Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 221334
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
534 AM AKDT FRI AUG 22 2014

.ANALYSIS AND UPPER LEVELS...

THE GENERAL CHARACTERISTICS OF THE UPPER AIR PATTERN CONTINUE TO
REMAIN THE SAME FROM PREVIOUS DAYS...WITH A CLOSED UPPER LOW OVER
THE WESTERN BERING SEA...A LARGE EASTERN PACIFIC RIDGE EXTENDING
NORTH INTO THE ALASKA PANHANDLE...AND AN ACTIVE SUBTROPICAL JET
STREAM WRAPPING AROUND THE PERIPHERY OF THE AFOREMENTIONED CLOSED
LOW. WEAK SHORTWAVE DISTURBANCES ARE EJECTING OFF THE SUBTROPICAL
JET AS THEY INTERACT WITH THE EASTERN PACIFIC HIGH...WITH TWO OF
THESE WAVES TRACKING INTO THE GULF OF ALASKA. WITH TIME...THE
WESTERN BERING LOW WILL BEGIN TO PROPAGATE EAST AS IT MERGES WITH
THE SUBTROPICAL JET...WITH AN ASSOCIATED WARM FRONT TRACKING INTO
SOUTHERN ALASKA LATE SATURDAY AND SUNDAY.

&&

.MODEL DISCUSSION...

THE NUMERICAL MODELS ARE IN DECENT AGREEMENT WITH THE LARGE SCALE
PATTERN THROUGH TUESDAY...BUT THEY CONTINUE TO STRUGGLE WITH THE
TIMING AND STRENGTH OF A PACIFIC FRONT MOVING INTO SOUTHERN ALASKA
THIS WEEKEND. THAT SAID...THE GUIDANCE HAS COME INTO MUCH BETTER
AGREEMENT FROM PREVIOUS DAYS...ALTHOUGH THE ECMWF CONTINUES TO BE
THE FASTEST. THE FORECAST WILL CONTINUE TO MAKE USE OF A BLEND OF
THE GFS AND ECMWF TO ACCOUNT FOR TIMING DIFFERENCES.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
A FAST MOVING DISTURBANCE MOVING IN FROM THE GULF OF ALASKA IS
SPREADING MID AND HIGH CLOUDS OVER SOUTHCENTRAL THIS MORNING...AND
WILL PROVIDE JUST ENOUGH LIFT TO ENHANCE SHOWER ACTIVITY THIS
AFTERNOON...ESPECIALLY OVER THE MOUNTAINS. A LIGHT SOUTH TO
SOUTHWEST STEERING FLOW WILL HELP MOVE SOME SHOWERS OFF THE
MOUNTAINS INTO LOWER ELEVATION LOCATIONS. PATCHY FOG NEAR COOK
INLET WILL DIMINISH RAPIDLY AFTER MORNING. BY SATURDAY...SHORTWAVE
RIDGING WILL BUILD IN...WITH CLEARING SKIES AND ONLY ISOLATED
SHOWERS OVER THE MOUNTAINS. A FRONT MOVING INTO THE SOUTHWEST GULF
WILL SPREAD RAIN INTO KODIAK AND THE KENAI COAST SATURDAY
AFTERNOON AND EVENING...THEN SPREAD INLAND LATE SUNDAY INTO
MONDAY.

SOUTHWEST ALASKA...
A WEAK DISTURBANCE ALOFT IS CURRENTLY SPREADING MID AND HIGH
CLOUDS OVER THE REGION TODAY. THERE WILL BE ENOUGH DIURNAL HEATING
TO HELP INITIATE CONVECTIVE SHOWERS IN THE AFTERNOON...BUT THE
CLOUDS WILL HELP LIMIT INSTABILITY ENOUGH TO KEEP COVERAGE
ISOLATED TO SCATTERED...AND MAINLY OVER THE MOUNTAINS. A WEAK
FRONT WILL MOVE INTO THE EASTERN BERING SATURDAY...WITH CLOUDS
OVERSPREADING SOUTHWEST. THE BEST CHANCES FOR RAIN WILL REMAIN
RELEGATED TO COASTAL LOCATIONS NEAR BRISTOL BAY...AND ALONG THE
ALASKA PENINSULA. SOUTHEAST WINDS...ESPECIALLY THROUGH GAPS IN THE
ALASKA AND ALEUTIAN RANGES...WILL INCREASE AS THE FRONT
APPROACHES...AND WILL ALSO HELP DOWNSLOPE SHADOW LOCATIONS IN THE
LEE OF THE ALASKA AND ALEUTIAN RANGES. A MUCH STRONGER FRONT
MOVES INTO SOUTHWEST ON SUNDAY...WITH WIDESPREAD RAIN MOVING INTO
THE AREA.

BERING SEA/ALEUTIANS...

RAIN WILL OVERSPREAD THE CENTRAL ALEUTIANS AND PRIBILOF ISLANDS
TODAY AND TONIGHT AS A LOW MAKES EASTWARD PROGRESSION...FOLLOWED
BY THE EASTERN ALEUTIANS SATURDAY. SHOWERS WILL LINGER ACROSS THE
CENTRAL AND EASTERN BERING THROUGH SUNDAY AS THE LOW MOVES EAST.
WEAK HIGH PRESSURE OVER THE WESTERN BERING WILL LINGER INTO
SATURDAY BEFORE ANOTHER LOW SPREADS RAIN INTO THE AREA SUNDAY AND
MONDAY.

&&

.LONG TERM FORECAST (TUESDAY AUG 26TH - FRI AUG 29)...

ON TUESDAY...THE REMNANTS OF THE BERING LOW WILL BE TRACKING INTO
THE YUKON...LEAVING SHOWERS AND CLOUDS OVER MOST OF SOUTHERN
ALASKA...ESPECIALLY OVER SOUTHCENTRAL. THERE IS QUITE A BIT OF
DISCREPANCY WITH THE TRACK OF A POTENTIAL LOW MOVING FROM THE
BERING INTO SOUTHERN ALASKA LATE WEEK...WITH THE ECMWF AND
CANADIAN GDPS FAVORING A SPLIT FLOW SCENARIO WITH THE LOW
REMAINING DISPLACED FROM THE NORTHERN STREAM JET...WHILE THE GFS
FAVORS A PHASED AND STRONG LOW. WITH THAT SAID...ALL THE GLOBAL
NUMERICAL GUIDANCE IS IN GOOD AGREEMENT WITH THE DEVELOPMENT OF A
LARGE VORTEX OVER NORTHERN ALASKA AND THE BEAUFORT SEA...KEEPING
SOUTHERN ALASKA UNDER THE THREAT OF INCREASED PRECIPITATION
CHANCES AS WEAK WAVES ALOFT ROTATE OVER THE REGION. IN OTHER
WORDS...NO SIGNIFICANT WARM OR DRY PERIODS ARE EXPECTED THROUGH
THE EXTENDED.

&&

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

$$

AHSENMACHER AUG 14


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