Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 191327
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
527 AM AKDT SAT JUL 19 2014

.ANALYSIS AND UPPER LEVELS...
THE COLD FRONT THAT ENTERED THE WEST COAST EARLY YESTERDAY MORNING
IS NOW WEAKENING RAPIDLY AS IT MOVES OVER THE WESTERN SLOPES OF
THE ALASKA RANGE. RAIN SHOWERS ON THE FRONT ARE HAVE NOW
DEVELOPED FROM THE SUSITNA VALLEY SOUTHWARD INTO KODIAK
ISLAND...AND WILL CONTINUE TO DEVELOP AND SPREAD TO THE SOUTH AS
THE MORNING PROGRESSES. THE PRIMARY UPPER LOW IS CAN NOW BE SEEN
ENTERING THE NORTHWEST COAST...AND HAS EVEN BROUGHT SOME EMBEDDED
THUNDERSTORMS TO THE WESTERN SEWARD PENINSULA AS COLD AIR ALOFT
RAPIDLY SURGES IN FROM THE NORTHWEST. BETWEEN THE WEAKENING FRONT
AND THE APPROACHING LOW IS A RELATIVELY SMALL AREA OF CLEARING
OVER THE SOUTHWEST MAINLAND. OUT WEST...A RIDGE OVER THE WESTERN
AND CENTRAL BERING CONTINUES TO BRING EXTENSIVE STRATUS AND FOG TO
THE CENTRAL AND WESTERN ALEUTIANS.

&&

.MODEL DISCUSSION...
MODEL AGREEMENT REMAINS VERY GOOD THROUGH THE SHORT TERM WITH THE
PROGRESSION OF THE UPPER LOW AS IT DIVES SOUTHWARD INTO THE GULF
BY LATE SUNDAY. EVEN WITH THE GOOD SYNOPTIC AGREEMENT...NONE OF
THE MODELS ARE TO BE CAPTURING THE RAIN BAND ALONG THE WEAKENING
FRONT THAT STRETCHES FROM THE SUSITNA VALLEY INTO KODIAK ISLAND.
OVERALL THE NAM/GEM REGIONAL WERE MOSTLY USED FOR THE MORNING
PACKAGE FOR THEIR HIGHER RESOLUTION...ESPECIALLY AS THE UPPER LOW
MOVES INTO THE GULF ON SUNDAY AND GAP WINDS DEVELOP. THE NAM
REMAINS A SLIGHT SOUTHERN OUTLIER WITH A CENTRAL ALEUTIAN LOW ON
MONDAY...HOWEVER THIS SHOULD HAVE LITTLE IMPACT TO OVERALL
FORECAST CONFIDENCE AS THERE IS GOOD GENERAL AGREEMENT.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...MOST OF SOUTHCENTRAL WILL SEE RAIN DEVELOPING
FROM THE WEST OVER THE COURSE OF THIS MORNING. A BIG CHALLENGE IN
THE FORECAST TODAY IS TRYING TO DETERMINE HOW MUCH CLEARING WILL
OCCUR LATE THIS MORNING AFTER THE FRONT PASSES...AND AS A RESULT
THE CHANCE OF ISOLATED AFTERNOON THUNDERSTORMS AS THE COLD CORE
LOW APPROACHES. THE MODELS KEEP SKIES MOSTLY CLOUDY FROM THE
SUSITNA VALLEY TO THE ANCHORAGE BOWL THROUGH THE EARLY
AFTERNOON...HOWEVER THE LACK OF SIGNIFICANT CLOUDCOVER OVER THE
SOUTHWEST MAINLAND INDICATES THAT THIS MAY BE OVERDONE. IF
SIGNIFICANT CLEARING DOES OCCUR...THE ADDED DAYTIME HEATING AHEAD
OF THE COLD CORE LOW SHOULD BE ENOUGH TO PRODUCE ISOLATED
THUNDERSTORMS OVER THE TALKEETNA MOUNTAINS AND COPPER RIVER
BASIN...WITH AN OUTSIDE CHANCE OF A STRIKE OR TWO REACHING THE
VALLEYS. THESE CONVECTIVE SHOWERS WILL ALMOST IMMEDIATELY BECOME
WIDESPREAD STRATIFORM RAIN AGAIN LATER THIS EVENING AND CONTINUE
INTO SUNDAY MORNING. AS THE TROUGH DIVES INTO THE GULF ON SUNDAY
AFTERNOON...A WARMING AND DRYING TREND WILL BEGIN AS OFFSHORE
FLOW TAKES OVER. GUSTY GAP WINDS WILL DEVELOP ALONG THE GULF
COAST...ESPECIALLY NEAR WHITTIER AND THROUGH PASSAGE CANAL.

SOUTHWEST ALASKA...NOW THAT RAINFALL FROM THE INITIAL FRONTAL
BAND HAS NOW MOVED MOSTLY OUT OF THE AREA...THE FOCUS QUICKLY
SHIFTS TO THE NEXT ROUND OF RAIN FROM THE UPPER LEVEL TROUGH FOR
LATER THIS MORNING. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS OVER
THE KUSKOKWIM DELTA OR LOWER KUSKOKWIM VALLEY THIS AFTERNOON AS
THE COLD/DRY AIR ASSOCIATED WITH THE UPPER TROUGH DESCENDS INTO
THE AREA THIS AFTERNOON...BUT THESE SHOULD BE ISOLATED AND
EMBEDDED WITHIN THE STRATIFORM RAIN. OTHERWISE THE ENTIRE AREA
WILL SEE RAIN MOVING IN FROM THE NORTHWEST IN THE LATE MORNING OR
EARLY AFTERNOON. THIS RAIN WILL THEN REMAIN THROUGH SUNDAY MORNING
BEFORE CLEARING OCCURS FOR LATER IN THE DAY AND CONTINUES INTO
MONDAY AS RIDGING QUICKLY MOVES INTO THE AREA.

BERING SEA/ALEUTIANS...WITH THE EXCEPTION OF A FEW STRAY RAIN
SHOWERS BEHIND THE DECAYING FRONT WILL CONTINUE THROUGH MID
MORNING ALONG THE BERING COAST OF THE AKPENN...CONTINUED RIDGING
WILL KEEP MUCH OF THE AREA WITH QUIET WEATHER AGAIN FOR TODAY.
OTHERWISE THE AREA WILL BE DOMINATED ONCE AGAIN BY THE USUAL
STRATUS AND FOG UNTIL SUNDAY...WHEN A WEAK LOW APPROACHING THE
CENTRAL ALEUTIANS WILL BRING IN THE NEXT CHANCE OF RAIN.


&&

.LONG TERM FORECAST...
THERE REMAINS VERY GOOD MODEL AGREEMENT THAT THE LOW THAT WILL
MOVE THROUGH THE CENTRAL ALEUTIANS ON MONDAY WILL STALL OUT THE
NORTHERN GULF BY MID WEEK...KEEPING THE THE SOUTHERN MAINLAND GENERALLY
CLOUDY WITH A CHANCE OF RAIN. THE GOOD NEWS IN THE LONG TERM
FORECAST IS THAT THERE IS INCREASING CONFIDENCE THAT THIS LOW WILL
MIGRATE FAR ENOUGH SOUTH INTO THE NORTHEAST PACIFIC BY LATE IN THE
WORK WEEK THAT RIDGING OVER THE BERING SEA SHOULD BE ALLOWED TO
SPREAD BACK INTO THE MAINLAND. THERE REMAINS SIGNIFICANT
UNCERTAINTY AS TO HOW LONG THIS RIDGE WILL BE ALLOWED TO STAY
HOWEVER...AS THE A NEARLY STATIONARY TROUGH OVER THE ARCTIC OCEAN
WILL PREVENT THE RIDGE FROM SPREADING FURTHER NORTH AND TAKING A
FIRM HOLD OVER THE MAINLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...GALE WARNING 120 130 131 181 185.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

DEK JUL 14


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