Gale Warning 935, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1230 PM AKST TUE NOV 9 2010

.ANALYSIS AND UPPER LEVELS...THE ALASKA REGION REMAINS ENVELOPED
WITHIN A FAIRLY PROGRESSIVE UPPER LEVEL PATTERN. THERE ARE SOME
FAIRLY STRONG SHORT-WAVE TROUGHS PROGRESSING EASTWARD ALONG THE
SUBTROPICAL JET. A LARGE CYCLONIC CIRCULATION DOMINATES THE BERING
SEA WITH MULTIPLE EMBEDDED LOW CENTERS. THE TROUGH WHICH EXTENDS
SOUTHWARD FROM THIS LOW COMPLEX IS AMPLIFYING OVER THE NORTH CENTRAL
PACIFIC DUE TO A JET STREAK IN THE BACK SIDE OF THE TROUGH. THIS
AMPLIFICATION WILL HELP PICK UP A RAPIDLY DEVELOPING SYSTEM JUST
TO THE SOUTH. THIS SYSTEM WILL BE THE MAJOR FOCUS THE NEXT COUPLE
DAYS AS IT MOVES INTO THE GULF. THE UPPER LOW RESPONSIBLE FOR MUCH
OF THE SNOW OVER SOUTHCENTRAL ALASKA THE PAST COUPLE DAYS HAS NOW
OPENED INTO A WAVE AND IS TRACKING NORTHEASTWARD TOWARD THE COPPER
RIVER BASIN. MIDDLETON ISLAND ALSO SHOWS A SURFACE LOW JUST WEST OF
MIDDLETON ISLAND WITH SOME IMPRESSIVE BANDS OF PRECIPITATION. THESE
COULD DROP A QUICK SEVERAL INCHES OF SNOW ACROSS EASTERN PRINCE
WILLIAM SOUND AS IT MOVES ONSHORE LATER THIS AFTERNOON THROUGH THIS
EVENING.

.MODEL DISCUSSION...GFS HAS BEEN CONSISTENT IN TRACKING THE
DEVELOPING PACIFIC LOW ACROSS THE WESTERN GULF. ALL OTHER MODELS
HAVE TRENDED TOWARD THIS SOLUTION AND THERE IS LITTLE SPREAD IN
THE GFS ENSEMBLE MEMBERS. THE CURRENT FORECAST IS NOT TOO FAR FROM
THE GFS SOLUTION. WITH INCREASED CONFIDENCE IN THIS SOLUTION WILL
BEGIN TO ADD IN MORE DETAIL AS THIS STORM REACHES SOUTHCENTRAL.
ELSEWHERE...MODELS ARE IN DECENT AGREEMENT WITH SYNOPTIC FEATURES
AND ONLY MINOR CHANGES WILL MADE TO EXISTING FORECASTS.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...UPPER LOW/TROUGH WILL EXIT TO THE NORTHEAST
TONIGHT AND A HIGH AMPLITUDE SHORT-WAVE RIDGE WILL BUILD IN.
COMBINATION OF FRESH SNOW PACK IN A LOT OF AREAS WITH SUBSIDENCE
UNDER THE RIDGE WILL PRODUCE AREAS OF FOG...SOME OF WHICH WILL
LIKELY BE DENSE. A MAJOR PACIFIC STORM WILL MOVE TO THE GULF
WEDNESDAY. THIS WILL SHIFT FLOW AROUND TO THE NORTH OVER MUCH OF
SOUTHCENTRAL. THERE SHOULD BE JUST ENOUGH WIND TO HELP ERODE THE
FOG BY WEDNESDAY AFTERNOON. THE CENTRAL PRESSURE WILL BOTTOM OUT
BEFORE THE LOW CENTER MOVES INTO THE GULF AND THE STORM WILL
QUICKLY BECOME VERTICALLY STACKED. THIS WILL PROVIDE LITTLE PUSH
BEHIND THE OCCLUDED FRONT WHICH WILL FALL APART ALONG THE NORTH
GULF COAST. THIS MEANS THAT THE WARM TROPICAL AIR ACCOMPANYING THE
SYSTEM WILL INITIALLY STAY JUST OFFSHORE AND PRECIPITATION WILL
FALL MAINLY IN THE FORM OF SNOW. WARM AIR WILL PENETRATE INLAND
THURSDAY AS THE LOW TRACKS TO SOUTH OF THE KENAI PENINSULA WHICH
WILL CHANGE PRECIPITATION OVER TO ALL RAIN ALONG THE COAST. THE
FRONTAL POSITION ALSO AFFECTS WINDS. THE STORM TRACK OFTEN FAVORS
STRONG WINDS THROUGH PASSAGE CANAL AND EASTERN TURNAGAIN ARM...BUT
WITH THE FRONT NEARLY STALLING ALONG THE COAST THE MEAN FLOW AHEAD
OF THE FRONT WILL REMAIN OUT OF THE NORTHEAST...SO DO NOT EXPECT
A WHOLE LOT OF WIND THROUGH THOSE AREAS. ONCE THE REMNANTS OF THE
FRONT DO PUSH THROUGH AND FLOW BECOMES DUE EAST THE WINDS WILL HAVE
SIGNIFICANTLY WEAKENED. OUT OVER THE GULF WATERS WILL BE A DIFFERENT
STORY WHERE WIDESPREAD GALE TO STORM FORCE WINDS CAN BE EXPECTED.
THERE IS LESS CONFIDENCE IN TRACK OF LOW INLAND...SO WILL HAVE TO
WAIT TO FIGURE OUT DETAILS OF HOW THE REST OF SOUTHCENTRAL WILL BE
IMPACTED.

SOUTHWEST ALASKA...BRISTOL BAY WILL BE ON THE OUTER FRINGE OF THE
GULF STORM...SO THERE WILL BE SOME GUSTY NORTHERLY WINDS AND A
CHANCE OF RAIN AND SNOW LATE WEDNESDAY INTO THURSDAY. A BERING LOW
WILL THE APPROACH THE SOUTHWEST ON FRIDAY BRINGING SNOW TO COASTAL
AREAS.

BERING SEA ALEUTIANS...UPPER LOW OVER THE BERING WILL WANDER AROUND
THE NEXT COUPLE DAYS BEFORE ULTIMATELY TRACKING TOWARD SOUTHWEST
ALASKA ON FRIDAY. AS IT DOES SO COLD AIR WILL ADVECT SOUTHWARD
ACROSS THE WESTERN TO CENTRAL BERING SETTING UP A VERY TYPICAL
PATTERN FOR THIS TIME OF YEAR WITH SHOWERS AND GUSTY NORTHERLIES.

.LONG TERM FORECAST...NEXT SHORT-WAVE HEADING OUT OF ASIA WILL
PHASE WITH ENERGY ROTATING SOUTHWARD FROM BERING SEA LOW COMPLEX
AND HELP CREATE A HIGHLY AMPLIFIED TROUGH OVER THE NORTH CENTRAL
PACIFIC BY THE END OF THE WEEK. THIS WILL MAINTAIN A STORM TRACK
FROM THE PACIFIC TO THE GULF OF ALASKA AND SOUTHCENTRAL. MODELS DO
INDICATE A RIDGE BUILDING OVER THE EAST PACIFIC EARLY NEXT WEEK...
SO WILL LIKELY SEE A TRANSITION TO A NEW LONG-WAVE PATTERN.
HOWEVER...STILL A LITTLE TOO FAR OUT TO HAVE CONFIDENCE IN THIS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...
MARINE...STORM WARNING...120 130 132 138 150.
         GALE WARNING...125 140 160.
FIRE WEATHER...NONE.

SEB NOV 10