Small Craft Advisory 987, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
428 PM AKST THU DEC 10 2015

.ANALYSIS AND UPPER LEVELS...
SOUTHCENTRAL...THE WEATHER REMAINS RELATIVELY QUIET THIS AFTERNOON
ACROSS MUCH OF MAINLAND SOUTHCENTRAL. THE ONLY REALLY ACTIVE
WEATHER IS OCCURRING NEAR KODIAK ISLAND AS A LOW THAT HAS BEEN
MEANDERING OFF THE COAST FOR THE PAST COUPLE DAYS CONTINUES TO
BRING RAIN TO THE AREA. THE MAIN WEATHER STORY FOR THE ANCHORAGE
AREA CONTINUES TO BE THE PERSISTENT INVERSION THAT HAS BEEN
PRESENT SINCE SUNDAY AFTERNOON ON THE ANCHORAGE SOUNDING.
CONTINUED WARMING OF THE LOWER LEVELS OF THE ATMOSPHERE HAS
ALLOWED SOME STATIONS IN THE MOUNTAINS EAST OF ANCHORAGE TO GET
ABOVE FREEZING. WHERE THE SPOTTY PRECIPITATION HAS BEEN ABLE TO
TRAVERSE THE MOUNTAINS...SUCH AS HOMER...BRIEF FREEZING RAIN HAS
BEEN REPORTED.

SOUTHWEST...DRY CONDITIONS ALSO PERSIST OVER MUCH OF SOUTHWEST
ALASKA THIS AFTERNOON AS WELL. WEAK SURFACE RIDGING HAS HELPED
DRAW COLD AIR A GOOD WAY DOWN THE ALASKA PENINSULA WITH FREQUENT
SUB-ZERO TEMPERATURES BEING REPORTED AWAY FROM THE COAST AND
SINGLE DIGITS TO TEENS NEAR THE COAST. BOTH KING SALMON AND
BETHELS 12Z SOUNDINGS INDICATE THAT IN A SIMILAR MANNER AS
SOUTHCENTRAL... THE COLD AIR IS VERY SHALLOW AS TEMPERATURES NEAR
THE FREEZING MARK 2000 FEET ABOVE GROUND LEVEL IN BOTH SOUNDINGS.
THE ONE EXCEPTION TO THE DRY WEATHER RULE HAS BEEN CAPE NEWENHAM
WHICH HAS BEEN REPORTING NEAR-BLIZZARD CONDITIONS IN A NARROW
AREA OF MODERATE TO HEAVY SNOW ASSOCIATED WITH A NEARLY STATIONARY
LOW CENTERED OFF THE COAST. THIS LOW IS IN AN AREA OF UPPER-LEVEL
DIFFLUENCE AHEAD OF A WEAK UPPER-LEVEL TROUGH...WHICH IS KEEPING
THE LOW INVIGORATED.

BERING...MANY AREAS OF THE BERING ARE WAITING WITH BAITED BREATH
IN THE CALM BEFORE THE STORM. CURRENTLY...SNOW SHOWER ACTIVITY IS
PERSISTING OVER THE EASTERN BERING...MOVING AROUND THE WEST SIDE
OF THE LOW OFF THE COAST OF CAPE NEWENHAM. BROAD...WEAK HIGH
PRESSURE IS IN PLACE OVER MUCH OF THE WESTERN BERING...WITH
RELATIVELY LITTLE ACTIVE WEATHER OCCURRING PRESENTLY. A STORM
CURRENTLY CENTERED OVER HONSHU ISLAND IN JAPAN WILL BE THE NEXT
BIG WEATHER MAKER OVER THE ENTIRE BERING THIS WEEKEND.&&

.MODEL DISCUSSION(THROUGH SUN AFTERNOON)...
OUT WEST...MODELS OVERALL ARE ADEQUATELY HANDLING THE WEAKENING
LOW OVER THE EASTERN BERING SEA. MODEL CONSENSUS IS BETTER ON THE
12Z MODEL RUNS WITH THE MAIN LOW FEATURE TO IMPACT THE BERING
SEA/ALEUTIANS AND SW ALASKA THIS WEEKEND. THE 12Z GFS OVERALL IS
THE PREFERRED SOLUTION WITH THIS DEVELOPING LOW.

IN THE EAST...MODELS ARE IN GENERALLY GOOD AGREEMENT ACROSS THE
GULF. SOME MINOR DIFFERENCES DO EXIST IN THE PRESSURE FIELDS WITH
THE PLACEMENT OF MESOSCALE FEATURES ACROSS THE KENAI PEN AND COOK
INLET REGION. OVERALL WILL LEAN TOWARD A GFS/ECMWF BLEND FOR THE
MAIN FEATURES. WILL ALSO INCORPORATE A LITTLE NAM TO CAPTURE THE
FINER SCALE FEATURES. NOTE...THE MODELS MAY BE UNDER DOING THE
QPF FIELDS FRI NIGHT/SAT MORNING AND RESULTING SNOWFALL POTENTIAL
ACROSS THE ANCHORAGE BOWL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LOW IN THE GULF CONTINUES TO WEAKEN AS IT TRACKS TOWARDS THE
BARREN ISLANDS BUT IS STILL BRINGING IN SOME LIGHT SHOWERS TO THE
GULF COAST. ON FRIDAY A TROUGH WILL PUSH IN FROM THE SOUTHWEST
FROM A LOW OVER THE EASTERN BERING THAT WILL BRING IN ANOTHER PUSH
OF MOISTURE TO THE SOUTHCENTRAL. THERE WILL ALSO BE COLD AIR
ADVECTION WITH THIS PUSH THAT WILL AID IN SNOW DEVELOPMENT. THE
MOST CHALLENGING PART OF THE FORECAST IS WITH THE POTENTIAL FOR AN
EASTERLY PUSH OVER THE ANCHORAGE AREA. THERE IS DISAGREEMENT
AMONGST THE GUIDANCE AS TO HOW STRONG THE EASTERLY PUSH WOULD BE
BUT IT BRINGS ABOUT THE POTENTIAL FOR CONVERGENCE OVER THE
ANCHORAGE AREA FRIDAY NIGHT. IF THIS BANDING HAPPENS HEAVIER
SNOWFALL COULD OCCUR...BUT CONFIDENCE IS CURRENTLY LOW FOR THIS
SOLUTION. HOWEVER...THERE IS STILL ENOUGH OF A PUSH FROM THE
TROUGH FOR SNOW TO MAKE IT INTO ANCHORAGE AND THE MATANUSKA
VALLEY FRIDAY NIGHT INTO SATURDAY MORNING.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
SNOW IS RETURNING TO THE MAINLAND THIS AFTERNOON AND EVENING AS A
COUPLE DISTURBANCES ALOFT COMBINE OVER THE BRISTOL BAY AREA. A
BAND OF SNOW WILL SETUP EAST OF DILLINGHAM TONIGHT...SLOWLY
PUSHING EASTWARD THROUGH THE OVERNIGHT HOURS INTO FRIDAY. LIGHT
SNOW WILL ALSO DEVELOP OVER THE KUSKOKWIM DELTA TONIGHT BUT
ACCUMULATION IS NOT EXPECTED. WINDS WILL CONTINUE TO WEAKEN AND
TEMPERATURES WILL MODERATE SLIGHTLY WITH THE INCOMING
PRECIPITATION. FRIDAY NIGHT INTO SATURDAY...THE UPPER LEVEL SYSTEM
WILL LINGER OVERHEAD KEEPING THE CHANCE FOR SHOWERS IN THE
FORECAST BEFORE DRYING OUT ON SATURDAY NIGHT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
SNOW SHOWERS WILL CONTINUE TO ENCOMPASS THE CENTRAL AND EASTERN
BERING SEA WITH NORTHERLY WINDS. THESE SHOWERS WILL SLOWLY PUSH
EASTWARD THROUGH SATURDAY WHILE WEAKENING. LATE TOMORROW NIGHT A
VERY STRONG LOW PRESSURE SYSTEM MOVES TOWARD THE WESTERN
ALEUTIANS. THE INITIAL FRONT WILL BRING A MIX OF RAIN AND SNOW AS
WELL AS SOLID STORM FORCE WINDS.

&&

.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...NONE.
MARINE...GALE 178
         HEAVY FREEZING SPRAY 161 180 181 185.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
108 AM AKST FRI DEC 11 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0107 AM     SNOW             KING SALMON             58.74N 156.54W
12/11/2015  M6.0 INCH                           AK   NWS EMPLOYEE

            SIX INCHES NEW SNOWFALL IN LAST SEVEN HOURS. STILL
            SNOWING AT TIME OF REPORT.

&&

RDUELL