Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 251304
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
504 AM AKDT MON AUG 25 2014

.ANALYSIS AND UPPER LEVELS...
THE COLD CORE STACKED SYSTEM IN THE EASTERN BERING SEA CONTINUES
TO DRIVE THE ACTIVE WEATHER ACROSS MUCH OF THE GREAT LAND THIS
MORNING. THE FRONTAL BOUNDARY ASSOCIATED WITH THE LOW HAS PUSHED
WELL INLAND AND STRETCHES FROM THE CANADIAN YUKON THROUGH THE
KUSKOKWIM RANGE INTO A BACK-BENT OCCLUSION THAT CROSSED THE FAR
TIP OF THE ALASKA PENINSULA. CURRENTLY THE TWO FACETS OF THE
SYSTEM FORCING ONGOING SHOWERS ARE THE PRESENCE OF COLD AIR
ALOFT...TEMPERATURES IN THE -20C TO -25C RANGE WITHIN THE UPPER
LOW...AND SEVERAL EMBEDDED VORTICITY MAXIMA WITHIN THE
SOUTHWESTERLY FLOW ON THE DOWNSTREAM SIDE OF THE TROUGH. WINDS ARE
RELATIVELY LIGHT ACROSS THE SOUTHCENTRAL WITH PLENTY OF LOW LEVEL
MOISTURE AFTER THE PREVIOUS RAINFALL...MAKING FOR LOTS OF
LINGERING LOW STRATUS AND PATCHY FOG. FURTHER OUT WEST...MUCH OF
THE SAME WITH THE EXCEPTION BEING STRONGER WINDS IN THE BERING.
PRESSURE RISES BEHIND THE BACK-BENT OCCLUSION ARE PROMOTING GALE
FORCE GUSTS.

&&

.MODEL DISCUSSION...
IN THE UPPER LEVELS GUIDANCE HANDLES THE UPCOMING SYNOPTIC
PATTERN QUITE SIMILARLY. THERE ARE SOME MINOR DIFFERENCES WITH HOW
THE CURRENT SYSTEM WEAKENS AND EXITS BUT THOSE ARE ALL DOWNSTREAM
OF OUR AREA AND SHOULD NOT BE SIGNIFICANT TO THE FORECAST. THE
GENERAL CONSENSUS IS THAT THE CURRENT SYSTEM WILL EXIT TO THE EAST
WITH NO SIGNIFICANT FEATURES UNTIL ANOTHER UPPER LOW DROPS IN FROM
EASTERN RUSSIA...EVENTUALLY CROSSING THE ALASKA PENINSULA INTO THE
GULF OF ALASKA.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...CATEGORICAL SHOWERS WILL BE THE FORECAST FOR
MOST AREA. PLENTIFUL COLD AIR ALOFT COMBINED WITH THE INCOMING
SHORTWAVE TROUGH WILL MAKE FOR A ROUND OF SHOWERS THIS MORNING
ACROSS THE MAINLAND. IT APPEARS AS IF THERE WILL BE A SHORT BREAK
IN THE LATE MORNING/EARLY AFTERNOON TIME PERIOD AS LIFT
DISSIPATES...BUT AFTERNOON INSTABILITY ALONG THE MOUNTAINS SHOULD
PROVIDE ANOTHER ROUND OF SHOWERS. INTO THE EVENING AND OVERNIGHT
HOURS A WEAK TROUGH LIES OVER COOK INLET KEEPING THE KENAI
PENINSULA THROUGH THE MATANUSKA VALLEY IN A CHANCE OF RAIN
SHOWERS. AFTER TONIGHT THE CHANCE FOR RAIN DIMINISHING FOR MOST
AREAS OUTSIDE OF SOME DIURNAL MOUNTAIN SHOWERS.

SOUTHWEST ALASKA...THE BULK OF THE UPPER TROUGH IS EXITING THE
AREA THIS MORNING. HIGH SURFACE MOISTURE AND PARTIAL CLEARING
OVERNIGHT HAS PROMOTED FOG DEVELOPMENT...ESPECIALLY IN RIVER
VALLEYS. SHOWERS WILL STILL REMAIN IN THE FORECAST THIS AFTERNOON
AND EVENING AS THE UPPER TROUGH EXITS BUT OVERALL THE MAINLAND
SHOULD SEE A DRYING TREND. AFTERNOON SHOWERS OVER THE
ALASKA RANGE WILL REMAIN POSSIBLE OVER THE NEXT COUPLE DAYS.

BERING SEA/ALEUTIANS...SHOWERS WILL BE WANING TODAY AS THE UPPER
LOW EXITS. GUSTY NORTHWESTERLY WINDS WILL CONTINUE THROUGH THE DAY
BEFORE LIGHTENING UP IN THE AFTERNOON/EVENING. A FAST MOVING
LOW/FRONT WILL AFFECT THE CHAIN TODAY THROUGH WEDNESDAY FROM WEST
TO EAST.


&&

.LONG TERM FORECAST...
AN UPPER LEVEL WEAK RIDGE WILL BUILD OVER THE NORTHERN GULF OF
ALASKA COASTLINE BY THURSDAY RESULTING IN THE TURNAGAIN ARM WINDS
PICKING UP THROUGH FRIDAY MORNING. THE INTERIOR OF THE SOUTHEAST
MAINLAND WILL HAVE DRY CONDITIONS THROUGH FRIDAY WITH A CHANCE OF
FOG FORMING AS THE RIDGE BUILDS INTO THE AREA. A LOW PRESSURE
SYSTEM WILL TRACK SOUTH OF KODIAK ISLAND BY THURSDAY MORNING. THIS
SYSTEM WILL BRING RAIN/STRATUS FOR KODIAK ISLAND AND THE NORTHERN
GULF AS THE LOW TRACKS TOWARD HAIDA GWAII BY FRIDAY EVENING. A
FRONTAL BOUNDARY WILL APPROACH THE ALASKA PENINSULA AND MOVE TO
THE NORTHEAST UP THROUGH THE COOK INLET BRINGING RAIN TO THE
REGION THROUGH NEXT WEEKEND. THE WESTERN BERING SEA WILL HAVE A
LOW PRESSURE SYSTEM APPROACHING THE AREA WITH THE FRONTAL
BOUNDARY POSITIONED THROUGH THE WESTERN ALEUTIANS BY THURSDAY.
THE CENTRAL TO EASTERN ALEUTIANS WILL BE UNDER AN UPPER LEVEL
RIDGE RESULTING IN LIGHT WINDS WITH STRATUS AND FOG BEFORE THE
RIDGE MOVES TO THE SOUTHEAST BY EARLY FRIDAY MORNING. THE LOW
ENTERING THE WESTERN ALEUTIANS WILL WILL TRACK THROUGH THE BERING
SEA AND REACH THE SOUTHWEST ALASKA COASTLINE BY SATURDAY AFTERNOON.
THIS SYSTEM WILL BRING WIDESPREAD RAIN WITH STRATUS AND FOG GOING
INTO NEXT WEEKEND.


&&

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

&&

$$
MTL
AUG 14


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