Small Craft Advisory 171, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
557 AM AKST SUN NOV 4 2012

.DISCUSSION...

UPPER AIR...TROUGH EXTENDING SOUTH FROM THE HIGH ARCTIC TO PRUDHOE
BAY TO MCGRATH WILL MOVE SLOWLY EAST OVER THE NEXT FEW DAYS. BY
TUE AFTERNOON THE TROUGH WILL BE EAST OF BANKS ISLAND WITH A
SOUTHWEST EXTENSION TO THE EASTERN ALASKA RANGE. A RIDGE OF HIGH
PRESSURE OVER EASTERN SIBERIA WILL MOVE EAST AND BY TUE AFTERNOON
THE AXIS OF THE RIDGE WILL EXTEND FROM SOUTHWEST MAINLAND ALASKA
TO MACKENZIE BAY.

SURFACE...1006 MB LOW 600 NM NORTH OF BARROW WILL MOVE EAST. IT
WILL BE 1010 MB 500 NM NORTHEAST OF PRUDHOE BAY BY MON MORNING.
AN ASSOCIATED WEATHER FRONT WILL MOVE SLOWLY EAST ACROSS THE
ARCTIC COAST TO THE BEAUFORT SEA SUN AND SUN NIGHT. 1030 MB HIGH
PRESSURE OVER EASTERN SIBERIA WILL EXPAND INTO THE CENTRAL TO
EASTERN BERING SEA SUN AND SUN NIGHT. LOW PRESSURE WILL DEVELOP
NORTH OF WRANGEL ISLAND MON THEN MOVE EAST ACROSS THE ARCTIC OCEAN
THROUGH WED.

NORTH SLOPE...ALL MARINE AREAS OF THE ARCTIC COASTAL WATERS ARE
UNDER HEAVY FREEZING SPRAY WARNINGS...EXCEPT FOR ZONES 240 AND
505...WHICH HAVE NO SEAS FORECAST DUE TO A LARGE PERCENTAGE OF ICE
PACK. A WEATHER FRONT MOVING EAST ACROSS THE NORTH SLOPE TODAY AND
TONIGHT WILL PRODUCE FLURRIES. WINDS WILL BE LIGHT TO MODERATE
THROUGH MON. BY MON NIGHT...LOW PRESSURE NORTH OF WRANGEL ISLAND
WILL BEGIN EFFECTING THE NORTH SLOPE. AS THE LOW MOVES EAST MON
NIGHT...WEST WINDS WILL BECOME BRISK...THE CONTINUE THROUGH WED.
SNOW WITH THE SYSTEM WILL BE RATHER LIGHT WITH ANY ACCUMULATIONS
LESS THAN ONE INCH.

WEST COAST...NORTH WINDS...WHICH HAVE BEEN LOCALLY MODERATE TO
NOT QUITE STRONG DURING THE PAST COUPLE OF DAYS...WILL CONTINUE TO
DIMINISH TODAY AND TONIGHT AS PRESSURE GRADIENT BETWEEN SIBERIAN
HIGH AND GULF OF ALASKA LOW WEAKENS. WINDS WILL CONTINUE RATHER
LIGHT...WITH NO PRECIPITATION THROUGH WED. HEAVY FREEZING SPRAY
WARNINGS WILL CONTINUE OVER MARINE ZONES...EXCEPT FOR ICE PACKED
KOTZEBUE SOUND...TODAY AND TONIGHT. WINDS MAY INCREASE AGAIN WED
NIGHT AND THU...BUT WILL LIKELY BE OUT OF THE SOUTHEAST.

INTERIOR...THE AREA OF THE EASTERN INTERIOR...TO THE EAST OF A
SLOW MOVING UPPER LEVEL TROUGH...WILL HAVE SNOW SHOWERS OR
FLURRIES TODAY THROUGH TUE MORNING. THE MOISTURE SOURCE FOR THE
SNOW WILL BE FROM A PERSISTENT GULF OF ALASKA LOW. SNOW
ACCUMULATIONS PER 6 HOUR PERIOD...TODAY THROUGH TUE...WILL BE
LIGHT. HOWEVER...THESE LIGHT ACCUMULATIONS MAY ADD UP TO MORE
SUBSTANTIAL 3 DAY ACCUMULATIONS OF AN INCH OR TWO...ESPECIALLY IN
THE 40 MILE COUNTRY AND NEAR THE CANADA BORDER. A HIGH PRESSURE
RIDGE BUILDING EAST INTO INTERIOR ALASKA WILL SLOWLY CUT OFF THE
MOISTURE SOURCE AND EVENTUALLY PUSH THE TROUGH EAST OF THE CANADA
BORDER BY TUE NIGHT.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...STRONG SOUTHEAST WINDS MAY
DEVELOP WED NIGHT OVER THE SAINT LAWRENCE ISLAND WATERS...THEN
EXPAND NORTH TO EAST OVER THE REST OF THE MARINE AND LAND AREAS OF
THE WEST COAST THU THROUGH FRI. COMPUTER WEATHER MODELS SHOW THE
USUAL DISAGREEMENT IN DETAILS FOR THAT FAR OUT IN TIME...HOWEVER
MODELS DO AGREE WITH THE BIG PICTURE...THAT IS AN INCREASE OF
WINDS AND THUS SEAS BUILDING.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
HEAVY FREEZING SPRAY WARNING FOR PKZ200-PKZ210-PKZ220-PKZ225-
PKZ230-PKZ240-PKZ245.
&&

DA NOV 12