Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 240721 AAA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
1021 PM AKST SUN NOV 23 2014

UPDATED SOUTHCENTRAL SHORT TERM DISCUSSION

ANALYSIS AND UPPER LEVELS...
A 980S MB LOW SE OF SAND POINT IS STACKED UNDER THE UPPER CENTER
AND IS SLOWLY DRIFTING EAST AND WEAKENING. WAVES EMBEDDED IN THE
BROAD UPPER LEVEL CYCLONIC FLOW PRODUCED RAIN SHOWERS ACROSS THE
GULF AND AK PEN WITH MIXED SHOWERS TO SNOW SHOWERS OVER BRISTOL
BAY AND THE REMAINDER OF SOUTHCENTRAL. AN ELEVATED WARM LAYER AND BELOW
FREEZING SURFACE TEMPS PRODUCED ISOLATED POCKETS OF LIGHT FREEZING
RAIN OVER THE EASTERN BRISTOL BAY ZONE THIS MORNING. THE KING
SALMON NEXRAD SHOWED ANOTHER BATCH OF MOISTURE MOVING NORTH THIS
AFTERNOON...SO THE THREAT OF FREEZING RAIN MAY CONTINUE UNTIL
SURFACE TEMPS RISE ABOVE FREEZING THIS AFTERNOON. GUSTY NORTHWEST
WINDS ON THE BACKSIDE OF LOW SOUTH OF THE AK PEN CONTINUE ALONG
THE WESTERN AK PEN AND EAST ALEUTIANS. GUSTY EAST WINDS CONTINUE
ACROSS THE NORTH GULF WITH NE WINDS OVER THE WESTERN GULF AND
NORTHERLY GAP FLOWS ACROSS THE MATANUSKA VALLEY.

MODEL DISCUSSION ...
THOUGH THERE ARE SOME MODEL DIFFERENCES THROUGH THE SHORT TERM
(TUE AFTERNOON) THE IMPACTS ARE FAIRLY SIMILAR. THE TIMING OF THE
FRONT ACROSS THE BERING SEA WITH ACCOMPANYING GALES AND RAIN ARE
SIMILAR AS WELL AS SHOWERS WITH WAVES MOVING NORTH ACROSS THE GULF
AND SOUTHCENTRAL. SIGNIFICANT DIFFERENCES DEVELOP OUT WEST WITH
THE TIMING OF THE NEXT WAVE WHICH APPROACHES THE EASTERN ALEUTIANS
TUE NIGHT. THE LAST 2 RUNS OF THE EC HAVE COME IN SIGNIFICANTLY
FURTHER SOUTH WITH THIS FEATURE...AND NOW KEEP IT ENTIRELY OUT OF
THE AOR. THE GFS/NAM/GEM ON THE OTHER HAND ARE IN GOOD AGREEMENT
WITH A GALE FORCE LOW APPROACHING THE EASTERN ALEUTIANS BY LATE
TUESDAY NIGHT. THIS FURTHER NORTH SOLUTION WAS PREFERRED FOR THE
AFTERNOON PACKAGE AS IT WAS CLOSER TO THE CURRENT FORECAST. LATER
RUNS WILL HOWEVER NEED TO BE MONITORED...AS AGREEMENT IN
SOUTHERLY SOLUTION WOULD RESULT IN A SIGNIFICANT CHANGE TO THE
FORECAST.

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A WEAK FRONT ALONG THE NORTH GULF COAST WILL KEEP SHOWER ACTIVITY
MOST ACTIVE ACROSS COASTAL LOCATIONS TONIGHT...WITH MUCH MORE
SPORADIC AND LIGHT SHOWER ACTIVITY INLAND. RAIN AND SNOW SHOWERS
WILL BE MOST ACTIVE FROM EASTERN PRINCE WILLIAM SOUND
EASTWARD...WITH ACCUMULATING SNOW ACROSS PORTIONS OF THOMPSON PASS
INTO THE SOUTHERN COPPER RIVER BASIN. EVENTUALLY THE LOW WILL
TRACK EAST TOMORROW...WITH SHOWERS GRADUALLY DIMINISHING THROUGH
TUESDAY NIGHT. MINOR ACCUMULATIONS WILL BE POSSIBLE ACROSS FAVORED
UPSLOPE REGIONS IN THE TALKEETNA MOUNTAINS AND NORTH OF TALKEETNA
THROUGH BROAD PASS INTO MONDAY NIGHT. HIGH PRESSURE BUILDS IN
WEDNESDAY AND THURSDAY...BRINGING DRY WEATHER TO ALL OF
SOUTHCENTRAL.

SHORT TERM FORECAST SOUTHWEST ALASKA (TONIGHT THROUGH WEDNESDAY)...
A WEAK SHORTWAVE ALOFT WILL BRING RAIN FROM THE ALASKA
PENINSULA...BECOMING SNOW MIXED WITH RAIN AS IT STRETCHES INTO
WESTERN BRISTOL BAY. THIS WILL BRING ACCUMULATING SNOW TO WESTERN
BRISTOL BAY THIS EVENING...ESPECIALLY IN THE DILLINGHAM
AREA...WHERE COLD AIR ALOFT STILL EXISTS. THERE IS A SLIGHT CHANCE
THAT ENOUGH WARM AIR ALOFT WILL REACH WESTERN BRISTOL BAY LATE
TONIGHT TO CREATE AREAS OF FREEZING RAIN...HOWEVER THIS SHOULD NOT
BE VERY WIDESPREAD. AREAS FURTHER EAST WILL REMAIN AS RAIN WITH
EASTERLY FLOW ALOFT.

THE ENTIRE AREA WILL THEN BEGIN TO CLEAR OUT ON MONDAY
MORNING AS THE STATIONARY UPPER TROUGH DISSIPATES AND WEAK
RIDGING CURRENTLY OVER THE BERING MOVES IN. THIS WILL KEEP SKIES
GENERALLY WITH PRECIPITATION LIMITED TO A FEW PASSING SHOWERS. A
WEAK FRONT WILL THEN APPROACH THE KUSKOKWIM DELTA ON
TUESDAY...BRINGING A CHANCE OF RAIN TO THE AREAS. RIDGING WILL
HOWEVER REMAIN OVER THE KUSKOKWIM VALLEY AND BRISTOL BAY...KEEPING
THE AREA DRY WITH LIGHT WINDS INTO MID WEEK.

SHORT TERM FORECAST BERING SEA/ALEUTIANS (TONIGHT THROUGH WEDNESDAY)...

AFTER A WEAKENING AREA OF RAIN AND SNOW SHOWERS FROM THE PRIBILOF
ISLANDS INTO THE AKPENN DISSIPATES LATE TONIGHT...THE WEATHER WILL
QUICKLY BECOME DOMINATED BY A FRONTAL SYSTEM CURRENTLY ENTERING
THE WESTERN ALEUTIANS. THIS SYSTEM WILL BECOME A LOW COMPLEX WITH
MULTIPLE CENTERS OVER THE WESTERN BERING BY MONDAY AFTERNOON. WITH
CONSIDERABLE MODEL DISAGREEMENT WITH BOTH THE LOCATION AND
INTENSITY OF THESE LOWS...FORECAST CONFIDENCE QUICKLY DIMINISHES
WITH A DEVELOPING LOW APPROACHING THE EASTERN ALEUTIANS TUESDAY.
IT DOES APPEAR THAT THIS SETUP WILL KEEP WET WEATHER OVER THE
BERING WITH A POTENTIAL FOR GALE FORCE WINDS IN THE EASTERN
ALEUTIANS BY WEDNESDAY.

LONG TERM FORECAST (DAYS 4 THROUGH 7)...
THE OUTCOME OF THE LONG TERM FORECAST REMAINS HIGHLY DEPENDENT
THE TRACK AND STRENGTH OF THE COMPLEX LOW AS IT BEGINS TO
CONSOLIDATE OVER THE BERING SEA WEDNESDAY. GLOBAL MODELS CONTINUE
TO STRUGGLE WITH THE DETAILS OF THIS SYSTEM...KEEPING FORECAST
CONFIDENCE LOW IN THE TIMING AND STRENGTH OF THE ASSOCIATED
FRONTAL SYSTEM AS IT PROGRESSES EASTWARD. THE MORE NORTHERLY GFS
SOLUTION IS SLOWER TO CONSOLIDATE THE LOW OVER THE NORTHERN
BERING...BUT QUICKEST WITH BRINGING FRONTAL WINDS AND
PRECIPITATION TO THE CENTRAL ALEUTIANS WEDNESDAY MORNING AND
EVENTUALLY INTO THE SOUTHWEST COAST THURSDAY MORNING. THE MORE
SOUTHERLY ECMWF SOLUTION CONSOLIDATES THE LOW QUICKER OVER THE
SOUTHERN BERING...BUT IS SLOWER TO BRING THE FRONTAL WINDS AND
PRECIPITATION INTO THE CENTRAL ALEUTIANS WEDNESDAY AFTERNOON AND
EVENTUALLY INTO THE SOUTHWEST COAST THURSDAY AFTERNOON.

GLOBAL GUIDANCE HAS BEEN SIGNALING THAT THIS ACTIVITY OUT WEST
WILL AMPLIFY A RIDGE OF HIGH PRESSURE IN THE GULF WHICH WILL ACT
TO SLOW THE PROGRESSION OF THIS PATTERN...AND WILL KEEP
SOUTHCENTRAL ALASKA DRY THROUGH THE END OF THE WEEK. EXPECT
SLIGHTLY ABOVE NORMAL TEMPERATURES AND LIGHT WINDS FOR THE WEEK.
CONFIDENCE BEGINS TO DIMINISH INTO THE WEEKEND...WHERE THE
LONGEVITY OF THIS PATTERN BECOMES HIGHLY DEPENDENT ON WHICH MODEL
SOLUTION VERIFIES. A MORE SOUTHERLY SOLUTION (ECMWF) REGARDING
THE LOW OUT WEST WOULD FAVOR DRIER CONDITIONS PERSISTING THROUGH
MUCH OF THE WEEKEND....WHEREAS THE MORE NORTHERLY SOLUTION (GFS)
DEAMPLIFIES THE RIDGE QUICKER AND BRINGS A WEAK SHORTWAVE THROUGH
SOUTHCENTRAL ON SUNDAY.

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


&&

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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...
SOUTHCENTRAL ALASKA...
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...
LONG TERM...


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