Small Craft Advisory 158, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
145 PM AKST THU FEB 20 2014

.ANALYSIS AND UPPER LEVELS...
A DECAYING UPPER LOW REMAINS OVER UPPER SOUTHERN ALASKA THIS
MORNING...CONTINUING AREAS OF LIGHT SNOW MAINLY AROUND COOK INLET. A
SURFACE LOW HAS SPUN UP IN THE NORTHWEST GULF WITH A SMALL BUT
IMPRESSIVE CIRCULATION NOTED ON RADAR IMAGERY. THE VAST MAJORITY OF
THE VIGOROUS SHOWER ACTIVITY ASSOCIATED WITH THIS LOW IS REMAINING
OFFSHORE...BARELY BRUSHING THE COAST NEAR CORDOVA. THE MAIN IMPACT
FROM THIS LOW HAS BEEN AN UPTICK OF OUTFLOW GAP WINDS ALONG THE COAST
FROM SEWARD TO WHITTIER AND ON TO THOMPSON PASS. OUT WEST...THE
ANTICIPATED AMPLIFICATION OF THE UPPER LEVEL PATTERN IS WELL UNDERWAY
AT THIS TIME...WITH INCREASINGLY MERIDIONAL FLOW USHERING WARMER AIR
INTO THE EASTERN BERING TOWARD THE SOUTHWEST MAINLAND. A PAIR OF
SMALL YET IMPACTFUL LOWS HAVE DEVELOPED ACROSS THE REGION. THE
FIRST...CURRENTLY WEST OF SHEMYA...BROUGHT SNOW AND BLOWING SNOW TO
THE WESTERN ALEUTIANS OVERNIGHT. CONDITIONS HAVE IMPROVED
SIGNIFICANTLY AS THE STRONGEST WINDS AND SNOWFALL HAVE MOVED OUT INTO
THE PACIFIC. THE SECOND SYSTEM CROSSED INTO THE SOUTHERN BERING
OVERNIGHT AND IS NOW WEAKENING SOUTHWEST OF THE PRIBILOF ISLANDS. AN
ASSOCIATED FRONT BROUGHT STRONG WINDS AND A SHORT PERIOD OF HEAVY
PRECIPITATION TO THE EASTERN ALEUTIANS AND ALASKA PENINSULA. FURTHER
NORTH...THE COMBINATION OF ENTRENCHED COLD AIR AND THIS FRONT IS
PRODUCING BLIZZARD CONDITIONS AROUND THE PRIBILOF ISLANDS WHICH WILL
CONTINUE THROUGH EARLY THIS AFTERNOON.

.MODEL DISCUSSION...
THE MODELS REMAIN IN GOOD SYNOPTIC AGREEMENT AND OVERALL FORECAST
CONFIDENCE IS ABOVE AVERAGE. THERE ARE A FEW DIFFERENCES WITH THE
TIMING OF THE FRONT MOVING INTO KODIAK ISLAND TONIGHT AS WELL AS THE
STRENGTH OF A WAVE THAT RIDES NORTHWARD ALONG A FRONTAL ZONE AND INTO
THE ALASKA PENINSULA ON SATURDAY NIGHT. FOR BOTH ISSUES THE ECMWF HAS
BEEN THE MOST CONSISTENT AND ALSO REPRESENTS A MIDDLE-GROUND BETWEEN
SOME OF THE OTHER MODEL SOLUTIONS. THUS THE ECMWF WILL BE USED TO
UPDATE THE FORECAST ON BOTH DOMAINS WITH THE AFTERNOON PACKAGE. THE
MOST SIGNIFICANT NET EFFECT WILL BE TO STRENGTHEN THE LOW MOVING UP
TOWARD THE ALASKA PENINSULA SATURDAY NIGHT.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE BIG QUESTION IS HOW LONG LOW CLOUDS AND FLURRIES
LINGER AROUND SOUTHCENTRAL...AND ESPECIALLY COOK INLET...TONIGHT.
ASSUMING A FEW BREAKS OF LATE SUN BY THIS EVENING...THINKING THERE
WILL BE A DECENT SHOT AT FOG FORMATION THIS EVENING AS THE ATMOSPHERE
WARMS AND BECOMES MORE STABLE AT ALL LEVELS. WORKING AGAINST THIS
WILL BE A GRADUALLY INCREASING NORTHERLY PRESSURE GRADIENT...BUT
STILL THINK SOME PATCHY FOG IS LIKELY ESPECIALLY AROUND ANCHORAGE. IN
TERMS OF MORE ACTIVE WEATHER...KODIAK ISLAND WILL BE THE CENTER OF
ATTENTION AS A WEAK FRONT MAKES SLOW NORTHWARD PROGRESS THIS EVENING.
TEMPERATURES WILL BE WARMING...BUT STILL THINK THERE WILL BE ENOUGH
COLD AIR TO RESULT IN AN INCH OR TWO OF SNOW. THIS FRONT WILL BE THE
FIRST IN A SERIES OF FRONTS THAT WILL ALL STALL IN THE VICINITY OF
KODIAK ISLAND OVER THE COMING DAYS...BRINGING NOTABLY WET WEATHER
THAT WILL FALL IN THE FORM OF RAIN BEGINNING THIS WEEKEND.

SOUTHWEST MAINLAND...THICKENING CLOUDS WILL GRADUALLY SPREAD INLAND
TONIGHT EVEN AS SURFACE WINDS BECOME INCREASINGLY OFFSHORE. PRECIP
ASSOCIATED WITH THE WEAKENING FRONT IN THE BERING WILL HAVE A HARD
TIME MAKING PROGRESS INLAND TONIGHT...BUT A MUCH MORE SUBSTANTIAL
FRONT FRI NIGHT NOW APPEARS IT WILL BE ABLE TO PUSH PRECIP INTO MUCH
OF THE AREA BY SATURDAY MORNING. WHILE PRECIP WILL BEGIN AS
SNOW...SIGNIFICANT WARM AIR ADVECTION WILL ALLOW A MIX OR CHANGEOVER
TO RAIN AT MANY LOCATIONS. THE BIGGEST IMPACT FROM THE UPCOMING
PATTERN CHANGE WILL BE A PROLONGED PERIOD OF A TIGHT PRESSURE
GRADIENT OVER THE AREA. THIS WILL RESULT IN AN EXTENDED PERIOD OF
STRONG SOUTHEASTERLY WINDS...ESPECIALLY ACROSS HIGHER ELEVATIONS OF
THE ALEUTIAN RANGE. AT THIS TIME IT LOOKS LIKE STRONG LOW-LEVEL
TEMPERATURE INVERSIONS WILL HELP KEEP THE STRONGEST CORE OF WINDS AT
THESE ELEVATED LOCATIONS...BUT THIS WILL BE WATCHED CLOSELY IN FUTURE
MODEL CYCLES.

BERING SEA AND ALEUTIANS...CONDITIONS ARE IMPROVING ACROSS THE
PRIBILOF ISLANDS AS THE ASSOCIATED LOW CONTINUES TO WEAKEN AND CURVE
WESTWARD INTO THE LONGWAVE TROUGH. THE NEXT IMPACTFUL SYSTEM IS
TAKING SHAPE SOUTH OF THE EASTERN ALEUTIANS...AND WILL CROSS INTO THE
SOUTHERN BERING BY MIDDAY FRIDAY. THE ALEUTIANS...ALASKA
PENINSULA...AND PRIBILOF ISLANDS WILL ALL LIKELY SEE PRECIPITATION IN
THE FORM OF RAIN EVEN AT THE VERY START OF THE STORM AS A SIGNIFICANT
SURGE OF WARM AIR MOVES INTO THE AREA. THIS LOW WILL BRING A
WIDESPREAD SWATCH OF GALE-FORCE WINDS TO THE EASTERN HALF OF THE
BERING...WHILE COOLER AND MORE SHOWERY PRECIP WILL PREVAIL OVER THE
FAR WESTERN BERING AND ALEUTIANS. THIS GENERAL PATTERN OF UNSETTLED
WEATHER OVER THE EASTERN SECTIONS OF THE BERING LOOKS AS IF IT WILL
CONTINUE THROUGH MUCH OF NEXT WEEK.

.LONG TERM FORECAST...
LONG RANGE MODELS ARE CONTINUING TO INDICATE A SIGNIFICANT WARM-UP
OVER MAINLAND ALASKA THIS WEEKEND AND CONTINUING THROUGH NEXT WEEK.
MOST AREAS WILL SEE TEMPERATURES NEAR OR ABOVE NORMAL FOR THE FIRST
HALF OF THE WEEK...WITH AN EVEN MORE SIGNIFICANT WARM-UP POSSIBLE FOR
THE LATTER HALF OF NEXT WEEK. MOST OF THE UNSETTLED WEATHER WILL
REMAIN OVER THE EASTERN BERING SEA AND KODIAK ISLAND...WITH AN
INCREASED CHANCE OF PRECIP BEGINNING TO AFFECT THE GULF COASTLINE BY
THE MIDDLE OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 130 131 138 155 160 170 172 174 176 179 180 181 185
         HEAVY FREEZING SPRAY 126 127 139
FIRE WEATHER...NONE

AMD FEB 14