Small Craft Advisory 118, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
502 PM AKST THU FEB 4 2016

.ANALYSIS AND UPPER LEVELS...

THE OVERALL PATTERN REMAINS UNCHANGED AND FEATURES A LONGWAVE
TROUGH WITH STATIONARY ANCHOR LOW OVER THE EASTERN BERING/ALASKA
PENINSULA. MAINLAND ALASKA REMAINS UNDER RELATIVELY WARM
SOUTHERLY/SOUTHEASTERLY FLOW WHILE THE WESTERN 2/3 OF THE BERING
SEA IS UNDER NORTHERLY FLOW WITH COLD AND GUSTY CONDITIONS. A 964
MB LOW SUPPORTED BY A FAIRLY ROBUST SHORTWAVE HAS MOVED INTO THE
GULF AND IS NOW TRACKING TOWARD THE BARREN ISLANDS. THE
ASSOCIATED WEATHER FRONT IS PRODUCING STORM-FORCE WINDS ACROSS THE
NORTHERN GULF...THOUGH THE FRONT IS CURRENTLY PUSHING INLAND
ACROSS THE KENAI PENINSULA AS OF MIDDAY WHICH WILL ALLOW WINDS TO
DECREASE THROUGH THE EVENING HOURS. THE COOK INLET AREA IS SHOWING
A FAIRLY TYPICAL DOWNSLOPE SIGNATURE...ALTHOUGH THE MORE NORTHEAST
TO SOUTHWEST ORIENTATION OF THE FRONT IS HELPING SOME FLURRIES OR
SPRINKLES TO "SPILL OVER" INTO THE ANCHORAGE AREA AND WESTERN
KENAI PENINSULA.

GENERALLY UNSETTLED BUT LOW-IMPACT WEATHER CONTINUES FOR SOUTHWEST
ALASKA AND THE EASTERN BERING. THE MORE SIGNIFICANT WEATHER IS OUT
IN THE FAR WESTERN ALEUTIANS WHERE MORE SIGNIFICANT COLD AIR
MOVING OFF THE RUSSIAN LANDMASS IS GENERATING FAIRLY ROBUST SNOW
SHOWER ACTIVITY WITH STRONG WINDS AND AREAS OF BLOWING SNOW.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN VERY GOOD GENERAL AGREEMENT AS THE LONGWAVE
PATTERN IS CHANGING SLOWLY. ALL MODELS DEPICT THE LOW CURRENTLY
MOVING QUICKLY THROUGH THE GULF WILL WEAKEN QUICKLY TONIGHT AND
WRAP INTO THE MAIN LOW CENTER OVER THE EASTERN BERING. BEHIND THIS
FRONT COLD AIR MOVING OVER THE WARM WATER WILL RESULT IN SEVERAL
PERIODS OF UNSTABLE AND SHOWERY CONDITIONS OVER THE GULF OF
ALASKA...WITH MOST (BUT NOT ALL) PRECIP FALLING ONCE AGAIN ACROSS
COASTAL AREAS. THE ECMWF/NAM WERE PREFERRED OVERALL FOR SOME
SUBTLE TIMING ISSUES OF THE PARENT LOW IN THE BERING SEA...BUT NO
MODELS WERE COMPLETELY DISCARDED TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN WEATHER MAKER FOR THE NEXT 24 HOURS WILL BE THE PASSAGE
OF THE FRONT ASSOCIATED WITH THE 966MB LOW MOVING INTO KODIAK
ISLAND THIS AFTERNOON. THIS FRONT IS PRODUCING WIDESPREAD
PRECIPITATION OVER THE NORTHERN GULF COAST WITH ENOUGH MOISTURE
PUSHING OVER THE KENAI AND CHUGACH MOUNTAINS TO PRODUCE ISOLATED
RAIN AND SNOW SHOWERS OVER UPPER COOK INLET THIS AFTERNOON. WINDS
WILL CONTINUE TO REMAIN ELEVATED THIS EVENING OVER THE BARRENS AS
WELL AS PRINCE WILLIAM SOUND INTO TURNAGAIN ARM AS THE PRESSURE
GRADIENT WILL GRADUALLY BEGIN TO DECREASE THROUGH THE EVENING
HOURS. COASTAL AREAS WILL SEE MOSTLY RAIN WITH HIGHER ELEVATIONS
AND INLAND AREAS SEEING SOME AREAS OF ACCUMULATING SNOW. THE FRONT
WILL GRADUALLY WEAKEN IN PLACE THROUGH SATURDAY MORNING OVER THE
REGION...KEEPING PRECIPITATION MAINLY OVER THE COAST BUT ENOUGH
MOISTURE WILL SLIDE OVER THE TERRAIN TO GIVE THE UPPER COOK INLET
REGION AN INCREASED CHANCE OF RAIN AND SNOW FRIDAY AFTERNOON.

ON THE BACKSIDE OF THIS LOW...A SECONDARY LOW IS EXPECTED TO FORM
NEAR THE SHUMAGINS LATE FRIDAY NIGHT AND MOVE NORTHEASTWARD TO
SOUTH OF SEWARD BY SATURDAY AFTERNOON. THIS LOW IS EXPECTED TO BE
FAIRLY WEAK AND MAINLY PROVIDE AN RE-ENFORCING SHOT OF PRECIPITATION
TO THE NORTHERN GULF COAST.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A SHORTWAVE APPROACHING BRISTOL BAY FROM THE SOUTHEAST WILL
BRING AN INCH OR SO OF ACCUMULATING SNOW TO THE AREA THROUGH
FRIDAY MORNING. MOST OF THIS SNOW SHOULD FALL OVER THE NORTHERN
PORTIONS OF BRISTOL BAY...BUT THERE IS A CHANCE SOME OF THIS
SNOWFALL MAY REACH AS FAR SOUTH AS THE DILLINGHAM AREA. A BETTER
CHANCE OF WIDESPREAD SNOW THROUGHOUT THE REGION LATE FRIDAY INTO
SATURDAY AS THE UPPER LEVEL TROUGH SWINGS OVERHEAD. THERE IS SOME
DISAGREEMENT WITH THE OVERALL TIMING OF THIS SNOW...BUT THERE IS
GOOD CONFIDENCE THAT MOST AREAS OF THE SOUTHWEST MAINLAND WILL SEE
ACCUMULATING SNOW BY SATURDAY EVENING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE UPPER LEVEL TROUGH WILL KEEP RAIN AND SNOW SHOWERS THROUGHOUT
THE REGION INTO THIS WEEKEND. OVER THE WESTERN BERING/ALEUTIANS...GALE
FORCE NORTHERLY FLOW ALONG WITH COLD AIR ADVECTION WILL BRING SNOW
SHOWERS TO THE REGION. HOWEVER THIS IS NO LONGER EXPECTED TO BE
HEAVY OR COLD ENOUGH TO BRING SIGNIFICANT BLOWING SNOW CONDITIONS
TO THE REGION. CONDITIONS THROUGHOUT THE AREA WILL BEGIN TO
IMPROVE ON FRIDAY AS THE LOW CURRENTLY OVER THE AKPEN WEAKENS AND
MAKES LANDFALL OVER BRISTOL BAY. THIS WILL LEAVE WEAKENING
NORTHERLY FLOW (LESS THAN GALE FORCE) OVER MUCH OF THE BERING
WITH DIMINISHING SNOW SHOWERS.

&&

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

A MID LEVEL LOW CENTERED OVER EASTERN RUSSIA CONTINUES TO STAY
ANCHORED WITH A LONG WAVE TROUGH EXTENDING TOWARD THE WESTERN GULF
OF ALASKA THROUGH THE LONG TERM FORECAST. A RIDGE TO THE EAST OF
THIS FEATURE WILL HAVE AN AXIS OVER BRITISH COLUMBIA. MODELS ARE
IN GOOD AGREEMENT WITH THE PATTERN...HOWEVER TIMING AND STRENGTH
DIFFERENCES FOR TWO CLOSED LOWS JUST SOUTH OF THE ALASKA PENINSULA
LEAD TO UNCERTAINTY IN PRECIPITATION AND WINDS FOR THE BEGINNING
OF NEXT WEEK. THIS GENERAL PATTERN KEEPS A WARMER THAN NORMAL
TEMPERATURE TREND THROUGH THE END OF NEXT WEEK WITH THE HIGHEST
PRECIPITATION CHANCES ACROSS THE AREA WATERS AND COASTS AS RIDGING
SHIFTS SLIGHTLY WEST AND AMPLIFIES OVER SOUTHERN ALASKA DURING
THE MIDDLE OF NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 125 129 130 131 132 139 141
              150 174 177 178 351 352
         STORM 155 172
         HEAVY FREEZING SPRAY 180 181 185.
&&

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...RF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...KH