Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 301317
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
517 AM AKDT MON MAR 30 2015

.ANALYSIS AND UPPER LEVELS...
MUCH OF THE REGION REMAINS UNDER THE INFLUENCE OF AN EXPANSIVE
LONGWAVE TROUGH THAT EXTENDS FROM THE WESTERN BERING SEA THROUGH
THE GULF OF ALASKA AND INTO THE NORTHEAST PACIFIC. THERE ARE THREE
MAIN LOW CENTERS EMBEDDED WITHIN THE LARGE SCALE TROUGH WHICH ARE
IMPACTING THE WEATHER ACROSS THE REGION...WITH ONE CENTERED
APPROXIMATELY 300 MILES SOUTH OF KODIAK ISLAND AND ANOTHER OVER
THE FAR WESTERN BERING NEAR ATTU. THE THIRD IS LOCATED NEAR THE
SEWARD PENINSULA WITH A TROUGH AXIS EXTENDING SOUTHWARD ALONG THE
WEST COAST TO NEAR NUNIVAK ISLAND. RAIN CONTINUES ALONG THE GULF
COAST IN BROAD SOUTHERLY FLOW IN THE WAKE OF THE FRONT AND UPPER
WAVE THAT MOVED OVER SOUTHCENTRAL AK YESTERDAY...WITH INLAND AREAS
IN THE LEE OF THE CHUGACH AND TALKEETNA MOUNTAINS REMAINING MOSTLY
DRY AS A RESULT OF CONTINUED STRONG CROSS BARRIER FLOW. THAT UPPER
WAVE HAS NOW PUSHED ACROSS THE ALASKA RANGE INTO SOUTHWEST
AK...BRINGING RAIN SHOWERS TO PORTIONS OF BRISTOL BAY AND THE LOWER
KUSKOKWIM VALLEY. MEANWHILE...A FRONT EXTENDING EASTWARD FROM THE
LOW OVER THE WESTERN BERING IS BRINGING LIGHT RAIN AND SNOW
SHOWERS TO MUCH OF THE ALEUTIAN CHAIN.

&&

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD OVERALL AGREEMENT WITH THE MAIN FEATURES IN
THE SHORT TERM AND HAVE ARRIVED AT A STRONGER CONSENSUS WITH THE
LOW SET TO SKIRT THE ALEUTIAN CHAIN THROUGH WEDNESDAY BEFORE
IT MOVES INTO THE SOUTHERN GULF. THE EC/GEM SOLUTIONS ARE STILL
SLIGHTLY AHEAD OF THE GFS ON THE TIMING OF THIS FEATURE BUT SHOW
CLOSER AGREEMENT THAN YESTERDAY...WHEREAS THE NAM HAS FALLEN IN
LINE WITH THE GFS AFTER BEING A CONSIDERABLE OUTLIER YESTERDAY.
THEREFORE...MAINLY USED THE GFS FOR THE MORNING FORECAST PACKAGE
GIVEN ITS SUPERIOR CONSISTENCY OVER THE PAST FEW DAYS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LOW COMPLEX IN THE GULF REMAIN TODAY WITH AN UPPER LEVEL WAVE
MAKING LANDFALL OVER THE KENAI PENINSULA AND UPPER COOK INLET
THIS MORNING. THIS IS KICKING UP THE WINDS THROUGH TURNAGAIN ARM
BUT THESE SHOULD RAPIDLY DIMINISH THROUGH THE MORNING. LOTS OF
DOWNSLOPE IS EVIDENT ON RADAR AGAIN THIS MORNING WITH VERY FEW
SHOWERS ABLE TO MAKE IT ACROSS THE MOUNTAINS WHILE THEY ARE
NUMEROUS ALONG THE COAST AND OVER COASTAL MOUNTAINS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE SURFACE WINDS OVER THE BRISTOL BAY REGION WILL CONTINUE IN
ONSHORE FLOW THROUGH TUESDAY BEFORE SHIFTING TO OFFSHORE FLOW BY
WEDNESDAY. THIS ONSHORE FLOW WILL RESULT IN STRATUS AND FOG DURING
TUESDAY MORNING. THE KUSKOKWIM DELTA REGION WILL HAVE LIGHT
NORTHWESTERLY WINDS AND ALSO LOOK FOR PATCHY MORNING FOG DURING
TUESDAY MORNING. BY WEDNESDAY A GALE FORCE NORTH PACIFIC LOW WILL
TRACK SOUTH OF KODIAK ISLAND. THIS WILL BRING WARMER TEMPERATURES
TO THE BRISTOL BAY REGION ACCOMPANIED BY SHOWERY PRECIPITATION
WITH THE HEAVIEST PRECIPITATION OCCURRING ALONG THE ALASKA RANGE
AND THE ALEUTIAN RANGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE CENTRAL ALEUTIANS WILL HAVE A STORM FORCE LOW POSITIONED
SOUTHWEST OF NIKOLSKI BY TUESDAY. THIS SYSTEM WILL CONTINUE TO
TRACK EASTWARD PARALLEL TO THE ALEUTIAN CHAIN AND BE LOCATED JUST
SOUTH OF KODIAK ISLAND BY WEDNESDAY. THIS WILL BRING WARM
TEMPERATURES WITH SOUTH TO SOUTHWESTERLY FLOW OUT AHEAD OF THE LOW
AS IT TRACKS EASTWARD...AND COOLER TEMPERATURES ON THE BACKSIDE OF
THIS SYSTEM. THEREFORE...THIS WILL COINCIDE WITH THE GUSTY NORTH
TO NORTHEASTERLY WINDS AND SNOW SHOWERS ON THE BACKSIDE OF THE LOW
THROUGH WEDNESDAY. THE WESTERN ALEUTAINS WILL HAVE A GALE FORCE
LOW DROPPING DOWN FROM KAMCHATKA PENINSULA WITH AN ASSOCIATED
WEATHER FRONT APPROACHING SHEMYA BY WEDNESDAY. THIS WILL BRING
GUSTY SOUTHERLY WINDS AND WARMER TEMPERATURES WITH RAIN TO THE
WESTERN ALEUTIANS. THE REST OF THE BERING SEA WILL CONTINUE IN
NORTHEASTERLY WINDS WITH AN UPPER LEVEL RIDGE OF HIGH PRESSURE
BUILDING INTO THE CENTRAL TO NORTHERN BERING SEA BY WEDNESDAY.
THIS UPPER LEVEL FEATURE WILL BE ACCOMPANIED BY STRATUS AND PATCHY
FOG GOING INTO THE MIDWEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A STACKED SYSTEM
MIGRATING FROM THE EASTERN ALEUTIANS/ALASKA PENINSULA INTO THE
GULF OF ALASKA BY LATE WEEK. THIS SYSTEM WILL BE WEAKENING AS IT
MOVES ACROSS WITH THE FRONTAL BOUNDARY JUST REACHING INTO THE
NORTHERN GULF. COLD TEMPERATURES ALOFT AND INCREASING CYCLONIC
FLOW SHOULD PROMOTE MOUNTAIN SHOWERS ACROSS MUCH OF THE NORTH GULF
COAST WHILE THIS SYSTEM STAYS OVERHEAD. AS THE UPPER LOW EXITS TOWARD
THE PANHANDLE A BRIEF PERIOD OF OUTFLOW TYPE CONDITIONS WILL
EXIST...HOWEVER THERE DOESN`T APPEAR TO BE ENOUGH COLD AIR TO
SUPPORT ANY KIND OF SIGNIFICANT WIND. OVER THE WEEKEND GUIDANCE IS
HINTING AT PATTERN AMPLIFICATION AS A SYSTEM OVER KAMCHATKA MOVES
INTO THE BERING SEA. THERE IS SOME DISAGREEMENT IN THE EVOLUTION
OF THE PATTERN BETWEEN FULL AMPLIFICATION OR CUTTING OFF OF THE
UPPER LEVEL ENERGY...LEADING TO A MORE PROGRESSIVE PATTERN. EXPECT
ABOVE NORMAL TEMPERATURES TO CONTINUE THROUGH MUCH OF THE PERIOD
WITH MAINLY DRY CONDITIONS...EXCEPT FOR THE CHANCE FOR RAIN AND
RAIN SHOWERS ALONG THE COAST LATE WEEK...DRYING OUT BY THE
WEEKEND.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CB
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...MTL


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