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.

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.