Small Craft Advisory 967, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
520 AM AKST FRI DEC 4 2015

.ANALYSIS...
AN UPPER LEVEL RIDGE IS PASSING OVER THE GULF WITH A CLOSED LOW
TO THE WEST...SPINNING SOUTH OF DUTCH HARBOR. SATELLITE IMAGERY IS
SHOWING ABUNDANT MOISTURE STREAMING NORTHWARD BETWEEN THE TWO
SYSTEMS...HOWEVER THE NORTHWARD EXTENT OF THE MOISTURE PLUME IS
MAINLY SOUTH OF THE ALASKA PENINSULA. LOW TO MID LEVEL CLOUDS ARE
MOVING INTO THE SOUTHERN AND CENTRAL BERING SEA AS SOME OF THE
MOISTURE FROM THE CUT OFF LOW FLOWS NORTH OF THE CORE. A MINOR
SHORTWAVE ALOFT IS THE FOCUS FOR SNOW SHOWERS ACROSS SOUTHCENTRAL
EARLY THIS MORNING WITH THE RADAR SHOWING ISOLATED TO NUMEROUS
SNOW SHOWERS ACROSS THE PRINCE WILLIAM SOUND...ANCHORAGE
BOWL...AND MAT- SU VALLEYS. TO THE WEST...DRY CONDITIONS PERSIST
ACROSS THE SOUTHWEST MAINLAND WITH NORTHEASTERLY WINDS. THE
BERING/ALEUTIANS ARE ALSO UNDER NORTHERNLY FLOW WITH A MIX OF RAIN
AND SNOW ACROSS THE EASTERN ALEUTIANS AND ALASKA PENINSULA AND
SNOW TOWARD THE PRIBILOF ISLANDS WITH SURFACE TEMPERATURES AT
SAINT PAUL/GEORGE IN THE LOW 30S.

.MODEL DISCUSSION...
THE GFS MODEL HAD A BETTER HANDLE WITH THE WEAK LOW TRACKING
THROUGH THE WESTERN PRINCE WILLIAM SOUND. WHILE THE NAM WAS
THE OUTLIER POSITIONING THIS LOW JUST SOUTH OF CORDOVA THIS
MORNING. THE COMPLEX LOW LOCATED SOUTH OF THE EASTERN
ALEUTIANS...THE ECMWF WAS THE PREFERRED MODEL AS IT CONSOLIDATES
THE MULTIPLE LOW PRESSURE SYSTEMS INTO ONE MAIN SYSTEM BY FRIDAY
AFTERNOON. THE NEXT WEATHER SYSTEM DROPS DOWN FROM THE KAMCHATKA
PENINSULA BEFORE ELONGATING WITH MULTIPLE LOWS AS WE HEAD INTO THE
WEEKEND. THE FORECAST CONFIDENCE IS AVERAGE DUE TO THE UNCERTAINTY
IN THE SMALLER SCALE FEATURES.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
SNOW SHOWERS WILL DIMINISH OR END DURING THE MORNING HOURS ACROSS
SOUTHCENTRAL ALASKA AS THE UPPER LEVEL SHORT-WAVE EXITS TO
INTERIOR ALASKA. A FEW SHOWERS WILL LINGER A BIT LONGER ALONG THE
ALASKA RANGE AND PRINCE WILLIAM SOUND WITH WEAK INSTABILITY AND
UPSLOPE FLOW. ANOTHER UPPER LEVEL SHORT-WAVE WILL LIFT NORTHWARD
ACROSS SOUTHWEST ALASKA...WITH THE COOK INLET TO SUSITNA VALLEY
CORRIDOR SITTING ON THE EASTERN PERIPHERY OF THE WAVE. WITH WEAK
VERTICAL MOTION AND A SLIGHTLY MORE STABLE ENVIRONMENT THAN WITH
THE PRIOR WAVE EXPECT NO MORE THAN ISOLATED TO SCATTERED
SHOWERS...MAINLY IN THE UPSLOPE AREAS OF THE NORTHERN SUSITNA
VALLEY. IN THE WAKE OF THIS WAVE SOUTHCENTRAL WILL SETTLE IN
UNDERNEATH AN UPPER LEVEL RIDGE. THIS WILL PROVIDE DRY AND
SEASONABLY COOL CONDITIONS.

MEANWHILE...KODIAK ISLAND AND THE GULF OF ALASKA CAN EXPECT MORE
ACTIVE WEATHER AS A SERIES OF DEEP LOWS TRANSIT THE NORTHEAST
PACIFIC. THE GULF WILL BE ON THE NORTHERN PERIPHERY OF THE MAIN
LOW CIRCULATION...WITH UPPER LEVEL WAVES AND SURFACE FRONTAL
BOUNDARIES TRACKING WESTWARD ACROSS THE GULF. THE AIR MASS SITTING
OVER KODIAK ISLAND THIS MORNING IS COLD ENOUGH TO SUPPORT
SNOW...BUT MUCH WARMER LOW LEVEL AIR WILL ADVECT IN FROM THE
EAST ON SATURDAY. THEREFORE...THE BULK OF PRECIP IN THE FORECAST
WILL FALL AS RAIN.

&&

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

BROAD OFFSHORE FLOW WILL KEEP SOUTHWEST ALASKA LARGELY DRY AND
COLD THROUGH SATURDAY NIGHT. THE COMBINATION OF COLD TEMPERATURES
AND BREEZY OFFSHORE WINDS WILL RESULT IN WIND CHILL VALUES AT
NIGHT AND IN THE MORNING HOURS DOWN TO 15 BELOW TO 30 BELOW AT
TIMES ACROSS THE KUSKOKWIM DELTA. A WEAK DISTURBANCE ALOFT WILL
MOVE INTO BRISTOL BAY SATURDAY AND SATURDAY NIGHT WITH THE
POSSIBILITY OF A FEW PASSING FLURRIES OR ISOLATED SNOW
SHOWERS...OTHERWISE DRY CONDITIONS WILL DOMINATE THE REMAINDER OF
THE REGION.

&&

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

WITH THE NORTH PACIFIC STORM TRACK SOUTH OF THE ALEUTIAN
CHAIN...THE REGION WILL REMAIN IN BETWEEN A STOUT ARCTIC HIGH OVER
THE CHUKCHI SEA AND STRONG LOWS OVER THE NORTH PACIFIC. THIS WILL
KEEP A GENERAL NORTHERLY FLOW REGIME AND OCEAN EFFECT RAIN AND
SNOW SHOWERS. A SLIGHTLY STRONGER LOW WILL DEVELOP SOUTH OF SHEMYA
LATE FRIDAY AND SATURDAY...WITH A TIGHTENING OF THE PRESSURE
GRADIENT AND SNOW AND RAIN ALONG THE FRONTAL ZONE AS IT CLIPS THE
WESTERN AND CENTRAL ALEUTIANS. OTHERWISE...A RATHER QUIET PERIOD
OF WEATHER WILL CONTINUE OVER THE BERING AS THE NORTH PACIFIC
STORM TRACK REMAINS SOUTH OF THE AREA THROUGH SATURDAY NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...SUN THROUGH THU)...THE
LONG TERM PATTERN WILL BE DOMINATED BY A FAST MOVING NORTH PACIFIC
ZONAL JET KEEPING MUCH OF THE ACTIVE WEATHER SOUTH OF THE
MAINLAND. MODELS NOTORIOUSLY HAVE A HARD TIME HANDLING THESE TYPE
OF PATTERNS. THEY STRUGGLE WITH WHERE EACH INDIVIDUAL LOW
DEVELOPS...WHICH ONE BECOMES THE DOMINANT LOW...AND HOW STRONG
THAT DOMINANT LOW WILL BE. THUS...THERE IS LOW TO MODERATE
FORECAST CONFIDENCE DURING THIS TIME PERIOD. TOWARD THE END OF
THE WEEKEND...A FEW REMNANT FRONTAL BOUNDARIES WILL BE WORKING
THEIR WAY FROM EAST TO WEST ACROSS THE GULF. MUCH LIKE
TONIGHT...ANY ONE OF THESE COULD BRING A BRIEF SHOT OF SNOW TO THE
GULF COAST AND SOUTHCENTRAL. BY MONDAY...A MORE DEFINED LOW WILL
WORK FROM SOUTH TO NORTH IN THE EASTERN GULF AND COULD BE ANOTHER
SNOW MAKER...ESPECIALLY ALONG THE GULF COAST NEAR CORDOVA AND
VALDEZ. MEANWHILE OVER THE BERING...A BROAD TROUGH WILL KEEP THE
ENTIRE AREA VULNERABLE TO SHOWERS. BUT WITHOUT ANY ESPECIALLY
STRONG FORCING...WE DON'T EXPECT MUCH IN THE WAY OF ACCUMULATIONS
AND WINDS SHOULD REMAIN RELATIVELY LIGHT.

BY TUE INTO WED...MODELS ARE SHOWING A MUCH STRONGER CONSOLIDATED
LOW TAKING SHAPE OVER THE NORTH PACIFIC AND MOVING INTO THE GULF
OF ALASKA. THERE HAS BEEN A GREAT DEAL OF UNCERTAINTY AMONG THE
MODELS AND THEIR ENSEMBLE MEMBERS IN DEALING WITH THIS FEATURE.
FOR NOW WE HAVE BROUGHT THE LOWEST CENTRAL PRESSURE DOWN INTO THE
LOW 950 MB RANGE. THIS WOULD MEAN AT LEAST SOME GALE FORCE WINDS
AND HEAVY PRECIPITATION FOR THE MARINERS BEFORE IT TRACKS TOWARD
SE AK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY 160 181 185.
         GALES 178.

&&

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...MO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
948 AM AKST FRI DEC 04 2015

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

0940 AM     SNOW             KENAI                   60.55N 151.21W
12/04/2015  E1.0 INCH                           AK   911 CALL CENTER

            ESTIMATED 1 INCH NEW SNOW FELL OVERNIGHT NEAR THE KENAI
            AIRPORT.

0940 AM     SNOW             CORDOVA                 60.55N 145.75W
12/04/2015  E4.0 INCH                           AK   911 CALL CENTER

            4 INCHES OF SNOW FELL OVERNIGHT IN THE TOWN OF CORDOVA.
            TRANSITIONED TO RAIN AROUND MILE 3 OR 4 OF THE COPPER
            RIVER HIGHWAY WITH THE AIRPORT STAYING ALL RAIN.

0940 AM     SNOW             ANCHORAGE               61.22N 149.87W
12/04/2015  M0.7 INCH                           AK   OFFICIAL NWS OBS

0940 AM     SNOW             EAGLE RIVER             61.32N 149.57W
12/04/2015  M1.2 INCH                           AK   NWS EMPLOYEE

0940 AM     SNOW             1 NNE POTTER MARSH      61.07N 149.77W
12/04/2015  E1.7 INCH                           AK   TRAINED SPOTTER

0940 AM     SNOW             VALDEZ                  61.08N 146.30W
12/04/2015  E6.0 INCH                           AK   911 CALL CENTER

            ESTIMATED 6 TO 9 INCHES OF SNOW FELL OVERNIGHT IN TOWN.

&&

RDUELL