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000
FXAK68 PAFC 250045
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
345 PM AKST TUE FEB 24 2015

.ANALYSIS AND UPPER LEVELS...

THE OVERALL FLOW ACROSS MAINLAND ALASKA AND THE BERING SEA REMAINS
OUT OF THE SOUTHWEST...THOUGH EMBEDDED SHORTWAVE FEATURES MOVING
THROUGH THIS FLOW ARE HAVING THE MOST IMPACT ON SENSIBLE WEATHER
AT ANY GIVEN LOCATION. THE MOST APPARENT FEATURE ON SATELLITE
IMAGERY IS A VERTICALLY STACKED 1000 MB LOW SOUTH OF THE ALASKA
PENINSULA THAT IS MOVING SLOWLY TOWARD THE SOUTHERN GULF OF
ALASKA. THICKER CLOUDS HAVE MOVED INTO KODIAK ISLAND...AND WILL
SOON BE FOLLOWED BY THE BEGINNING OF RAINFALL. ELSEWHERE ACROSS
THE SOUTHERN MAINLAND...CLOUDS CONTINUE TO SLOWLY GIVE WAY TO
SUNSHINE AT MANY PLACES AS SUBSIDENCE ASSOCIATED WITH SHORTWAVE
RIDGING MOVES INTO THE AREA FROM THE SOUTH.

THE OTHER FEATURE OF NOTE ON SATELLITE IMAGERY THIS MORNING IS A
FRONT AFFECTING THE WESTERN ALEUTIANS. THIS FRONT IS ASSOCIATED
WITH A LOW THAT WILL SKIRT THE NORTHWESTERN BERING AND HEAD INTO
FAR EASTERN RUSSIA. THE EASTWARD PROGRESS OF THIS LOW IS SLOWING
DOWN AS A SEPARATE NORTH PACIFIC RIDGE IS ALREADY SHOWING SIGNS
OF BUILDING OVER THE EASTERN BERING/ALEUTIANS.

&&

.MODEL DISCUSSION...

WITH SLOW OVERALL EVOLUTION OF MAJOR WEATHER FEATURES OVER THE
COMING DAYS...ALL MODELS ARE IN EXCELLENT SYNOPTIC AGREEMENT. THE
HIGHER RESOLUTION MODELS (NAM AND GEMRGL) WILL BE INCORPORATED
INTO THE FORECAST TODAY TO CAPTURE ADDITIONAL DETAILS AROUND
COMPLEX TERRAIN.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A WEAK BOUNDARY ACROSS THE SUSITNA VALLEY AND ALONG THE GULF COAST
AND A WEAK SHORTWAVE ALOFT WILL INITIATE A FEW RAIN AND SNOW
SHOWERS TONIGHT...HOWEVER NO ACCUMULATIONS ARE EXPECTED AS A
COOLER AND DRIER AIR MASS SETTLES ACROSS THE AREA FROM THE WEST.
THE STORM SYSTEM MOVING INTO THE SOUTHERN GULF TONIGHT WILL BRING
GUSTY WINDS AND RAIN INTO THE CENTRAL GULF BY MORNING.
PRECIPITATION WILL BE LARGELY CONFINED TO THE GULF WATERS
INCLUDING KODIAK ISLAND AS SURFACE RIDGING BUILDS ACROSS CENTRAL
AREAS OF THE STATE WEDNESDAY INTO THURSDAY. AN INCREASE OF WINDS
ACROSS FAVORED GAPS PICK UP WITH PRESSURE GRADIENT TIGHTENING
ALONG THE COAST LATE WEDNESDAY THROUGH THURSDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE BUILDING OVER THE SOUTHWEST MAINLAND WILL YIELD
BENIGN CONDITIONS ACROSS THE REGION INTO THE LATTER HALF OF THE
WEEK. DRY NORTHERLY FLOW WILL HELP TO LIMIT FOG POTENTIAL TONIGHT
FROM BRISTOL BAY TO THE LOWER KUSKOKWIM VALLEY...BUT SOME PATCHY
FOG WILL BE POSSIBLE ACROSS THE KUSKOKWIM DELTA WITH LIGHTER WINDS
AND LINGERING LOW LEVEL MOISTURE IN PLACE. FOG POTENTIAL LOOKS TO BE
MORE WIDESPREAD ACROSS THE REGION BY WEDNESDAY NIGHT AS NORTHERLY
WINDS DIMINISH AND SUBSIDENCE TAKES HOLD BENEATH THE BUILDING
RIDGE...WITH DRY AIR IN PLACE AT THE SURFACE ACTING AS THE MAIN
LIMITING FACTOR.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE MOST ACTIVE WEATHER WILL REMAIN CONFINED TO THE WESTERN HALF
OF THE BERING THROUGH THURSDAY AS THE GALE FORCE FRONT BRINGING A
MIX OF RAIN AND SNOW TO THE WESTERN ALEUTIANS TRACKS SLOWLY
EASTWARD TOWARDS THE CENTRAL ALEUTIANS. HIGH PRESSURE WILL
CONTINUE TO SUPPORT BENIGN CONDITIONS OVER THE EASTERN HALF OF THE
BERING...WITH GUSTY NORTHERLY WINDS GRADUALLY DIMINISHING BY
WEDNESDAY AFTERNOON AS A LOW PASSING SOUTH OF THE ALASKA PENINSULA
MOVES AWAY FROM THE AREA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE LATTER PART OF THIS WEEK LOOKS TRANSITIONAL AS AN UPPER LEVEL
RIDGE QUICKLY BUILDS OVER THE SOUTHERN MAINLAND. HOWEVER...A PIECE
OF ENERGY COMING FROM THE NORTH PACIFIC WILL QUICKLY FOLLOW
BRINGING SOME MOISTURE UP INTO THE WESTERN GULF OF ALASKA. THIS
FEATURE WILL BE TRANSIENT ALONG WITH ANY WARM AIR THAT FOLLOWS THE
RIDGING AS A TROUGH FROM THE WESTERN BERING SEA PROGRESSES OVER
THE MAINLAND FROM WEST TO EAST AND BRINGS SOME COLD AIR ALONG WITH
IT. IT IS A LITTLE FAR OUT FOR CONFIDENCE BUT CURRENTLY LOOKS LIKE
THE FIRST LEGIT SNOW THREAT IN A WHILE OVER MOST AREAS. BEYOND THE
WEEKEND...GUIDANCE IS HINTING AT MORE AMPLIFICATION OF THE UPPER
LEVELS WHICH WOULD MEAN MORE WARM AIR AND ABOVE AVERAGE
TEMPERATURES BUT THE OVERALL PATTERN SEEMS PROGRESSIVE AND NOT
BLOCKY AT ALL SO IT COULD BE SHORT LIVED.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...131 132 150 155 175-178 185
FIRE WEATHER...NONE.

&&

$$

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