Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 281434
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
534 AM AKST WED JAN 28 2015

.ANALYSIS AND UPPER LEVELS...
THE FRONT ASSOCIATED WITH A COMPLEX LOW CENTERED TO THE SOUTH OF
THE EASTERN ALEUTIANS CAN BE SEEN MOVING NORTHWARD THROUGH THE
SOUTHERN GULF. RAIN AND SNOW SHOWERS FROM THIS FRONT STRETCH FROM
THE AKPEN THROUGH KODIAK ISLAND INTO THE CENTRAL GULF...AND ARE
BEGINNING TO SHOW UP ON THE SOUTHERN EXTENT OF THE MIDDLETON
ISLAND RADAR. TO THE NORTH OF THIS FRONT...HIGH PRESSURE IS
KEEPING TEMPERATURES SEASONABLY COLD UNDER MOSTLY CLEAR SKIES.
WITHIN THE ALEUTIAN LOW COMPLEX...TWO DISTINCT FEATURES CAN BE
SEEN ON SATELLITE IMAGERY. THE FIRST IS LOCATED ROUGHLY 250 NM
SOUTHWEST OF SAND POINT AND IS HEADING SOUTH INTO THE NORTH
PACIFIC. THE SECOND IS NEARLY 500 MILES SOUTH OF KODIAK
ISLAND...AND IS TRACKING NORTHWARD TOWARDS THE AKPEN. OVER THE
WESTERN BERING...RIDGING IS BEGINNING TO BUILD AS IT SPREADS INTO
THE NORTHERN BERING. THE TIGHT PRESSURE GRADIENT BETWEEN THIS
RIDGE AND THE ALEUTIAN LOW COMPLEX CAN BE SEEN WITH GALE FORCE
NORTHERLY WINDS AND THE RESULTING COLD AIR ADVECTION INSTABILITY
SHOWERS THAT CONTINUE FROM THE CENTRAL BERING INTO THE WESTERN
ALEUTIANS.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN VERY GOOD SYNOPTIC AGREEMENT THROUGH THE END
OF THE WEEK...BUT THERE ARE STILL SOME MINOR DISAGREEMENT WITH
THE SMALLER SCALE FEATURES. THE MOST SIGNIFICANT OF THESE EXISTS
WITH TIMING OF THE PRECIPITATION INTO THE PRINCE WILLIAM SOUND AS
THE FRONT DISSIPATES OVER THE GULF THIS EVENING. THE GLOBAL MODELS
ARE SLIGHTLY FASTER THAN THE HIGHER RESOLUTION NAM/GEM REGIONAL
(WITH THE GEM BEING SIGNIFICANTLY SLOWER THAN THE REST) IN
BRINGING THIS RAIN AND SNOW TOWARDS VALDEZ LATE TONIGHT. THIS MUCH
SLOWER GEM REGIONAL SOLUTION WAS THROWN OUT AS AN OUTLIER...AN A
CONSENSUS OF THE NAM AND THE GLOBAL MODELS WAS USED FOR TIMING IN THIS
MORNINGS PACKAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE FIRST FRONTAL SYSTEM LIFTING NORTH HAS BEEN BRINGING GALES TO
MUCH OF THE GULF AS IT APPROACHES THE STATIONARY UPPER LEVEL
RIDGE STRETCHING FROM EAST TO WEST ACROSS THE NORTHERN GULF AND
OVER THE BERING. THE FRONT WILL WEAKEN AND SHEAR APART AS IT
CONTINUES NORTH KEEPING PRECIPITATION TODAY MAINLY LIMITED TO GULF
COASTAL AREAS. ADDITIONALLY THE DRY NORTH TO NORTHEASTERLY WINDS
WILL FURTHER DELAY THE PRECIPITATION REACHING THE EASTERN KENAI
PENINSULA...COOK INLET AND POINTS NORTH.

MORE WIDESPREAD PRECIPITATION...IN THE FORM OF SNOW IN ALL BUT
THE MOST COASTAL LOCATIONS...WILL SPREAD FROM EAST TO WEST ACROSS
THE NORTHERN GULF COAST AND INTO PRINCE WILLIAM SOUND TONIGHT AND
TOMORROW AS A SECONDARY FRONT FROM THE LARGE LOW TO THE SOUTH
ROTATES UP INTO THE GULF. WITH CONTINUED VERY COLD AND DRY
NORTHEASTERLY WINDS THROUGH THOMPSON PASS...THE ADDITION OF NEW
FALLING SNOW MAY CREATE SOME VISIBILITY REDUCTIONS...BUT LIGHT
OVERALL SNOWFALL AMOUNTS SHOULD KEEP CONDITIONS ABOVE BLIZZARD
CRITERIA.

MEANWHILE...WITH A LACK OF DOWNSLOPING CROSS BARRIER FLOW...MOISTURE
WILL GRADUALLY START SPREADING WEST OVER THE CHUGACH MOUNTAINS ON
THURSDAY BRINGING A CHANCE OF SNOW TO THE ANCHORAGE AREA AND
MATANUSKA VALLEY. SNOW CHANCES WILL INCREASE THURSDAY NIGHT AS THE
SUPPLY OF MOISTURE AT MOUNTAIN TOP LEVEL AND ABOVE INCREASES.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THIS AREA WILL BE MARKED BY MAINLY CLEAR AND COLD CONDITIONS
CONTINUING FOR THE NEXT COUPLE DAYS. THE EXCEPTION WILL BE SOME
SNOW ALONG THE ALASKA PENINSULA TODAY AND TONIGHT AS THE FRONT
SOUTH OF THE ALEUTIANS SWINGS NORTHWARD TOWARD THE AREA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE NORTHEAST FLOW WILL CONTINUE ACROSS MUCH OF THE BERING SEA AND
ALEUTIAN CHAIN THROUGH THIS PERIOD. CLOUDS ACROSS THE CENTRAL
BERING WILL CONTINUE TO PUSH SOUTHWARD...LIKELY SOUTH OF THE
PRIBILOFS BY TONIGHT. THE STRONG WINDS WILL GRADUALLY DIMINISH AS
WELL...ESPECIALLY OVER BERING SEA AS HIGH PRESSURE BUILDS OVER
THE CENTRAL BERING TODAY AND THURSDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
SNOW SHOWERS WILL LINGER ALONG THE GULF COAST INTO FRIDAY NIGHT AS
A FRONT GRADUALLY WEAKENS OVER THE NORTHERN GULF. AFTER THAT...
MODELS HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE PAST 24
HOURS WITH PLACEMENT OF THE UPPER HIGH THAT WILL MIGRATE EASTWARD
FROM THE BERING SEA TO THE MAINLAND THIS WEEKEND. THIS WILL HELP
TO KEEP A BROAD NORTH PACIFIC LOW WELL SOUTH OF THE REGION THROUGH
EARLY NEXT WEEK AS IT REMAINS IN THE VICINITY OF 50 DEGREES NORTH
LATITUDE. THE PRECIPITATION ASSOCIATED WITH THIS FEATURE IS THUS
EXPECTED TO REMAIN SOUTH OF THE AREA WITH THE BULK OF THE IMPACTS
LIMITED TO THE SOUTHERN GULF AND KODIAK ISLAND AS WELL AS THE
ALASKA PENINSULA. THIS WILL KEEP THE SOUTHERN MAINLAND IN A DRY
OFFSHORE FLOW PATTERN AS TEMPERATURES GRADUALLY MODERATE TO NEAR
NORMAL VALUES...WITH A FAVORABLE PRESSURE GRADIENT SUPPORTING
GUSTY WINDS ALONG THE NORTHERN GULF COAST.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 176.
         GALE WARNING 119 120 127 130 131 132 138 150 155 165
           170 171 172 173 174 175 177 179 180.
         HEAVY FRZ SPRAY 127 128 139 140 141 160 180 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHCENTRAL ALASKA...JER
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MBS
LONG TERM...TP



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