Gale Warning 881, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
422 PM AKST WED DEC 9 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL PATTERN TODAY SHOWS A CLOSED LOW OVER THE GULF OF
ALASKA WITH A SECONDARY TROUGH OVER THE WESTERN BERING. A WEAK
FINGER OF THE JET EXTENDS NORTH OF THE LOW IN THE GULF BUT THE
PRIMARY UPPER LEVEL ENERGY STILL REMAINS SOUTH OF THE FORECAST
AREA IN THE NORTHERN BERING. AT THE SURFACE THIS UPPER LEVEL
PATTERN IS REFLECTED IN A MATURE LOW IN THE GULF OF ALASKA AND A
SECONDARY WEAK LOW OUT IN THE WESTERN ALEUTIANS. NORTHERLY FLOW IS
CONTINUING ACROSS THE FORECAST AREA TODAY AND REMAINS FAIRLY
STRONG AND GUSTY ACROSS THE WEST COAST AND BERING WHERE THE
GRADIENT BETWEEN THE MAIN LOW AND THE SURFACE HIGH OVER EASTERN
SIBERIA IS A BIT TIGHTER. THIS GRADIENT IS EXPECTED TO WEAKEN
SLIGHTLY OVER THE NEXT 24 HOURS BUT OTHERWISE NO SIGNIFICANT
CHANGES TO THE SYNOPTIC SITUATION ARE EXPECTED IN THE SHORT TERM. THE
GULF LOW IS FORECAST TO MOVE NORTH AND WESTWARD OVER THE NEXT 24
HOURS...BRINGING AN ASSOCIATED FRONT ONSHORE IN THE SOUTHCENTRAL
REGION. THIS WILL CHANGE THE LOW LEVEL AIRMASS IN SOUTHCENTRAL
WHICH IS CURRENTLY BEING DOMINATED BY A STRONG INVERSION...AS
APPARENT ON THIS MORNINGS SOUNDINGS.

&&

.MODEL DISCUSSION...
MODELS ARE IN BETTER AGREEMENT THAN THEY HAVE BEEN OVER THE PAST
FEW DAYS BUT THERE ARE STILL SOME MINOR DIFFERENCES THAT COULD
AFFECT THE FORECAST SLIGHTLY. THE ECMWF IS THE MODEL OF CHOICE IN
THE SHORT TERM FOR BOTH EAST AND WEST AS IT SEEMED TO HAVE THE
BEST HANDLE ON THE SITUATION OVER THE NEXT 24 HOURS...HOWEVER FOR
24 TO 48 HOURS GFS WAS PREFERRED IN THE EAST AS IT HAS BEEN MORE
CONSISTENT ON TIMING.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE GULF LOW IS SLOWLY TRACKING WEST AND WILL CURVE NORTHWEST
TOWARD THE BARREN ISLANDS THURSDAY NIGHT. THIS KEEPS WARM
SOUTHEAST FLOW OVER THE SOUTHCENTRAL INTO FRIDAY. THE MAJORITY OF
THE PRECIPITATION WILL FALL ON THE GULF SIDE THIS EVENING AND
LOCATIONS NEAR THE GULF WILL SEE A RAIN AND SNOW MIX. SOME SNOW
SHOWERS MAY MAKE IT PAST THE COASTAL RANGES BUT WITH MINIMAL UPPER
LEVEL SUPPORT ACCUMULATIONS WILL ALSO BE MINIMAL. ON FRIDAY THE
WEAKENING LOW WILL BE REINFORCED BY A TROUGH MOVING UP FROM THE
SOUTH THAT WILL BRING ANOTHER PUSH OF PRECIPITATION TO THE AREA.
THIS LOOKS TO BE COLDER AND FALL PREDOMINATELY AS SNOW. THERE IS
STILL SOME UNCERTAINTY AS TO HOW WIDESPREAD THIS SNOW WILL BE AND
HOW MUCH WILL MAKE IT TO MORE INTERIOR LOCATIONS.

THE OTHER CONCERN FOR THE SOUTHCENTRAL IS WINDS. THE STRONGEST
WINDS HAVE BEGUN DIMINISHING AND WILL CONTINUE THAT TREND
OVERNIGHT BUT SOME OF THE NORTH TO SOUTH ORIENTED GAPS LIKE
THOMPSON PASS WILL STILL HAVE STRONG ENOUGH WINDS OVERNIGHT WHERE
BLOWING SNOW CONDITIONS MAY OCCUR. HOWEVER...NEW SNOWFALL STILL
LOOKS TO BE LIGHT AND WITH NO TRANSPORTABLE SNOW VISIBILITIES
SHOULD STAY ABOVE ONE MILE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
DRY CONDITIONS REMAIN FOR TONIGHT AS WEAK OUTFLOW PERSISTS OVER
THE MAINLAND. GUSTY NORTHERLY WINDS WILL REMAIN OVER THE KUSKOKWIM
DELTA...GRADUALLY TAPERING DOWN THURSDAY AFTERNOON. AT THIS
TIME...A SYSTEM BACKING TOWARD THE AREA FROM THE GULF WILL SET UP
A BAND OF SNOW OVER THE GREATER BRISTOL REGION...BEGINNING IN THE
LATE AFTERNOON AND INCREASING IN INTENSITY DURING THE EVENING
HOURS. THIS BAND WILL SET UP SOMEWHERE BETWEEN DILLINGHAM AND
KOLIGANEK WHERE THE GREATEST CHANCE FOR ACCUMULATING SNOW WILL
RESIDE. THE RESPONSIBLE UPPER LEVEL SYSTEM WILL SPIN OVERHEAD
THROUGH LATE FRIDAY KEEPING SNOW SHOWERS OR LIGHT SNOW OVER THE
AREA...BUT THE MAIN THREAT FOR ACCUMULATING SNOW WILL MOVE OVER
THE ALASKA RANGE AND DISSIPATE ON FRIDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A WEAK TROUGH SITTING OVER THE CENTRAL BERING WILL SLOWLY SPREAD SNOW
AND RAIN EASTWARD FROM THE EASTERN ALEUTIANS THROUGH THE ALASKA
PENINSULA TONIGHT. THURSDAY INTO FRIDAY...ARCTIC AIR POURING INTO
THE CENTRAL AND EASTERN BERING WILL BE THE FOCUS FOR SNOW SHOWERS
OVER MUCH OF THAT AREA AND WILL CONTINUE THROUGH FRIDAY. A WEAK
FRONTAL BOUNDARY AND MULTIPLE DISTURBANCES ALOFT WILL KEEP A
CHANCE OF LIGHT SNOW OR SNOW SHOWERS OVER THE WESTERN ALEUTIANS
FOR THE NEXT COUPLE DAYS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
IT APPEARS MORE AND MORE LIKELY WITH THE MOST RECENT MODEL RUNS THAT
SOUTHWEST AND SOUTHCENTRAL ALASKA ARE HEADING INTO QUITE AN ACTIVE
WEATHER PATTERN STARTING FRIDAY. WE WILL START ACROSS SOUTHCENTRAL
ALASKA WHERE AN AREA OF LOW PRESSURE SITUATED OVER THE KENAI
PENINSULA 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. THIS WILL AMPLIFY THE UPPER LEVEL PATTERN OVER
SOUTHCENTRAL ALASKA BY PUSHING THE UPPER LEVEL TROUGH ACROSS
SOUTHCENTRAL ALASKA (MAINLY THE COOK INLET REGION)...HELPING TO
INCREASE SNOW CHANCES. MOST MODEL PRECIPITATION FIELDS CONTINUE TO
SHOW ONLY LIGHT SNOW ACCUMULATION ACROSS THE REGION. HOWEVER...
THERE REMAINS THE POTENTIAL FOR SLIGHTLY HIGHER SNOW ACCUMULATION
OVER AREAS THAT EXPERIENCE SOME MESOSCALE BANDING AND POCKETS OF
HEAVIER SNOWFALL. CURRENTLY THE MODELS ARE SETTING UP THE HEAVIER
SNOWFALL AMOUNTS ACROSS THE KENAI PENINSULA AND AREAS SURROUNDING
PRINCE WILLIAM SOUND.HOWEVER...WITH THE SLIGHT DIFFERENCES IN THE
MODELS STILL...WE CAN NOT RULE OUT THE POTENTIAL FOR HIGHER SNOW
AMOUNTS FOR ANCHORAGE AND PARTS OF THE MATANUSKA AND SUSITNA
VALLEYS.

OUT WEST...NORTHWESTERLY FLOW AND COLD AIR ADVECTION SHOWERS OVER
THE EASTERN ALEUTIANS AND ALASKA PENINSULA WILL GRADUALLY
DIMINISH...AS THE RIDGING MENTIONED ABOVE STARTS PUSHING INTO THE
AREA TO START OFF THE WEEKEND. THE SOUTHWEST MAINLAND WILL SEE A
VERY BRIEF BREAK FROM PRECIPITATION SATURDAY EVENING AND INTO
SUNDAY MORNING AS THIS RIDGE MOVES OVER THE AREA. A RAPIDLY
EVOLVING NORTH PACIFIC LOW WILL TRACK AN ASSOCIATED FRONT INTO
THE WESTERN ALEUTIANS SATURDAY MORNING...THEN CONTINUE TO SPREAD
WET AND WINDY CONDITIONS NORTH AND EASTWARD ACROSS THE BERING SEA
THROUGH THE WEEKEND. THE FRONT WILL THEN TRACK INTO THE SOUTHWEST
MAINLAND BY SUNDAY NIGHT AND BEGIN TO WEAKEN AS IT TRACKS FURTHER
INTO MAINLAND ALASKA BY THE BEGINNING OF THE WEEK. MODELS HAVE
COME INTO BETTER AGREEMENT WITH THE STRENGTH AND TRACK OF THIS
SYSTEM...BRINGING A STORM FORCE SYSTEM AND ROUGH SEAS TO THE
CENTRAL BERING FROM THE NORTH PACIFIC OVER THE WEEKEND...THEN
TRACKING THE LOW CENTER INTO FAR NORTHEASTERN RUSSIA BY TUESDAY
NEXT WEEK. WE ARE EXPECTING THE STRONGER WINDS TO REMAIN ON THE
WESTERN FLANK OF THE SYSTEM WITH A FAIR AMOUNT OF COLD AIR
ADVECTION HELPING TO MIX GUSTIER WINDS DOWN FROM ALOFT. THESE
GUSTIER WINDS HAVE THE POTENTIAL TO WRAP AROUND THE SOUTHERN FLANK
OF THE SYSTEM AS IT TRACKS TOWARD THE BERING STRAIT. THIS CAN
CREATE A DECENT FETCH OF WESTERLY WINDS OVER THE BERING SEA AND
DIRECTED AT THE SOUTHWESTERN COAST DURING THE BEGINNING OF THE
WEEK. THIS RAISES SOME CONCERN FOR COASTAL FLOODING ALONG THE
BRISTOL BAY AND KUSKOKWIM DELTA COAST. 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.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY...160 180 181 185
   		GALE...119 127.

&&

SYNOPSIS AND MODEL DISCUSSION...LF
SOUTHCENTRAL ALASKA...DK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...TP