Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 281733 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
506 AM AKDT SUN SEP 28 2014

..STRONG WIND EVENT COMING TO COASTAL SOUTHCENTRAL ALASKA MONDAY
AND TUESDAY...


.ANALYSIS AND UPPER LEVELS...

A PAIR OF STACKED LOW PRESSURE SYSTEMS SOUTH OF THE STATE CONTINUE
AS THE PRIMARY DRIVERS OF SIGNIFICANT WEATHER ACROSS THE ANCHORAGE
OFFICE AREA OF RESPONSIBILITY...AT LEAST FOR A FEW MORE
HOURS. THE FIRST LOW IS LOCATED ALONG THE BORDER OF THE GULF OF
ALASKA WITH THE NORTHEAST PACIFIC..AND THE OTHER IS A FEW HUNDRED
MILES SOUTH OF THE WESTERN AND CENTRAL ALEUTIANS.

THE FIRST LOW IS CURRENTLY BRINGING RAIN AND SOME SNOW AS WELL AS
LOCALLY DENSE FOG TO EASTERN PORTIONS OF THE COPPER RIVER BASIN
ZONE...AND DIMINISHING SHOWER COVERAGE TO THE VICINITY OF PRINCE
WILLIAM SOUND AS A SHORTWAVE DISTURBANCE BEGINS TO SHEAR APART
OVER THE AREA AND THE PARENT LOW BEGINS TO MOVE EAST FURTHER AWAY
FROM THE AREA.

THE SECOND LOW IS PUSHING A FRONT TO JUST SOUTH OF THE CENTRAL
ALEUTIANS MAINLY BETWEEN ADAK AND SHEMYA AND BRINGING GALE-FORCE
WINDS TO THE COASTAL WATERS ALONG AND JUST SOUTH OF THE ISLANDS.

MEANWHILE...THE NEXT SYSTEM...A FAIRLY POTENT UPPER LEVEL TROUGH
PUSHING A SURFACE FRONT ACROSS THE NORTHERN BERING...WILL BE THE
PRIMARY WEATHER MAKER OVER THE SOUTHERN MAINLAND THE NEXT COUPLE
OF DAYS...MAINLY IN THE FORM OF RAIN AND/OR SNOW NEAR THE ALASKA
RANGE...AND IN THE FORM OF STRONG OFFSHORE OUTFLOW WINDS OVER
SOUTHERN AND COASTAL AREAS OF THE STATE.


&&

.MODEL DISCUSSION...

MODELS REMAIN TIGHTLY CLUSTERED AROUND THE MODEL CONSENSUS
SOLUTION...YIELDING FAIRLY HIGH CONFIDENCE IN THE OVERALL
FORECAST FOR THE UPCOMING WEEK.


&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...

THE SHORTWAVE DISTURBANCE BRINGING SHOWERS TO PRINCE WILLIAM SOUND
AND RAIN AND SNOW TO THE COPPER RIVER BASIN WILL WEAKEN THROUGH
TODAY AS THE ENERGY SPLITS AND SHEARS WITH THE PARENT LOW MOVING
TOWARD HAIDA GWAII (QUEEN CHARLOTTE ISLANDS). SHORTWAVE RIDGING
AND WEAK OFFSHORE FLOW WILL RESULT IN BENIGN WEATHER CONDITIONS
OVER MOST OF THE REST OF THE REGION TODAY...WITH MOSTLY CLEAR
SKIES AND LIGHT WINDS.

CONDITIONS BEGIN TO CHANGE THIS EVENING AS NORTHWESTERLY WINDS
BEGIN TO INCREASE ALOFT AHEAD OF THE SYSTEM APPROACHING FROM THE
NORTHERN BERING. THE COMBINATION OF BUILDING HIGH PRESSURE OVER
THE SOUTHWEST MAINLAND AND SURFACE LOW PRESSURE DEVELOPMENT OVER
THE NORTHERN GULF IN ASSOCIATION WITH THE APPROACHING UPPER LEVEL
LOW WILL RESULT IN INCREASING OFFSHORE OUTFLOW
WINDS...PARTICULARLY STRONG NEAR WHITTIER...BUT ALSO IMPACTING
SEWARD...KODIAK...AND NORTHEAST PRINCE WILLIAM SOUND.

WHILE WINDS WILL LIKELY BE QUITE STRONG...THE LACK OF A TRUE
ARCTIC AIR MASS WILL LIKELY HELP RESULT IN WINDS REMAINING BELOW
HIGH WIND CRITERIA...SO WATCHES AND/OR WARNINGS ARE NOT
ANTICIPATED AT THIS TIME. HOWEVER...THESE OUTFLOW WINDS ARE LIKELY
TO PERSIST FROM LATE TONIGHT INTO TUESDAY (DEPENDING ON LOCATION)
BEFORE TOTALLY RELAXING.

WITH THE UPPER LEVEL SYSTEM HAVING IMPRESSIVE DYNAMICS...THE OTHER
CONCERN WILL BE FOR THE DEVELOPMENT OF SNOW OVER AREAS OF THE
SOUTHERN INTERIOR NOT USUALLY IMPACTED BY THE OFFSHORE/OUTFLOW
WINDS. THIS WILL MAINLY BE IN HIGHER ELEVATION AREAS AWAY FROM
CHANNELED TERRAIN. MINOR SNOW ACCUMULATIONS OF WET SNOW COULD OCCUR
IN THESE LOCATIONS...MAINLY ALONG THE DENALI HIGHWAY AND THE
NORTHEAST COPPER RIVER BASIN. A FRESH COATING OF SNOW ALONG THE
TALKEETNA MOUNTAINS OVERLOOKING THE MATANUSKA VALLEY IS ALSO QUITE
POSSIBLE.

THIS SYSTEM WILL ALSO BRING GUSTY WINDS TO ANCHORAGE MOST LIKELY
MONDAY AFTERNOON INTO EVENING AS CLEAR SKIES AND INCREASING COLD
AIR ALOFT ALLOW FOR INCREASING INSTABILITY AND STRONG MIXING.


SOUTHWEST ALASKA...

AS THE APPROACHING UPPER TROUGH PUSHES A COLD FRONT ACROSS
NORTHERN AREAS TODAY AND TONIGHT...A FEW LIGHT RAIN SHOWERS CAN BE
EXPECTED. AS COLDER AIR MOVES INTO THE AREA TONIGHT INTO
MONDAY...THESE RAIN SHOWERS WILL CHANGE OVER TO SNOW ESPECIALLY
TOWARD THE ALASKA RANGE. OTHERWISE...NORTHWESTERLY OFFSHORE
OUTFLOW WINDS WILL IMPACT AREAS ALONG THE WESTERN SLOPES OF THE
ALASKA RANGE SOUTH INTO MAINLY INTERIOR BRISTOL BAY.
OTHERWISE...SEASONABLY COOL BUT BENIGN WEATHER IS EXPECTED AS
HIGH PRESSURE BUILDS OVER THE REGION THROUGH EARLY NEXT WEEK.



BERING SEA/ALEUTIANS...

MOST OF THE ACTION THE NEXT COUPLE OF DAYS WILL BE IN CENTRAL
ALEUTIANS AS LOW PRESSURE DRIFTS SLOWLY EAST WELL TO THE SOUTH OF
THE CHAIN...WITH A FRONTAL BOUNDARY BRINGING GALE FORCE WINDS
MAINLY TO THE ADJACENT PACIFIC COASTAL WATERS AND STEADY RAIN TO
THE ADAK AND ATKA AREAS. THIS SYSTEM WILL PUSH SOUTH AND EAST INTO
THE PACIFIC BY LATE MONDAY INTO TUESDAY BRINGING DECREASING WINDS
AND IMPROVING SKIES.


&&

.LONG TERM FORECAST(WED OCT 1ST - SAT OCT 4)...

CONFIDENCE CONTINUES TO INCREASE IN THE EXTENDED RANGE PERIOD AS
AN IMPRESSIVE HIGH LATITUDE BLOCKING HIGH FORMS OVER THE BERING
SEA. THIS FEATURE WILL HELP SUPPORT THE DEVELOPMENT OF AN ARCTIC
TROUGH ACROSS MAINLAND ALASKA...WITH PERSISTENT OFFSHORE FLOW AND
COOLER AND DRIER AIR INFILTRATING SOUTHERN ALASKA. PRECIPITATION
THREATS THROUGH THURSDAY WILL BE RELEGATED TO THE NORTHERN SLOPES
OF THE ALASKA RANGE AS WAVE DISTURBANCES IN NORTHWEST FLOW TRACK
OVER THE REGION. THE TRACK OF A NORTH PACIFIC LOW MOVING INTO THE
GULF OF ALASKA WILL ALLOW ARCTIC AIR TO INFILTRATE MOST OF
SOUTHERN ALASKA BY SATURDAY...WITH THE THREAT FOR PRECIPITATION
ACROSS PARTS OF THE COPPER BASIN AS THE LOW TRACKS INTO THE
EASTERN GULF. THIS FORECAST WILL TAKE A CONSERVATIVE MIDDLE GROUND
APPROACH WITH THE GULF LOW LATE WEEK...YIELDING CHANCE
PRECIPITATION THREATS MAINLY ACROSS THE COPPER BASIN...AND MAINLY
DRY AND COLD ELSEWHERE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...130 131 150 174-177.
FIRE WEATHER...NONE.

&&

$$

CC SEP 14



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