Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 291505 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
455 AM AKDT FRI APR 29 2016

.ANALYSIS AND UPPER LEVELS...
THE NORTHERN PACIFIC AND ALASKA REMAINS IN A BROAD LONGWAVE TROUGH
WITH A BROAD CLOSED UPPER LOW CENTERED OVER THE WESTERN ALASKA
PENINSULA WITH SHORTWAVE RIDGES OVER THE NORTHWESTERN PACIFIC TO
THE WEST AND OVER WESTERN CANADA TO THE EAST. MULTIPLE SHORTWAVES
CAN BE SEEN IN SATELLITE IMAGERY ROTATING THROUGH THE REGION
AROUND THE LOW. THE POLAR JET REMAINS SOUTH OF THE FORECAST AREA
BUT HAS BECOME MORE MERIDIONAL OVER THE LAST 24 HOURS AS A
SHORTWAVE /CURRENTLY AROUND 170W/ IN THE BROAD TROUGH DEEPENS AS
IT PROGRESSES EASTWARD. THE BRANCH OF THE POLAR JET JUST EAST OF
THIS SHORTWAVE HAS A MAXIMUM SPEED OF 130-140 KT...THUS PROVIDING
SOME SUPPORT TO THE CLOSED CYCLONE THAT IS DEVELOPING WITHIN THIS
SHORTWAVE.

AT THE SURFACE...A BROAD 995 MB LOW IS CENTERED UNDER THE CLOSED
LOW OVER THE WESTERN ALASKA PENINSULA AND IS SLOWLY DISSIPATING. A
980MB LOW IS RAPIDLY DEVELOPING AROUND 44N 167W UNDER THE
SHORTWAVE TROUGH MENTIONED ABOVE. THE REMNANTS OF THE OCCLUDED
FRONT THAT WAS ASSOCIATED WITH A WEAK LOW NEAR KODIAK ISLAND IS
MOVING ON SHORE THROUGH SOUTHERN ALASKA...PRODUCING SHOWERS ALONG
MOST OF THE GULF COAST WESTWARD INTO THE BRISTOL BAY REGION AND
THROUGH THE SOUTHERN SUSITNA VALLEY.

&&

.MODEL DISCUSSION...
THE QUARTET OF MODELS AT 00Z ALL INITIALIZED FAIRLY WELL WITH ONLY
MINOR ISSUES AROUND THE RAPIDLY DEVELOPING LOW NEAR 44N 167W AND THE
POTENTIAL ASSOCIATED DOWNSTREAM IMPACTS TOWARD SOUTHCENTRAL THIS
WEEKEND (MENTIONED IN THE SOUTHCENTRAL SHORT TERM FORECAST).
OTHERWISE...ALL MODELS THROUGH DAY 3 ARE IN REASONABLE AGREEMENT
WITH THE PLACEMENT AND MOVEMENT OF THE MAJOR FEATURES. THIS FORECAST
PACKAGE LEANS TOWARDS THE GFS FOR THE MAJOR SYNOPTIC FEATURES WITH
SOME USE OF THE NAM ON THE EASTERN DOMAIN FOR DETAIL.

&&

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

THE MAIN FOCUS IN THE SHORT TERM FORECAST THROUGH SATURDAY NIGHT
SURROUNDS THE STRONG FRONT MOVING UP FROM THE NORTH PACIFIC TOWARD
KODIAK ISLAND THIS EVENING. NEARLY STEADY CONDITIONS WILL OCCUR
TODAY AHEAD OF THIS SYSTEM WITH SHOWERS ALONG THE GULF AND DRY
INLAND. SOUTHEASTERLY FLOW WILL BE STRONGER T0DAY AS A RIDGE
BUILDS ACROSS SOUTHCENTRAL WHILE LOW PRESSURE MOVES CLOSER TO THE
SOUTHERN GULF. THE ANTICIPATED FRONT PUSHES INTO THE SOUTHERN
WATERS THIS EVENING WITH THE SURFACE LOW GAINING MOMENTUM
OVERNIGHT. WIDESPREAD GALE TO STORM STRENGTH WINDS INCREASE
QUICKLY SPREADING TO THE NORTHERN GULF BY EARLY SATURDAY MORNING.
THE KENAI PENINSULA WILL SEE CONDITIONS DIMINISH OVERNIGHT WITH
THE HEAVIEST RAIN ALONG THE EASTERN KENAI INITIALLY...THEN HEAVIER
AMOUNTS SPREADING INTO PRINCE WILLIAM SOUND AND THE NORTHEAST GULF
FOR SATURDAY. FORECAST WINDS AND PRECIPITATION SHOULD BE MONITORED
FOR UPDATES THROUGH THIS WEEKEND DUE TO UNCERTAINTY ON THE TRACK
OF THIS SYSTEM. THE MAIN CHALLENGES WITH A DIFFERENT TRACK COULD
BRING STRONGER WINDS THROUGH EAST TO WEST GAPS AND GREATER CHANCES
FOR PRECIPITATION FOR THE COPPER RIVER VALLEY ON SATURDAY.

&&

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

THE WEAK FRONTAL SYSTEM CURRENTLY STRETCHED ACROSS THE BRISTOL BAY
AREA WILL CONTINUE TO FALL APART WITH SHOWERS BECOMING MORE
SCATTERED IN COVERAGE OVERNIGHT. THE NEXT TROUGH WILL ROTATE
THROUGH ON FRIDAY BRINGING MORE NUMEROUS SHOWERS TO THE BRISTOL
BAY AREA IN THE MORNING AND THE KUSKOKWIM VALLEY AND DELTA IN THE
AFTERNOON. SHOWERS WILL TAPER BACK OFF FRIDAY NIGHT AND SATURDAY AS
A STRONGER FRONT MOVES INTO THE SOUTHWEST GULF AND INCREASES DRIER
NORTHEASTERLY FLOW OVER SOUTHWEST ALASKA.

&&

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

BROAD CYCLONIC FLOW OVER THE BERING WILL CONTINUE AS ANOTHER NORTH
PACIFIC LOW TRACKS TOWARD THE EASTERN ALEUTIANS LATE THIS AFTERNOON.
THE ASSOCIATED GALE FORCE FRONT WILL BRING STEADY RAIN TO THIS AREA
AND SHOWERS TO THE CENTRAL ALEUTIANS...WITH MUCH DRIER NORTHERLY
FLOW OVER THE REMAINDER OF THE BERING AND ALEUTIANS. HIGH PRESSURE
BUILDS OVER THE CENTRAL BERING SATURDAY WITH A WEAKENING FRONT
MOVING INTO THE WESTERN ALEUTIANS AND BERING SATURDAY NIGHT AND
SUNDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN UPPER LEVEL CLOSED LOW AT 500 MB WILL TRACK NEAR KODIAK BY
SATURDAY WITH AN ASSOCIATED SHORTWAVE DIGGING INTO THE BASE OF THE
LONGWAVE TROUGH. THIS FEATURE WILL RESULT IN THE STRONG SOUTHERLY
JET STREAM IN THE GULF BEFORE TRANSITIONING TO A MORE
SOUTHEASTERLY FLOW. THIS RESULTS IN AN NEGATIVELY TILTED AMPLIFIED
RIDGE OVER THE YUKON TERRITORY EXTENDING INTO THE ALASKA RANGE AND
CENTRAL INTERIOR. THEREFORE...SEVERAL SHORTWAVES WILL MOVE THROUGH
THE SOUTHCENTRAL AND THE GULF THROUGH TUESDAY. THIS SYNOPTIC
PATTERN WILL BRING PLENTY OF MOISTURE AND HEAVY RAIN AT TIMES TO
THE NORTHERN AND WESTERN COASTAL COMMUNITIES THROUGH THE WEDNESDAY.
WHILE THE BERING AND THE ALEUTIANS WILL START OUT WITH A SHOWERY
REGIME WITH NORTHERLY TO NORTHEASTERLY FLOW THIS WEEKEND. A GALE
FORCE LOW WILL DROP DOWN OFF THE KAMCHATKA PENINSULA BY SATURDAY
WITH AN ASSOCIATED WEATHER FRONT MOVING THROUGH THE WESTERN
ALEUTIANS BY SATURDAY EVENING. THIS LOW PRESSURE SYSTEM WILL THEN
TRACK ALONG THE CHAIN HEADING THROUGH THE MIDWEEK. THIS WILL BRING
A SWATH OF STRATUS WITH RAIN AND GUSTY SOUTHEASTERLY WINDS AS THE
FRONT MOVES THROUGH THE WESTERN ALEUTIANS THIS WEEKEND. AS THIS
SYSTEM MOVES ALONG THE CHAIN THIS WILL PRODUCE A SHOWERY WEATHER
REGIME ON THE BACKSIDE OF THE LOW PRESSURE. THE WESTERN BERING AND
THE ALEUTIANS WILL TRANSITION TO NORTHEASTERLY FLOW AS THE LOW
PRESSURE SYSTEM MOVES EAST HEADING INTO THE MIDWEEK TIME FRAME.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 119 131
         GALE 120 125 130 132 136 137 138 139 150 351 352

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA/LIW
LONG TERM...PD



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