Small Craft Advisory 1027, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
453 PM AKST FRI DEC 25 2015

.ANALYSIS AND UPPER LEVELS...

A POWERFUL STORM CENTERED IN THE EASTERN BERING DOMINATES THE
WEATHER ACROSS ALL OF SOUTHERN ALASKA THIS CHRISTMAS AFTERNOON. AS
THE LOW CENTER PASSED ALMOST DIRECTLY OVER COLD BAY THIS
MORNING...THE RECORDED PRESSURE DROPPED TO A VERY IMPRESSIVE 954
MB. THIS VERTICALLY STACKED LOW HAS CARVED A DEEP UPPER LEVEL
TROUGH ACROSS THE BERING AND SOUTHWEST ALASKA...WITH DOWNSTREAM
RIDGING OVER THE COPPER RIVER BASIN AND EASTERN ALASKA. THE
STRUCTURE OF THE STORM IS MOST IMPRESSIVE ON WATER VAPOR SATELLITE
IMAGERY. THE HIGH TOPPED CIRRUS DECK STRETCHES TO WESTERN CANADA
AND THE AK PANHANDLE...WITH THE WESTERN EDGE OF THE CLOUD DECK
REACHING ATKA...THOUGH THE ASSOCIATED WIND FIELD COVERS ALL OF THE
ALEUTIANS. A VERY POTENT FRONT ASSOCIATED WITH THE LEADING EDGE OF
THE DRY SLOT EXTENDS FROM THE KUSKOKWIM RIVER IN SOUTHWEST
ALASKA...AND ACROSS THE ALASKA RANGE AND THE SOUTHERN KENAI
PENINSULA INTO THE GULF.

WARMING TEMPERATURES ARE A KEY FEATURE WITH THE STORM. THE RAIN-
SNOW LINE HAS REACHED AS FAR NORTH AND INLAND AS SPARREVOHN AND
ANIAK IN SOUTHWEST ALASKA...AND ABOVE FREEZING TEMPS ARE BEING
REPORTED ALONG KACHEMAK BAY AND LOWER ELEVATIONS NEAR PRINCE
WILLIAM SOUND.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN GENERAL AGREEMENT ON THE SHORT TERM TRACK AND
LOCATION OF THE BERING LOW. EXCEPT FOR THE MOVEMENT OF MINOR
FEATURES...THE LOW IS EXPECTED TO BECOME NEARLY STATIONARY
OVERNIGHT AS WEAKENING BEGINS. THE MODEL DIFFERENCES BECOME MORE
EVIDENT OVER THE WEEKEND AS A STORM THAT CURRENTLY IS A TROUGH OF
LOW PRESSURE MOVING ACROSS THE NORTHWEST PACIFIC INTENSIFIES INTO
A NEW LOW SOUTH OF THE WESTERN ALEUTIANS...MOVING EASTWARD WITH
THE PREVAILING UPPER LEVEL WINDS IN THE AREA. SINCE THIS WAVE IS
POORLY RESOLVED BY A LACK OF OBSERVATIONS OVER THE NORTHWEST
PACIFIC...THAT HAS RESULTED IN THE LARGE MODEL DIFFERENCES OVER
THE WEEKEND REGARDING THE INTERACTION OF THIS NEW LOW WITH THE
CURRENT BERING STORM. THE GFS AND NAM WERE PREFERRED...DUE TO
BEING THE MORE CONSISTENT MODELS IN HANDLING THIS INTERACTION.
FORECAST CONFIDENCE IS BELOW NORMAL DUE TO THE WIDELY DIFFERING
SOLUTIONS BETWEEN THE MODELS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE STORM FORCE FRONT OVER THE NORTHERN GULF WILL STALL ALONG THE
COAST TONIGHT AND BEGIN TO GRADUALLY WEAKEN AS IT LOSES UPPER
LEVEL SUPPORT. INLAND PORTIONS OF WESTERN PRINCE WILLIAM SOUND
WILL CONTINUE TO BEAR THE BRUNT OF THE IMPACTS FROM THIS SYSTEM AS
HEAVY SNOW CONTINUES THROUGH EARLY SATURDAY MORNING...WITH
ADDITIONAL ACCUMULATIONS UP TO 16 INCHES POSSIBLE ALONG THE
SEWARD HIGHWAY CORRIDOR FROM GIRDWOOD THROUGH TURNAGAIN PASS.
CONDITIONS WILL BEGIN TO IMPROVE BY SATURDAY MORNING AS THE
DISSIPATING FRONT GIVES WAY TO A RELATIVELY UNSTABLE ONSHORE FLOW
REGIME. THIS PATTERN WILL KEEP ABUNDANT SHOWER ACTIVITY FOCUSED
ALONG THE COAST THROUGH THE WEEKEND AS VARIOUS UPPER LEVEL WAVES
MOVE OVERHEAD AND PERIODICALLY ENHANCE PRECIPITATION. MEANWHILE...
STRONG CROSS BARRIER FLOW WILL CONTINUE TO DOMINATE FROM INLAND
PORTIONS OF THE KENAI PENINSULA UP THROUGH ANCHORAGE AND THE MAT-
SU REGION...KEEPING THESE AREAS MOSTLY DRY THROUGH THE WEEKEND

&&

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

SNOWFALL WILL CONTINUE TO TAPER OFF ACROSS THE KUSKOKWIM DELTA
THIS EVENING AS THE WARM FRONT CONTINUES TO PUSH THROUGH THE AREA
AND DRIER AIR BEHIND THIS FRONT FILTERS ACROSS THE AREA. BLOWING
SNOW CONDITIONS WILL LIKELY CONTINUE INTO THE OVERNIGHT HOURS BUT
VISIBILITIES WILL BEGIN TO IMPROVE EARLY THIS EVENING AS SNOWFALL
TAPERS OFF. GUSTY WINDS OF 45 TO 60 MPH WILL BE SEEN THROUGH THE
EVENING BEFORE THE PRESSURE GRADIENT BEGINS TO RELAX AND WIND
GUSTS DROPPING INTO THE 35 TO 50 MPH RANGE AFTER MIDNIGHT...WITH
THE STRONGEST GUSTS REMAINING OVER COASTAL LOCATIONS. THE
KUSKOKWIM DELTA WILL LIKELY REMAIN ON THE DRY SIDE HEADING INTO
THE BEGINNING OF NEXT WEEK AS THE LOW IN THE SOUTHEASTERN BERING
SEA SLOWLY WEAKENS AS IT MEANDERS SOUTH. TEMPERATURES WILL REMAIN
ABOVE NORMAL AND WINDS OF 20 TO 35 MPH WILL LIKELY BE OBSERVED
THROUGH THE FORECAST PERIOD.

LOOKING SOUTH TOWARD BRISTOL BAY...THE HIGH WIND WARNING VERIFIED
THIS MORNING WITH 2 TO 3 HOURS OF HURRICANE FORCE WIND GUSTS AT
PORT HEIDEN BUT OBSERVATION SITES (AT SEA LEVEL) HAVE FAILED TO
REPORT HURRICANE FORCE WIND GUSTS SINCE THIS MORNING. WHILE THE
WIND GUSTS HAVE NOT BEEN OBSERVED BY AN OBSERVING SITES...IT IS
STILL LIKELY THAT LOCATIONS ALONG THE ALEUTIAN RANGE AND WESTERN
CAPES SAW SPORADIC WIND GUSTS TO HURRICANE FORCE. WENT AHEAD AND
CANCELLED THE HIGH WIND WARNING A FEW HOURS EARLY AS THE FRONT
THAT BROUGHT THE STRONGEST WINDS HAS SHIFTED NORTH OF THE AREA.
STRONG CROSS BARRIER FLOW HAS KEPT MUCH OF THE INLAND LOCATIONS
OF BRISTOL BAY ON THE DRY SIDE...ALTHOUGH A FEW SHOWERS HAVE BEEN
ABLE TO MAKE IT INTO KING SALMON AND A FEW OTHER AREAS. THESE
DOWNSLOPING CONDITIONS WILL CONTINUE THROUGH MUCH OF THE WEEKEND
AS THE LOW IN BRISTOL BAY MAKES LITTLE PROGRESS TO THE SOUTH AND
EAST AND CONTINUES TO PRODUCE ADIABATIC WARMING AND DRYING ON THE
LEE SIDE OF THE ALASKA AND ALEUTIAN RANGES. THIS WILL KEEP THE
BRISTOL BAY ZONE ABOVE FREEZING AND TEMPERATURES 10 TO 15 DEGREES
ABOVE NORMAL THROUGH MONDAY.

&&

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

GALE FORCE WINDS WILL CONTINUE TO BE SEEN WITH THE LOW OVER
SOUTHEASTERN BERING SEA THROUGH LATE SATURDAY WHEN THE LOW
FINALLY BEGINS TO DISSIPATE. A SHOT OF 60 TO 65 MPH WINDS WILL BE
SEEN ACROSS THE EASTERN ALEUTIANS TONIGHT AS A WEAK RIDGE OF HIGH
PRESSURE TRIES TO BUILD IN BEHIND THE LOW IN THE SOUTHEASTERN
BERING SEA. THE ISALLOBARIC FLOW SHOULD HELP STRENGTHEN THE WINDS
THROUGH NIKOLSKI AND DUTCH HARBOR BUT IT LOOKS LIKE THE STRONGEST
WINDS WILL BE CLOSER TO NIKOLSKI AT THIS TIME. THE STRONG WINDS
WILL DIMINISH ON SATURDAY AS ISALLOBARIC FLOW WEAKENS AND THE LOW
MEANDERS TO THE EAST A BIT. A TRIPLE POINT LOW WILL DEVELOP NEAR
THE CENTRAL ALEUTIANS SATURDAY AFTERNOON BRINGING ANOTHER SHOT OF
GALE FORCE WINDS AND RAIN TO THE SOUTHERN BERING SEA THROUGH EARLY
NEXT WEEK...BUT IS NOT EXPECTED TO BE ANYWHERE AS STRONG AS THE
LOW THAT BROUGHT HURRICANE FORCE WINDS TO ADAK LAST NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
MOVING INTO NEXT WEEK ALL GUIDANCE IS TRENDING TOWARDS A DEEP
SYSTEM MOVING INTO THE BERING. HOWEVER...THE OPERATIONAL RUNS ARE
STRUGGLING WITH THE TIMING OF THIS FEATURE AND WHETHER OR NOT TO
KEEP IT AS A CONSOLIDATED LOW. BECAUSE OF THIS THE ENSEMBLE MEANS
WERE PREFERRED FOR NEXT WEEK WHICH HAVE BEEN CLOSE TOGETHER AND
CONSISTENT FROM RUN TO RUN. THE ENSEMBLES TRACK THE LOW INTO THE
CENTRAL BERING BY LATE MONDAY WHERE IT SITS FOR MUCH OF THE WEEK.
THIS LOOKS TO BRING PRECIPITATION THROUGHOUT THE BERING FOR THE
WEEK. IT WILL ALSO BRING SOUTH TO SOUTHEAST WINDS TO THE SOUTHERN
MAINLAND WHICH WILL KEEP MOST OF THE PRECIPITATION ALONG THE NORTH
GULF COAST. THE CONSTANT SOUTHERLY FLOW SHOULD ALSO KEEP
TEMPERATURES FOR THE SOUTHERN MAINLAND AND SOUTHWEST ALASKA AT OR
ABOVE NORMALS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING FOR HEAVY SNOW 125.
MARINE...GALE 127 129 132 139 140 150-171 177 178 179 181 185.
         STORM 119 120 125 172-176 180.
		 HEAVY FREEZING SPRAY 181.
&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...CB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1017 PM AKST FRI DEC 25 2015

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

0625 PM     SNOW             8 NW HOMER              59.72N 151.68W
12/25/2015  M8.5 INCH                           AK   CO-OP OBSERVER

            24-HR TOTAL. SNOW DEPTH 18 INCHES

&&

KUTZ