Extreme Cold in Alaska, January 3, 2012

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
355 PM AKST MON JAN 2 2012

.DISCUSSION...
THE GFS COMPUTER WEATHER FORECAST MODEL BASED ON DATA FROM 9 AM
TODAY DIFFERS FROM THE OTHER FORECAST MODELS AND FROM THE GFS
MODEL BASED ON DATA FROM 3 AM THIS MORNING. THE NEW GFS MODEL RUN
FORECASTS A STRONG SURFACE LOW TO MOVE NORTHWARD JUST OFFSHORE THE
SOUTHEAST ALASKA COAST ON WEDNESDAY. THE OTHER MODELS PREDICT A
MODERATELY STRONG LOW TO MOVE ON ROUGHLY THE SAME PATH. IT APPEARS
THAT THE LATEST GFS RUN IS AN OUTLIER...SO IT HAS NOT BEEN USED IN
THE FORECASTS TODAY.

THE FLOW PATTERN ALOFT IS FORECAST IN A SIMILAR WAY BY ALL OF THE
COMPUTER MODELS. LOW PRESSURE AND COLD AIR ALOFT ARE EXPECTED TO
REMAIN OVER THE WESTERN THIRD OF NORTHERN ALASKA FOR THE REST OF
THIS WEEK. A TROUGH OF LOW PRESSURE ALOFT MOVED NORTHWARD OVER THE
ALASKA RANGE LAST NIGHT. THE TROUGH IS NOW OVER NORTHERN INTERIOR.
THERE HAS BEEN WIDESPREAD LIGHT SNOW WITH THIS TROUGH. THIS TROUGH
ALOFT IS EXPECTED TO CONTINUE MOVING NORTH...AND TO BE OFFSHORE OF
THE EASTERN ARCTIC COAST OF ALASKA TUESDAY NIGHT.

SOUTHERLY FLOW ALOFT FROM THE GULF OF ALASKA...NORTHWARD TO THIS
TROUGH...IS EXPECTED TO WARM TEMPERATURES ALOFT. MOST OF THE
WARMING ALOFT WILL BE ABOVE 5 THOUSAND FEET OVER THE EASTERN
INTERIOR...SO TEMPERATURES NEAR THE SURFACE ARE NOT EXPECTED TO
WARM AS MUCH AS ALOFT. THE ORIGIN OF THE INCOMING FLOW ALOFT IS
ONLY NEAR 50 DEGREES NORTH LATITUDE. BELOW 10 THOUSAND
FEET...LIGHT SOUTH WINDS ARE FORECAST THROUGH TUESDAY...FOLLOWED
BY EAST WINDS TUESDAY NIGHT AND WEDNESDAY. THESE ARE THE REASONS
THAT THE INFLOW OF WARMER AIR THIS WEEK IS NOT EXPECTED TO HAVE A
GREAT IMPACT IN NORTHERN ALASKA. ONLY 10 TO 15 DEGREES OF WARMING
IS EXPECTED BY MID WEEK THIS WEEK.

NEXT WEEK LOOKS DIFFERENT. STRENGTHENING SOUTH WINDS ALOFT WILL
LIKELY BRING IN EXTENSIVE RISING TEMPERATURES INTO THE TEENS
ABOVE IN THE EASTERN AND CENTRAL INTERIOR.

IN THE ARCTIC AND OVER THE WESTERN ZONES OF NORTHERN
ALASKA...GENERALLY ONSHORE FLOW IS EXPECTED TO BRING SCATTERED
SNOW SHOWERS TO THESE AREAS. SINCE THE SEA IS TOTALLY ICE COVERED
IN THESE REGIONS THERE WILL BE LITTLE MOISTURE AVAILABLE...AND
THEREFORE LITTLE SNOWFALL. IN THE INTERIOR...GENERALLY SOUTH WINDS
ALOFT WILL HOLD MOST OF THE INBOUND MOISTURE FROM THE GULF OF
ALASKA SOUTH OF THE CREST OF THE ALASKA RANGE.

OVERALL...THIS IS A SETTING FOR COLD WEATHER FOR THE REST OF THIS
WEEK...AND FOR LITTLE SNOWFALL FROM NOW INTO NEXT WEEK.

A TROUGH OF LOW PRESSURE EXTENDING FROM MACKENZIE BAY TO 50 NM
NORTH OF BARTER ISLAND TO CAPE HALKETT WILL REMAIN THROUGH TUE
AFTERNOON. THIS FEATURE IS OFTEN ASSOCIATED WITH BRISK WEST WINDS
OVER THE EASTERN ALASKA ARCTIC COAST. HENCE THE ADVISORIES FOR
WINDS AND WIND CHILLS OVER THAT AREA FOR TONIGHT.

EARLY AFTERNOON SATELLITE IMAGERY SHOWS LOW AND MIDDLE ALTITUDE
CLOUDS OVER THE ARCTIC...IN ADVANCE OF THE TROUGH ALOFT. THE CLOUD
COVER ELSEWHERE IN THE REALM IS AT LOWER ALTITUDES AND ONLY
LOOSELY ORGANIZED. AS IS OFTEN THE CASE IN COLD MIDWINTER WEATHER
HERE...THERE ARE AREAS OF ICE FOG NEAR THE SURFACE AND HAZE ALOFT.
THESE SHOULD DIMINISH A LITTLE THIS WEEK.

ONGOING COLD NORTH WINDS CONTINUE TO ABET SOUTHWARD EXPANSION AND
INCREASING THICKNESS OF THE ICE PACK IN THE BERING SEA.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY FOR AKZ204-AKZ207-AKZ213.

BRISK WIND ADVISORY FOR PKZ210-PKZ220-PKZ225-PKZ245.
&&

TF JAN 12