More Cold

Scott Bachmeier sent a link to this false color infrared image from early Friday morning (I've reoriented the original image to be longitudinally centered over Alaska):

The purple colors are radiance derived temperatures -50C (-58F) and lower. Over mainland Alaska any temperatures this cold are surface temperatures. These are a bit lower than the surface observations. The difference comes from several different sources, the most of significant of which are satellite calibration and the fact that "surface observations", i.e. METARS, cooperative obs, etc are from thermometers exposed above the surface. Nominal exposure 1.5 to 2 meters above the ground, though some are routinely higher (SNOTEL, RWIS). The presence of the mid-winter snowpack makes the actual thermometer exposure something like 0.5 meters lower in most places north of the Alaska Range.
Skies cleared by mid-morning over Fairbanks. By Noon temperatures have been down to 41 below at the Airport and 42 below at Fort Wainwright and Goldstream Valley.

Now it's Getting Cold

The 320am NOAA-19 Polar Orbiter infrared image shows it is cold over the western Interior. Fairbanks is near one of the last remaining areas of clouds.

As of 7a Friday, lows include:

Tanana 56 below
Hulsia: 56 below
Galena Airport: 53 below
Kaltag: 50 below

More to come…

Really Cold on the North Slope

FAA webcam image from Barrow Tuesday after with thin ice fog and 35 below:

Low temperatures so far Tuesday:

Barrow -45F
Deadhorse Airport: -50F
Umiat RAWS: -59F
Ikpikpuk River: -59F
Nuiqsut: -62F

Near Record Cold January in the Works

Here's an updated plot of daily mean temperatures thus far this winter (through January 23rd). The winds and clouds the past few days have kept temperatures up near normal. Through Monday (the 23rd), the mean January temperature at the Fairbanks Airport is -25.0F. The rest of the month looks to average at least this cold, and probably colder. This will be one of the coldest Januarys of record.

Colder Air Moves in, Temperature Warms 30 Degrees

Here's a plot of the low level temperatures from Friday morning and Sunday morning. The airmass overall has cooled a bit, but the wind has mixed down to the valley floor in many area. The miracle of mixing. Here are the 8am Temperatures from Friday and Sunday:
Fairbanks Airport -33F -4F
Keystone Ridge +2F -10F

The Way Inversions Die

Here's a plot of temperatures and winds from Fort Yukon Saturday. Fort Yukon is an AWOS and reports a full observation every 20 minutes. When the winds broke through the inversion, the temperatures rose 29 degrees inside of 20 minutes.

Mid-Day Image

Nice infrared image from 1pm Thursday from the NOAA-19 Polar Orbiter showing lots of clouds on the North Slope and pushed up into north side of the Brooks Range (note the wavy looking clouds near the crest). Clear skies prevail again over the Interior and West Coast.

Inversion's Growing

Here's the 3pm sounding from Fairbanks. The inversion is growing. Temperatures above 2300' MSL have approached 0F today, and I expect overnight there will be 40 degrees or more between rural valley bottoms and higher elevations. High today at Fairbanks Airport has been -35F; Clearly Summit -3F. Here at Keystone Ridge the temperature has risen from -18F at 3pm to -10pm at 5pm, all without any evident breeze.

How Cold has January Been?

Through the first 16 days of January, the average temperature at the Fairbanks Airport was -25.8F, almost 18 degrees below normal. Temperatures over the next week look to continue to be cold, though nowhere near records for any given day. A reasonable guess would be that by January 24th the average temp for the month will be similar to the current value. What happens thereafter is yet unknown, but temperatures this month will almost certainly finish up being far below normal. So how unusual is this?

Well, in recent years, reasonably unusual. Since 1976, there have been five calender months with an average temperature lower than 20 below: January 2006 (-22.0F), February 1990 (-21.7F), January 1989 (-21.3F), December 1980 (-24.0F) and February 1979 (-25.3F)

So, while the current cold spell is unusual, it is in no sense "unprecedented", even in the context of post-pipeline era Fairbanks, when there is an undeniable urban effect on Fairbanks temperatures, at least in ice fog situations. If anything is unusual, it's the lack of extremely low temperatures, not just in Fairbanks (low so far a paltry -48F) but anywhere in the Interior. Even the 58 below at Chicken is not excessive by their standards. There has only been one or two daily record low temperatures set (at Galena); most places have not even been close. With a comparatively moderate airmass aloft, that situation does not look to change the before the weekend at the earliest.

Not Much Change

Here's the 9am AST Monday surface analysis from NWS Anchorage, showing a big high covering much of mainland Alaska. The coldest weather this afternoon is in the eastern Interior, where afternoon temperatures barely cracked 40 below. Sunday morning the cooperative station at Chicken reported the lowest official temperature thus far this event, 58 below.



The soundings from Fairbanks shows very little change in near surface temperatures between 3am and 3pm AST Monday. Temperatures at the higher elevation stations have approached 10 below today, while valleys have been stuck near 30 below.

Cold with Growing Inversion

Here's the lowest kilometer of the morning sounding at Fairbanks: the inversion is growing. Notice that right off the surface the inversion is not super sharp, showing the effects of the ice fog. The nearly constant temperature between 300 and 600 meters is interesting. There is not much wind in this layer, but above that, where temperature warm to almost 0F, there are west winds around 20 mph.


Overnight lows include:

Goldstream Creek: -51F
Woodsmoke PWS -49F (near North Pole)
Fairbanks Airport: -48F (both Saturday evening and since midnight, the lowest temperature since February 2008)
UAF West Ridge: -42F

Lows from cooperative observations reported Saturday evening included 54 below at North Pole and 48 below at Goldstream Valley Bottom.

Updates on the Cold

Here are a couple of updates from the past couple days. Temperatures are about as stable as can be with clear skies and light winds here on Keystone Ridge. The low of 33 below is the lowest temperature here since Jan 2, 2009 when the low was also -33F.

The afternoon sounding from Fairbanks shows the warming compared to Friday afternoon is underway above 450 meters AGL and will be progressing down in the next day (note that there may be an encoding error in the surface temperature on the 3pm Saturday sounding). This will result in an increasingly strong valley based inversion. The high this afternoon at the Fairbanks Airport was 39 below.

Coldest Morning of the Winter

Updated, as of 11am AST,

Overnight low temperatures:

Fairbanks area:
Goldstream Creek: -45F
Fairbanks Airport: -47F (For reference, the record low today in Fairbanks is 66 below set in 1934, the all-time record low).
Eielson AFB: -47F
Woodsmoke PWS: -48F (near North Pole)
UAF West Ridge: -39F
Keystone Ridge: -33F
Goldstream Toboggan: -32F
Moose Mountain PWS: -29F

Elsewhere in the Interior:
Nenana: -45F
Circle Hot Springs: -48F
Manley Hot Springs: -49F
McGrath: -51F
Arctic Village: -53F
Tanana: -53F
Bettles: -54F

Unofficial but reasonable:

Livengood RAWS: -55F
Coldfoot SNOTEL: -58F
Coldfoot PWS: -63F
Jim River PWS: -63F

Here's the big scale 3AM AST surface analysis from the Alaska Aviation Weather Unit showing the now big high over the Interior:


Here's the 537am AST NOAA-19 Polar Orbiter infrared image at 1.1km resolution:

Have a Cold One

The 4pm AST NOAA_15 infrared image shows skies clear or clearing over most of Interior Alaska as big high pressure…surface and aloft…builds, current about 1046mb centered near Galena.


The airmass is still cold. The afternoon high temperature at Bettles was 48 below, and temperatures throughout the Interior are now falling sharply in the valleys. Fairbanks Airport fell to 37 below at 4pm, an 11 degree drop since noon. In the Fairbanks area hills temperatures have continued to creep down during the day, with 4pm temperatures of 29 below on Cleary Summit. Here on Keystone Ridge, the 4pm temperature of 32 below is the lowest temperature in more than three years. The afternoon sounding from Fairbanks shows very little temperature change in the lowest 1000 meters of the atmosphere:



That will change over the weekend as the airmass starts to warm from above. But for now, we've got a cold one.

The Slow Decline

Here's a plot of hourly temperatures at Keystone Ridge since Wednesday. A slow and steady decline: the temperature has held steady or fallen every hour since 4pm Wednesday.

Briter in Barrow

First sunrise is still about tens days away in Barrow, but it's getting brighter. Here's a FAA webcam image from near solar noon on Thursday.

Fairbanks above Zero

The temperature at the Fairbanks Airport at 11am AST Tuesday was +5F. This is the first time temperature has been above zero at the airport since 9pm AST December 23. Through 3pm AST it's been up to +15F.

If you're keeping score at home, that's 17 days and 14 hours continuously below zero. That's the longest such streak since Jan 13-Feb 4, 2006.

Here's the 330pm NOAA-15 GOES image showing the storm responsible for the break in the cold weather.

Warming Up

Warming up aloft at least, with a pretty good inversion developing up Monday evening. The 8pm AST GOES-15 infrared image shows the leading edge of the cirrus associated with the complex low in the North Pacific approaching Fairbanks, though the deep cloud layer is only to the Kenai peninsula.

At 8pm AST Monday,

Fairbanks Aiport -35F
Goldstream Creek: -35F

Clearly Summit: -6F
Keystone Ridge -10F

Another 40 below Day at Fairbanks

Blazing noon-time sunshine in downtown Fairbanks (webcam image courtesy of the News-Miner). The temperature at the airport snuck down to 41 below around 2am this morning. This makes this the 6th day with a low of 40 below or lower this month, and the 7th thus far this winter.

Just Like Winter

Here's a plot of temperatures and wind speeds today from the Eagle Summit Snotel, at 3700' MSL on the Steese Highway. At 11pm, 31 below with 30 mph hourly average wind speed. That's just like winter. Only colder.

Update:

The wind chill at Eagle Summit bottomed out at -69F at midnight: -32F with sustained 29 mph winds.

Temperature Update

Forget all this complex analysis stuff, here's a simple plot daily temperatures here Fairbanks thus far this winter.

The gray line is the 1981-2010 normal and the gray band around that is one standard deviation, so temperatures within that band would be "typical" for the season.

Tok Snowfall

There are two cooperative stations right in Tok.

One has reported about 27 inches of snow thus far this season, with 23 inches on the ground on January 6th. The other has reported 46 inches for season with 20 inches on the ground.

At Tok, an area that does not get too much wind, a 23 inch snow depth with 27 inches for the season by early January is not physically realistic.

A total of 46 inches is much more realistic for a 20 inch snow depth. Snowfall is indeed significantly above normal thus far this season in Tok.

Updated:

Here's a plot of the Feb 01 (more or less) snow depth at Tok since 1960 at the NRCS snow course.

Alaska Grab Bag

Some miscellaneous tidbits from around Alaska in this active winter weather:

It's another cold one Saturday morning in the western Interior. Lows through 10am include 54 below in Huslia and Tanana and 53 below at Galena and Kaltag. Here's an icy foggy webcam shot (courtesy of the FAA) from Ambler late Saturday morning, where it was 40 below at the airport, up on the ridge above town.

On Thursday, Nome dipped to 40 below for the first time since 1999, and Friday was the 10th straight day with a low of 30 below or lower. This is now the most severe cold snap in the Gold Rush City since January 1989, the big kahuna of western Alaska cold snaps.

Valdez received 38.5 inches of snow Thursday and Friday, with 272.1 inches of snow for the season and a snow depth of 76 inches. The record winter snowfall in Valdez is 560.7 inches in 1989-90.

The Beat Goes on, Still

Here's an updated plot of the standardized temperature departures thus far this winter. The correlation between the valley (Fairbanks Airport) and hills (Keystone Ridge) is 0.85, good but nowhere near perfect given that the two sites are only 14 miles apart.

After the 1-2 inches of snow Friday, skies cleared quickly around sunset and valley temperatures dipped to around 40 below late Friday evening, with overnight lows of 42 below at the airport and 41 below at Goldstream Creek. Here on the hill the temperature hit 27 below about 9pm.

Like a Yoyo

Wild temperature swings in Fairbanks-land. Still, Friday is the 10th day in a row here at Keystone Ridge with a low temperature of 20 below or longer, the longest such streak since the great 1999 cold snap (which was far colder than this).

That’s a Lot of Warming

Here’s a plot of the soundings from Fairbanks for 3pm Wednesday and 3am and 3pm Thursday. That is a lot of warming, though there is not any front involved in any usual mid-latitude sense.

Temperatures be a'changing

Temperatures since noon yesterday at Keystone Ridge (1600' MSL) and the Fairbanks Airport.

Deep Cold Air

This morning's upper air sounding is a fairly typical one for a deep cold airmass in Interior Alaska. There is a shallow layer near the surface with temperatures nearly constant, a transition layer where the temperature increases fairly smartly with height, and then the "warmest" air is above that. On this morning's sounding, between 3000 and 10000 feet above the ground, the temperature only varies by a few degrees, and the warmest temperature (+1F) was at nearly 7000' AGL.

This illustrates nicely that super strong inversions are NOT a feature of deep cold; the strongest inversions occur when skies are clear and it is warming aloft.

Low temperatures in the valley this morning were a couple hours either side of midnight, with the Airport bottoming out at 39 below. Clouds have since come in broken the small inversion that formed late last evening. At hill elevations that are still in the coldest layer, temperatures have been close to 30 below since yesterday. The very highest weather stations in Fairbanks-land, those above 2300' MSL, are the only sites reporting temperatures warmer than 10 below this morning. At the Caribou Peak RAWS, at 2500' MSL north of Poker Flats, temperatures in the past 24 hours have held between zero and 9 below.

Normalcy Departs

Steep inversions are the rule this time of year in Interior Alaska, but this is not one of those times. The afternoon sounding reveals a more than 20C inversion, but it's quite gradual by Interior standards. Temperatures at typical residential hillside elevations are back down to around -30F this evening; it's only above about 2000' MSL that temperatures are near -10F.

One interesting feature of this sounding is in the lowest 100 meters, where the temperature is constant (jargon=isothermal). This is typical in ice fog.

Normalcy Returns

All is right with the world, or at least as it concerns Interior Alaska inversions. With clear skies, temperatures in the valleys have been falling for more than 12 hours now, while temperatures have been slowly rising at elevation. The inversion is not yet especially steep, so elevations where appreciable numbers of people live are still chilly, but mostly warmer than it was Monday afternoon:

Low elevation min temperatures through 9am include:

Fairbanks Airport: -44F
Fort Wainwright: -44F
Eielson AFB: -42F
Goldstream Creek: -42F
UAF West Ridge: -38F

High elevation temperatures around 9am:
Munson Ridge: -7F
Clearly Summit: -8F
Keystone Ridge: -15F
Goldstream Toboggan: -27F

Still Cold

Here's an updated plot of the soundings from Monday: free air temperatures are a little bit warmer at low levels and a little cooler above 400 meters AGL.



Temperatures here one Keystone Ridge have been between 27 and 31 below all day: the low of -31F occurred most recently at 257pm, one minute before sunset.

How Much Solar Heating is there in Interior Alaska

Solar heating, or lack thereof, is a major driver in Interior Alaska. But why is it anymore (or less) important than anywhere else? Reader Trung has commented repeatedly about this. So, rather that spout some hand-wavy blather, let's deploy some actual physical modeling.



Here are some results using the Bird Clear Sky Model that produces quantitative estimates of solar radiation at the erath's surface using a variety of estimates of relevant variables (but with, not surprisingly, CLEAR skies). For this example I've left everything constant (e.g. albedo, water vapor). Using the spreadsheet from the National Renewable Energy Laboratory, I've summed the hourly values of global horizontal radiation, and then plotted the daily sums. The plots shows the huge annual variation at 65 (latitude of Fairbanks), from more than 8200 W/m² at summer Solstice to 12 W/m² at Winter Solstice (because these are the sums of the hourly values, these do not represent the total daily global horizontal radiation, but are computationally easier).

If we do exactly the same calculations, leaving all the variables the same except for latitude, at 40N we get 8700 W/m² at Summer Solstice to 2500 W/m² at Winter Solstice. So in the Summer Solstice, Fairbanks gets 94% of the solar heating as received at 40N, but at Winter Solstice Fairbanks 0.5% of what is received that day at 40N.

Put another way, at 40N, Winter Solstice receives about 29% of the heating received at Summer Solstice. In Fairbanks, Winter Solstice receives about 0.1% of the heating received at Summer Solstice.

So, I go on about solar heating (or lack thereof) because it varies so darn much over the year, far more than at mid-latitudes.

Cold Snow

About half an inch of snow and 28 below at 8am on Keystone Ridge. Here's how it snows at these cold temperatures. The morning sounding shows the deep cold air (-30C and colder) is about 400 meters thick. The snow producing clouds have a temperature around -20C to -23C. This is reflected in the sand-like consistency of the snow this morning.

Denali Sunrise

Sunrise late Sunday morning from Lake Minchumina, with Denali to the left (east) of the sun; image from the FAA webcam.

December 2011 and Annual Summary

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1220 PM AKST SUN JAN 1 2012

...DECEMBER WEATHER SUMMARY FOR FAIRBANKS ALASKA...
...2011 WEATHER IN REVIEW...

THE FIRST THREE WEEKS OF DECEMBER WERE AMONG THE WARMEST EVER
RECORDED IN FAIRBANKS. THERE WERE EIGHT DAYS WHEN THE DAILY AVERAGE
TEMPERATURE WAS 20 OR MORE DEGREES ABOVE NORMAL. HOWEVER...THE
WEATHER TURNED SHARPLY COLDER RIGHT BEFORE CHRISTMAS AND THIS
CONTINUED THROUGH NEW YEARS EVE. THE LAST TWO DAYS OF THE MONTH
WERE MORE THAN 20 DEGREES COLDER THAN NORMAL.

OVERALL...THE AVERAGE HIGH TEMPERATURE AT THE AIRPORT WAS 14 ABOVE
AND THE AVERAGE LOW TEMPERATURE WAS 6 BELOW. THE MONTHLY AVERAGE
TEMPERATURE OF 4.0 ABOVE WAS MORE THAN 8 DEGREES WARMER THAN NORMAL
AND TIES WITH 1963 AS THE 10TH WARMEST DECEMBER IN 107 YEARS OF
OBSERVATIONS. IN THE PAST 20 YEARS ONLY DECEMBER 2002 WAS WARMER.
THE HIGHEST TEMPERATURE AT THE AIRPORT WAS 47 DEGREES ON THE 4TH.
THIS IS THE WARMEST TEMPERATURE EVER RECORDED IN FAIRBANKS DURING
DECEMBER EXCEPT FOR FIVE STRAIGHT DAYS IN DECEMBER 1934 WHEN HIGH
TEMPERATURES WERE IN THE 50S. THE LOW OF 36 BELOW OCCURRED ON THE
LAST TWO DAYS OF THE MONTH.

PRECIPITATION WAS WELL ABOVE NORMAL IN DECEMBER. A TOTAL OF 0.95
INCHES WAS MEASURED AT THE AIRPORT...WHICH IS ABOUT A THIRD OF AN
INCH ABOVE NORMAL...AND MAKES THIS THE WETTEST DECEMBER SINCE
1992. SNOWFALL TOTALED 12.2 INCHES...WHICH IS ALMOST EXACTLY
NORMAL. SNOW DEPTHS AT THE AIRPORT INCREASED FROM 7 INCHES ON THE
FIRST TO 14 INCHES ON THE 31ST. SNOWFALL WAS SUBSTANTIALLY HIGHER
TO THE NORTHWEST OF TOWN. THE GOLDSTREAM VALLEY BOTTOM COOPERATIVE
STATION MEASURED 16.9 INCHES OF SNOW...AND THE KEYSTONE RIDGE
STATION...NEAR MURPHY DOME...REPORTED 26.4 INCHES FOR THE MONTH.

DURING THE FIRST THREE WEEKS OF DECEMBER...IT WAS MUCH BREEZIER THAN
IS NORMAL IN FAIRBANKS IN MID-WINTER...TOPPED OFF BY STRONG WINDS
ON THE 4TH AND 5TH WHICH PEAKED AT 51 MPH...THE HIGHEST WIND GUST
OF RECORD IN DECEMBER IN FAIRBANKS. DURING THE COLD WEATHER LATE
IN THE MONTH...WINDS WERE NEARLY CALM.

LOOKING AHEAD TO JANUARY...THIS IS TYPICALLY THE COLDEST MONTH OF
THE YEAR IN FAIRBANKS. THE AVERAGE HIGH TEMPERATURE IS 1 ABOVE AND
THE AVERAGE LOW IS 17 BELOW. OVER THE PAST 108 YEARS...JANUARY
TEMPERATURES HAVE RANGED FROM A HIGH OF 52 ABOVE IN 2009 TO A LOW
OF 66 BELOW IN 1934. POSSIBLE SUNSHINE INCREASES FROM 4 HOURS ON
THE FIRST TO JUST UNDER 7 HOURS ON THE 31ST.

THE CLIMATE PREDICTION CENTER FORECAST FOR JANUARY IS FOR AN
INCREASED CHANCE FOR SIGNIFICANTLY BELOW NORMAL TEMPERATURES IN
FAIRBANKS.

OBSERVED LAST MONTH...12/2011

OBSERVED RANK
AVG MAX TEMP (F) 14.4 7TH WARMEST OF 107 YEARS
AVG MIN TEMP (F) -6.4 14TH WARMEST OF 108 YEARS
AVG TEMP (F) 4.0 10TH WARMEST OF 107 YEARS
TOTAL PRECIP (IN) 0.95 19TH WETTEST OF 97 YEARS


...WEATHER SUMMARY FOR 2011...

2011 WAS A MEMORABLE YEAR WEATHER-WISE IN FAIRBANKS. LATE FEBRUARY
BROUGHT TWO MAJOR STORMS THAT WERE...MOST UNUSUALLY...ACCOMPANIED
BY STRONG WINDS AND EVEN SOME BLOWING SNOW. THE STORM ON FEBRUARY
20 AND 21ST BROUGHT A WHOPPING 17.1 INCHES OF SNOW IN 24 HOURS...
THE SECOND HIGHEST 24 HOUR SNOWFALL EVER MEASURED IN FAIRBANKS.
THE SPRING WAS EXTREMELY DRY...AND SOME OF THE WARMEST WEATHER
EVER RECORDED IN MAY OCCURRED LATE THAT MONTH. THE WARM AND DRY
CONDITIONS CONTRIBUTED TO THE MOOSE MOUNTAIN AND HASTING FIRES
THAT STARTED IN LATE MAY. THE REST OF THE SUMMER BROUGHT A
GENERALLY QUIET FIRE SEASON. THE AUTUMN WAS PERSISTENTLY MILD
UNTIL MID- NOVEMBER...WHEN THE COLDEST SUSTAINED WEATHER OF RECORD
BEFORE THANKSGIVING GRIPPED THE AREA...ONLY TO BE FOLLOWED BY THE
EXTREME WARMTH OF THE FIRST THREE WEEKS OF DECEMBER. OVERALL...THE
AVERAGE TEMPERATURE FOR THE YEAR OF 27.9 DEGREES WAS ALMOST
EXACTLY NORMAL. THE HIGH FOR THE YEAR WAS 88 DEGREES ON JUNE 25TH.
THE LOW WAS 44 BELOW ON FEBRUARY 15TH. THE TOTAL PRECIPITATION OF
9.54 INCHES WAS ABOUT 12 PERCENT BELOW NORMAL.

$$
RT/JM JAN 12

First 40 below of the Cold Snap

Through 11am AST the low temperature at the Fairbanks airport has been 43 below. This is the first 40 below of this cold snap at the Airport. Eielson AFB has been down to 45 below.

Updated:

53 below at McGrath, Galena, Huslia, Nikolai, Kaltag, Tanana and Manley Hot Springs

No Solar Heating

Here's the plot of low level temperatures over the past week from a weather station located off the trail behind the IARC Building on UAF West Ridge (there are temperatures from four different heights above the ground). The vertical grid lines are at midnight. This clearly illustrates the lack of solar heating; changes in temperature are being driven entirely by variations in cloud cover.

Sunshine at Fort Yukon

News Years Eve noontime sunshine and 26 below at Fort Yukon. Photo courtesy of the FAA.

Low Temperatures Saturday Morning

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
949 AM AKST SAT DEC 31 2011

COLD MORNING IN INTERIOR ALASKA...

A COLD AIRMASS COVERS INTERIOR ALASKA THIS MORNING. THE LOWEST
TEMPERATURES THUS FAR HAVE BEEN IN THE WESTERN INTERIOR...WHERE
SKIES HAVE BEEN GENERALLY CLEAR FOR A DAY OR MORE. IN THE CENTRAL
AND EASTERN INTERIOR...CLOUD COVER IS MORE WIDESPREAD...AND THIS
IS HELPING TO KEEP VALLEY TEMPERATURES FROM FALLING ESPECIALLY
LOW. HOWEVER...TEMPERATURES IN THE HILLS ARE QUITE COLD.

OVERNIGHT LOW TEMPERATURES THROUGH 9AM SATURDAY INCLUDE...

HUSLIA...............54 BELOW
RUBY 14 NE...........51 BELOW
BETTLES..............49 BELOW
KALTAG...............48 BELOW
GALENA...............47 BELOW
MCGRATH..............46 BELOW
RUSSIAN MISSION......45 BELOW

IN THE FAIRBANKS AREA....

FAIRBANKS AIRPORT....36 BELOW
GOLDSTREAM CREEK.....36 BELOW
UAF WEST RIDGE.......32 BELOW
EIELSON AFB..........32 BELOW
KEYSTONE RIDGE.......29 BELOW
CLEARY SUMMIT........23 BELOW

$$
RT DEC 11

Still Cold

The Environment Canada 500mb analysis valid 3am Saturday Dec 31 2011 shows the cold closed low just west of Nome, with a weaker center near McGrath. East of 150W there are more clouds than clear. so in spite of a cold airmass, valley temperatures are not excessively cold. To the west, more clear than clouds, and it is consequently colder. 8AM Saturday temperatures include 53 below at Huslia, 48 below at Kaltag and 36 below at Fairbanks Airport.

It's a Cold One

A cold airmass covers mainland Alaska today, with temperatures mostly 20 below or lower. Through noon Friday the lowest temperatures have been 51 below at both Tanana and Huslia. In Fairbanks-land, the Airport has been to 36 below and Eielson 39 below, but even in the hills most places haven well into the 20s below, including 25 below at Keystone Ridge and 23 below at the Parks Highway RWIS at the FNSB border. Cloud cover will periodically moderate temperatures somewhat east of 150W the next few days but only a slight, short lived warming of the airmass is now expected New Years Day.

50 Years Ago Today

It was 50 year ago today, Sergeant Pepper taught the band to play...

Opps, wrong event.

It was 50 year ago today though that one of the greatest Interior Alaska cold snaps of record was ending. At the left is the front page of the News-Miner.

The temperature was 40 below or lower at the Fairbanks Airport from 11am AST Dec 20th until 4am Dec 30th, 232 consecutive hours, and -55F or lower from 10pm AST Dec 27th until 1am Dec 30th, 50 consecutive hours.

Low temperatures for the event included:

Fairbanks Airport: -62F , all-time record for December
College Observatory -66F, all time record
Eielson AFB: -61F all-time record for December
Nenana: -69F

Arctic Air

The afternoon sounding from Fairbanks shows reasonably deep cold air, with the entire sounding colder than minus 20C. I've plotted this one up to 2000 meters, as it shows that the warmest temperature in the RAOB is up near 1800 meters. This highly elevated warmest tropospheric temperature is a good marker of true "arctic air"

Cold at Last

The airmass has finally cooled in earnest in Fairbanks-land, and the effects are showing as skies clear (technical: 12Z 850mb temp -26.7C, 1000-500mb thickness 499dm). Here is the NOAA-19 Polar Orbiter infrared image from just after 5am AST Thursday, as skies were starting to clear just west of Fairbanks.



In the middle Yukon River valley, where it has been cleared for more than a day, valley temperatures were down near 40 below.

By 10am, temperatures in the Fairbanks area were down to 28 below at the Fairbanks Airport, 26 below at Goldstream Creek, 23 below at Keystone Ridge and 19 below on Cleary Summit. The North Pole and Eielson took longer to clear but will soon catch up.

Inversion

Interesting inversion on the Monday afternoon sounding from Fairbanks, with four distinct layers evident in the lowest 1000 meters. The inversion right off the surface is not particularly steep (by Fairbanks standard), followed by a nearly isothermal layer between 200 and 400 meters AGL and a shallower isothermal layer between 400 and 550 meters AGL and finally a warming layer above that. Some of this stratification is wind driven, with winds here at Keystone Ridge gradually increasing during the day.

A Clear Boxing Day

Skies cleared in the Fairbanks early Monday morning, allowing for strong valley cooling. Here is the NOAA-19 polar orbiter infrared image taken about 4am AST Monday, courtesy of the NWS Alaska Region, showing the clear skies and cold valleys in the middle Tanana valley. Temperatures cooled 20+ degrees in the valleys, while in the hills temperatures fell only a few degrees. At 10am Monday, Fairbanks area temperatures vary from the mid 20s below in the cooler valley spots to 0 to 5 above at higher elevations. Here on Keystone Ridge (1600' MSL), the top of the inversion is close by, with temperatures mid-morning swinging between -4F and +3F in a matter of minutes.

My post from last Wednesday, Winter to Return, demonstrates the difficulties the numerical models have been having recently. On Wednesday both the GFS and the ECMWF, two major mid-range models were both forecasting deep cold by Monday (today). As it turned out, the observed 1000-500 mb thickness this morning at Fairbanks was 5038 gpm, an error of nearly 120 meters. That is a very large error and the result is temperatures zero to 20 below instead of 20 to 40 below.

It's a White Christmas

To no one's surprise, it's another white Christmas in Fairbanks: snow depth at 3am Sunday was 12 inches (photo of Pioneer Park in winter from Bootsnall.com)

But there was once a Christmas that was not white. The autumn of 1934 was unusually dry and mild, and the few inch snow cover was sublimated/melted away in the super chinook of early December, when the temperature reached 50+ five straight days. After the chinook ended it remained dry. There was just over an inch of snow December 9-12th, but by the 15th there was only a trace of snow on the ground. There then was no precipitation at all until the day after Christmas. Ironically, the late winter of 1934-35 turned out to bring much above normal snowfall, and April 1935 was quite cool. As a result, the winter snowpack, after being reestablished on December 26th, did not melt out until May 8th, one of the latest dates for the spring snow melt of record.

Although snow depth data is sketchy prior to 1929, what data there is strongly suggests that this is the only "brown" Christmas since the founding of Fairbanks in 1901.

Temperature Pops

Here's the WeatherUnderground Plot of temperature (and dew point) at the Two Rivers PWS near 24 Mile Chena Hot Springs Road. The temperature jump between 8 and 9pm is the result of an east wind picking up. Only a few mph, but enough to break the inversion. This is common in the middle Chena River valley.

The Return of Normal

Skies cleared Friday evening, and with the cooler airmass in place temperatures have returned to something like normal.

Low temperatures Saturday morning through 9AM AST include:

Eielson AFB: -29F
Woodsmoke PWS: -28F (near North Poke)
Fairbanks Airport: -25F
Goldstream Creek: -22F
Chena Hot Springs PWS: -21F
UAF West Ridge: -16F
Two Rivers PWS: -15F

Keystone Ridge: -9F
Goldstream Toboggan PWS -9F (east of Ballaine Road intersection)
Cleary Summit -6F

As an added bonus, there was a lovely aurora shining in the sky around midnight.

Hot December so Far

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
124 AM AKST THU DEC 22 2011

THE AVERAGE TEMPERATURE AT THE FAIRBANKS INTERNATIONAL AIRPORT
FOR THE FIRST THREE WEEKS OF DECEMBER WAS 13.5 DEGREES...A STUNNING
16.8 DEGREES ABOVE NORMAL. THIS IS THE SECOND WARMEST FIRST THREE
WEEKS OF DECEMBER IN MORE THAN A CENTURY OF WEATHER OBSERVATIONS
IN FAIRBANKS. THE ONLY WARMER START TO DECEMBER WAS IN 1986...WHEN
THE AVERAGE TEMPERATURE THROUGH THE 21ST WAS 13.8 DEGREES.

$$
RT DEC 11

Winter to Return

The warm pattern that has been in place since November 30th is coming to an end, to replaced by chilly, though not super cold temperatures. Here is the forecast for 3am Monday December 26th from the GFS. The dashed lines are 1000-500mb thickness, a measurable of the mean air temperature in the lowest half of the atmosphere. The 492 thickness contour right near Fairbanks (=4920 geopotential meters) is pretty cold and will easily support valley temps in the -40s and -50s IF and WHERE skies are clear. Regardless, this should be good for teens and 20s below at elevation.

More on Normalized Departures

Here's a composite image of winter (Oct 1-Mar 31) Fairbanks daily mean normalized temperature departures from normal for winters 2008-09 through this winter. Three of the four are La Niña years.

2011 Temperatures, Reprise

Here's an updated plot of normalized daily temperature departures for 2011. The unrelenting mild weather of December is starting to rival that in May for persistence but not for (normalized) magnitude.