Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 292148
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
148 PM AKDT WED OCT 29 2014

.ANALYSIS AND UPPER LEVELS...
UPPER LEVELS...SATELLITE IMAGERY SHOW A LARGE AREA OF CU OVER THE
GULF WITH SEVERAL VORTICES ROTATING AROUND THE STACKED CENTER OVER
THE SOUTHWESTERN GULF. A SHORT WAVE CAN ALSO BE SEEN MOVING
WESTWARD ACROSS THE WESTERN COOPER RIVER BASIN. THE RIDGE IS STILL
HOLDING ON OVER THE EASTERN BERING SEA. THE UPPER FLOW OVER THE
WESTERN BERING SEA IS BECOMING MORE SOUTHERLY AS THE TROUGH NEAR
KAMCHATKA DIGS.

SURFACE...
OUTFLOW WINDS PERSISTED OVER PRINCE WILLIAM SOUND AS WELL AS THE
MATANUSKA(MAT) VALLEY WITH AREAS OF FINE GLACIAL SILT BEING
OBSERVED. SHOWERS WITH WAVES ROTATING NORTH AND WEST ACROSS THE
GULF WERE STARTING TO IMPACT THE NORTH GULF COAST THIS AFTERNOON.
LOW CLOUDS CONTINUED ONCE AGAIN OVER THE COPPER RIVER BASIN.

OUT WEST...BRISK NORTHERLY WINDS PERSISTED OVER THE AK PEN. WINDS
SHIFTED TO A SW DIRECTION IN RESPONSE TO AN APPROACHING FRONTAL
SYSTEM. THE SW MAINLAND GENERALLY HAD DRY CONDITIONS WITH
NORTHERLY FLOW. THE DELTA WAS THE EXCEPTION WITH SNOW
SHOWERS/FLURRIES ASSOCIATED WITH A A WEAK TROUGH.

&&

.MODEL DISCUSSION (SHORT TERM)...
MODEL DIFFERENCES CONTINUE THROUGH THE SHORT TERM AS FAVORED
SOLUTIONS DIFFER BY AREA AND TIMEFRAME. IN THE EAST...THE GEM
REGIONAL IS DOING A BETTER JOB CAPTURING THE PRESSURE FIELD AND
RESULTANT MESOSCALE WINDS ACROSS THE GULF AND MAT VALLEY. THE
GFS/EC ARE IN FAIRLY GOOD AGREEMENT AND SOMEWHAT REASONABLE WITH
THE SYNOPTIC TRENDS. OUT WEST...THE ECMWF WESTWARD SOLUTION IS A
SIGNIFICANT OUTLIER WITH THE STRONG LOW IMPACTING THE
ALEUTIANS/BERING SEA THU AND FRI. THE OTHER MODELS(GFS/NAM/GEM
GLOBAL) ALL HAVE SIMILAR PRESSURES BUT CARRY THE LOW FURTHER EAST BY
FRI AFTERNOON. THAT SAID...CONFIDENCE IS INCREASING FOR THE
POTENTIAL FOR HIGH WIND CONDITIONS FOR THE WEST AND CENTRAL
ALEUTIANS AND SOUTHERN BERING SEA THU.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
SURFACE AND UPPER TROUGHS WILL CONTINUE FAIRLY HIGH CHANCES OF
SHOWERS ALONG THE NORTH GULF COAST THROUGH THU WITH SLIGHTER
CHANCES OF SNOW SHOWERS INLAND. CHANCES OF SNOW OR MIX INCREASE
INLAND ACROSS THE KENAI...ANCHORAGE BOWL...MATSU FRI AND SAT AS A
LOW OVER THE NORTHERN GULF MOVES INLAND OVER THE KENAI PEN AND A
FRONTAL SYSTEM MOVES IN FROM THE SOUTH AND WEST. PRESSURE
GRADIENTS WILL GENERALLY HOLD TONIGHT ACROSS THE NORTH GULF AND
MAT VALLEY...SO EXPECT SOME OUTFLOW WINDS AGAIN ACROSS PRINCE
WILLIAM SOUND AND MAT. PRESSURE GRADIENTS (NEG ANCHORAGE TO
WHITTIER) WILL INCREASE THU AND PRODUCE GUSTY WEST WINDS NEAR
WHITTIER.

SOUTHWEST ALASKA...
A FEW SNOW SHOWERS WILL LINGER INTO THIS EVENING ALONG THE
KUSKOKWIM DELTA...BUT OTHERWISE THE SOUTHWEST MAINLAND WILL REMAIN
MOSTLY DRY FOR THE NEXT FEW DAYS AS OFFSHORE FLOW TAKES HOLD IN
THE WAKE OF THE DEPARTING LOW. THE NEXT CHANCE FOR PRECIPITATION
LOOKS TO BE ON FRIDAY AS THE FRONT ASSOCIATED WITH THE NEXT BERING
LOW REACHES THE BRISTOL BAY COAST AND THEN ADVANCES INLAND.

BERING SEA/ALEUTIANS...
THE FRONTAL TROUGH OVER THE BERING SEA WEAKENS AS IT SHIFTS EAST
TONIGHT. THE MAIN PLAYER WILL BE LARGE LOW HEADING TOWARD THE
ALEUTIANS TONIGHT. THE LOW RAPIDLY INTENSIFIES UNDER A STRONG
UPPER JET AS IT MOVES TO NEAR AMCHITKA IN THE UPPER 970S/LOWER
980S THU MORNING THEN CONTINUES TO DEEPEN INTO THE 960S OVER THE
EASTERN BERING SEA FRI. AS MENTIONED IN THE MODEL
DISCUSSION...THERE IS SOME DISAGREEMENT ON LOW POSITIONING.
HOWEVER...IT DOES APPEAR THAT HURRICANE FORCE WINDS ARE POSSIBLE
ON THE SOUTHERN FLANK OF THE LOW AFTER IT MOVES NORTH OF THE
ALEUTIANS. WILL BE ISSUING A HIGH WIND WATCH FOR THE CENTRAL AND
WEST ALEUTIANS(E OF KISKA) FOR THU. NOT AS CONFIDENT THAT WARNING
LEVEL WINDS WILL REACH UNALASKA AT THIS POINT AS THERE IS STILL
SOME UNCERTAINTY OF LOW TRACK. WARM ADVECTION SHOULD BE STRONG
ENOUGH THAT PRECIPITATION WILL BE ALL RAIN.

&&

.LONG TERM FORECAST...
EVEN WITH GOOD MODEL AGREEMENT (INCLUDING FROM THE ENSEMBLES)
YESTERDAY...THERE STILL MANAGED TO BE A SIGNIFICANT CHANGE IN THE
PROJECTED LOW TRACK THIS WEEKEND FROM THE OVERNIGHT RUNS. THE
MODELS HAVE TRENDED TOWARDS A MUCH SLOWER SOLUTION FROM THE
PRIMARY LOW THROUGH THE BERING ON FRIDAY...AND ARE NOW BEGINNING
TO DEVELOP A DISTINCT TRIPLE POINT LOW OR WEAK WAVE OVER THE GULF
BY EARLY SATURDAY. THIS DID NOT CHANGE THE PRECIPITATION FORECAST
FOR THE GULF COAST (WHICH REMAINS RAINY THROUGH NEXT WEEK) BUT IT
NOW APPEARS THAT DOWNSLOPING FROM THE CHUGACH RANGE WILL KEEP THE
ANCHORAGE BOWL AND MATANUSKA VALLEY MOSTLY DRY THROUGH THE
WEEKEND. THE BERING LOW IS NOW EXPECTED TO ENTER THE GULF EARLY
NEXT WEEK AND BECOME NEARLY STATIONARY THROUGH MID WEEK. THIS
SETUP WOULD KEEP A CHANCE OF PRECIPITATION AND OUTFLOW WINDS FOR
THE GULF COAST WITH GENERALLY A GENERALLY DRY CONDITIONS AND
OFFSHORE FLOW FOR SOUTHCENTRAL.

ONCE THE SYSTEM IN THE GULF BEGINS TO DISSIPATE EARLY NEXT
WEEK...THE LONG TERM FORECAST QUICKLY SHIFTS TO A FRONT ASSOCIATED
WITH A SIBERIAN LOW MOVING INTO THE WESTERN ALEUTIANS EARLY NEXT
WEEK. AN ENSEMBLE BLEND WAS USED AGAIN FOR THIS SYSTEM...THOUGH
THERE IS REASONABLY GOOD AGREEMENT FROM THE OPERATIONAL MODELS
WITH MINOR TIMING DIFFERENCES. THE SIBERIAN LOW IS STILL PROJECTED
TO SPREAD INTO THE BERING OVER THE COURSE OF THE NEXT
WEEK...DOMINATING THE WEATHER OVER THE BERING SEA AND ALEUTIANS
NEXT WEEK.


&&

AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WATCH FOR 187 AND 191
MARINE...HURRICANE FORCE 175 176 177.
         STORM 170 171 172 173 174.
         GALE 127 155 165.
FIRE WEATHER...NONE

$$

RMC/DEK OCT 14



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