Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 261224
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
424 AM AKDT SUN OCT 26 2014

.ANALYSIS AND UPPER LEVELS...
A LARGE LOW PRESSURE ALOFT...NEAR 500 DECAMETERS...SITS CENTERED
OVER THE CHUKCHI PENINSULA. THE CYCLONIC CIRCULATION ALOFT
ENCOMPASSES THE BERING SEA AND THE ALEUTIAN CHAIN...AND TO A
LESSER EXTENT...MAINLAND ALASKA. ON WATER VAPOR SATELLITE A VERY
STRONG SHORTWAVE TROUGH IS ROUNDING THE BASE OF THE UPPER LOW INTO
THE WESTERN BERING SEA. A MOISTURE PLUME AHEAD OF THE WAVE AND
SUBSIDENCE DRYING BEHIND ARE APPARENT. A MUCH WEAKER WAVE IS
CROSSING OVER THE ALASKA RANGE FROM THE SOUTHWEST MAINLAND INTO
THE SOUTHCENTRAL. THE OTHER LARGE FEATURE IS WELL SOUTH OF THE
GULF OF ALASKA...AN UPPER LEVEL LOW PRESSURE THAT IS PHASING WITH
THE REMNANTS OF THE TROPICAL SYSTEM ANA...WHICH LOOKS TO STAY
SOUTH OF OUR AREA.

A WEAK SURFACE LOW STILL SPINS IN THE NORTHERN GULF WITH ISOLATED
TO SCATTERED SHOWER ACTIVITY. THE COOK INLET REGION HAS MOSTLY
CLEARED OUT AS FAR AS LOW CLOUDS ARE CONCERNED BUT SOME TRAPPED
MOISTURE IS STILL HANGING OUT IN THE MATANUSKA VALLEY.
HIGHER CLOUDS ASSOCIATED WITH THE INCOMING SHORTWAVE TROUGH ARE
STREAMING OVER THE ALASKA RANGE BUT SHOULD NOT BE ANY MORE THAN
THAT. LIGHT WINDS ENCOMPASS MOST OF THE SOUTHCENTRAL. LOW DEW
POINT DEPRESSIONS ALONG KNIK ARM HINT AT POSSIBLE FOG DEVELOPMENT
BUT COULD BE DEPENDENT ON CLEARING OUT THAT MID-LEVEL CLOUD DECK.

FURTHER OUT WEST...SNOW IS STRUGGLING TO COMPETE WITH DRY AIR OVER
THE LOWER KUSKOKWIM VALLEY AND BRISTOL BAY REGION. CLEARING BEHIND
THE SHORTWAVE IS ALREADY PROMOTING FOG/MIST OVER THE KUSKOKWIM
DELTA.

&&

.MODEL DISCUSSION...
GUIDANCE IS HONING IN ON A SOLUTION TO THE BERING SEA SYSTEM.
THERE IS GOOD GENERAL AGREEMENT WITH DEEPENING THE SURFACE LOW TO
SUB 970 MB WEST OF SAINT LAWRENCE ISLAND. ONCE THE SYSTEM PEAKS IN
INTENSITY THERE IS SOME DISAGREEMENT WITH WHERE THE LOW WILL TRACK
AS IT MOVES BACK SOUTH TOWARD BRISTOL BAY. OTHERWISE MODEL
AGREEMENT WITH THE FRONT IS REALLY GOOD AS WELL AS AGREEMENT ON
DEVELOPMENT OF A SECONDARY SURFACE LOW NEAR THE ALASKA PENINSULA
AS ANOTHER SHORTWAVE ROUNDS THE TROUGH. THE WEST DOMAIN FAVORS THE
EUROPEAN MODEL SOLUTION WHILE THE EAST DOMAIN FAVORS THE CANADIAN
REGIONAL IN THE SHORT TERM FOLLOWED BY THE EUROPEAN MODEL.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...HIGH CIRRUS WILL STREAM OVERHEAD EARLY THIS
MORNING AS A DISTURBANCE PASSES OVERHEAD. THE BEST LIFT ASSOCIATED
WITH THE WAVE WILL PASS TO THE SOUTH WITH THE MAIN EFFECTS FELT TO
THE EAST OF OUR FORECAST AREA. EXPECT DECREASING CLOUDS IN THE
COOK INLET REGION WITH CLOUDS LINGERING IN THE COPPER RIVER BASIN.
OUTFLOW WINDS WILL CONTINUE ALONG THE NORTH GULF COAST TODAY BUT
BEGIN TO SLACKEN OVERNIGHT INTO MONDAY AS THE SURFACE LOW IN THE
GULF WEAKENS AND MOVES TO THE EAST. AN UPPER LEVEL RIDGE WILL
BUILD OVERHEAD TONIGHT ALLOWING FOR SOME EFFICIENT RADIATIONAL
COOLING DESPITE WARMING 850 MB TEMPERATURES. SEASONABLE
TEMPERATURES WILL CONTINUE ALONG WITH GENERALLY LIGHT WINDS
THROUGH TUESDAY. A DEVELOPING LOW PRESSURE SYSTEM AND FRONT WILL
AFFECT KODIAK ISLAND ON TUESDAY BUT THIS SYSTEM WILL REMAIN IN THE
GULF AND AWAY FROM THE MAINLAND.

SOUTHWEST ALASKA...THE MAINLAND LIES BETWEEN SYSTEMS THIS MORNING
WITH A FEW LINGERING SNOW SHOWERS ALONG THE ALASKA/ALEUTIAN
RANGES. WINDS IN THE KUSKOKWIM DELTA ARE STARTING TO TURN TO THE
SOUTHEAST IN RESPONSE TO THE DEVELOPING SYSTEM IN THE BERING SEA.
RADIATIONAL COOLING AND ANTECEDENT MOISTURE IS PROMOTING SOME
AREAS OF FOG AND MIST BUT INCREASING WINDS SHOULD KEEP THINGS WELL
MIXED...KEEPING VISIBILITY AND CEILINGS UP. THE FRONT ASSOCIATED
WITH THE BERING SYSTEM WILL PUSH ASHORE THE DELTA LATE THIS
MORNING SPREADING A RAIN SHIELD FROM EAST TO WEST. THE FRONT WILL
SLOW DOWN PROGRESS AND STALL OVER THE MAINLAND ON MONDAY AS A NEW
SYSTEM DEVELOPS TO THE SOUTH. THE FOCUS FOR RAIN THEN SHIFTS TO
BRISTOL BAY AND THE LOWER KUSKOKWIM VALLEY AS THE NEXT SYSTEM
TAKES SHAPE IN THE GULF.

BERING SEA/ALEUTIANS...A SOLID GALE FORCE LOW PRESSURE IS IN THE
PROCESS OF DEVELOPING IN THE WESTERN BERING SEA THIS MORNING.
SOUTHWEST WINDS WILL RAPIDLY INCREASE AND SPREAD EASTWARD
THROUGHOUT THE DAY ALONG WITH A FRONTAL RAIN BAND. BEHIND THE
FRONT...WHICH WILL BE IN THE EASTERN BERING SEA EARLY MONDAY
MORNING...SNOW SHOWERS WILL DOMINATE THE BERING SEA ALONG WITH
VERY GUSTY NORTHWESTERLY WINDS.


&&

.LONG TERM FORECAST...
WHILE THE MODELS ARE CONTINUING TO STRUGGLE WITH THE TRACK OF A
DEVELOPING LOW FROM THE GULF INTO THE NORTH PACIFIC THROUGH THE
MIDDLE OF NEXT WEEK...THE GENERAL LONG TERM PATTERN REMAINS
LARGELY UNCHANGED. A LONG WAVE TROUGH EXTENDING FROM THE WEST
COAST INTO THE AKPENN ON MONDAY WILL DISSIPATE AND FORM A CUTOFF
LOW OVER THE EXTREME SOUTHERN GULF BY WEDNESDAY. THIS WILL ALLOW
FOR RIDGING TO SPREAD THROUGHOUT MUCH OF THE MAINLAND...KEEPING
CONDITIONS DRY WITH NEAR TO BELOW NORMAL TEMPERATURES THROUGH THE
MIDDLE OF NEXT WEEK. THERE IS ALSO A POSSIBILITY THAT THIS PERIOD
OF QUIET WEATHER FOR THE MAINLAND COULD CONTINUE THROUGH THE WORK
WEEK.

OUT WEST...THERE REMAINS VERY GOOD AGREEMENT IN THE TIMING OF AN
ALEUTIAN LOW THAT WILL BEGIN MOVING THROUGH THE WESTERN ALEUTIANS
ON LATE TUESDAY. THIS SYSTEM WILL THEN SPREAD INTO THE CENTRAL
BERING BY LATE IN THE WORK WEEK...KEEPING CLOUDY SKIES WITH A
CHANCE OF RAIN FOR THE REGION THROUGH THE WORK WEEK.

DUE TO THE FAIRLY LARGE UNCERTAINTY IN THE LOW TRACK THROUGH THE
GULF AND NORTH PACIFIC FROM TUESDAY INTO THURSDAY...THE LONG TERM
FORECAST ONCE AGAIN HEAVILY USED WPC GUIDANCE. THIS KEEPS THE LOW
TRACK MOSTLY TO THE SOUTH OF THE AOR...TREATING THE FURTHER NORTH
TRACK TOWARDS THE NORTH GULF COAST FROM PREVIOUS RUNS OF THE GFS
AS AN OUTLIER. THE EC AND GFS ENSEMBLE MEANS HAVE BEEN RELATIVELY
CONSISTENT WITH THIS LOW TRACK...LEADING TO INCREASED CONFIDENCE
IN QUIET WEATHER MOVING INTO THE SOUTHERN MAINLAND BY MID WEEK.



&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 185.
         GALE 170 172 173 174 175 176 177 178 179 181.
FIRE WEATHER...NONE. &&

$$

MTL OCT 14



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