Small Craft Advisory 6, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1245 PM AKST TUE JAN 1 2013

.ANALYSIS AND UPPER LEVELS...
THE DOMINANT FEATURE ON THE WEATHER MAP THIS AFTERNOON CONTINUES TO
BE THE LARGE LOW CROSSING THE ALASKA PENINSULA INTO BRISTOL BAY.
SATELLITE IMAGERY CONFIRMS THE DRY AIR HAS WRAPPED INTO THE LOW
CENTER MULTIPLE TIMES AND THE STORM IS NOW WEAKENING. THE ASSOCIATED
FRONTAL BAND HAS STALLED ALONG THE NORTH GULF COAST...AND IS SIMPLY
WEAKENING IN PLACE. INTERESTINGLY...A WEAK SHORTWAVE MOVED NORTHWARD
ALONG THE FRONT THIS MORNING AND HAS ACTUALLY BEEN STRONG ENOUGH TO
RETROGRADE THE FRONTAL PRECIPITATION SHIELD SLIGHTLY BACK TO THE
WEST. STEADY RAIN IS FALLING ACROSS THE NORTH GULF COAST...BECOMING
SNOW TOWARD VALDEZ AND THOMPSON PASS. FURTHER WEST...MODERATE RAIN
AND SNOW SHOWERS ARE BECOMING MORE NUMEROUS ACROSS BRISTOL BAY AND
THE KUSKOKWIM DELTA AS THE ACTUAL LOW CENTER MOVES INTO THE AREA. WAY
OUT WEST...A VERY ELONGATED AND FAIRLY WEAK FRONT IS STRETCHING OUT
ACROSS THE WESTERN AND CENTRAL ALEUTIANS TODAY AS AN UPPER TROUGH
DIGS INTO THE LONGWAVE TROUGH JUST SOUTH OF THE CHAIN.

.MODEL DISCUSSION...
MODELS ARE IN PRETTY GOOD AGREEMENT ON THE EVOLUTION OF THE MAJOR
FEATURES OVER THE NEXT SEVERAL DAYS. THE 974 MB LOW OVER SOUTHWEST
ALASKA WILL CONTINUE TO WEAKEN RAPIDLY TONIGHT AND DISSIPATE JUST
OFFSHORE THE DELTA BY MORNING. MEANWHILE...THE UPPER TROUGH DIGGING
SOUTH OF THE ALEUTIANS WILL DEVELOP A SURFACE LOW SOUTH OF DUTCH
HARBOR OVERNIGHT...AND THIS LOW WILL TAKE A TURN BECOMING THE
DOMINANT CIRCULATION CONTAINED IN THE BROAD LONGWAVE. THIS LOW WILL
MAKE STAY FURTHER SOUTH AND WEST AND BE SHORTER-LIVED THAN THE
PREVIOUS THREE STORMS...THE TURNAGAIN ARM AREA A BREAK FROM
WARNING-LEVEL WINDS. BY THE END OF THE WEEK...MODELS HAVE COME INTO
BETTER AGREEMENT THAT A MODERATE STRENGTH LOW WILL DEVELOP IN THE
EASTERN GULF OF ALASKA BEFORE WEAKENING AND RE-CURVING TO THE
NORTHWEST. OVERALL...THE FORECAST WILL SHOW A SLIGHT PREFERENCE
TOWARD THE GFS SOLUTION DUE TO SUPERIOR RUN-TO-RUN CONSISTENCY OVER
THE LAST SEVERAL DAYS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...DEEP-LAYER SOUTHEASTERLY WINDS WILL KEEP CLASSIC
DOWNSLOPE PATTERN LARGELY INTACT TONIGHT ACROSS THE REGION. THE FRONT
HUNG UP ALONG THE NORTH GULF COAST WILL DISSIPATE AND THE AREA WILL
FALL UNDER THE GENERAL CYCLONIC INFLUENCE OF THE LOW ITSELF...RATHER
THAN THE FRONT. THIS WILL ALLOW LOW-LEVEL FLOW ACROSS THE NORTHERN
GULF AND PRINCE WILLIAM SOUND TO BECOME MORE SOUTHWESTERLY. THIS
SHOULD KEEP STEADY SNOW FALLING AROUND VALDEZ AND THOMPSON PASS FOR
MUCH OF THE NIGHT...ESPECIALLY AS A MID-LEVEL TROUGH IMPACTS THE
COAST LATE THIS EVENING AND ENHANCES SYNOPTIC LIFT. AT THE SAME
TIME...DECREASING WINDS ALOFT AND A WEAK UP-INLET GRADIENT SHOULD
ALLOW LIGHT SOUTHERLY WINDS TO SPREAD INTO ANCHORAGE...KEEPING
OVERNIGHT TEMPS RIGHT AROUND FREEZING.

SOUTHWEST...THE LOW MOVING ALONG THE COASTLINE TONIGHT WILL KEEP
SHOWER ACTIVITY PLENTIFUL ACROSS THE REGION. AT THE SAME TIME...COLD
AIR IS FILTERING INTO THE AREA FROM THE SOUTHWEST AS THE LOW WEAKENS.
THIS WILL HELP MOST LOCATIONS TRANSITION FROM A RAIN/SNOW MIX TOWARD
ALL SNOW BY MORNING WITH SOME MINOR ACCUMULATIONS POSSIBLE. AFTER A
BRIEF BREAK IN THE CLOUDS AND PRECIPITATION DURING THE DAY
WEDNESDAY...CLOUDS AND WIND MOVE BACK IN FROM SOUTHEAST BY LATE
WEDNESDAY AFTERNOON.

BERING SEA AND ALEUTIANS...STRETCHED OUT FRONT OVER THE WESTERN HALF
OF THE ALEUTIAN CHAIN WILL GRADUALLY CONSOLIDATE INTO A DEVELOP LOW
SOUTH OF DUTCH HARBOR LATE TONIGHT. A RAIN/SNOW MIX FROM ADAK
WESTWARD WILL GRADUALLY DIMINISH TONIGHT. BY WEDNESDAY EVENING...THE
EASTERN ALEUTIANS SHOULD SEE A PERIOD OF STEADY SNOW AS THE LOW
PIVOTS INTO THE EASTERN BERING FROM THE PACIFIC.

.LONG TERM FORECAST...
EXTENDED MODEL RUNS ARE STILL SUGGESTING A BIT OF A WESTWARD SHIFT IN
THE POSITION OF THE LONGWAVE TROUGH BY THE WEEKEND. AS THIS
HAPPENS...MAINLAND ALASKA WILL REMAIN IN GENERAL SOUTHERLY FLOW...BUT
WEATHER MAY BE LESS ACTIVE AS MOST LOWS REMAIN IN THE CENTRAL BERING.
THIS WILL LIKELY ALLOW TEMPERATURES TO DROP A FEW DEGREES CLOSER TO
NORMAL ACROSS THE AREA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 120 130 132 150 155 160 172 175 176
         HEAVY FREEZING SPRAY 185
FIRE WEATHER...NONE

AMD JAN 13