Small Craft Advisory 924, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
537 PM AKST WED NOV 19 2014

.ANALYSIS AND UPPER LEVELS...
LARGE ANCHOR LOW CONTINUES TO SPIN OVER THE FAR SOUTHERN BERING
SEA WITH NUMEROUS DISTURBANCES ROTATING AROUND. OVER THE SOUTHERN
MAINLAND...THE MAIN WEATHER STORY HAS BEEN FROM THE NORTHERN GULF
TO THE SUSITNA VALLEY...WHERE A STRENGTHENING DISTURBANCE HAS
BROUGHT RAIN TO AREAS NEAR SEA LEVEL NEAR ANCHORAGE AND WET SNOW
WITH MINOR ACCUMULATIONS ABOVE 750 FEET ELEVATION. THIS SYSTEM
WILL CONTINUE TO PUSH NORTH THROUGH THE MAT-SU VALLEY SOUTHEAST
THROUGH PRINCE WILLIAM SOUND THROUGH LATE THIS AFTERNOON AND THIS
EVENING.

THE OTHER SIGNIFICANT AREA OF INTEREST RESIDES WITH LOW PRESSURE
THAT IS JUST FINISHING RAPIDLY INTENSIFYING SEVERAL HUNDRED MILES
SOUTH OF THE ALEUTIANS AND WILL MOVE NORTHEAST THROUGH THURSDAY TO
A LOCATION ABOUT 150 MILES SOUTHEAST OF SAND POINT...THEN DRIFT
NORTH AND THEN WEST NEAR OR OVER THE ALASKA PENINSULA ON FRIDAY.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT SYNOPTICALLY THE NEXT FEW DAYS. THE
ONE AREA OF DISAGREEMENT RESIDES IN WHERE EXACTLY TO STALL OUT THE
STRENGTHENING LOW CURRENTLY WELL SOUTH OF THE ALEUTIANS. IT SEEMS
AS THOUGH ALL MODELS NOW STALL THE LOW OVER THE CENTRAL ALASKA
PENINSULA LATE THU NIGHT INTO FRI...THEN DRIFT IT WEST ACROSS THE
FAR SOUTHEASTERN BERING SEA BEFORE LOOPING BACK TO THE SOUTH OF
THE PENINSULA AND DRIFTING EAST OR NORTHEAST. THE ASSOCIATED
WEATHER FRONT WILL MOVE INTO THE GULF THU AND THEN REACH THE
NORTHERN GULF BY FRI AFTERNOON.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE POTENT UPPER LEVEL DISTURBANCE WHICH MOVED THROUGH ANCHORAGE
AND THE MAT-SU TODAY WILL RAPIDLY EXIT TO THE NORTH TONIGHT.
SATELLITE IMAGERY SHOWS AN AREA OF CLEAR SKIES BETWEEN THIS
DISTURBANCE AND ANOTHER ONE MOVING INTO THE SOUTHWEST GULF EARLY
THIS AFTERNOON. WITH GENERALLY LIGHT WINDS ACROSS THE AREA WILL
ALLOW FOR EFFECTIVE RADIATIONAL COOLING THIS AFTERNOON AND EVENING
BEFORE CLOUDS BEGIN TO ROLL BACK IN. THUS...ANY LIQUID ON THE
ROADS WILL FREEZE BACK UP.

THE NEXT DISTURBANCE ENTERING THE GULF LOOKS A LITTLE WEAKER THAN
THE ONE WHICH MOVED THROUGH TODAY. THE MORE IMPORTANT DISTINCTION
HOWEVER IS THAT LOW LEVEL FLOW WILL BEGIN TO BACK OUT AHEAD OF THE
DEEP LOW SOUTH OF THE ALEUTIANS AS IT CURVES NORTHWARD TOWARD THE
ALASKA PENINSULA TONIGHT. THIS SHIFT IN FLOW WILL CONFINE THE BULK
OF PRECIP TO UPSLOPE AREAS OF THE KENAI PENINSULA AND THE WEST
SIDE OF COOK INLET.

THE DEEP LOW MOVING TOWARD THE ALASKA PENINSULA WILL PRIMARILY
AFFECT THE GULF COAST AND KODIAK ISLAND. THE MAIN FORECAST
CHALLENGE IS DETERMINING HOW FAR NORTH THE FRONTAL SYSTEM WILL
PROGRESS ACROSS THE GULF AND THUS HOW MUCH PRECIP WILL FALL IN THE
PRINCE WILLIAM SOUND/KENAI PENINSULA AREAS. NOT ONLY WILL THE LOW
STALL ALONG THE AKPENN...BUT UPPER LEVEL FLOW BEHIND THE SURFACE
FRONT WILL BE SPLIT WITH SOME ENERGY HEADED WESTWARD AROUND THE
LOW CENTER AND SOME SHOOTING EASTWARD TOWARD SOUTHEAST ALASKA.
THIS TYPE OF FLOW LEADS TO A SLOWING AND WEAKENING FRONT AS IT
ELONGATES UNDER THE DIVERGENT FLOW ALOFT. IN ADDITION...LOW LEVEL
OFFSHORE FLOW AHEAD OF THE FRONT WILL MAINTAIN DRY AIR IN THE LOW
LEVELS. FOR NOW HAVE TRENDED THE FORECASTS TOWARD A MORE SOUTHERLY
POSITION OF THE FRONT AND CONFINED PRECIP PRIMARILY TO WESTERN
PRINCE WILLIAM SOUND AND THE SOUTHERN TIP OF THE KENAI PENINSULA.

LACKING ANY WIND OR LOW CLOUDS ACROSS INTERIOR SOUTHCENTRAL...A
GRADUAL COOLING TREND WILL PERSIST OVER THE NEXT COUPLE DAYS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS...
AS ONE LOW IN THE SOUTHERN BERING WEAKENS A NEW LOW APPROACHES THE
AREA FROM THE NORTH PACIFIC. THIS NEW LOW WILL START TO BRING
STRONGER WINDS TO THE ALASKA PENINSULA LATER TONIGHT AND TO THE
BRISTOL BAY AREA AND ALEUTIAN RANGE TOMORROW. THE STRONGER WINDS
WILL DIMINISH AS THE LOW BEGINS TO WEAKEN THURSDAY NIGHT BUT WILL
STILL LAST INTO FRIDAY. BOTH LOWS WILL ALSO BRING WITH THEM RAIN
TO THE ALEUTIANS AND IN THE BRISTOL BAY AREA. HOWEVER...NOT MUCH
IS EXPECTED TO MAKE IT INTO THE KUSKOKWIM RIVER VALLEY. OUT WEST
NORTHERLY FLOW WILL CONTINUE BRINGING RAIN SHOWERS TO THE ISLANDS
THROUGH THE REST OF THE WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

MODELS HAVE REALLY COME INTO MUCH BETTER AGREEMENT FOR THE
BEGINNING OF THIS PERIOD IN THE PAST DAY OR SO...WITH THE LOW
REMAINING NEARLY STATIONARY AS IT WEAKENS OVER/NEAR THE ALASKA
PENINSULA. THERE ARE STILL SOME SLIGHT DIFFERENCES AT THIS
POINT...BUT THERE WILL BE A GENERAL IMPROVING TREND TO THE WEATHER
DURING THE WEEKEND ACROSS SOUTHCENTRAL AND SOUTHWEST ALASKA. WITH
THE UPPER RIDGE BREAKING DOWN OVER THE WESTERN US THIS WEEK...MORE
ZONAL FLOW SETS UP ACROSS THE ALEUTIANS AND GULF OF ALASKA. THIS
WILL BRING A TREND TOWARD MORE SEASONABLE TEMPERATURES FROM WEST
TO EAST AS THE WEAKENED LOW GRADUALLY MOVES OFF TO THE EAST. AT
THIS POINT IT APPEARS THAT ANY PRECIPITATION EXPECTED WILL BE
ALONG THE COASTAL AREAS...AS WELL AS ACROSS THE BERING SEA AND
ALEUTIANS AS ANOTHER LOW MOVES IN FROM THE WEST EARLY NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 130 131 132 136 137 138 139 150 155 160 165
180 351 352 FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...MBS