being the eastern-most of these stations), where the max temp occurred with a short pulse of weak southwest wind following the trough. At elevation (Keystone Ridge), there was no spike in temperature at all, where most of the wind occurred Tuesday evening.

High temps (not just hourly) occurred 5-7am:

Eielson AFB: 26F
Keystone Ridge: 21F
Fairbanks Airport: 16F
Woodsmoke PWS: 11F (near North Pole)
Goldstream Creek: 7F

Solar Heating or Lack Thereof

Here's a plot of the daily duration of solar heating at 65N (latitude of Fairbanks), defined as the duration the sun is 5° or more above the horizon. Note the plot extends for 15 months so to show the winter minimum. We are a week into the two months with no significant solar heating. Changes in surfaces temperatures during this time are modulated by horizontal movement of air (advection), vertical mixing (mostly wind) and presence of absence of clouds significant to reduce the continuous cooling of the top of the snow pack (long wave radiation).

Big warm-up on the Way

Trung asked about the big warm-up in the current forecast in a couple days. Here's why:

Big pattern change is underway for Alaska and will bring much milder weather to the Interior by midweek. First, here is the 500mb heights and 850mb temperatures for this past Saturday morning (from the ECMWF). This shows a closed low west of Anchorage and a fairly chilly airmass over most of mainland Alaska; the blue colors are 850mb (~4500 MSL) temperatures of -16C or lower.



Now, here is the forecast from the 12Z Sunday ECMWF valid at 3am AST Wednesday Nov 30th. Deep southwest flow from the north Pacific covers most of the state, with the chilly air having retreated the Brooks Range. This could wind up being a fairly snowy pattern for Fairbanks-land, but as always in these situations, if the winds aloft are just a little bit too southerly, then we will "chinook out". At this point though it looks to me like the best forecast is for some snow the middle and end of this week.

Inversion

The Sunday afternoon sounding from Fairbanks shows a decent 15C inversion in the lowest 500 meters. This is reflected in the late afternoon temperatures, which remain in the 20s below in the valleys and a little above zero in the hills. As usual, most of the increase is in the lowest 100 meters.

Big Inversion

A pretty decent inversion has developed overnight, with valley temperatures pushing 30 below and higher elevations near zero.

10AM Sunday temperatures include:

Woodsmoke PWS: -33F (near North Pole)
Eielson AFB: -29F
Fairbanks Airport: -27F
Goldstream Creek: -27F


Cleary Summit: +2F
Little Chena Ridge +1F (south of the Steese Highway)
Gilmore Trail PWS: -1F (1440' MSL)
Keystone Ridge: -2F

Cold in Context

Here's another view of the recent cold weather: the daily mean temperature plotted against the 1981-2010 normals; grey shading of plus/minus one standard deviation.



Here are standardized daily departures for 2011. Looked at this way, the recent cold snap was about as far from normal as the hot weather in late May. The coldest day, the 17th, with an average temperature of -35F, was 2.7 standard deviations below normal, almost the same as warmest day in, when the 28th was 2.9 standard deviations above normal. The height of cold snap was a couple days longer than the hot spell in May, but the total "excessive" (the area under the curve) will likely be somewhat greater in May than in the cold snap.

Thanksgiving Day

305pm November 24th from UAF West Ridge

Cold Persists near the Alaska Range

Unlike the Fairbanks area, clear skies have prevailed near the Alaska Range for past 36 hour. Here's the 1pm photo from Denali National Park right near the train station. The lack of clouds have allowed the cold temperatures to persist. At the Denali Park AWOS (partially visible in the photo just beyond the brown building), the high today was 20 below and low 36 below. At the DVCA2 RAWS, which is near the Wilderness Access Center and at a slightly lower in elevation than the AWOS, the high was -27F and the low -38F.

Recap of the November Cold Snap

The record setting cold snap of November 2011 is history. So, without the media hoopla, here’s what happened. It's important to emphasize that the "news" here is the early occurrence of the cold snap, rather than the absolute values of the temperatures. The exact same temperatures anytime between Thanksgiving and Valentines Day would be unexceptional.

The mean 500mb heights (30dm contours) for November 15-21 (courtesy of ESRL and NCEP/NCAR Reanalysis) show a classic pattern for cold weather in Interior Alaska, with a high over Chukotka and fairly low height northerly flow across most of mainland Alaska (I’ve added centers and arrows to indicate wind direction.



In the Fairbanks area, this was easily the coldest pre-Thanksgiving week of record. At the Airport, the lowest 7-day average temperature was -30.1F for November 15-21. The previous record was -26.5F was set November 7-13, 1989. For November as a whole, this was the third coldest event; November 24-30, 1909 and the same week in 1927 were colder.

Record lows were set at the Airport on six days (November 16th did not have a new record) and record low maximum temperatures were set November 16-19. The high temperature of -30F on the 17th is the second earliest high of -30F or lower in the winter (November 9, 1989 is the earliest). The low temperature of -41F on the 17th is the fifth earliest occurrence of -40F in the winter. Here's the plot of November record lows:




Elsewhere around the area, temperatures varied pretty much as is typical for this time of year. The average temperature for November 15-21 at the North Pole cooperative station was -37.7F, with six days with lows in the -40s and an absolute low of -49F on the 17th. At the other extreme, Keystone Ridge cooperative station, at 1600’ MSL, had an average temperature of -13.4F the same week and an absolute low of -28F on the 21st.

Most places with a long period of observations set six or seven daily records. Lowest temperatures for the cold snap include:

University Experiment Station: -41F
Eielson AFB: -41F
UAF West Ridge: -40F

As more cooperative info becomes available I'll update the extremes.

Impact of Clouds on Temperatures

The last 24 hours have featured a textbook example of the impact of clouds on valley temperatures in Interior Alaska in winter. Here is a plot of the hourly temperature at the Fairbanks Airport. Variations in temperature are completely related to changes in clouds cover: clears out for a few hours, the temperature drops 20 degrees. Clouds return, and the temperature pops right back up. In contrast, here on Keystone Ridge, the temperature has varied by 5 degrees in the same time, -1F to -5F

Inversion Collapses: Cold Snap Ends

Temperatures aloft warmed dramatically over the past 36 hours, and persistent cloud cover and a moderate pressure gradient have taken their toll on the inversion. Here is a plot of the lowest 1000 meters from the morning sounding from today and Monday.


At 2am today (Nov 23) the temperature at the Fairbanks Airport rose to 2 above. This effectively ends the cold snap. The numerical models have not distinguished themselves in glory with the end of this event, and that is directly related to the inability of the models to effectively resolve the processes in the very near surface (boundary layer). That said, the airmass remains chilly and if and when clouds break temperatures will again fall in the valley. However, the unprecedented nature of this cold snap is over. I'll have a wrap-up in the next couple days.

Fairbanks Cold Snap Update

For the week ending Nov 21, the average temperature at Fairbanks was -30.1F. This is, by far, the coldest 7-day average temperature so early in the season and the coldest week in November in the WB/NWS era (since 1930). In the early years, when observations were done by cooperative observers, the week ending on Nov 30th in 1909 and 1927 were colder.

Clouds and some light snow have arrived and overnight temperatures have been mostly in the 20s below in the valleys. On exposed hillsides and channeled valleys a breeze picked up too. Here at Keystone ridge at 6am, -10F with northeast winds about 15mph with gusts to about 25 mph. Air quality is good!

Solar Noon in Barrow

Here's the FAA webcam shot looking south from the Barrow airport. The photo was taken at 116pm AST, which is very close to solar transit.

Updated Records

Here's am update showing the record lows that have been set this month at Fairbanks. The low of -38F this morning breaks the previous record of -35 set in 1904.

Dramatic Cooling

Here are plots of the temperatures in the lowest 1000 meters from the upper air sounding at Fairbanks from 3am AST Sunday and 3am AST Monday. While the surface temperature was only about 3C cooler Monday morning that Sunday morning, temperatures aloft fell much more: over 10C at 100 meters above the ground; the temperatures aloft are now as cold or colder than last week.

The NOAA-19 Polar orbiter infrared image from 5am AST Monday shows lots of cloud scraps across the interior but not much organized yet.

Coldest Early Season Week of Record at Fairbanks

The airmass cooled dramatically during the day Sunday but few clouds showed up, allowing for another very cold day. At the Fairbanks Airport, the morning low of 34 below, but the temperature fell to 37 below during evening, breaking the previous record of 36 below set in 1993.

For the week of Nov 14-20, the average temperature at the Fairbanks Airport was -27.6F. This is the lowest weekly average temperature of record so early in the season. The previous record was -26.5F set Nov 7-13, 1989. It is also very close to the coldest week anytime in November since 1930, when the Weather Bureau began observations: currently that record is -27.9F set November 21-27, 1948. That record will likely be broken after today. Prior to 1930, there are a couple of end-of-November cold snaps that far exceed what we've had thus far: In 1927, the average temperature Nov 24-30 was -36.6F and the same week in 1909 had an average temperature of -34.3F

Cold Moving East

The eastern Interior hung on to clouds a couple days longer that central and western sections, but skies have cleared now and temperatures fallen. The low of 46 below at Northway ties the record low for November 20th. Other low temperatures include 46 below at the Tok PWS, 45 below at Chicken and 43 below at Eagle before the wind picked up.

This morning's photo is the 11am view from Lake Minchumina, looking southeast toward Denali and the sunshine.

How Unusual is this Cold Snap?

An interesting, and increasingly asked question is: "how unusual is this cold snap?"

First some more numbers, just looking at Fairbanks (1904-2010):

Saturday (Nov 19) was the fifth day (in a row) with the daily minimum temperature 35 below or lower. Only four other Novembers have had five or more days with low temperatures of 35 below or lower.

Thus far, three days have had maximum temperatures of -20F or lower (Saturday will likely be the fourth). Eleven other Novembers have had three or more such days and six have had four or more.

The lowest temperature (thus far) has been -41F; this been exceeded in nine other Novembers.

However, this event is occurring not toward end of November, but around the middle of the month.

At the close of Saturday, the 7-day average temperature will be about -22F; there have been five other years that had a 7-day average temperature of -20F or lower ending November 20th or earlier. The coldest 7-day average temperature ending on or before November 20th is -26.5F, which occurred on the week ending November 13, 1989. In second place is Nov 11-17, 1956 at -23.9F.

Another way to look at this, though probably of dubious value, is to ask when the last time a cold snap set four daily record lows? Answer: September 1992, a "black swan" event if ever there was one in Interior Alaska. I say dubious because three of the four records broken were what are sometimes called "low hanging fruit", as can be seen in this plot of November daily record lows for Fairbanks:



Disclaimer: While I have doubts about the veracity of some of the pre-1930 data, it's what the NWS uses for daily records, so I include it here.

The three record lows of 33 below were the only records that high after November 4th. From this point onward only one day has a record lower warmer than -36F.

So, is this event unprecedented; no. Unusual? You bet; similar cold snaps at this time of year have occurred only a handful times in the past 106 years, and this may approach the coldest early season prolonged cold snap (before late November), though I'd guess at this point the 7-day record low mean of -26.5F set in 1989 will stand.

Strong Inversion

Back home now, so more useful posts, and I can comment too!!

Here's a plot of the lowest 500 meters of the upper air sounding from Fairbanks this (Saturday) morning. A fairly typical "strong inversion" situation, worth 30+ degrees F. Readily reflected in the surface observations.

At 8am…

Fairbanks Airport -35F
Eielson AFB -37F
Woodsmoke PWS -41F (near North Pole)

Cleary Summit -3F
Keystone Ridge -5F
Parks Highway RWIS -8F (at FNSB border)

Looks like this will change early next week as a tight cold low drops south from the high Arctic into the western Interior. I expect the inversion will largely break with clouds and light snow. There is a good chance that the hills will have somewhat lower temperatures than earlier this week while the lowlands will be substantially warmer than it has been.

Cold Continues

Summary from my colleague Corey B. with a nice summary of where this cold snap stands for so early in the season:

Public information Statement
National Weather Service Fairbanks AK
304 Am AKST Sat Nov 19 2011


…The Records Continue to Fall at Fairbanks...

The early winter November cold snap continues to re-write the
record books at Fairbanks. The current cold snap will go down in
the record Books as one Of the most severe early season cold snaps
at Fairbanks.

The high temperature yesterday at the Fairbanks International
Airport was 21 below. This breaks the previous record low maximum
temperature Of 19 below Which was established in 1969. The low
temperature yesterday Of 36 below breaks the previous record low
For the date Of 33 below also set in 1969.

At 213 Am this Morning...the temperature at the Airport dropped to
36 below. This breaks the old record low For November 19th of 33
below in 1969.

Today (Saturday) marks the 5th consecutive day with a low
temperature Of 30 below or colder at the Airport. This Ties with
1956...1969 and 1989 For the most consecutive days with a
temperature of 30 below or colder so early in the winter season.

The low temperature has now been 35 below or colder each Of the
last 5 days. This has never happened before so early in the
winter season at Fairbanks. The old record was only 2 days...and
was Last recorded in 1989.

The high temperature has now been 20 below or colder each Of the
last 3 days. This ties with 1989 For the most consecutive days
with a high temperature Of 20 below or colder so early in the
winter season.

Temperatures Over the Next Week Are Expected to Remain Well below
normal. A Cold low will drop out Of the Arctic and into the
western Interior early next week. The Airmass aloft will be colder
than the airmass currently across the Interior. However...there is
fairly high confidence that this next push Of cold air will be
accompanied by clouds and flurries. The clouds will act as an
insulator and keep temperatures somewhat warmer than this past
week. Temperatures much of next week Are expected to be in a range
of 10 to 25 below. There will likely be little difference in the
temperatures next week between the hills and valleys as the clouds
and depth of the cold air will prevent a low level inversion.

$$

CB

Record Low Friday

Update:

Another record so far early Friday, thanks to the record lows being significantly warmer. Fairbanks Airport 39 below breaks the previous record of 33 below set in 1969.

Low temperatures for Friday will be completely dependent on end time of the climate day, as temperatures are rising. For example, the low of 39 below at UAF West Ridge is a record; that was the temperature at 9am Thursday, and at 9am Friday it was up to 23 below. Temperatures in the hills are approaching zero, so about a 30 degree inversion this morning.

Few more record lows

A few more record lows were set Thursday in the Interior.

Fairbanks Airport: -41F old record -39F in 1969
North Pole: -49F old record -46F n 1969
Eielson: -43F old record -40F in 1969
UAF West Ridge: -40F old record -35 in 1969

The reported low in the Interior of -54F at Manley Hot Springs looks suspect, as this is seven degrees colder than the 9am temperature, when there was ice fog and no wind. Manley does not usually run so much colder than Tanana (low -42F) in these situations. Not impossible, but suspect.

Why are North Pole and Eielson Colder than Fairbanks?

While the North Pole and Eielson areas aren't always colder than Fairbanks, that is often then case in the winter (when there is not a Chinook) and for summertime low temperatures.

First, even more so than Fairbanks, North Pole is a flat land with lots of old sloughs and channels of the Chena and Tanana Rivers that provide good places for cold air to pool.

Second, there hardly any human development to the east and northeast of North Pole, while to the northeast of the Fairbanks Airport is, well, Fairbanks City. This is important in winter because the prevailing drainage flow of air is from higher to lower elevations, which in both cases is (north)east to (south)west.

Third, the North Pole is in "collection" area for cold air draining down the Chena River valley and far from any significant ridges. This helps keep wind speeds in North Pole very low in winter. The Fairbanks airport, in part influenced by nearby Chena Ridge, sometimes gets more wind in the winter than North Pole, which allows for more mixing of air, which keeps it from being quite as cold as North Pole.

More Record Lows

Here's the NOAA-19 Polar orbiter infrared image from 2pm AST Wednesday, showing cold air pooled in the valleys and clouds south and east of Fairbanks.

A few more record lows have been registered in the Fairbanks area, including 37 below at UAF West Ridge and 46 below at North Pole. This is not the coldest weather so early in the season. In 1989 a similar cold snap produced a low temperature of 46 below to North Pole and 44 below at Eielson AFB on November 13th.

Record Low at Fairbanks and Eielson AFB

The low temperature Tuesday at Fairbanks International reached 35 below at 1114pm. This is a new record for November 15th, breaking the previous record of 33 below set in 1969. Eielson AFB has already set a record low for Wednesday, November 16th. At 4am AST the temperature at Eielson was 38 below, breaking the previous record for 37 below set in 1956. North Pole had a low of 39 below on Tuesday, one degree shy of the record low of 40 below also set in 1969.

The inversion is slowly growing, with temperatures in the hills steady in the teens below.

Cold is Here

Not much of an inversion on this afternoon's RAOB from Fairbanks. Here's the plot from the University of Wyoming. At least a few record lows are likely to fall over the next 24 hours. Fairbanks is 28 below at 6pm, and the record is 33 below. The record for Wednesday at Bettles is only 42 below, which cold also be broken.

First 40 Below

The first 40 below temperatures of the season occurred overnight in the northern Interior. Some low temperatures through 5am Tuesday include 44 below at Arctic Village, 43 below at the Coldfoot SNOTEL and 40 below at Chalkyitsik RAWS (half way bewteen Chalkyitsik and Fort Yukon)

November Chill Starts

Updated:

Temperatures are falling smartly now over most of the Interior as the airmass cools and cloud cover begins to break. Here is the NOAA-19 infrared image from 5am AST Monday. Some lows through 10am AST temperatures include 38 below at Arctic Village, 36 below at Norutak Lake, west of Bettles, 33 below at the Beaver Creek RAWS southwest of Fort Yukon and 32 below at the Coldfoot SNOTEL and the Jim River DOT camp at Mile 136 Dalton Highway.

Record lows at Fairbanks are 33 below on Tuesday (in serious jeopardy) and 41 below on Wednesday, which also might go down.

We are now close enough to winter solstice that there will be very little solar based diurnal trend.

Cold Weather on the Way

Unusually cold weather is on the way for Interior Alaska for the upcoming weak. Here is the 12Z ECMWF valid at 3am AST Wednesday 500mb heights and 850mb temperatures (the color field). I've flipped the image so that the view is "Alaska-centric". The purple color over the eastern Interior and the western Yukon is -24C, and there is a core of colder than -28C over east of Northway. This is easily cold enough to support valley temperatures of 40 to 50 below in places the go clear and calm for a couple of days. This is pretty cold for mid November. With the airmass this cold inversions will not start off especially strong, but by late in the week inversions may become stronger.