Small Craft Advisory 139, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
412 PM AKST FRI FEB 13 2015

.ANALYSIS AND UPPER LEVELS...
A LOW WHICH DEVELOPED OVER THE NORTHEAST PACIFIC ON THURSDAY HAS
BECOME VERTICALLY STACKED OVER THE CENTRAL GULF OF ALASKA THIS
MORNING. IT WILL NOW BEGIN TO WEAKEN AS THE UPPER JET SUPPORT
HEADS OFF TO THE EAST AND THE LOW IS FORCED WESTWARD DUE TO
RIDGING OVER THE SOUTHERN MAINLAND OF ALASKA. AN OCCLUDED FRONT IS
TRACKING OUT AHEAD OF THIS LOW TOWARD SOUTHCENTRAL ALASKA...WITH
PRECIP MOVING INTO THE PRINCE WILLIAM SOUND AREA. FOG WAS QUITE
EXTENSIVE OVERNIGHT FROM THE WESTERN KENAI TO ANCHORAGE AND THE
MAT VALLEY... BUT MOST OF THAT HAS DISSIPATED AND ARRIVAL OF
CLOUDS WILL KEEP FOG FROM REFORMING TONIGHT.

OUT WEST A WEAK SURFACE LOW IS LINGERING NEAR DUTCH HARBOR. A FRONTAL
BOUNDARY EXTENDING NORTH FROM THIS LOW TO AROUND THE PRIBILOF ISLANDS
IS PUSHING SLOWLY WESTWARD ACROSS THE CENTRAL BERING. SNOW CONTINUES
ALONG AND AHEAD OF THIS...WITH REDUCED VISIBILITIES IN BLOWING
SNOW ON THE PRIBILOF ISLANDS. EAST OF THE BOUNDARY MUCH WARMER AIR
IS PRODUCING AREAS OF RAIN ALONG THE EASTERN ALEUTIANS AND SOUTHERN
ALASKA PENINSULA.

&&

.MODEL DISCUSSION...
THERE ARE MINOR DIFFERENCES IN TRACK OF THE LOW OVER THE GULF AND
LOW NEAR DUTCH HARBOR...BUT NOTHING WHICH GREATLY AFFECTS THE
SENSIBLE WEATHER. CONFIDENCE HAS INCREASED GREATLY WITH GULF LOW
TRACKING TO COOK INLET REGION SATURDAY EVENING. GENERALLY PREFER
THE DETAILS OF THE HI-RES MODELS AS THE LOW NEARS THE SOUTHERN
KENAI PENINSULA. THIS IS A FAVORABLE TRACK FOR STRONGER WINDS
ALONG TURNAGAIN ARM AND POSSIBLY EVEN A LITTLE WIND GETTING INTO
THE ANCHORAGE BOWL AND MAT VALLEY. ANY WIND AT ALL WILL HELP
SURFACE TEMPS JUMP WELL ABOVE FREEZING. ALL OF THIS WILL BE
REFLECTED IN THE AFTERNOON FORECASTS. ACROSS THE WIDER FORECAST
AREA CONFIDENCE IS GENERALLY ABOVE AVERAGE FOR THE NEXT COUPLE
DAYS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
RAIN WILL CONTINUE TO DEVELOP ALONG THE SURFACE LOW IN THE
NORTHERN GULF TONIGHT BRINGING PERIODS OF RAIN TO COASTAL AREAS
WITH A FEW RAIN AND SNOW SHOWERS WORKING INLAND. PATCHY FOG WILL
DEVELOP AGAIN TONIGHT...HOWEVER WILL NOT BE AS DENSE AS THIS
MORNING DUE TO A DRIER AIR MASS AND INCREASING CLOUDS.

MAINLY SMALL CRAFT WINDS WILL BE ASSOCIATED WITH THE GULF LOW
THROUGH SATURDAY NIGHT. AS THIS LOW PUSHES CLOSER TO COOK INLET
SATURDAY...WINDS ARE EXPECTED TO INCREASE ACROSS TURNAGAIN ARM
AND COOK INLET. STRONG WINDS ACROSS THE ANCHORAGE HILLSIDE AND
TURNAGAIN ARM SHOULD PEAK SATURDAY EVENING AND THEN TAPER DOWN
AFTER MIDNIGHT. THE NEXT SYSTEM ORGANIZES IN THE NORTH PACIFIC
LATE SATURDAY NIGHT MOVING INTO THE SOUTHERN GULF EARLY SUNDAY.
THIS SYSTEM WILL BRING GUSTY GALE WINDS OR STRONGER ALONG WITH
HEAVY RAINFALL AS IT MOVES NORTH.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE OF ELONGATED UPPER LEVEL TROUGHS MOVING UP FROM THE
NORTHEAST PACIFIC BEHIND THE LOW OVER THE GULF WILL PHASE JUST
SOUTH OF THE ALASKA PENINSULA SATURDAY AFTERNOON. THIS WILL
STRENGTHEN THE TROUGH...BUT IT WILL STILL BE ON THE WEAK SIDE.
THUS EXPECT PRECIP TO BE LIGHT AND SHORT-LIVED AS IT MOVES THROUGH
THE REGION. MARGINALLY COOLER AIR WILL BE MOVING IN FROM THE SOUTH
WITH THE TROUGH. THERE MAY BE SOME RAIN ALONG THE ALASKA PENINSULA...
BUT EXPECT AREAS NORTH AND WEST TO BE COLD ENOUGH FOR ALL SNOW.
ATTENTION WILL THEN SHIFT TO A MUCH MORE SIGNIFICANT PACIFIC STORM
SYSTEM WHICH WILL BEGIN TO AFFECT THE ALASKA PENINSULA AND BRISTOL
BAY AREAS SOMETIME SUNDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE LOW NEAR DUTCH HARBOR WILL EXIT TO THE SOUTH TONIGHT AND
SATURDAY. MORE IMPORTANTLY THE BAROCLINIC ZONE WHICH HAS BEEN
SITTING OVER THE CENTRAL TO EASTERN BERING (NEAR THE PRIBILOF
ISLANDS) WILL PUSH SOUTHWESTWARD AND THE AIR MASS WILL BECOME
MUCH MORE HOMOGENEOUS. THIS WILL BRING AN END TO STEADY SNOW AND
BLOWING SNOW ON THE PRIBILOF ISLANDS. THERE WILL STILL BE SOME
SNOW SHOWERS ACROSS THE REGION...BUT NOTHING ORGANIZED.

&&

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

A SEASONABLY STRONG NORTH PACIFIC LOW AND ASSOCIATED FRONT WILL BE
IN THE PROCESS OF TRACKING INTO THE EASTERN BERING SEA AND NORTH
GULF COAST. HEAVY RAIN WILL BE IMPACTING COASTAL LOCATIONS...WITH
SIGNIFICANT DOWNSLOPE SHADOWING KEEPING MOST INLAND LOCATIONS
LARGELY DRY WITH ONLY SPORADIC SHOWERS. THE EXCEPTIONS WILL BE THE
WESTERN KENAI PENINSULA AND NORTHERN SUSITNA VALLEY...AS WELL AS
MOST OF SOUTHWEST ALASKA. THE LOW TRACK REMAINS SOMEWHAT
UNCERTAIN...WITH THE GFS FAVORING A TRACK OVER THE PRIBILOF
ISLANDS...WHILE THE ECMWF AND CANADIAN GDPS FAVOR THE EASTERN
BERING CLOSER TO BRISTOL BAY. WITH THAT SAID...THE PRESSURE
GRADIENT WILL BECOME FAVORABLE FOR STRONG ACCELERATED GAP WINDS
THROUGH FAVORED TERRAIN SUCH AS TURNAGAIN ARM AND THROUGH THE
ILIAMNA GAP. DOWNSLOPE WARMING WILL BE AIDED MONDAY EVENING AND
NIGHT AS THE FRONT LIFTS INLAND...WITH WARMER MARITIME AIR
SWEEPING INTO MOST OF SOUTHERN ALASKA. THIS WILL HELP PUSH
TEMPERATURES WELL ABOVE AVERAGE THROUGH THE REMAINDER OF THE WORK
WEEK.

A SERIES OF SHORTWAVE TROUGHS ALOFT EMANATING FROM THE NORTH
PACIFIC WILL SUPPORT AN ACTIVE WEATHER PATTERN INTO THE
WEEKEND...WITH CONTINUED WARM ANOMALIES ACROSS MOST OF SOUTHERN
ALASKA.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 120 130 131 139
         HEAVY FREEZING SPRAY 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...JA