Small Craft Advisory 133, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
330 PM AKST WED FEB 12 2014

.ANALYSIS AND UPPER LEVELS...
A DEEP UPPER TROUGH CONTINUES TO DIG SOUTHWARD ACROSS THE MAINLAND
ACCOMPANIED BY VERY COLD ARCTIC AIR AND GUSTY WINDS. A SURFACE LOW IN
THE NORTHWEST GULF IS DEVELOPING AS EXPECTED...AND IS ENHANCING
PRESSURE GRADIENTS AND ASSOCIATED OUTFLOW GAP WINDS ACROSS THE GULF
COAST. THE BULK OF THE ARCTIC AIRMASS IS DROPPING AROUND THE WEST
SIDE OF THE ALASKA RANGE INTO SOUTHWEST ALASKA...WHERE TEMPERATURES
AND WIND CHILL VALUES ARE ALREADY WELL BELOW ZERO AND WILL CONTINUE
DROPPING THROUGHOUT THE NIGHT. OUT WEST...THERE IS A RELATIVELY
LOW-AMPLITUDE RIDGE OVER THE WESTERN BERING WITH A SHORTWAVE JUST
BEGINNING TO DROP DOWN THE FRONT/EAST SIDE. A WEAK AND ELONGATED
SURFACE LOW HAS DEVELOPED IN RESPONSE TO THIS WAVE...BUT IS STRONG
ENOUGH TO GENERATE A SMALL AREA OF NORTHWESTERLY GALE-FORCE WINDS
MOVING INTO THE WESTERN BERING.

.MODEL DISCUSSION...
MODELS ARE IN UNCHARACTERISTICALLY OUTSTANDING AGREEMENT THROUGHOUT
THE SHORT TERM WITH ALL MAJOR FEATURES. IT WILL BE VERY DIFFICULT TO
PINPOINT MORE THAN 6-12 HOURS IN ADVANCE EXACTLY WHERE INDIVIDUAL
SURFACE LOWS WILL PINWHEEL AROUND IN THE NORTHWEST GULF OVER THE NEXT
FEW DAYS...SO WILL ADOPT A FAIRLY BROAD-BRUSHED APPROACH THAT FOCUSES
ON IMPACTS AND GAP WINDS...AND RELY ON RADAR AND SATELLITE TRENDS TO
FINE-TUNE THE FORECASTS WHILE THIS PATTERN PERSISTS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...COVERAGE AND INTENSITY OF SNOW BANDS WILL CONTINUE TO
INCREASE ACROSS THE NORTHERN GULF AND COASTAL LOCATIONS. THE PRIMARY
FORECAST CHALLENGE WILL REMAIN SNOW AMOUNTS AROUND THE REGION...WITH
THE HIGHEST AMOUNTS FALLING AROUND AND EAST OF PRINCE WILLIAM SOUND.
WHILE SNOWFALL RATES WILL BE MODERATE BY RELATIVE STANDARDS...THE
LONGEVITY OF THE SNOWFALL OVER THE COMING DAYS WILL BECOME FAIRLY
SIGNIFICANT...ESPECIALLY GIVEN THE RECENT LONG RUN OF DRIER THAN
NORMAL WEATHER. AS THE LOW IN THE GULF BECOMES MORE VERTICALLY
STACKED TONIGHT...DEEP-LAYER SOUTHEAST FLOW IS STILL EXPECTED TO
ALLOW WARMER AIR AND AN OVERRUNNING PRECIPITATION PROCESS TO SPREAD
SOME SNOW BACK INTO UPPER COOK INLET...THOUGH SNOW AMOUNTS SHOULD BE
MINOR. THE MORE IMPACTFUL WEATHER WILL BE THROUGH THOMPSON
PASS...WHERE WINDS SHOULD REMAIN HIGH ENOUGH TO CREATE SOME BLOWING
SNOW CONCERNS THROUGH MIDDAY THURSDAY AND POTENTIALLY BEYOND.

SOUTHWEST...CONTINUED COLD ADVECTION AND MODERATELY GUSTY WINDS WILL
CREATE DANGEROUS WIND CHILL CONDITIONS ACROSS MOST OF THE AREA
THROUGH FRIDAY. WITH WEAK UPPER LEVEL WAVES MOVING SOUTHWARD THERE IS
ALSO A GOOD CHANCE THAT A FEW SNOW SHOWERS WILL PERSIST ALONG THE
COAST OF THE KUSKOKWIM DELTA. THE STRONGEST WINDS WILL CONTINUE AND
EVEN STRENGTHEN THROUGH TERRAIN GAPS ALONG THE ALEUTIAN RANGE AND
ALASKA PENINSULA AS A POTENT POTENTIAL VORTICITY ANOMALY DROPPING
DOWN FROM THE NORTH HELPS SQUEEZE THE LOWEST LAYERS OF THE ATMOSPHERE
AND ACCELERATE WINDS.

BERING SEA AND ALEUTIANS...AS MENTIONED ABOVE A SHORTWAVE COMING DOWN
THE FRONT OF THE RIDGE WILL BRING A QUICK SHOT OF WIND AND SNOW TO
THE CENTRAL AND EASTERN ALEUTIANS AS WELL AS THE PRIBILOFS THROUGH
THIS EVENING. AS THIS FEATURE MOVES OUT INTO THE PACIFIC THE ARCTIC
AIRMASS WILL BEGIN TO ELONGATE WESTWARD FROM THE MAINLAND AND
KICK START SNOW SHOWER ACTIVITY OVER THE EASTERN HALF OF THE BERING
SEA ON THURSDAY. COUPLED WITH THE ENHANCED WIND SPEEDS (SEE PREVIOUS
SECTION) THERE IS AN INCREASING LIKELIHOOD OF SIGNIFICANT BLOWING
SNOW CONCERNS DEVELOPING THURSDAY AFTERNOON FROM DUTCH HARBOR
EASTWARD ALONG THE PENINSULA. HAVE ISSUED A BLIZZARD WATCH FOR THE
PENINSULA AND THE DUTCH HARBOR AREA FOR TOMORROW AFTERNOON AND NIGHT.

.LONG TERM FORECAST FROM PREVIOUS DISCUSSION...
NOT MUCH CHANGE IN THINKING FOR THE EXTENDED TERM AS FORECAST
CONFIDENCE REMAINS HIGHER THAN NORMAL WITH THE DEEP UPPER LOW
DROPPING SOUTHWARD FROM THE ARCTIC AND REMAINING ENTRENCHED OVER THE
WESTERN GULF OF ALASKA THROUGH THE MIDDLE OF NEXT WEEK. THIS WILL
GENERALLY CONTINUE TO YIELD COLD TEMPERATURES AND GUSTY OUTFLOW WINDS
FOR THE SOUTHERN HALF OF THE MAINLAND...WITH THE BEST CHANCE FOR
PRECIPITATION REMAINING ALONG THE NORTHERN GULF COAST. PRECIPITATION
WILL ALSO BE POSSIBLE FOR INLAND PORTIONS OF SOUTHCENTRAL AK
DEPENDING ON THE EXACT POSITION OF THE LOW AND THE VARIOUS WAVES
ROTATING AROUND IT. MEANWHILE...A MORE ACTIVE PATTERN WILL BE IN
STORE FOR THE BERING AS THE RIDGE OVER THE WESTERN BERING BREAKS DOWN
AND SEVERAL SYSTEMS MOVE THROUGH...PROVIDING OCCASIONAL CHANCES FOR
PRECIPITATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 181 185
         WIND CHILL ADVISORY 131 152 155 161
         WINTER WEATHER ADVISORY 131
MARINE...GALE 121 127 128 130 131 132 150 155 165 170 171 172 173
              174 175 176 177 178 179 180 185 411 412 413 414
         HVY FRZG SPRY 121 126 127 128 129 130 131 132 136 137 138

                       139 140 141 150 155 160 165 170 171 179 180
                       185 352 411 412 414
FIRE WEATHER...NONE

AMD FEB 14