Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 160037
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED...RESENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
337 PM AKST MON DEC 15 2014

CORRECTED FOR GALE WARNINGS

.ANALYSIS AND UPPER LEVELS...
THERE IS AN ELONGATED UPPER LEVEL TROUGH STRETCHING FROM THE
KAMCHATKA PENINSULA ACROSS THE BERING SEA AND INTO THE GULF OF
ALASKA. THERE ARE A NUMBER OF UPPER LOWS ASSOCIATED WITH THIS
TROUGH. ONE IS OVER THE SOUTH CENTRAL BERING SEA...ONE IS OVER THE
ALASKA PENINSULA/SOUTHERN GULF AND ONE NEAR THE WESTERN ALEUTIANS.
THERE IS AN EAST/WEST ORIENTED UPPER LEVEL RIDGE OVER CENTRAL
ALASKA.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH ABOUT
FORECAST HOUR 60 (3PM AKST WEDNESDAY) THEN BEGIN TO
DIVERGE...ESPECIALLY FOR A LOW SOUTHWEST OF THE GULF OF ALASKA.
THE MODELS ARE FINALLY COMING INTO DECENT AGREEMENT ON A
DEVELOPING LOW IN THE GULF TONIGHT INTO TUESDAY. THE GFS AND NH
GEM ARE IN AGREEMENT A LITTLE FURTHER WEST WITH THE LOW AND THE
NAM/ECMWF/REGIONAL GEM ARE IN AGREEMENT ON THE LOW BEING FURTHER
EAST...BUT ALL THE MODELS ARE IN "TIGHTER" AGREEMENT THAN IN
PREVIOUS RUNS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THERE ARE TWO SYSTEMS IN THE NORTHERN GULF THAT WILL AFFECT THE
AREA THROUGH TUESDAY. THE FIRST IS SITUATED ALONG THE NORTH GULF
COAST. THIS SYSTEM WILL SLIDE THROUGH SOUTH CENTRAL TONIGHT...WITH
MOST OF THE PRECIPITATION (MAINLY RAIN) CONFINED TO COASTAL AREAS.
THE NEXT SYSTEM/FRONT/UPPER VORTICITY MAXIMUM THAT IS CURRENTLY
OVER KODIAK AND THE CENTRAL GULF WILL PUSH INTO THE SOUTH CENTRAL
ON TUESDAY...AND THEN ACROSS THE AREA LATE TUESDAY INTO WEDNESDAY
MORNING. THIS WILL BRING A BETTER CHANCE OF PRECIPITATION TO
INLAND AREAS AS THE TROUGH IS SHARP ENOUGH TO CREATE DECENT LIFT
AN BRIEFLY TURN THE UPPER WINDS TO SOUTHWEST. YET ANOTHER FRONT
WILL PUSH TOWARD THE COAST ON WEDNESDAY. A DEEPER LOW WILL MOVE
INTO THE SOUTHWEST GULF LATER WEDNESDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE PATTERN WILL REMAIN FAIRLY BLOCKY EARLY IN THE LONG TERM
PORTION OF THE FORECAST. THERE WILL BE A DEEP LOW (SURFACE
PRESSURE PROBABLY IN THE 960`S) IN THE GULF ON DAY 3 (THURSDAY)
AND A COUPLE OF WEAKER LOWS OVER THE NORTHWEST BERING AND TO THE
SOUTH OF THE WESTERN ALEUTIANS. THE PATTERN WILL BEGIN TO
TRANSITION TO MORE PROGRESSIVE LATER IN THE WEEK...AND BECOME
RATHER PROGRESSIVE BY EARLY NEXT WEEK. WPC MADE USE OF THE
ENSEMBLE MEANS EXCLUSIVELY...WITH A 70 PERCENT/30 PERCENT BLEND OF
THE ECMWF/GFS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TUESDAY AND WEDNESDAY)...
AN UPPER LEVEL CLOSED LOW WILL CONTINUE TO BE LOCATED NORTHWEST
OF THE PRIBILOF ISLANDS THROUGH WEDNESDAY. AT THE SURFACE THIS IS
REFLECTED WITH A GALE FORCE LOW WEST OF NUNIVAK ISLAND RESULTING
IN ONSHORE SOUTHWESTERLY FLOW THROUGH SOUTHWEST ALASKA. THIS WILL
BRING STRATUS AND FOG ALONG THE COASTLINE DURING THE OVERNIGHT
HOURS BEFORE DISSIPATING BY THE AFTERNOON HOURS. THE PREDOMINANT
PRECIPITATION WILL BE A WINTRY MIX THROUGH WEDNESDAY. ALONG THE
COASTLINE THE TEMPERATURES WILL BE IN THE MID 30S WITH MIXED
SCATTERED RAIN/SNOW SHOWERS. THE INLAND TEMPERATURES ARE COOLER
WITH TEMPERATURES IN THE MID TEENS TO UPPER 20S WITH THE
PRECIPITATION OCCURRING AS SCATTERED SNOW SHOWERS THROUGH
WEDNESDAY...WHILE THE HEAVIEST SNOWFALL WILL OCCUR ALONG THE
AHKLUN MOUNTAINS AND ALONG THE ALASKA RANGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TUESDAY AND WEDNESDAY)...
THE EASTERN SIBERIAN HIGH PRESSURE REMAINS IN PLACE WITH A GALE
FORCE LOW POSITIONED NORTH OF THE PRIBILOF ISLANDS. THIS LOW WILL
GRADUALLY MOVE TOWARD SAINT MATTHEW ISLAND BY WEDNESDAY. THE
PRESSURE GRADIENT BETWEEN THE AFOREMENTIONED SYNOPTIC FEATURES
WILL CONTINUE TO PRODUCE NORTHERLY GALE FORCE WINDS THROUGH THE
BERING STRAIT SOUTHWARD INTO THE NORTHERN BERING SEA. THE
TEMPERATURES WILL REMAIN BELOW FREEZING FOR MAJORITY OF THE BERING
SEA WITH THE GALE FORCE LOW NEAR SAINT MATTHEW ISLAND AIDING IN
PRODUCING SNOW SHOWERS THROUGH WEDNESDAY. ALONG THE ALEUTIAN CHAIN
THE TEMPERATURES ARE MORE MODIFIED RESULTING IN RAIN SHOWERS FROM
THE CENTRAL ALEUTIANS EASTWARD.. THE WESTERN ALEUTIANS WILL START
TO RECEIVE SOME COLD AIR ADVECTION FROM THE NORTH BY TUESDAY. THIS
WILL RESULT IN A WINTRY MIX OF SCATTERED RAIN/SNOW SHOWERS THROUGH
WEDNESDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 125 155 179 185.
         HEAVY FREEZING SPRAY WARNING...181 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PLD
LONG TERM...BL


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