Small Craft Advisory 959, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
519 AM AKST TUE DEC 2 2014

.ANALYSIS AND UPPER LEVELS...

A LARGE AND EXPANSIVE SEASONABLY STRONG LOW PRESSURE COMPLEX
CONTINUES TO SPIN OVER THE BERING SEA...WITH A STRONG UPPER RIDGE
AXIS NOW PUSHED NORTH AND EAST TO A UNALAKLEET- GLENNALLEN-
YAKUTAT LINE. A VERY STRONG UPPER LEVEL DISTURBANCE WITH AN
ASSOCIATED FRONT IS SITUATED ALONG OR NEAR A BETHEL-SPARREVOHN-
SELDOVIA LINE EXTENDING EAST-SOUTHEAST INTO THE GULF OF ALASKA. TO
THE NORTH OF THIS FRONT VERY IMPRESSIVE DYNAMICS EXIST IN AN
ATMOSPHERE LOADED WITH MOISTURE (200 PERCENT OR HIGHER THAN
NORMAL) TO THE NORTH OF THE FRONT.

THE 12 UTC ANCHORAGE SOUNDING DEPICTS A VERY SHALLOW LAYER JUST
ABOVE THE SURFACE WITH DOWNSLOPE DRYING CONDITIONS. THIS IS BEING
COMPLETELY OVERWHELMED BY THE MOISTURE BEING WRUNG OUT WITH THE
IMPRESSIVE DYNAMICS OVER THE AREA. THE POTENTIAL FOR FREEZING RAIN
HAS SEEMINGLY FAILED TO MATERIALIZE TOWARD ANCHORAGE AND THE
MATANUSKA VALLEY FOR THE MOST PART GIVEN TEMPERATURES FAILING TO
GET AS WARM AS FORECASTED JUST ABOVE THE SURFACE...BUT AS OF 3 AM
THE THREAT IS NOT TOTALLY DIMINISHED.

&&

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT IN THE SHORT TERM IN PUSHING THE COLD
FRONT INLAND THIS MORNING AND NORTH THROUGH COOK INLET AND INTO
THE INTERIOR. THERE IS SOME DISAGREEMENT AFTERWARDS IN DEPICTION
OF ADDITIONAL DISTURBANCES THAT WILL MAY BRING ADDITIONAL CHANCE
FOR SNOW TO THE COOK INLET REGION THROUGH THURSDAY UNDER LESS
STABLE CONDITIONS.

OUT WEST...A GALE FORCE LOW OVER THE SOUTHERN BERING WILL DROP
SOUTH AND EAST WHILE WEAKENING INTO THE NORTH PACIFIC SOUTH OF
COLD BAY TONIGHT...THEN MOVE OFF TO THE EAST AWAY FROM OUR AREA OF
RESPONSIBILITY. THE OCCLUDED FRONT WILL REMAIN FAIRLY STRONG AS
WELL AS STATIONARY FROM THE SOUTHEAST BERING SEA NORTH INTO THE
Y-K DELTA REGION THROUGH AT LEAST WEDNESDAY NIGHT.

ADDITIONALLY...A KAMCHATKA LOW WILL MOVE EAST JUST TO THE SOUTH OF
THE ALEUTIAN CHAIN EARLY WEDNESDAY THROUGH THURSDAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

SNOW HAS PERSISTED OVER THE ANCHORAGE AREA THROUGH THE
NIGHT...WITH ACCUMULATIONS EXCEEDING THE FORECASTED AMOUNT. THE 12
UTC ANCHORAGE SOUNDING INDICATES A MUCH SHALLOWER WARM DOWNSLOPE
LAYER THAN WAS PREVIOUSLY EXPECTED. THIS WILL KEEP ANY PERIOD OF
FREEZING RAIN THAT COULD DEVELOP IN THE NEXT SEVERAL HOURS FAIRLY
MINIMAL. STRONG SOUTHWEST LOW-LEVEL FLOW PUSHES NORTH UP COOK
INLET LATER THIS MORNING AND WILL COMBINE WITH SOUTHERLY FLOW
ALOFT TO GENERATE WHAT IS EXPECTED TO BE AN INTENSE BAND OF
OVERRUNNING SNOW OVER ANCHORAGE AND THE MAT-SU VALLEYS BEGINNING
AS EARLY AS AROUND 9 AM THIS MORNING FOR SOUTH ANCHORAGE...WITH A
STARTING TIME APPROACHING 10 AM TO NOON TOWARD PALMER. WHILE
MODERATE TO HEAVY SNOW IS ANTICIPATED DURING THIS TIME...THE SNOW
SHOULD LAST JUST A FEW HOURS AS THIS SYSTEM...RESULTING IN LOWER
ACCUMULATIONS.

THE ATMOSPHERIC REGIME BEHIND THIS SYSTEM WILL BECOME MUCH LESS
STABLE OVER THE NEXT COUPLE OF DAYS. WHILE THERE IS NOT A LOT OF
CONFIDENCE IN THE TIMING AND PLACEMENT OF INDIVIDUAL DISTURBANCES
AS THEY TRACK NORTH AND ACROSS SOUTHCENTRAL...THE LACK OF
STABILITY WILL INHIBIT ANY DOWNSLOPE DRYING RESULTING IN MODERATE
CONFIDENCE THAT MOST LOCATIONS WILL SEE AT LEAST A FEW SNOW
SHOWERS THROUGH WEDNESDAY AND POSSIBLY EVEN THURSDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

CYCLONIC FLOW ALOFT WILL KEEP A SHOWERY REGIME OVER THE AREA
THROUGH WED NIGHT. THE FRONT ASSOCIATED WITH THE BERING/ALEUTIAN LOW
WILL BRING COOLING TEMPERATURES. RAIN AND SNOW SHOWERS TODAY AND
TONIGHT WILL BE FOLLOWED ON WED AND WED NIGHT WITH SNOW SHOWERS
THAT WILL GRADUALLY BECOME LESS WIDESPREAD.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

MAINLY RAIN SHOWERS OVER THE EASTERN ALEUTIANS...A MIX OF RAIN
AND SNOW SHOWERS WEST OF ADAK...AND ALL SNOW SHOWERS OVER THE
PRIBILOFS CAN BE EXPECTED THROUGH WED NIGHT. STRONG WIND FROM ADAK
WEST WILL DIMINISH TODAY AND TONIGHT AS THE SURFACE LOW MOVES INTO
THE NORTH PACIFIC.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

IT STILL APPEARS THAT A SERIES OF WEAK UPPER LOWS WILL DEVELOP
OVER THE BERING AND NORTH PACIFIC BY LATE IN THE WEEK AND KEEP THE
WEATHER ACTIVE THROUGHOUT THE BERING SEA AND THE GULF...HOWEVER NO
MAJOR SYSTEMS ARE EXPECTED. THE MODELS ARE TRENDING SLIGHTLY
DEEPER WITH THE NORTH PACIFIC TROUGH ON THURSDAY AND FRIDAY...WHICH
SHOULD ALLOW FOR WEAK RIDGING OVER THE PANHANDLE TO STRETCH INTO
THE EASTERN INTERIOR. THIS WILL LIMIT PRECIPITATION CHANCES IN
COPPER RIVER BASIN BY LATE IN THE WEEK...HOWEVER OTHER THE REST OF
SOUTHCENTRAL AND THE SOUTHWEST MAINLAND WILL REMAIN WEST OF THIS
RIDGE AXIS AND ALLOW FOR PERIODS OF SNOW MIXED AND RAIN. THE
BERING SEA REGION WILL REMAIN SEASONABLY SHOWERY AND GUSTY. THIS
PATTERN THEN LOOKS TO CONTINUE INTO THE WEEKEND AS A DEEP AND
STATIONARY UPPER TROUGH OVER NORTHCENTRAL CANADA WILL CAUSE AN
OMEGA BLOCK TO TEMPORARILY FORM...THEN POTENTIALLY BEGIN TO BREAK
UP BY EARLY NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 150 155 174 175 176 177 178.
         HEAVY FREEZING SPRAY 181.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DS
LONG TERM...DEK

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1232 PM AKST TUE DEC 2 2014

AKZ101-111-030945-
ANCHORAGE-MATANUSKA VALLEY-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON
1232 PM AKST TUE DEC 2 2014

...SLIPPERY ROAD CONDITIONS THROUGH TONIGHT...

RAIN FALLING ON FROZEN SURFACES IS CREATING SLICK DRIVING
CONDITIONS FOR THE AFTERNOON COMMUTE. WARMER AIR COMING OFF
TURNAGAIN ARM TURNED SNOW TO RAIN JUST AS PRECIPITATION WAS ENDING
ACROSS THE ANCHORAGE BOWL. PRECIPITATION WILL CONTINUE TO DIMINISH
FROM SOUTH TO NORTH THIS AFTERNOON WHILE WARMER SOUTHERLY WINDS
WILL CONTINUE TO FACILITATE THE CHANGE OVER FROM SNOW TO RAIN
TOWARD THE MATANUSKA VALLEY. CAUTION SHOULD BE EXERCISED WHILE OUT
ON THE ROADWAYS. EXPECT COLDER AIR TO SETTLE IN THIS EVENING AND
OVERNIGHT ALONG WITH SCATTERED SNOW SHOWERS KEEPING ROADS SLICK.