Small Craft Advisory 1034, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST SUN DEC 22 2013

.ANALYSIS AND UPPER LEVELS...

A STRONG UPPER LEVEL JET STREAK DIVING INTO THE BASE OF THE TROUGH
MOVING ACROSS SOUTHCENTRAL THIS EVENING WILL STRENGTHEN THE TROUGH
SUBSTANTIALLY AS IT MOVES EAST INTO THE OVERNIGHT HOURS. WHILE THIS
PHASING WILL COME TOO LATE TO AFFECT ANCHORAGE...LOCATIONS TO THE EAST
AND NORTH FROM PALMER AND INTO THE COPPER RIVER BASIN WILL LIKELY SEE
ENHANCED SNOWFALL RATES BEFORE ENDING OVERNIGHT. AS THE TROUGH PASSES
AND THE JET STREAK MOVES ACROSS THE AREA TONIGHT...STRONG OFFSHORE
FLOW DEVELOPS AND WILL RESULT IN INCREASED WINDS THROUGH THOMPSON
PASS...NEAR WHITTIER...AND NEAR SEWARD.

UPPER LEVEL RIDGING BUILDS FROM THE SOUTH OVER SOUTHERN ALASKA MONDAY
THROUGH TUESDAY MORNING. ATTENTION TURNS TO A VERY LARGE 961 MB LOW
ABOUT 400 NM SOUTHWEST OF SHEMYA THAT WILL MOVE TO 100 NM SOUTH OF
ADAK BY LATE TUESDAY AFTERNOON. AN ASSOCIATED STRONG WEATHER FRONT
WILL PUSH ACROSS THE BERING REGION FROM SOUTH TO NORTH...THEN MAKE IT
TO SOUTHWEST ALASKA MAINLAND BY LATE TUESDAY. SEVERAL WEAK TRIPLE
POINT LOWS WILL ATTEMPT TO FORM ALONG THIS FRONT...BY MODELS ARE
SUGGESTING THAT NO ONE TRIPLE POINT LOW WILL BE ABLE TO SUSTAIN ITSELF
EXCEPT FOR ONE IN THE SOUTHWEST BERING MOVING WEST TOWARD RUSSIA
MONDAY NIGHT INTO TUESDAY.

.MODEL DISCUSSION...

MODELS ARE HANDLING THE CURRENT SNOW EVENT WELL OVER
SOUTHCENTRAL...WITH THIS SYSTEM WINDING DOWN TONIGHT INTO EARLY
MONDAY. THE NAM WAS PREFERRED FOR ITS ENHANCED RESOLUTION AND ABILITY
TO HELP WITH FLOW THROUGH RESTRICTED TERRAIN. OUT WEST...THE EUROPEAN
MODEL WAS PREFERRED DUE TO ITS USUALLY MORE CONSISTENT HANDLING OF
DEVELOPMENT OF TRIPLE POINT LOWS. THE EXACT PLACEMENT AND TRACK OF
THESE TRIPLE POINT LOWS WITH ASSOCIATED UPPER LEVEL SHORTWAVE
DISTURBANCES WILL PLAY A LARGE ROLE IN THE DETAILS OF THE FORECAST
OVER THE NEXT FEW DAYS...ESPECIALLY AS ONE IS FORECAST BY THE MODELS
TO DEVELOP AND MOVE NORTH AND EAST INTO THE GULF BY LATE CHRISTMAS EVE
AND CHRISTMAS DAY.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

SNOW WILL WIND DOWN THIS EVENING FROM SOUTHWEST TO NORTHEAST ACROSS
SOUTHCENTRAL. PHASING OF THE UPPER LEVEL TROUGH JUST AS IT MOVES
ACROSS ANCHORAGE WILL LIKELY MEAN HIGHER ACCUMULATIONS TO THE NORTH
AND EAST...WHICH JUSTIFIES THE CONTINUATION OF THE WINTER WEATHER
ADVISORY FOR SNOW FOR THE COPPER RIVER BASIN. THIS MAY ALSO CONTRIBUTE
TO SNOW LASTING LONGER ALONG THE MATANUSKA RIVER VALLEY FROM PALMER
NORTH AND EAST...SO WILL LIKELY BUMP UP ACCUMULATIONS FOR THIS EVENING
IN THOSE LOCATIONS WITH THE AFTERNOON PACKAGE.

THE NEXT CONCERN IS WITH THE UPPER LEVEL JET STREAK COMBINING WITH
OFFSHORE FLOW TO GENERATE POTENTIALLY HIGH WINDS...ESPECIALLY NEAR
WHITTIER TONIGHT INTO MONDAY AFTERNOON. THE INGREDIENTS ARE THERE AND
WITH A FAVORABLE PRESSURE GRADIENT AND THE UPPER LEVEL SUPPORT WE WILL
BE ISSUING THE HIGH WIND WARNING FOR NEAR WHITIER. WE DO NOT
ANTICIPATE WIND BEING STRONG ENOUGH IN THOMPSON PASS TO SUPPORT
BLIZZARD CONDITIONS AND WILL UPGRADE THE WATCH TO A BLOWING SNOW
ADVISORY.

SOUTHWEST...

THE MAIN CONCERN THROUGH THIS EVENING IS WITH A SMALL LOW MOVING
INLAND OVER THE KUSKOKWIM DELTA THIS AFTERNOON BRINGING A BRIEF PERIOD
OF LIGHT SNOW. THIS SYSTEM IS MOVING VERY QUICKLY AND THUS SNOW
ACCUMULATIONS WILL GENERALLY REMAIN UNDER 1 INCH. THE MOISTURE WITH
THIS SMALL DISTURBANCE WILL BECOME WRUNG OUT OVER THE KUSKOKWIM
MOUNTAIN RANGE THIS EVENING. ANOTHER SUCH SMALL DISTURBANCE WILL
AFFECT NORTHERN COASTAL LOCATIONS OF THE Y-K DELTA REGION TONIGHT AND
BRING SIMILAR ACCUMULATIONS. OTHERWISE...SKIES WILL GENERALLY REMAIN
MAINLY CLEAR WITH A DRIER AND COOLER AIR MASS DROPPING SOUTH INTO THE
REGION...EXCEPT FOR PERIODS OF CLOUDS WITH ONSHORE FLOW FOR THE DELTA
REGION.

THE NEXT FRONT AFFECTS THE REGION TUESDAY AFTERNOON THROUGH TUESDAY
EVENING. LATEST MODEL INDICATIONS ARE THAT THIS FRONT WILL DIMINISH
SIGNIFICANTLY...WITH UPPER LEVEL ENERGY SPLITTING BEFORE REACHING THE
SOUTHWEST MAINLAND. PRECIPITATION LIKELY WILL BE LIGHT SNOW ALONG THE
COAST WITH FLURRIES INLAND.

BERING SEA/ALEUTIANS...

GALE FORCE FRONT MOVING ACROSS THE WESTERN AND CENTRAL ALEUTIANS THIS
AFTERNOON AND EVENING MOVES NORTH TO THE NORTHERN BERING TO
SOUTHEASTERN BERING TUESDAY MORNING. THERE IS JUST ENOUGH COLD AIR IN
PLACE FOR PRECIPITATION TO START AS SNOW...BUT THEN QUICKLY CHANGES TO
RAIN WITH WARM AIR SURGING NORTH ALONG THE FRONT. A SERIES OF MUCH
WEAKER WEATHER FRONTS WITH SHOWERS THEN MOVES NORTH ACROSS THE CENTRAL
AND EASTERN ALEUTIANS LATE MONDAY NIGHT THROUGH LATE TUESDAY.

.LONG TERM FORECAST...

THE EC AND WPC ARE SIMILAR IN BRINGING THE NORTH PACIFIC LOW TO THE
ALEUTIANS AND DEVELOPING A TRIPLE POINT LOW IN THE CENTRAL BERING ON
TUE. THIS WILL KEEP RAIN SHOWERS OVER THE BERING...ALEUTIANS...AND
SOUTHWEST AK ON TUE. AS THE BERING LOW WEAKENS INTO A BROAD AREA OF
LOW PRESSURE...COLDER AIR WILL RETURN TO THE WESTERN ISLANDS WED WITH
SOME SNOW SHOWERS. ON THU THE NEXT NORTH PACIFIC LOW TAKES AIM AT THE
CENTRAL ALEUTIANS...WITH ANOTHER ROUND OF RAIN FOR THE EASTERN
ALEUTIANS AND SOUTHWEST AK...AND SNOW SHOWERS FOR THE WESTERN
ALEUTIANS...PERSISTING INTO THE WEEKEND.

FOR SOUTHEAST OF THE AK RANGE...THE BERING FRONT WILL SPREAD SNOW
CHANGING TO RAIN ALONG THE COAST INTO WED...WITH SOME SNOW SPREADING
ACROSS THE COASTAL MOUNTAINS AND REACHING THE EASTERN FLANK OF THE AK
RANGE. THESE CONDITIONS WILL THEN PERSIST INTO THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING ZONE 125...NEAR WHITTIER.
MARINE...STORM 130 411.
         GALE 119 120 121 127 128 129 131 132 136 137 138 150 155 165
              170 171 172 173 174 175 176 177 178 179 180 181 185 351
              352 412 413 414
         HEAVY FREEZING SPRAY 121 126 127 129 130 136 137 138 139 150
                              181 185.
         FIRE WEATHER...NONE.

CC/SAM DEC 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1019 PM AKST SUN DEC 22 2013

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

0940 PM     SNOW             8 SSE EAGLE RIVER       61.23N 149.44W
12/22/2013  M6.3 INCH                           AK   NWS EMPLOYEE

            SINCE MIDNIGHT WITH .51 WATER EQUIVELENT.

&&

DSTRICKL