Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 201342
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
542 AM AKDT SUN JUL 20 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL LOW THAT ENTERED THE NORTHWEST COAST EARLY
YESTERDAY MORNING HAS NOW MOVED TO THE SOUTHEAST AND HAS NOW
BECOME A SHARP TROUGH OVER THE SOUTH MAINLAND. THIS SYSTEM HAS
BROUGHT WIDESPREAD RAIN...WHICH HAS BEEN QUITE HEAVY AT TIMES
OVERNIGHT...TO MUCH OF SOUTHCENTRAL. THE STRONG JET ASSOCIATED
WITH THIS SYSTEM CAN BE SEEN WELL ON WATER VAPOR IMAGERY
STRETCHING FROM THE WESTERN INTERIOR TO THE WESTERN GULF. THIS JET
WILL CONTINUE DIGGING THE TROUGH OVER THE COURSE OF THIS
MORNING...EVENTUALLY CAUSING IT TO DETACH FROM THE PRIMARY ARCTIC
LOW AND MOVE INTO THE NORTHERN GULF IN THE AFTERNOON. TO THE WEST
OF THIS UPPER LOW...A RIDGE OF HIGH PRESSURE STRETCHES FROM THE
EASTERN ALEUTIANS/AKPENN INTO THE WESTERN BERING. THIS RIDGE IS
SLOWLY BUILD TO THE EAST BEHIND THE DEPARTING LOW...AND WILL HELP
TO CLEAR OUT MUCH OF THE SOUTHERN MAINLAND BY THIS EVENING. A WEAK
LOW IS APPROACHING THE CENTRAL ALEUTIANS IS BEGINNING TO SPREAD
RAIN TO THE ADAK AREA. THIS SYSTEM WILL BRING LIGHT RAIN INTO THE
EASTERN ALEUTIANS IS IT CONTINUES TRACKING TO NORTHEAST AND
WEAKENING.

&&

.MODEL DISCUSSION...
WHILE THE MODELS REMAIN IN GREAT SYNOPTIC AGREEMENT THROUGH THE
SHORT TERM...THEY CONTINUE TO HAVE MAJOR ISSUES WITH DEPICTING THE
RAIN CURRENTLY FALLING OVER SOUTHCENTRAL. THE 00Z GFS DID AN
ACCEPTABLE JOB AT CAPTURING THE RAINFALL OVER THE SUSITNA
VALLEY...BUT THE LATEST 06Z RUN HAS COME MORE IN LINE WITH THE
REST OF THE MODELS BY KEEPING THE RAINFALL TOO FAR TO THE EAST.
THIS SHOULD HOWEVER ONLY HAVE AN IMPACT TO TIMING EXACTLY WHEN THE
RAIN WILL END OVER SOUTHCENTRAL. THERE STILL IS GOOD CONFIDENCE IN
THE GENERAL TREND OF IMPROVING CONDITIONS FROM THE WEST OVER THE
COURSE OF THIS MORNING. OTHERWISE...AS MENTIONED ABOVE THERE
REMAINS GREAT AGREEMENT WITH THE MOVEMENT OF THE TRANSITORY RIDGE
MOVING OVER THE MAINLAND LATER TODAY...AND SLIGHTLY LESS AGREEMENT
WITH THE THE PROGRESSION OF THE ALEUTIAN LOW IS IT BECOMES
ABSORBED IN THE NEXT WAVE ENTERING THE WEST MAINLAND LATE TUESDAY.


&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE RAIN CURRENTLY FALLING FROM ANCHORAGE
NORTHWARD INTO THE MATANUSKA VALLEY AND EASTERN SUSITNA VALLEY
WILL BEGIN TO DIMINISH FROM WEST TO EAST BY LATE MORNING AS THE
UPPER TROUGH CONTINUES TO CUTOFF FROM THE PRIMARY LOW AND DRIFT
INTO THE NORTHERN GULF. AREAS FURTHER EAST WILL REMAIN CLOUDY AND
RAINY FOR A MAJORITY OF THE DAY...BUT THEN CLEAR OUT RAPIDLY
THIS EVENING AS OFFSHORE FLOW TAKES OVER THROUGHOUT THE SOUTH
MAINLAND. THIS TREND WILL THEN CONTINUE INTO MONDAY...CAUSING THE
ENTIRE AREA TO HAVE A CLEAR AND DRY START TO THE WEEK. GUSTY
OFFSHORE WINDS WILL FORM ALONG THE GULF COAST OF THE KENAI
PENINSULA TODAY (ESPECIALLY NEAR SEWARD AND WHITTIER) DUE TO
PRESSURE FALLS AND GOOD JET SUPPORT REMAINING OVER THE AREA.
CLOUDY SKIES WITH A CHANCE OF RAIN WILL THEN RETURN LATE TUESDAY
AS YET ANOTHER WAVE APPROACHES THE AREA FROM THE WEST COAST.

SOUTHWEST ALASKA...WITH THE EXCEPTION OF THE STRAY RAIN SHOWERS
OVER THE ALASKA AND ALEUTIAN RANGES THIS MORNING...THE SOUTHWEST
MAINLAND WILL REMAIN DRY UNTIL TUESDAY. CLOUDS WILL RAPIDLY
DIMINISH LATE THIS MORNING AS RIDGING OVER THE BERING BUILDS OVER
THE WEST COAST. THIS WILL PRODUCE A CHANCE OF DIURNAL FOG
OVERNIGHT TONIGHT...ESPECIALLY FOR COASTAL BRISTOL BAY AND THE
DELTA DUE TO AN ALREADY MOISTENED BOUNDARY LAYER FROM RECENT
RAINS. THIS STRETCH OF GOOD WEATHER HOWEVER LOOKS TO BE VERY SHORT
LIVED...AS THE NEXT BAND OF RAIN BEGIN TO ENTER THE WEST COAST
LATE MONDAY NIGHT AND SPREAD THROUGHOUT THE AREA FOR TUESDAY.

BERING SEA/ALEUTIANS...THE NORTH PACIFIC LOW CURRENTLY APPROACHING
THE ALEUTIANS WILL BRING THE NEXT CHANCE OF RAIN TO THE CENTRAL
ALEUTIANS. THIS LOW WILL THEN MOVE INTO THE EASTERN ALEUTIANS AND
BECOMING ABSORBED INTO ANOTHER TROUGH DESCENDING ONTO THE WEST
COAST ON TUESDAY...KEEPING THE AREAS FROM DUTCH HARBOR EAST CLOUDY
WITH A CHANCE OF RAIN INTO WEDNESDAY.


&&

.LONG TERM FORECAST...
THERE CONTINUES TO BE GOOD AGREEMENT THAT THE ELONGATED WAVE THAT
WILL MOVE OVER THE MAINLAND ON TUESDAY WILL BECOME A NEARLY
STATIONARY CUTOFF LOW OVER THE NORTHERN GULF ON WEDNESDAY. THIS
IS SLIGHTLY FURTHER NORTH THAN THE MODELS HAD BEEN DEPICTING
YESTERDAY...AND SHOULD KEEP MUCH OF THE SOUTH MAINLAND CLOUDY WITH
A RISK OF SHOWERS UNTIL LATER IN THE WEEK. A BERING RIDGE WILL
THEN LOOKS TO ONCE AGAIN BUILD OVER THE WESTERN MAINLAND ON
FRIDAY...AND SPREAD INTO THE SOUTH MAINLAND FOR THE WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 120 130 131.
FIRE WEATHER...NONE.

&&

$$

DEK JUL 14



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