Small Craft Advisory 881, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST TUE DEC 4 2012

.ANALYSIS AND UPPER LEVELS...
THE BLOCKING UPPER LEVEL HIGH HAS RETREATED TO THE RUSSIAN ARCTIC
COAST AS THE RIDGE WHICH HAD BEEN IN PLACE OVER THE BERING SEA HAS
BEEN CUTOFF BY A PAIR OF LONG WAVE TROUGHS...WITH ONE CENTERED OVER
THE KAMCHATKA PENINSULA TO ITS WEST AND ANOTHER EXTENDING FROM THE
CENTRAL ALASKAN MAINLAND INTO THE NORTHEASTERN PACIFIC OCEAN. A
CLOSED UPPER LOW DROPPING SOUTH OVER THE AKPEN AND KODIAK ISLAND HAS
BECOME THE DOMINANT FEATURE WITHIN THE TROUGH AS ANOTHER EMBEDDED LOW
PRESSURE CENTER CONTINUES TO WEAKEN OVER THE NORTHEASTERN PACIFIC. A
COMPLEX SURFACE LOW RESIDES OVER THE GULF WITH COLD AIR REMAINING
ENTRENCHED AT THE SURFACE OVER THE COPPER RIVER BASIN...SUPPORTING A
CONTINUATION OF GUSTY OUTFLOW WINDS THROUGH FAVORED AREAS OF
SOUTHCENTRAL AK.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD AGREEMENT THROUGH THE SHORT TERM WITH RESPECT
TO OVERALL SYNOPTIC FEATURES. LOW PRESSURE WILL REMAIN OVER THE GULF
THROUGH THURSDAY AS THE UPPER LOW NEAR KODIAK ISLAND MOVES EASTWARD.
MEANWHILE...WEAK TROUGHING WILL BECOME ESTABLISHED ACROSS THE
ALEUTIANS AS THE KAMCHATKA LOW BECOMES CUT OFF AND DRIFTS SOUTHWARD.
MODELS SOLUTIONS BEGIN TO DIVERGE SIGNIFICANTLY TOWARDS THE END OF
THE WEEK...WITH GENERAL AGREEMENT ON A STRONG NORTH PACIFIC SURFACE
LOW MOVING SOUTH OF THE CENTRAL/EASTERN ALEUTIANS BY SATURDAY
MORNING...BUT WITH LARGE DISCREPANCIES IN LOCATION AND INTENSITY.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE COLD AND DRY PATTERN WILL PREVAIL FOR A FEW MORE DAYS OVER MUCH
OF SOUTHCENTRAL AK AS THE UPPER LOW MOVES INTO THE GULF. KODIAK
ISLAND WILL CONTINUE TO SEE SNOW SHOWERS THROUGH WEDNESDAY NIGHT IN
THE VICINITY OF THE LOW BEFORE IT MOVES OFF TO THE EAST ON
THURSDAY... WITH ISOLATED SNOW SHOWERS ALSO POSSIBLE ALONG THE GULF
COAST.

SOUTHWEST ALASKA...
MORE OF THE SAME AS NORTHERLY FLOW CONTINUES TO YIELD COLD AND DRY
CONDITIONS OVER THE SOUTHWEST MAINLAND THROUGH THE LATTER PART OF THE
WEEK...WITH A FEW SNOW SHOWERS POSSIBLE ALONG THE AKPEN.

ALEUTIANS/BERING SEA...
A WEAK FRONTAL BOUNDARY WILL CONTINUE TO BRING A MIX OF RAIN AND SNOW
SHOWERS TO THE CENTRAL ALEUTIANS BEFORE DISSIPATING TONIGHT. A CHANCE
OF PRECIPITATION WILL REMAIN IN THE FORECAST THROUGH THURSDAY FOR THE
WESTERN AND CENTRAL PARTS OF THE CHAIN WITH THE WEAK TROUGH OVERHEAD.

.LONG TERM FORECAST...
MODELS CONTINUE TO INDICATE A CHANGE TO A MUCH MORE PROGRESSIVE
PATTERN IN THE EXTENDED TERM...WITH ZONAL FLOW SETTING UP OVER THE
SOUTHERN MAINLAND AND BRINGING AN INCREASED CHANCE OF PRECIPITATION
BY THIS WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING 121 127 128 130 160 172
         HEAVY FREEZING SPRAY WARNING 121 126 127 128 129 130 138
                                      140 141 150 160 165 179 185
FIRE WEATHER...RED FLAG WARNING 111

CB DEC 12