Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 250305
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
605 PM AKST MON NOV 24 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS A DEEP (503 DM AT 500 MB) UPPER LOW OVER THE SOUTHWEST
BERING SEA. THERE IS A BUILDING RIDGE OVER THE EASTERN BERING.
THERE IS A BROAD NORTH/SOUTH TROUGH OVER THE ALASKA MAINLAND AND
THE GULF OF ALASKA. THERE IS A LONG OCCLUDED FRONT ASSOCIATED WITH
THE SOUTHWEST BERING LOW THAT STRETCHES FROM THE KAMCHATKA
PENINSULA EAST INTO THE CENTRAL BERING AND THEN SOUTHEAST TO NEAR
ATKA...THEN AS A COLD FRONT SOUTHWEST INTO THE NORTH PACIFIC.
THERE IS SOME MOISTURE ASSOCIATED WITH THE MAINLAND/GULF TROUGH
PRODUCING SOME ISOLATED/SCATTERED SHOWERS OVER THOSE AREAS.

&&

.MODEL DISCUSSION...
THE MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH 60 HOURS
(WEDNESDAY AFTERNOON). THE MAIN DIFFERENCES INVOLVE THE SURFACE
LOWS OUT WEST. THE 12Z MODELS ARE IN MUCH BETTER AGREEMENT THAN
PREVIOUS RUNS WITH A LOW THAT FORMS ON THE COLD FRONT OVER THE
NORTH PACIFIC AND RACES NORTH ACROSS THE ALEUTIANS AND INTO THE
BERING SEA TUE NIGHT INTO EARLY WEDNESDAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 2)...

A DISTURBANCE ACROSS CENTRAL ALASKA WILL BEGIN TO MOVE EAST
TUESDAY...WITH INCREASING MOISTURE SPREADING NORTH INTO THE
SUSITNA AND MATANUSKA VALLEY. THE BEST CHANCE FOR
ACCUMULATING LIGHT SNOW WILL BE ALONG THE TALKEETNA MOUNTAINS
NORTHWARD TOWARDS THE ALASKA RANGE...WITH LIGHTER AND MORE
SPORADIC SNOW SHOWERS TOWARD THE CHUGACH MOUNTAINS AND ANCHORAGE.
THE ATMOSPHERE WILL RAPIDLY DRY OUT ON WEDNESDAY AS AN UPPER RIDGE
BUILDS OVER SOUTHCENTRAL. NORTHWEST FLOW ALOFT WILL PROMOTE AN
OFFSHORE PRESSURE GRADIENT...WITH INCREASING GAP WINDS NEAR THE
GULF COAST. THE STRONGEST WINDS WILL BE AROUND PRINCE WILLIAM
SOUND AND TOWARD THE COPPER RIVER BASIN.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TONIGHT THROUGH THURSDAY)...
STRONG INVERSIONS THAT HAVE DEVELOPED FROM THE KUSKOKWIM VALLEY
INTO BRISTOL BAY WILL CAUSE FOR PERSISTENT FOG AND STRATUS IN LOW
LYING AREAS AT LEAST UNTIL TUESDAY...AND POSSIBLY CONTINUING INTO
WEDNESDAY. THIS STRATUS WILL KEEP OVERNIGHT LOWS SLIGHTLY WARMER
THAN PREVIOUSLY EXPECTED...ESPECIALLY IN THE CENTRAL KUSKOKWIM
VALLEY. PRECIPITATION WILL BE LARGELY LIMITED TO A FRONTAL SYSTEM
THAT WILL BRING RAIN AND SNOW TO THE KUSKOKWIM DELTA TUESDAY
AFTERNOON INTO MONDAY MORNING. OTHERWISE THE WEATHER WILL REMAIN
FAIRLY QUIET WITH RIDGING CONTINUING UNTIL EARLY THURSDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TONIGHT THROUGH
THURSDAY)...
THE FRONTAL SYSTEM ASSOCIATED WITH THE LOW CENTERED NORTHWEST OF
SHEMYA WILL BECOME LOW COMPLEX OVER MUCH OF THE BERING THROUGH MID
WEEK. THERE IS NOW MUCH BETTER AGREEMENT THAT A LOW APPROACHING
ATKA LATE TUESDAY WILL BRING RAIN AND GUSTY GALE FORCE WINDS TO THE
CENTRAL TO EASTERN ALEUTIANS THROUGH WEDNESDAY AFTERNOON. YET
ANOTHER GALE FORCE LOW WILL THEN QUICKLY DEVELOP BEHIND IT ON
WEDNESDAY...WHICH WILL SPREAD RAIN AND GALE FORCE WINDS INTO THE
BERING AND APPROACHING THE PRIBILOF ISLANDS BY THURSDAY.


&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
MODELS REMAIN IN GOOD AGREEMENT WITH A HIGH AMPLITUDE BLOCKING
RIDGE DEVELOPING OVER MAINLAND AK AND THE GULF WEDNESDAY...WITH A
CUT-OFF LOW EMBEDDED IN A TROUGH OVER THE BERING SEA. THIS CREATES
FAIRLY HIGH CONFIDENCE THAT SOUTHCENTRAL WILL REMAIN DRY BENEATH
THE RIDGE THROUGH THE END OF THE WEEK. THE RIDGE WILL REMAIN IN
PLACE INTO FRIDAY WHEN THE BERING CUT-OFF LOW CUTS THROUGH THE
RIDGE...CHANGING THE DRIER AND COOLER HIGH AMPLITUDE PATTERN INTO
ONE WITH SHORTWAVES TRACKING THROUGH THE FORECAST AREA. AS A
RESULT...AREAS AROUND THE SOUTHWEST MAINLAND AND NORTHERN GULF
COAST MAY EXPERIENCE SOME SHOWERY CONDITIONS BEGINNING FRIDAY AND
PERSISTING THROUGH THE WEEKEND. AS IS TYPICAL WITH WAVES MOVING
THROUGH RELATIVELY ZONAL FLOW...THERE IS LESS CONFIDENCE IN THE
TIMING AND STRENGTH OF THESE WAVES AS THEY TRAVERSE THE AREA.

THE FORECAST FOR THE BERING IS OF LOWER CONFIDENCE DUE TO
CONTINUED TIMING UNCERTAINTY. HOWEVER...MODELS HAVE COME SLIGHTLY
CLOSER TO A SOLUTION REGARDING THE COMPLEX LOW AND MULTIPLE
VORTICIES THAT TRACK THROUGH THE CENTRAL/EASTERN ALEUTIANS AND
BERING BEFORE CONSOLIDATING OVER THE BERING SEA THURSDAY. MODELS
HAVE STARTED TO COME CLOSER TO THE EXPECTED MIDDLE GROUND SOLUTION
BETWEEN THE GFS AND ECMWF FROM PREVIOUS RUNS. THIS SOLUTION WILL
TRACK THE LOW IN THE NORTHERN PACIFIC THROUGH INTO THE CENTRAL
BERING BY THURSDAY...KEEPING PRECIPITATION AND GUSTY WINDS AROUND
THE AREA THROUGH THE END OF THE WEEK. A NEW LOW OFF THE COAST OF
JAPAN WILL APPROACH THE WESTERN/CENTRAL ALEUTIANS
SATURDAY...BRINGING ANOTHER WAVE OF RAIN AND GUSTY WINDS TO THE
CHAIN THROUGH EARLY NEXT WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 170 172 173 174 175 176 178 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...JA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...TP



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