Gale Warning 893, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1240 PM AKST WED NOV 10 2010

.ANALYSIS AND UPPER LEVELS...THE FOCUS FOR TODAY IS A MAJOR STORM
ABOUT 400 MILES SOUTH OF KODIAK ISLAND. A TROUGH EXTENDS FROM THIS
LOW NORTHWESTWARD INTO THE BERING. A STRONG JET STREAK ON THE BACK
SIDE OF THE TROUGH IS FEEDING ARCTIC AIR INTO THE SYSTEM. SATELLITE
IMAGERY INDICATES COLD AIR IS ALREADY WRAPPING BACK AROUND THE
CENTER AND THE SYSTEM IS OCCLUDING. WINDS ARE RAPIDLY INCREASING
ACROSS THE GULF OF ALASKA AND ALONG THE ALASKA PENINSULA AS THE
SYSTEM APPROACHES. A SHORT-WAVE RIDGE DOWNSTREAM OVER SOUTHCENTRAL
WAS PARTIALLY RESPONSIBLE FOR PRODUCING AREAS OF STRATUS AND FOG
OVERNIGHT. AN INCREASE IN WINDS ALONG COASTAL AREAS HAS ERODED
MUCH OF THIS BUT STRATUS REMAINS QUITE EXTENSIVE OVER INLAND
AREAS...ESPECIALLY ACROSS THE COPPER RIVER BASIN. OUT WEST
CONDITIONS ARE VERY QUIET WITH JUST A FEW AREAS OF SHOWERS.

.MODEL DISCUSSION...MODELS INITIALIZED WELL WITH THE MAJOR PACIFIC
LOW BUT THERE ARE KEY DIFFERENCES IN THE TRACK OF THE LOW AS IT
MOVES TO THE NORTHERN GULF LATE THURSDAY AFTERNOON. THE GFS HAS
BEEN THE MOST CONSISTENT MODEL BUT IS FARTHER WEST THAN ANY OTHER
SOLUTIONS. THE ECMWF...WHICH HAD BEEN TRENDING TOWARD THE WESTERN
GFS SOLUTION HAS NOW TRENDED WAY TO THE EAST. THE NAM/UKMET/GEM
ARE ALL CLOSE TOGETHER IN BETWEEN THE GFS AND ECMWF SOLUTIONS.
A LOOK AT GFS ENSEMBLES SHOWS VERY LITTLE VARIATION IN POSITION.
ALSO...WITH AN INCREASING NEGATIVELY TILTED TROUGH THESE LOWS HAVE
A TENDENCY TO MOVE BACK TOWARD THE COLD AIR. THEREFORE...PREFER TO
GO WITH A SOLUTION CLOSER TO THE GFS PERHPAS TEMPERED A BIT BY THE
MIDDLE GROUND SOLUTION OF THE NAM/UKMET/GEM. THE TRACK WILL HAVE
HUGE RAMIFICATIONS ON THE WIND AND PRECIP FORECAST ACROSS
SOUTHCENTRAL.

MODELS ALSO DIFFER ON TIMING AND STRENGTH OF NEXT SYSTEM WHICH JET
RAPIDLY DRIVES INTO THE GULF THURSDAY NIGHT. GFS/ECMWF BLEND SEEMS
LIKE A NICE COMPROMISE. SOME OF THE MODELS HINT AT YET ANOTHER WEAK
LOW FOLLOWING THIS...BUT CONFIDENCE IS LOW IN THE FAST FLOW ALOFT.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE OCCLUDED FRONT WILL BEGIN TO SHEAR APART
AS IT REACHES THE NORTH GULF COAST. THEREFORE...DON'T EXPECT THE
STORM FORCE WINDS TO PENETRATE INLAND OR INTO PRINCE WILLIAM SOUND.
THE OTHER IMPORTANT AFFECT OF THIS IS THAT THE MUCH WARMER AIR WILL
INITIALLY BE HELD OUT OVER THE GULF SO THAT PRECIPITATION TYPE WILL
BE PREDOMINANTLY SNOW ACROSS THE KENAI PENINSULA AND PRINCE WILLIAM
SOUND REGIONS THIS TONIGHT. WARMER AIR WILL MAKE PROGRESS INLAND
THURSDAY...SO PRECIPITATION TYPE WILL TRANSITION TO ALL RAIN ALONG
THE COASTAL AREAS. THE LOW CENTER WILL LAG WELL BEHIND THE OCCLUDED
FRONT. AS IT APPROACHES THE KENAI PENINSULA THURSDAY AFTERNOON WINDS
WILL INCREASE ALONG THE NORTH GULF COAST AND ANOTHER SLUG OF PRECIP
WILL MOVE IN. THERE IS SOME UNCERTAINTY IN THE TRACK OF THE LOW. THE
MOST LIKELY SCENARIO SEEMS TO TAKE THE LOW OVER THE KENAI PENINSULA
TOWARD COOK INLET. THIS TRACK WILL RESULT IN STRONG EASTERLY WINDS
FROM CORDOVA TO EASTERN TURNAGAIN ARM. THE SYSTEM WILL QUICKLY
DISSIPATE THURSDAY NIGHT AND FRIDAY AND TRACK INLAND...SO MOST
PLACES WILL LIKELY SEE A QUICK SHOT OF PRECIP. WITH LOTS OF WARM
AIR THIS WILL MAINLY BE IN THE FORM OF RAIN OR A MIX OF RAIN AND
SNOW.

RIGHT BEHIND THIS SYSTEM MODELS INDICATE A SHORT-WAVE MOVING OUT OF
SOUTHWEST ALASKA ON SATURDAY AND ANOTHER PACIFIC SYSTEM MOVING TO
SOUTHCENTRAL BY SATURDAY NIGHT. THEREFORE...UNSETTLED WEATHER WILL
CONTINUE.

SOUTHWEST ALASKA...BRISTOL BAY WILL BE ON THE OUTER EDGE OF THE
SYSTEM TRACKING NORTHWARD ACROSS THE GULF TONIGHT AND THURSDAY.
THERE WILL BE SOME DECENT OVERRUNNING...SO EXPECT AREAS OF LIGHT
PRECIP TO DEVELOP THIS AFTERNOON THROUGH TONIGHT. TEMPERATURES
ALOFT WILL GRADUALLY WARM SO THAT THERE IS A CHANCE FOR A VARIETY
OF PRECIPITATION TYPES FROM SNOW TO FREEZING RAIN TO ALL RAIN.
FURTHER NORTH FROM THE KUSKOKWIM VALLEY TO KUSKOKWIM DELTA THE
ONLY IMPACT FROM THIS SYSTEM WILL BE GUSTY NORTHERLY WINDS. THE
UPPER LOW WHICH HAS BEEN SITTING OVER THE BERING SEA FOR THE PAST
WEEK OR MORE WILL LIFT OFF TO THE NORTHEAST ACROSS SOUTHWEST ALASKA
FRIDAY NIGHT AND SATURDAY. DYNAMICS LOOK PRETTY WEAK AS THE LOW
OPENS INTO A WAVE...SO JUST EXPECT SOME LIGHT SNOW AS THIS MOVES
THROUGH.

BERING SEA/ALEUTIANS...A SYSTEM SOUTH OF KAMCHATKA THIS MORNING
WILL DIVE SOUTHEAST INTO THE NORTH CENTRAL PACIFIC CREATING A
HIGHLY AMPLIFIED PATTERN. THIS WILL ENSURE THAT MAJOR STORMS
STAY AWAY FROM THE BERING AND ALEUTIANS. INSTEAD A COLD ADVECTION
PATTERN WILL SET-UP RESULTING IN GUSTY NORTHERLIES AND SNOW SHOWERS
THROUGH THE WEEKEND.

.LONG TERM FORECAST...ALTHOUGH THERE ARE LARGE VARIATIONS IN THE
MEDIUM RANGE MODELS. HOWEVER...THERE IS GENERAL AGREEMENT ON
BUILDING OF A RIDGE OVER THE BERING SEA EARLY NEXT WEEK. THIS WOULD
LEAD TO THE FIRST MAJOR ARCTIC AIR OUTBREAK OVER MAINLAND ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...120 130 132 138 140 150.
         GALE WARNING...125 141 155 160 165.
FIRE WEATHER...NONE.

SEB NOV 10