Small Craft Advisory 988, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
544 AM AKST FRI DEC 11 2015

.ANALYSIS AND UPPER LEVELS...

THE PATTERN IS STARTING TO SHOW SOME
SIGNS OF MORE ACTIVE WEATHER. WORKING FROM WEST TO EAST...YET
ANOTHER WEAK LOW IS CLIPPING THROUGH THE WESTERN ALEUTIANS. OVER
THE EASTERN BERING...A CLOSED LOW IS NOW CLEARLY SEEN ON SATELLITE
AND WITH SCATTEROMETER WINDS. THIS LOW IS WRAPPING COLD AIR BACK
INTO BRISTOL BAY AND CREATING PLENTY OF SHOWERS ON THE BERING SIDE
OF THE ALASKA PENINSULA. MEANWHILE MOISTURE ASSOCIATED WITH THE
VERTICALLY STACKED LOW IN THE GULF HAS MADE ITS WAY OVER THE
ALASKA RANGE AND IS ALSO PARKED OVER BRISTOL BAY. WHEN ADDING
THE COLD AIR AND THE MOISTURE TOGETHER...THE RESULT IS A FAIRLY
IMPRESSIVE DEFORMATION ZONE WITH MODERATE SNOWFALL. KING SALMON
REPORTED 6 INCHES OF NEW SNOW AND IT IS STILL FALLING. THIS BAND
WILL SHIFT SLOWLY TO THE EAST AND WEAKEN THROUGH THIS MORNING.
MEANWHILE...THE AFOREMENTIONED LOW IN THE GULF CONTINUES ITS SLOW
JOURNEY NORTH. WE ARE STARTING TO SEE SOME RADAR RETURNS
APPROACHING THE COAST AND THE EXTREME SOUTHWEST TIP OF THE KENAI
PENINSULA. WITH THE JET CONTINUING TO BE WELL SOUTH OF THE
MAINLAND...THIS LOW WILL HAVE LIMITED UPPER LEVEL SUPPORT.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN VERY GOOD SYNOPTIC AGREEMENT
IN THE SHORT TERM. THERE ARE STILL A FEW DISCREPANCIES THAT WILL
IMPACT THE FORECAST. FIRST...HOW WELL DOES THE DEFORMATION BAND IN
BRISTOL BAY HOLD TOGETHER AND HOW FAR EAST DOES IT SLIDE.
SECOND...HOW MUCH DOWNSLOPING WILL THERE BE WITH THE LOW AS IT
SLIDES UP COOK INLET TONIGHT INTO SAT MORNING. THE HIGHER
RESOLUTION MODELS WERE USED TO HANDLE BOTH OF THESE FINER SCALE
ITEMS. IT DOES APPEAR THAT EVEN THE MORE BULLISH NAM IS NOW
STARTING TO BACK OFF A BIT ON PRECIPITATION AMOUNTS OVER COOK
INLET. AS COLD AIR SLIDES IN FROM THE WEST AND HELPS TO STRENGTHEN THE
LOW...THIS RESULTS IN SLIGHTLY STRONGER SOUTHEAST FLOW. THIS WOULD
RESULT IN MORE DOWNSLOPING...AT LEAST INITIALLY. THE BEST CHANCE
FOR SNOW NOW APPEARS TO BE SAT AS THE UPPER LEVEL LOW ACTUALLY
MOVES OVERHEAD TO CUT OFF THE DOWNSLOPING AND WE SEE SOME COLD AIR
ADVECTION OFF THE COOK INLET. MEANWHILE...THE ECMWF SEEMS TO HAVE
"LOCKED ON" TO A SOLUTION WITH THE STRONG BERING LOW OVER THE
WEEKEND. THE OTHER MODELS HAVE TRENDED TOWARDS ITS TRACK
OVERNIGHT. IT IS CURRENTLY THE STRONGEST SOLUTION BY SEVERAL
MILLIBARS...SO WE USED MORE OF AN AVERAGE WHEN IT CAME TO CENTRAL
PRESSURE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

A LOW PRESSURE CENTER OVER THE NORTHWESTERN GULF WILL MOVE ACROSS
THE KENAI PENINSULA THIS AFTERNOON AND EVENING BEFORE SLOWLY
DISSIPATING OVER COOK INLET ON SAT. THIS SYSTEM WILL BRING SNOW TO
COASTAL AREAS THIS MORNING...WITH SOME MIXING WITH RAIN POSSIBLE
NEAR HOMER AND CORDOVA IN THE AFTERNOON. PRECIPITATION WILL CHANGE
BACK TO SNOW OVER THOSE AREAS TONIGHT AND SAT BEFORE DRYING
RETURNS SAT NIGHT. FOR INLAND AREAS...SOUTHEAST FLOW ACROSS THE
CHUGACH WILL KEEP ANCHORAGE AND THE MATANUSKA VALLEY DOWNSLOPED
UNTIL TONIGHT. LIGHT SNOWFALL WILL THEN SPREAD ACROSS THOSE AREAS
THROUGH SAT BEFORE TAPERING OFF TO SHOWERS. SNOW SHOWERS WILL ALSO
AFFECT THE SUSITNA VALLEY AND THE EXTREME SOUTHERN COPPER RIVER
BASIN TONIGHT THROUGH SAT NIGHT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

NUMEROUS SNOW SHOWERS WILL CONTINUE TO DEVELOP ACROSS THE
SOUTHWEST MAINLAND WITH TWO UPPER LEVEL CENTERS MOVING ALONG A
BROAD TROUGH. BRIEF RIDGING TRANSITS THE AREA SATURDAY NIGHT WITH
A STRONG WEATHER FRONT MOVING INTO THE SOUTHWEST COAST EARLY
SUNDAY MORNING. STRONG GUSTY WINDS AND PRECIPITATION WILL
ACCOMPANY THE FRONT WITH A REINFORCING SURGE MOVING THROUGH
SUNDAY NIGHT.

THE ALASKA PENINSULA STAYS IN NORTH TO WESTERLY FLOW WITH SNOW
SHOWERS THROUGH SATURDAY AFTERNOON. THE STRONG WEATHER FRONT MOVES
ACROSS SATURDAY NIGHT BRINGING A WIND SHIFT TO THE SOUTH AND
PRECIPITATION ALONG THE FRONTAL BOUNDARY. SNOW DEVELOPS ALONG THE
FRONT AND CHANGES QUICKLY TO RAIN AS THE BOUNDARY LIFTS NORTH.
STRONG SOUTHWEST TO WEST WINDS PERSIST INTO THE BEGINNING OF THE
WEEK AS THE SURFACE LOW TRACKS INTO THE NORTHERN BERING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

A WEAK SURFACE LOW AND FRONT MOVES ACROSS THE WESTERN BERING/ALEUTIANS
THIS MORNING AND INTO THE CENTRAL BERING THIS AFTERNOON. NO
WEATHER IMPACTS ARE EXPECTED WITH THIS SYSTEM...HOWEVER THE NEXT
SYSTEM WILL BE QUICKLY DEVELOPING IN THE NORTH PACIFIC ON
SATURDAY. WINDS ARE EXPECTED TO RAPIDLY INCREASE LATE TONIGHT
ACROSS THE WESTERN AND CENTRAL ALEUTIANS AS THE LOW CENTER
APPROACHES. WINDS ACROSS THE EASTERN ALEUTIANS AND BERING INCREASE
ON SATURDAY. A HIGH WIND WATCH WAS ISSUED WITH THE MORNING PACKAGE
FOR THE WESTERN AND CENTRAL ALEUTIANS AS CONFIDENCE INCREASES TO
SEE HURRICANE FORCE WIND GUSTS DEVELOP ON THE BACKSIDE OF THIS
SYSTEM SATURDAY EVENING. THIS SYSTEM MAINTAINS STRENGTH AS IT
LIFTS NORTHWEST OF THE PRIBILOF ISLANDS ON SUNDAY AND SHOULD BE
MONITORED FOR UPDATES INTO THE BEGINNING OF NEXT WEEK.

&&

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

AN ACTIVE WEATHER PATTERN WILL START TO TAKE SHAPE OVER THE AREA
AS WE HEAD INTO THE WEEKEND...WITH THE MAIN FEATURE BEING A STRONG
FRONTAL SYSTEM ASSOCIATED WITH A DEEPENING NORTH PACIFIC LOW
ENTERING THE BERING SEA SATURDAY. AS THIS SYSTEM SPREADS VERY
WINDY AND WET CONDITIONS NORTH AND EASTWARD THROUGH THE BERING AND
ALEUTIANS OVER THE WEEKEND...THE MORE CLEAR AND DRY CONDITIONS
OVER THE SOUTHWEST MAINLAND WILL WRAP UP BY SUNDAY MORNING AS THE
FRONT STARTS TO PUSH IN OVER THE AREA. AS THE LOW CENTER TRACKS
INTO THE CENTRAL BERING AND PROGRESSES NORTHWARD...WE EXPECT THE
STRONGEST WINDS TO REMAIN ON THE WESTERN AND SOUTHERN FLANK OF THE
SYSTEM WITH A FAIR AMOUNT OF COLD AIR ADVECTION HELPING TO MIX
GUSTIER WINDS DOWN FROM ALOFT. THE STRONG WESTERLY WINDS ALONG THE
SOUTHERN FLANK OF THE SYSTEM HAVE RAISED SOME CONCERN FOR COASTAL
FLOODING ALONG THE BRISTOL BAY AND KUSKOKWIM DELTA COAST FOR THE
BEGINNING OF NEXT WEEK. CURRENTLY WE ARE EXPECTING MINIMAL IMPACTS
TO THE COASTAL AREAS WITH MINIMAL AMOUNTS OF ICE PILING UP...
HOWEVER THIS IS SOMETHING WE WILL CONTINUE TO MONITOR AS THE
SYSTEM EVOLVES OVER THE NEXT FEW DAYS. FORECAST CONFIDENCE IS
BEGINNING TO RISE AS MODELS ARE STARTING TO COME INTO BETTER
AGREEMENT WITH THE STRENGTH OF THE SYSTEM...HOWEVER...THE MODELS
ARE STILL STRUGGLING WITH THE EXACT TRACK OF THIS SYSTEM. THE GFS
IS NOW SHOWING A MORE EASTERLY SOLUTION WHEN IT HAS BEEN SHOWING
THE FURTHEST WEST SOLUTION FOR THE PAST FEW DAYS....AND THE EC DID
THE POLAR OPPOSITE WITH BECOMING THE WESTERN MOST SOLUTION WHEN IT
HAD BEEN THE MORE EASTERLY SOLUTION IN PRIOR RUNS. IT IS SAFE TO
SAY THAT THE MODELS ARE STILL IN THE PROCESS OF WORKING OUT THE
TRACK DETAILS...LEAVING FORECAST CONFIDENCE ON THE LOWER END OF
THE SPECTRUM.

FURTHER EAST...AN AREA OF LOW PRESSURE SITUATED OVER THE GULF
BEGINS TO WEAKEN AND PUSH EASTWARD BY SUNDAY...AS A RIDGE TO THE
WEST DEVELOPS AHEAD OF A DEEPENING LOW PUSHING INTO THE BERING
SEA. SHOWERY CONDITIONS OVER SOUTHCENTRAL SATURDAY WILL DIMINISH
BY SUNDAY MORNING AS THE RIDGE BUILDS IN FROM THE WEST...THEN MORE
STRATIFORM PRECIPITATION AND WINDY CONDITIONS WILL PICK BACK UP
AS THE FRONTAL SYSTEM MENTIONED ABOVE TRACKS THROUGH THE SOUTHERN
MAINLAND OVERNIGHT SUNDAY AND INTO MONDAY. AS THE FRONT PUSHES
FURTHER INLAND DURING THE EARLY PART OF THE WEEK...SHOWERY
CONDITIONS WILL REMAIN OVER MUCH OF SOUTHCENTRAL AS MULTIPLE WAVES
COMING OFF THE STRONG BERING LOW WORK THEIR WAY OVER THE AREA FROM
THE SOUTHWEST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WATCH 187 191.
MARINE...HURRICANE FORCE 413.
	     STORM FORCE 173 174 175 176 177 178 411 412.
	     HEAVY FREEZING SPRAY 160 180 181 185.
	     GALE 130 170 172 179 185 414.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...DS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...TP