Gale Warning 752, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
421 AM AKST FRI NOV 6 2015

.ANALYSIS AND UPPER LEVELS...
THE MAIN PLAYER ALOFT CONTINUES TO BE THE FILLING STACKED
UPPER/LOWER SYSTEM...NOW CROSSING THE ALASKA PENINSULA INTO THE
GULF. THE LONGWAVE HAS SHIFTED EASTWARD AND IS ALSO PUMPING UP
RIDGING ALOFT FROM WESTERN CANADA NORTHWARD INTO NORTHERN ALASKA.
THE OCCLUDED FRONT IS WEAKENING AND SHIFTING EASTWARD ACROSS THE
NORTHERN GULF...THE STEADIER STRATIFORM PRECIPITATION ENDING AND
TRANSITIONING TO AN UNSTABLE SHOWERY FLOW BEHIND THE FRONT.
STRONG WINDS CONTINUE TO WRAP AROUND THE WESTERN AND SOUTHERN SIDE
OF THE SYSTEM FROM THE EASTERN BERING SEA INTO THE GULF WHERE A
TIGHT PRESSURE GRADIENT AND MODEST COLD ADVECTION ARE ALLOWING
FOR STRONGER GUSTS TO MIX DOWN TO THE SURFACE. THE SOUTHWESTERN
MAINLAND IS SEEING AREAS OF RAIN AND SNOW AS DISTURBANCES ROTATE
AROUND THE UPPER LOW CENTER...ENHANCED BY A POCKET OF COLD AIR
ALOFT.

FURTHER OUT WEST TOWARD KAMCHATKA...ANOTHER STRONG LONGWAVE TROUGH
SITS OVER THE PENINSULA WITH A ZONAL FLOW OR WEAK RIDGING BETWEEN
THE TWO LOW PRESSURE SYSTEMS. THE EAST ASIAN JET IS BRIDGING THESE
TWO SYSTEMS WITH A WEAK WARM FRONT ENTERING THE WESTERN BERING
SEA.

&&

.MODEL DISCUSSION...
GUIDANCE CONTINUES TO BE IN GREAT AGREEMENT SPATIALLY AND
TEMPORALLY WITH THE LARGE SCALE FEATURES...NAMELY THE WEAKENING
LONGWAVE TROUGH/LOW OVERHEAD. HOWEVER THE SYSTEM DEVELOPING OFF
KAMCHATKA IS NOT AS WELL AGREED UPON WITH STRENGTH...POSITION OR
TIMING...HOWEVER THESE DIFFERENCES SHOULD HAVE LITTLE EFFECT ON
OUR FORECAST AREA. THERE ARE SOME SMALLER SCALE DIFFERENCES THAT
WOULD HAVE BIG IMPACTS ON THE FORECAST TODAY. AS A TROUGH ROTATES
AROUND THE BASE OF THE WEAKENING SYSTEM TOWARD THE MAINLAND...IT
INTERACTS WITH THE CONVECTIVELY UNSTABLE AIR ALOFT. HIGHER
RESOLUTION MODELS ARE DEPICTING A DEFORMATION ZONE/FRONTOGENESIS
BAND OVER THE SOUTHERN COPPER RIVER BASIN THIS AFTERNOON INTO THE
OVERNIGHT. THE SOLUTION IS LOW CONFIDENCE BUT HAS POTENTIAL FOR
LARGER ACCUMULATING SNOW.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LARGE UPPER LEVEL LOW OVER ALASKA WILL SLOWLY WEAKEN AND
MOVE EAST OVER THE NEXT COUPLE OF DAYS. MUCH OF SOUTH CENTRAL IS
UNDER CYCLONIC FLOW AND ON THE EAST SIDE OF THIS LOW. THIS WILL
KEEP SHOWERS OVER THE AREA INTO TONIGHT...SLOWLY DIMINISHING.
PRECIPITATION TYPE IS AGAIN A FORECAST CHALLENGE WITH TEMPERATURES
HOVERING NEAR FREEZING. SHOWERS WILL END FROM WEST TO EAST
BEGINNING TONIGHT AND FINALLY CLEAR EVEN THE COPPER RIVER BASIN BY
LATE SATURDAY NIGHT. AN UPPER LEVEL RIDGE WILL BRIEFLY BUILD OVER
THE AREA IN BETWEEN THIS EXITING LOW AND THE NEXT SYSTEM RAPIDLY
APPROACHING FROM THE WEST...NEARING KODIAK ISLAND LATE SATURDAY
NIGHT. THIS RIDGE WILL USHER IN A PERIOD OF LOW LEVEL OUTFLOW
WINDS...WITH STRONG WINDS PUSHING ACROSS THE ALEUTIAN RANGE AND
THROUGH THE BARREN ISLANDS AS WELL AS SHELIKOF STRAIT AND KODIAK
ISLAND. OTHER FAVORED AREAS SUCH AS SEWARD AND WHITTIER SHOULD
DEVELOP GUSTY WINDS BEGINNING LATER TODAY. WINDS WILL BEGIN TO
RELAX SATURDAY NIGHT AS THE RIDGE WEAKENS AHEAD OF THE NEXT
WEATHER SYSTEM DUE SUNDAY.

&&

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

THE STRONG AREA OF LOW PRESSURE THAT HAS BEEN PUSHING ACROSS THE
BRISTOL BAY AREA OVERNIGHT HAS FINALLY SHIFTED INTO THE WESTERN
GULF OF ALASKA. HOWEVER...THE EFFECTS ARE STILL BEING FELT ACROSS
THE ALASKA PENINSULA AND THROUGH THE GAPS OF THE ALASKA/ALEUTIAN
RANGES WHERE GUSTY WINDS ARE BEING OBSERVED. THE STRONGEST WINDS
ARE CURRENTLY OCCURRING THROUGH NORTHWEST ORIENTED GAPS ACROSS THE
ALASKA PENINSULA WHERE GUSTS OF 50-60 MPH ARE BEING OBSERVED. AS
THE LOW PUSHES FURTHER EAST INTO THE GULF OF ALASKA...THE PRESSURE
GRADIENT WILL BEGIN TO RELAX AND WINDS WILL CONTINUE TO DIMINISH.
GUSTY WINDS WILL CONTINUE DUE TO DECENT COLD AIR ADVECTION ON THE
BACK SIDE OF THE LOW BUT THE MAGNITUDE OF THESE GUSTS WILL CONTINUE
TO GRADUALLY DIMINISH. PRECIPITATION CHANCES ARE ALSO ON THE
DOWNSWING AS MUCH OF THE MOISTURE SHIFTS FURTHER EAST AND MOST OF
THE UPPER LEVEL SUPPORT AND LIFT ASSOCIATED WITH THE LOW ALSO
SHIFT EASTWARD. MUCH OF THE PRECIPITATION WILL CONTINUE TO FALL
AS RAIN ACROSS THE SOUTHERN HALF OF THE BRISTOL BAY AREA WHILE
NORTH OF DILLINGHAM AND ACROSS THE LOWER KUSKOKWIM VALLEY WILL SEE
SNOW AS TEMPERATURES ARE LOW ENOUGH AND WET BULB ZEROES AROUND 30
TO 32 DEGREES. BY SATURDAY...MUCH OF THE PRECIPITATION WILL HAVE
TAPERED OFF WITH THE EXCEPTION OF SHOWERS ALONG THE ALEUTIAN RANGE
AND SNOW ACROSS THE LOWER KUSKOKWIM VALLEY.

A STRONG WARM FRONT ASSOCIATED WITH A RAPIDLY DEEPENING AREA OF
LOW PRESSURE OVER THE NORTHERN BERING SEA WILL DRIVE A POTENT WARM
FRONT TOWARD THE WEST COAST OF ALASKA LATE SATURDAY. THIS WILL
BRING A VERY WARM AIR MASS TO THE REGION BUT WILL BE SHORT LIVED
AS COLD AIR QUICKLY REPLACES THE WARM AIR AS THE FRONT OCCLUDES
OVER SOUTHWEST ALASKA. PRECIPITATION TYPE GETS A LITTLE TRICKY
DEPENDING ON HOW QUICKLY THE COLD AIR REPLACES THE WARM AIR BUT
IT LOOKS LIKE A VERY GOOD SHOT OF MODERATE RAINFALL BEFORE THE
CHANGE OVER TO SNOW LATER ON SUNDAY.

&&

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

A PROGRESSIVE WEATHER PATTERN WILL CONTINUE ACROSS THE BERING SEA
AS AS BUILDING UPPER LEVEL RIDGE OVER THE BERING SEA IS THE RESULT
OF THE AN AMPLIFYING TROUGH OVER KAMCHATKA. A WEAK SURFACE LOW
CURRENTLY OVER THE NORTHERN BERING SEA WILL CONTINUE TO DRIFT
EASTWARD AND WEAKEN. HOWEVER...THE AMPLIFYING TROUGH WILL SHIFT
OVER THE NORTHERN BERING SEA ON SATURDAY AND INTERACT WITH THIS
DECAYING LOW. A VERY POTENT JET STREAK WILL RE-INVIGORATE THIS SFC
LOW AND A NEW LOW CENTER DEVELOPS JUST TO THE WEST OF THE DECAYING
LOW AND RAPIDLY DEEPENS DURING THE DAY ON SATURDAY. THIS WILL
DRIVE A GALE FORCE FRONT ACROSS THE BERING SEA AS WELL AS BRING A
QUICK SHOT OF WARMER TEMPERATURES.

COLDER AIR QUICKLY BEGINS TO FILTER IN BEHIND THE LOW LATE SATURDAY
INTO SUNDAY WHICH SHOULD START TO CHANGE SOME RAIN TO SNOW ACROSS
THE WESTERN HALF OF THE BERING SEA. HOWEVER...A SECOND JET STREAK
DEVELOPS OVER THE CENTRAL ALEUTIANS LATE SATURDAY AND INTERACTS
WITH THE STRENGTHENING LOW OVER THE BERING SEA. THIS WILL LEAD TO
MAX GALES AND POSSIBLY MINIMUM STORM FORCE WINDS ACROSS THE
NORTHERN AND CENTRAL BERING SEA AS A SECOND SHOT OF CYCLOGENESIS
COUPLES WITH SOME OF THE COLDEST AIR OF THE YEAR SEEN THIS FAR
SOUTH. WAVE HEIGHTS WILL ALSO BE ON THE INCREASE AS SEAS WILL
BUILD TO 25 TO 30 FT OVER THE CENTRAL AND NORTHERN BERING SEA BY
THE END OF THE WEEKEND.

&&

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

THE MOST IMPACTFUL CONCERN FROM SUNDAY ONWARD IS THE POTENTIAL FOR
A BRIEF BUT SIGNIFICANT SNOW EVENT FOR SOUTHCENTRAL ALASKA SUNDAY
INTO MONDAY ACROSS THE REGION...WITH RAIN ALONG THE NORTHERN GULF
COAST. ALL MODEL SOLUTIONS DEPICT A ROBUST UPPER LEVEL SYSTEM WITH
EXTREMELY IMPRESSIVE JET DYNAMICS MOVING FROM THE BERING EAST
ACROSS THE NORTH GULF COAST SUNDAY INTO SUNDAY NIGHT. SIGNIFICANT
TRAVEL DISRUPTIONS WOULD BE POSSIBLE IN OR NEAR THE BIGGER
POPULATION AREAS...INCLUDING ANCHORAGE...LATE SUNDAY AFTERNOON
THROUGH SUNDAY EVENING...WITH MODERATE TO OCCASIONALLY HEAVY SNOW
RATES. PRELIMINARY SNOWFALL ESTIMATES OF 3 TO 7 INCHES WITH
ISOLATED HIGHER AMOUNTS APPEAR POSSIBLE AREA-WIDE EXCEPT FOR ALONG
THE IMMEDIATE NORTH GULF COAST WHERE PRECIPITATION WILL FALL AS
RAIN.

OUTSIDE OF THE STORM POTENTIAL MENTIONED ABOVE...THE MAIN WEATHER
STORY THROUGH MID-WEEK WILL BE THE NUMEROUS ENERGETIC DISTURBANCES
ROTATING THROUGH THE BERING AND INTO AND ACROSS THE SOUTHERN
ALASKA MAINLAND...MAINLY BRINGING SHORT-DURATION LIGHT SNOW
EVENTS TO MOST AREAS...AND THIS WILL BE COUPLED WITH THE ARRIVAL
OF THE COLDEST AIR MASS OF THE SEASON INTO SOUTHERN INTERIOR
AREAS FOR NEXT WEEK. THERE WILL ALSO BE A LARGE AREA OF WESTERLY
GALE-FORCE WINDS ACROSS THE BERING WILL BRING HIGH SEAS AND
POTENTIALLY HIGH SURF CONDITIONS ALL THE WAY TO THE SOUTHWEST
MAINLAND COASTLINE...AND HAVE THE POTENTIAL TO APPROACH HIGH SURF
ADVISORY CRITERIA...THOUGH THIS WILL CONTINUE TO BEAR CLOSE
WATCHING.

A STRONG GALE-FORCE OR STORM-FORCE LOW MAY MOVE QUICKLY WEST TO
EAST ACROSS THE ALEUTIAN CHAIN TUESDAY THROUGH EARLY THURSDAY IF
THE VERY LATEST MODEL SOLUTIONS WERE TO VERIFY. GRIDS WERE UPDATED
DURING THIS TIME TO TREND A BIT TOWARD THIS STRONGER
SOLUTION...BUT WILL WAIT FOR MORE MODEL CONTINUITY BEFORE
COMPLETELY ADOPTING THESE STRONGER AND MORE IMPACTFUL LATEST MODEL
SOLUTIONS INTO THE GRIDDED FORECASTS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...130-132 136 137 150 155 160 165 170 172-180 185.

&&

SYNOPSIS AND MODEL DISCUSSION...MTL
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...CC

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
114 PM AKST FRI NOV 6 2015

AKZ101-111-121-125-131-141-145-071015-
ANCHORAGE-MATANUSKA VALLEY-WESTERN KENAI PENINSULA-
WESTERN PRINCE WILLIAM SOUND-NORTHEAST PRINCE WILLIAM SOUND-
COPPER RIVER BASIN-SUSITNA VALLEY-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON...KENAI...
SOLDOTNA...HOMER...COOPER LANDING...WHITTIER...SEWARD...
GIRDWOOD...MOOSE PASS...VALDEZ...THOMPSON PASS...GLENNALLEN...
EUREKA...MCCARTHY...PAXSON...SLANA...TALKEETNA...WILLOW...
CANTWELL
114 PM AKST FRI NOV 6 2015

...SNOWFALL EXPECTED THROUGHOUT SOUTHCENTRAL STARTING SUNDAY...

THE NEXT ROUND OF ACCUMULATING SNOW WILL MOVE INTO TO THE
SOUTHERN MAINLAND ON SUNDAY...AND POTENIALLY CONTINUING INTO
MONDAY MORNING. THERE IS GOOD CONFIDENCE IN THE TIMING OF THE
SNOWFALL...HOWEVER THERE STILL REMAINS SOME QUESTION IN HOW MUCH
WILL ACCUMULATE.

FOR THE ANCHORAGE BOWL AND MATANUSKA/SUSITNA VALLEYS: SNOW SHOULD
BEGIN ON SUNDAY AFTERNOON (AS A RAIN/SNOW MIX SOUTH OF WILLOW). BY
SUNDAY EVENING ALL AREAS SHOULD SWITCH OVER TO SNOW...WHEN THE
HEAVIEST SNOWFALL IS ALSO EXPECTED TO OCCUR. SNOWFALL WILL THEN
BEGIN TO DIMINISH ON MONDAY MORNING.

FOR THE KENAI PENINSULA: RAIN AND SNOW SHOULD BEGIN IN THE LATE
MORNING OR EARLY AFTERNOON...WITH MOST OF THE SNOWFALL OCCURRING
OVER INLAND AREAS TO THE NORTH OF CLAM GULCH. AREAS ALONG COOK
INLAND AND SOUTH OF CLAM GULCH WILL LIKELY SEE MOSTLY RAIN FROM
THIS SYSTEM...WITH LITTLE IF ANY SNOW ACCUMULATIONS.

FOR THE COPPER RIVER BASIN AND THOMPSON PASS: SNOW SHOULD BEGIN ON
SUNDAY EVENING AND PERSIST THROUGH MONDAY MORNING. THERE IS GOOD
CONFIDENCE THAT ANY PRECIPITATION WILL FALL IN THE FORM OF SNOW IN
THIS AREA...WITH THE HEAVIEST SNOWFALL EXPECTED LATE SUNDAY NIGHT
INTO MONDAY MORNING.

FOR THE LATEST FORECAST FOR HOW THIS SYSTEM MAY IMPACT YOUR
AREA...VISIT WWW.WEATHER.GOV/ANCHORAGE.

SPECIAL WEATHER STATEMENT...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
114 PM AKST FRI NOV 6 2015

AKZ101-111-121-125-131-141-145-071015-
ANCHORAGE-MATANUSKA VALLEY-WESTERN KENAI PENINSULA-
WESTERN PRINCE WILLIAM SOUND-NORTHEAST PRINCE WILLIAM SOUND-
COPPER RIVER BASIN-SUSITNA VALLEY-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON...KENAI...
SOLDOTNA...HOMER...COOPER LANDING...WHITTIER...SEWARD...
GIRDWOOD...MOOSE PASS...VALDEZ...THOMPSON PASS...GLENNALLEN...
EUREKA...MCCARTHY...PAXSON...SLANA...TALKEETNA...WILLOW...
CANTWELL
114 PM AKST FRI NOV 6 2015

...SNOWFALL EXPECTED THROUGHOUT SOUTHCENTRAL STARTING SUNDAY...

THE NEXT ROUND OF ACCUMULATING SNOW WILL MOVE INTO TO THE
SOUTHERN MAINLAND ON SUNDAY...AND POTENIALLY CONTINUING INTO
MONDAY MORNING. THERE IS GOOD CONFIDENCE IN THE TIMING OF THE
SNOWFALL...HOWEVER THERE STILL REMAINS SOME QUESTION IN HOW MUCH
WILL ACCUMULATE.

FOR THE ANCHORAGE BOWL AND MATANUSKA/SUSITNA VALLEYS: SNOW SHOULD
BEGIN ON SUNDAY AFTERNOON (AS A RAIN/SNOW MIX SOUTH OF WILLOW). BY
SUNDAY EVENING ALL AREAS SHOULD SWITCH OVER TO SNOW...WHEN THE
HEAVIEST SNOWFALL IS ALSO EXPECTED TO OCCUR. SNOWFALL WILL THEN
BEGIN TO DIMINISH ON MONDAY MORNING.

FOR THE KENAI PENINSULA: RAIN AND SNOW SHOULD BEGIN IN THE LATE
MORNING OR EARLY AFTERNOON...WITH MOST OF THE SNOWFALL OCCURRING
OVER INLAND AREAS TO THE NORTH OF CLAM GULCH. AREAS ALONG COOK
INLET AND SOUTH OF CLAM GULCH WILL LIKELY SEE MOSTLY RAIN FROM
THIS SYSTEM...WITH LITTLE IF ANY SNOW ACCUMULATIONS.

FOR THE COPPER RIVER BASIN AND THOMPSON PASS: SNOW SHOULD BEGIN ON
SUNDAY EVENING AND PERSIST THROUGH MONDAY MORNING. THERE IS GOOD
CONFIDENCE THAT ANY PRECIPITATION WILL FALL IN THE FORM OF SNOW IN
THIS AREA...WITH THE HEAVIEST SNOWFALL EXPECTED LATE SUNDAY NIGHT
INTO MONDAY MORNING.

FOR THE LATEST FORECAST FOR HOW THIS SYSTEM MAY IMPACT YOUR
AREA...VISIT WWW.WEATHER.GOV/ANCHORAGE.