Area Forecast Discussion
Issued by NWS Anchorage, AK

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

000
FXAK68 PAFC 251428
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
528 AM AKST TUE NOV 25 2014

.ANALYSIS AND UPPER LEVELS...

LARGE AND SEASONABLY STRONG LOW PRESSURE CONTINUES TO SPIN IN
PLACE OVER THE FAR WESTERN BERING JUST EAST OF KAMCHATKA RUSSIA
THIS MORNING...WITH A STRONG AMPLIFYING RIDGE DOWNSTREAM BUILDING
NORTH AND EAST OVER THE SOUTHEASTERN BERING AND SOUTHWESTERN
MAINLAND OF ALASKA. AN ASSOCIATED WEAKENING OCCLUDED FRONT IS
MOVING NORTH AND EAST OVER THE NORTHERN AND EASTERN BERING IN THE
DIRECTION OF THE KUSKOKWIM DELTA REGION.

BETWEEN THE PARENT LOW OVER THE FAR WESTERN BERING AND THE
AMPLIFYING RIDGE OVER THE WESTERN MAINLAND...AN EXTREMELY ACTIVE
STORM TRACK PATTERN ASSOCIATED WITH THE VIGOROUS EAST ASIAN JET
EXTENDS FROM OFF THE COAST OF JAPAN NORTH AND EAST TO THE CENTRAL
BERING SEA.

A SEASONABLY STRONG 979 MB LOW WITH STORM FORCE WINDS IS
CURRENTLY LOCATED 430 NAUTICAL MILES SOUTH OF ADAK AND IS MOVING
NORTH TO NORTH-NORTHEAST IN THE GENERAL DIRECTION OF THE CENTRAL
ALEUTIANS AND CENTRAL BERING SEA.

MEANWHILE...A WEAK DISTURBANCE IS MOVING ALONG THE NORTH SIDE OF
THE BUILDING RIDGE OVER SOUTHWEST ALASKA AND HEADING TOWARD
SOUTHCENTRAL ALASKA THIS MORNING. THIS LOW IS RESPONSIBLE FOR SOME
LIGHT RAIN OVER INTERIOR BRISTOL BAY THIS MORNING...WITH GENERALLY
LOW CLOUDS AND FOG OTHERWISE IN THE LARGE-SCALE SUBSIDENCE
UNDERNEATH THE BUILDING RIDGE.

&&

.MODEL DISCUSSION...

THE GFS AND EUROPEAN MODELS HAVE THE BEST AGREEMENT AND WERE
PREFERRED WITH THE ACTIVE STORMY PATTERN FROM THE NORTHWEST
PACIFIC TO THE BERING SEA. BOTH MODELS HAVE INITIALIZED THE
PRINCIPLE WEATHER FEATURES IN THE BERING FAIRLY WELL...AND ANY
DIFFERENCES IN THE OVERALL TRACKS OF THE LOWS TO IMPACT THE REGION
ARE RELATIVELY MINOR.

THE FAR WESTERN BERING SURFACE AND PARENT LOW WILL SLOWLY WEAKEN
THROUGH WEDNESDAY NIGHT BEFORE BECOMING ABSORBED INTO A DEVELOPING
STORM WHICH IS CURRENTLY LOCATED NEAR JAPAN BUT WILL MOVE ACROSS
THE WESTERN AND CENTRAL ALEUTIANS INTO THE SOUTHERN BERING
WEDNESDAY INTO THURSDAY. THE CURRENT 979 MB LOW 430 NAUTICAL
MILES SOUTH OF THE ALEUTIANS WILL MOVE NORTH AND INTO THE CENTRAL
BERING SEA WEDNESDAY MORNING BEFORE BECOMING ABSORBED INTO THE
GENERAL CIRCULATION OF THE WESTERN BERING LOW. WHILE THIS IS
OCCURRING...THE RIDGE OVER THE NORTH PACIFIC AND EXTENDING NORTH
OVER THE WESTERN MAINLAND WILL CONTINUE TO AMPLIFY THROUGH
THURSDAY AND SLOWLY CRAWL EASTWARD...WITH ITS RIDGE AXIS LIKELY
REACHING THE COOK INLET REGION THURSDAY AFTERNOON AS A WARM FRONT
BEGINS TO PUSH NORTH AND EAST ACROSS THE BERING TOWARD THE
SOUTHWEST MAINLAND.


&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN WEATHER FEATURES OF IMPORTANCE FOR THE SHORT TERM
FORECAST PERIOD INCLUDE A SHORTWAVE TROUGH CROSSING INTERIOR
ALASKA AND A DIFFUSE UPPER TROUGH AND DISSIPATING SURFACE LOW
CROSSING THE GULF OF ALASKA. THE SHORTWAVE TROUGH MOVING THROUGH
TO THE NORTH IS BRINGING LIGHT SNOW AS IT CROSSES THE AREA TODAY.
THE TALKEETNA MOUNTAINS WILL SEE THE MOST ACCUMULATIONS DUE TO
UPSLOPE FLOW. THERE IS UNCERTAINTY IN THE SOUTHERN EXTENT OF
SNOWFALL. WITH WEAKER VERTICAL MOTION FURTHER TO THE SOUTH EXPECT
SNOW FALL ACCUMULATIONS TO TAPER OFF WITH MINIMAL ACCUMULATIONS BY
THE TIME YOU REACH THE SOUTHERN MAT VALLEY AND ANCHORAGE AREAS.
THE SNOW WILL PUSH EAST AND RAPIDLY TAPER OFF TONIGHT AS THE FLOW
ALOFT TURNS MORE NORTHWESTERLY AND DRIER AIR SPREADS ACROSS THE
AREA.

OFFSHORE FLOW WILL STRENGTHEN WEDNESDAY AS THE RIDGE ALOFT TO THE
WEST CONTINUES TO AMPLIFY AND PUSHES A 500 MB JET OVER CENTRAL
ALASKA. THE STRONGEST OFFSHORE GRADIENT WILL FORM BETWEEN HIGH
PRESSURE BUILDING INLAND OVER THE COPPER RIVER BASIN AND THE
SURFACE LOW DEPARTING THE EASTERN GULF MAKING THE VALDEZ AND
COPPER RIVER DELTA AREAS THE PRIMARY CONCERNS FOR WINDS. HOWEVER
WITH LIMITED COLD AIR ADVECTION AND PROGRESSIVE UPPER LEVEL FLOW
THIS EVENT WILL BE SHORT LIVED AND FAIRLY WEAK.

AS THE RIDGE BUILDS OVER NORTHERN COOK INLET THE ENVIRONMENT WILL
RAPIDLY STABILIZE AND BECOME FAVORABLE FOR DEVELOPMENT OF FOG.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TONIGHT THROUGH THURSDAY)...
A WARM FRONT ALONG THE EASTERN BERING IS PUSHING INTO THE WEST
COAST FROM HOOPER BAY TO CAPE NEWENHAM. PRECIPITATION ALONG THE
FRONT DEVELOPS AS SNOW EARLY THIS MORNING AND THEN MIXES WITH
RAIN LATE MORNING AS THE WARMER AIR MASS NUDGES INLAND.
PRECIPITATION MAINLY STAYS CONFINED TO THE KUSKOKWIM DELTA AS THE
ASSOCIATED LOW PUSHES INTO THE NORTHERN BERING. TEMPERATURES WILL
BE SLOWER TO WARM AT THE SURFACE AND THEREFORE ISOLATED POCKETS OF
FREEZING RAIN WILL BE POSSIBLE. PRECIPITATION TAPERS OFF THIS
EVENING AS THE FRONT DIMINISHES. FOG HAS DEVELOPED ACROSS A MOIST
STABLE BOUNDARY LAYER ACROSS THE KUSKOKWIM VALLEY AND INLAND AREAS
OF BRISTOL BAY...EXPECT IMPROVEMENT DURING THE AFTERNOON AND THEN
REDEVELOPMENT OVERNIGHT AS TEMPERATURES DROP.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TONIGHT THROUGH
THURSDAY)...
A WARM FRONT HAS SPREAD ACROSS THE CENTRAL BERING BRINGING RAIN
INTO THE NORTHERN WATERS. SLIGHTLY COOLER TEMPERATURES HAVE
WORKED INTO THE WESTERN BERING BEHIND THE MAIN FRONT BRINGING A
CHANCE FOR SCATTERED RAIN AND SNOW SHOWERS TODAY AS A WEAK
SHORTWAVE MOVES AHEAD OF LOW PRESSURE OFF OF THE KAMCHATKA
PENINSULA. THE MAIN CHALLENGE IN THE CURRENT FORECAST IS THE LOW
CURRENTLY HEADING TOWARD THE CENTRAL ALEUTIANS. THIS STORM LOOKS
TO MOVE UP FASTER THAN ORIGINALLY ANTICIPATED WITH STORM FORCE
WINDS AROUND THE CORE OF THE SYSTEM. THE STORM QUICKLY TRACKS INTO THE
CENTRAL ALEUTIANS THIS AFTERNOON MAKING IT TO THE PRIBILOFS ON
WEDNESDAY. MODERATE TO HEAVY RAIN WILL ACCOMPANY THIS SUBTROPICAL
SYSTEM WITH ANOTHER STRONG STORM SYSTEM TO FOLLOW WEDNESDAY NIGHT
AS THE NEXT FRONT PUSHES INTO WESTERN/CENTRAL ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

ON THU AND FRI MODELS AGREE THAT A BLOCKING UPPER RIDGE WILL BE
OVER MAINLAND AK WITH A A CUT-OFF LOW EMBEDDED IN A LARGE TROUGH
OVER THE BERING. ANOTHER RIDGE WILL BE NEAR KAMCHATKA WITH A
DEVELOPING TROUGH EAST OF JAPAN. ON FRI NIGHT A PATTERN CHANGE
BEGINS AS THE KAMCHATKA RIDGE BEGINS TO MIGRATE EAST. THIS WILL
PINCH OFF THE SOUTHERN PORTION OF THE BERING TROUGH...WHICH THEN
UNDERCUTS THE MAINLAND AK RIDGE. THIS BREAKDOWN OF THE BLOCKING
RIDGE WILL ALLOW THE KAMCHATKA RIDGE TO MOVE TO THE BERING ON SAT
AND WESTERN AK ON SUN.

AT THE SURFACE...HIGH PRESSURE WITH WEAK DISTURBANCES WILL REMAIN
OVER THE GULF THROUGH EARLY NEXT WEEK. A LOW IN THE BERING WILL
DRIFT NORTH TO THE BERING STRAIT AND DISSIPATE ON SAT...WHILE AN
ASSOCIATED FRONT MOVES INTO WESTERN AK. FINALLY...A LOW ASSOCIATED
WITH THE DEVELOPING TROUGH OFF JAPAN WILL APPROACH THE WESTERN
ALEUTIANS SAT INTO SUN. MODELS BEGIN TO LOSE AGREEMENT WHEN IT
COMES TO THE DISPOSITION OF THIS LOW. FOR NOW THE FORECAST REMAINS
WITH THE WPC SOLUTION OF KEEPING THE LOW SOUTH OF THE BERING.

FORECAST CONFIDENCE REMAINS HIGH THAT GENERALLY DRY
CONDITIONS ARE EXPECTED FOR SOUTHCENTRAL THROUGH MON...ALTHOUGH
RAIN AND SNOW MAY AFFECT COASTAL ZONES BY THE WEEKEND. CONFIDENCE
IS ALSO HIGH THAT RAIN AND SNOW SHOWERS WILL BEGIN TO AFFECT
SOUTHWEST AK BEGINNING ON FRI. THE ALEUTIANS WILL ALSO HAVE RAIN
INTO EARLY NEXT WEEK...AND WINDS ARE EXPECTED TO INCREASE
BEGINNING THIS WEEKEND.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 165 171 175 177 178
         STORMS 170 172 173 174 176 179 181 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JER/SEB
LONG TERM...DS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.