Brisk Wind Advisory 24, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
359 PM AKST SUN JAN 16 2011

.DISCUSSION...
THE NAM AND GFS COMPUTER WEATHER FORECAST MODELS HAVE SIMILAR
PROJECTIONS THROUGH TUESDAY AFTERNOON. THE HIGH PRESSURE AREA
ALOFT THAT PERSISTED FOR DAYS OVER ALASKA HAS MOVED WEST AND IS
OVER SIBERIA. THE NORTHEAST FLOW ALOFT NOW OVER NORTHERN ALASKA
HAS BROUGHT IN DRY AND COLDER AIR ALOFT. BOTH MODELS FORECAST
LOWERING TEMPERATURES ALOFT...AND A FAST MOVING SHORT WAVE ALOFT
MOVING SOUTHEASTWARD OUT OF THE CHUKCHI SEA DOWN TO THE
SOUTHEASTERN MAINLAND OF ALASKA MONDAY AFTERNOON THROUGH TUESDAY
NOON.

POLAR ORBITING WEATHER SATELLITE IMAGERY HAS SHOWN THE CLOUDS IN
ADVANCE OF THIS SHORT WAVE OVER THE EASTERN CHUKCHI SEA. AS THE
SHORT WAVE MOVES DOWN OVER NORTHERN ALASKA THERE WILL BE A 12 TO
24 HOUR PERIOD OF MOSTLY CLOUDY WEATHER...WITH SOME FLURRIES OVER
THE ARCTIC AND THE WEST. SKIES WILL THEN CLEAR AS THE SHORT WAVE
EXITS.

THE STRONG HIGH PRESSURE AREA OVER THE YUKON TERRITORY AND STRONG
LOW PRESSURE IN THE GULF OF ALASKA ARE FORECAST TO WEAKEN
SUBSTANTIALLY TONIGHT. ALTHOUGH THE WINDS AT BIG DELTA WERE
GUSTING TO ALMOST 40 MILES AN HOUR AT 3 PM SUNDAY...THE WEAKENING
OF THE GRADIENT BETWEEN THE HIGH AND LOW IS EXPECTED TO RESULT IN
A RAPID DECREASE OF THE WINDS IN THE SOUTHEASTERN INTERIOR BY 6
PM.

TODAYS POLAR ORBITING SATELLITE IMAGERY HAS ALSO SHOWN TWO DECKS
OF STRATOCUMULUS CLOUDS THAT HAVE MOVED FROM THE YUKON TERRITORY
INTO THE EASTERN INTERIOR. THE FIRST CAME FROM THE SOUTHERN YUKON
TERRITORY OVER TO THE FORTYMILE COUNTRY AND THE EASTERN ALASKA
RANGE. THE SECOND MOVED FROM THE UPPER PORCUPINE VALLEY TO THE
EASTERNMOST PORTION OF THE BROOKS RANGE. BOTH OF THESE AREAS OF
CLOUDS ARE EXPECTED TO CLEAR TONIGHT AS WINDS ALOFT SHIFT FROM
EASTERLY TO NORTHERLY.

THE ARCTIC COAST EAST OF CAPE HALKETT HAS HAD EXTENSIVE FOG...JUST
ALONG THE COAST...ALL DAY. POLAR ORBITING SATELLITE IMAGERY HARDLY
SHOWS THIS...SO THE FOG BANK COVERS JUST THE IMMEDIATE COASTAL
ZONE. THE INBOUND SHORT WAVE FROM THE CHUKCHI SEA HAS BROUGHT
STRATOCUMULUS AND ALTOSTRATUS CLOUDS TO THE ARCTIC WEST OF CAPE
HALKETT. THIS AREA OF CLOUDS IS EXPECTED TO EXPAND EASTWARD AND
SOUTHWARD TONIGHT AND MONDAY.

THERE IS A VERY RAPIDLY STRENGTHENING STORM IN THE NORTH PACIFIC
WHILE WILL BE HEADED TOWARD THE ALEUTIANS MONDAY NIGHT AND
TUESDAY. EASTERLY WINDS OVER THE YUKON DELTA AND SAINT LAWRENCE
ISLAND ZONES WILL INCREASE TUESDAY AND TUESDAY NIGHT. THIS LOW
WILL REMAIN ON A PATH WELL TO THE SOUTH OF THE REALM. THE
INCREASING EAST WINDS WILL BE THE ONLY EFFECT THIS SYSTEM HAS IN
NORTHERN ALASKA.

THE OTHER AREA OF INCREASING COASTAL WINDS IS THE COASTAL MARINE
AREA FROM CAPE HALKETT TO THE CANADA BORDER. AS HIGH PRESSURE FROM
SIBERIA BUILDS IN BEHIND THE CHUKCHI SEA WEATHER FRONT ON
MONDAY...BRISK WESTERLY WINDS WILL DEVELOP OVER THIS AREA...AND
THEN WEAKEN BY TUESDAY EVENING.

WEATHER BALLOON DATA CONTINUES TO SHOW VERY STRONG TEMPERATURE
INVERSIONS OVER THE INTERIOR. THIS PATTERN OF COLD TEMPERATURES ON
VALLEY FLOORS AND CONSIDERABLY WARMER TEMPERATURES IN THE HILLS
AND AT LOWER ELEVATIONS WHERE THERE IS SOME WIND IS EVIDENT FROM
SURFACE WEATHER OBSERVATIONS. FOR EXAMPLE...AT 3 PM...

TANANA...EAST WIND 11 MPH...TEMPERATURE 5 BELOW ZERO
FAIRBANKS...WINDS CALM MOST OF THE DAY...TEMPERATURE 26 BELOW

THE MEDIUM RANGE COMPUTER WEATHER FORECAST MODELS HAVE SIMILAR
PROJECTIONS THROUGH WEDNESDAY NIGHT. ON THURSDAY THE GFS MODEL
MOVES AN EXPECTED STRONG SHORT WAVE ALOFT TO MOVE MORE SLOWLY
THAN THE EUROPEAN MODEL DOES. FOR THIS THURSDAY...THE GFS
FORECASTS AN STRONG SHORT WAVE ALOFT TO TRANSIT THE CHUKCHI SEA
AND TO REACH THE NORTHWEST ALASKA COAST. THE EUROPEAN MODEL
FORECASTS THE SHORT WAVE TO MOVE MORE RAPIDLY...REACHING THE
CENTRAL INTERIOR ON THURSDAY. BOTH MODELS FORECAST STRONG WESTERLY
FLOW ALOFT OVER THE ARCTIC THROUGH FRIDAY. AND BOTH MODELS
FORECAST RETURN FLOW FROM THE GULF OF ALASKA TO BEGIN NO EARLIER
THAN FRIDAY...AND TO BE LIMITED TO THE SOUTHEASTERN INTERIOR.

NONE OF THE MODEL OUTPUT POINTS TO SEVERE COLD...BUT SOME 50 BELOW
WEATHER IS A GOOD BET IN THE NORTHERN INTERIOR AT MID WEEK...AND
PERHAPS BEYOND. A SIGNIFICANT SHIFT TO WARMER THAN NORMAL
TEMPERATURES WILL PROBABLY NOT OCCUR UNTIL THE LAST 4 DAYS OF THE
MONTH.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

BRISK WIND ADVISORY FOR PKZ240-PKZ245.
&&

TF JAN 11