Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 140137
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
437 PM AKST SAT FEB 13 2016

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL PATTERN THIS MORNING SHOWS A BROAD TROUGH EXTENDING
FROM THE NORTH PACIFIC THROUGH THE NORTHWEST ARCTIC. THE JET
STREAM LIES MOSTLY SOUTH OF THE REGION...MOVING FROM THE NORTH
PACIFIC TOWARD THE PANHANDLE. AS A RESULT THE LOW PRESSURE SYSTEMS
MOVING INTO THE ANCHORAGE FORECAST AREA DO NOT HAVE A LOT OF UPPER
LEVEL SUPPORT AND ARE FAIRLY WEAK.

AT THE SURFACE THE UPPER LEVEL PATTERN IS REFLECTED IN A BROAD
AREA OF LOW PRESSURE OVER THE ALEUTIANS AND EXTENDING INTO THE
GULF OF ALASKA. AT THE MOMENT A STRONGER LOW CENTER IS LOCATED
JUST SOUTH OF DUTCH HARBOR WITH A WEAK TROUGH EXTENDING TOWARDS
ANOTHER LOW IN THE SOUTHERN GULF OF ALASKA. THIS WEAK TROUGHING IS
BRINGING CLOUDS AND SHOWERS THROUGH THE EASTERN BERING...AK
PEN...AND SOUTHWEST ALASKA. SURFACE FLOW IN THIS AREA REMAINS
NORTHERLY AND PRECIPITATION IS FALLING FROM SAINT PAUL THROUGH
KING SALMON THIS MORNING WHILE AREAS SOUTH REMAIN MOSTLY RAIN.

THIS SECOND LOW IN THE GULF OF AK HAS A FRONT THAT EXTENDS ACROSS
THE GULF OF ALASKA TOWARD THE PANHANDLE WHICH IS EXPECTED TO
ROTATE NORTHWARD ONTO THE MAINLAND OVERNIGHT TONIGHT. REMNANTS OF
A LOW AND ASSOCIATED TROUGH THAT MOVED ONSHORE YESTERDAY ARE
LINGERING OVER THE INTERIOR...WITH THE REMAINING CLOUDS AND
SHOWERS EXTENDING FROM SOUTHWEST ALASKA THROUGH SOUTHCENTRAL.
AS THE TROUGH PASSED THROUGH THE AREA EASTERLY WINDS INCREASED A
BIT IN SOUTHCENTRAL BUT AS THE PRESSURE RISES BEHIND THE FRONT
HAVE DROPPED OFF SO HAVE THE WINDS. EASTERN PORTIONS OF THE
FORECAST AREA ARE IMPROVING AS CLOUDS AND SHOWERS RAPIDLY
DISSIPATE WITH WEAK INTERIM RIDGING MOVING IN AHEAD OF THE NEXT
FRONT.

&&

.MODEL DISCUSSION...
MODELS ARE IN FAIR AGREEMENT DURING THE SHORT TERM. ALTHOUGH THEY
DIFFER SLIGHTLY ON THE ANALYSIS OF THE LOW IN THE GULF DURING THE
INITIALIZATION THEY COME TOGETHER QUICKLY AND BY THE FORECAST
PERIOD ARE PRETTY MUCH IN STEP. CANADIAN REGIONAL (GEM) WAS CHOSEN
AS THE MODEL OF THE DAY FOR THE BEST TIMING AND RESOLUTION ON
WINDS ASSOCIATED WITH THE MOVEMENT OF THE VARIOUS TROUGHS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
BROAD SOUTHERLY FLOW WILL KEEP ABUNDANT PRECIPITATION FOCUSED
ALONG THE GULF COAST THROUGH SUNDAY NIGHT AS A NUMBER OF EMBEDDED
UPPER LEVEL WAVES TRACK INLAND AND ALSO HELP TO ENHANCE SHOWER
POTENTIAL ON THE LEE SIDE OF THE COASTAL RANGES. THE FIRST OF
THESE WAVES WILL LIFT NORTHWARD ON SUNDAY AND BRING SCATTERED RAIN
SHOWERS TO THE COOK INLET AND MAT-SU REGIONS...WITH ANOTHER WAVE
PUSHING UP THE INLET ON SUNDAY NIGHT POTENTIALLY BRINGING ANOTHER
SHOT OF RAIN OR SNOW SHOWERS TO THESE AREAS THROUGH EARLY MONDAY
MORNING. A DRYING TREND WILL THEN BEGIN TO TAKE HOLD ON MONDAY AS
THE PERSISTENT ONSHORE FLOW REGIME FINALLY WEAKENS AND GIVES WAY
TO AN UPPER LEVEL RIDGE BUILDING IN FROM THE WEST.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

A WEAKENING LOW NEAR KODIAK WILL CROSS THE ALASKA PENINSULA THEN
WEAKEN AND STALL TONIGHT AND TOMORROW. INTERMITTENT LIGHT RAIN AND
SNOW SHOWERS WILL BE MOST PREVALENT ACROSS BRISTOL BAY...WITH
ONLY ISOLATED TO SCATTERED SHOWERS ACROSS THE KUSKOKWIM DELTA AND
LOWER KUSKOKWIM VALLEY. SHOWERS WILL BEGIN TO DIMINISH SUNDAY
NIGHT AND MONDAY AS HIGH PRESSURE BUILDS OVER SOUTHWEST.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

WEAK LOW PRESSURE OVER THE BERING WILL SUPPORT RAIN AND SNOW
SHOWERS ACROSS THE REGION BEFORE HIGHER PRESSURE SETTLES IN AND A
SLOW DRYING TREND DEVELOPS. A TROUGH OF LOW PRESSURE MOVING IN
NORTHWEST FLOW WILL SKIRT THE FAR WESTERN ALEUTIANS
TONIGHT...BRINGING LIGHT SNOW ACCUMULATIONS. A STRONG GALE FORCE
WEATHER LOW AND ASSOCIATED FRONT WILL ENTER THE WESTERN BERING
MONDAY AND MAKE FAST EASTWARD PROGRESS TO THE CENTRAL BERING AND
PRIBILOF ISLANDS BY MONDAY NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A DRY PERIOD IS ON TAP FOR THE EARLY PORTION OF THE EXTENDED
FORECAST AS A RIDGE OF HIGH PRESSURE BUILDS OVER ALASKA. THIS IS
IN RESPONSE TO A PATTERN CHANGE IN WHICH THE STORM TRACK IS TAKING
A MORE NORTHERLY PATH. THE STRONG UPPER LOW NEAR THE KAMCHATKA
PENINSULA WILL DRIVE THE STORM SYSTEM IN THE CENTRAL BERING AND
ALEUTIANS EASTWARD MONDAY THROUGH TUESDAY. THE LEADING FRONT WITH
THIS SYSTEM WILL REACH THE SOUTHWEST MAINLAND TUESDAY
NIGHT...BRINGING SOME PRECIPITATION TO THAT AREA BUT NOT INTO
SOUTH CENTRAL. THIS SYSTEM WILL THEN SPLIT AS IT HITS THE ALASKAN
RIDGE. MOST OF THE ENERGY WILL DIVE SOUTH INTO THE GULF OF ALASKA
BY THURSDAY. AT THE SAME TIME THE KAMCHATKA LOW WILL BREAK INTO
TWO LOWS...WITH ONE OF THESE MOVING INTO THE ALEUTIANS. ALL OF
THIS WILL DRIVE THE MAIN STORM TRACK FURTHER SOUTH AGAIN. THE
EXTENDED GUIDANCE IS BASED HEAVILY ON THE ECMWF AND ITS ENSEMBLE
MEAN EARLY...THEN ON A BLEND OF ENSEMBLE MEANS LATER ON.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 120 130 131 178.

&&

$$

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



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