Small Craft Advisory 19, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SUN JAN 6 2013

.MODEL DISCUSSION...SYNOPTIC INITIALIZATIONS ARE SIMILAR AND
REASONABLE. THE 500 MB FORECASTS ARE SIMILAR IN THE HANDLING OF THE
MAIN FEATURES. THE DIFFERENCES AS ALWAYS LAY IN THE HANDLING OF THE
ASSOCIATED SURFACE FEATURES. IN THE EAST THE LOW HEADING TOWARD
KODIAK ISLAND IS FULLY OCCLUDED AND STACKED...THE MODELS SIMILARLY
HANDLE THIS SYSTEM...THOUGH THE NAM MAY BE A LITTLE TOO FAR EAST. THE
ECMWF LOOKS TO BE THE BEST COMPROMISE IN POSITIONING. OUT
WEST...MODELS HAVE A SIMILAR HANDLING OF THE FRONTAL TROUGH
APPROACHING THE ALEUTIANS MON. THE WIND FIELDS ASSOCIATED WITH THIS
FEATURE ARE SOMEWHAT SIMILAR. THE MAIN DIFFERENCES CAME IN WITH THE
POSITIONING OF A FRONTAL WAVE WHICH CROSSES THE ALEUTIANS MON NIGHT.
THE GFS/ECMWF/UKMET HAVE SIMILAR FORECASTS WITH THIS FEATURE. THE
ECMWF 00Z ALSO SHIFTED TOWARD THE GFS SOLUTION. SO FOR NOW LEAN
TOWARD GFS OUT WEST THIS FORECAST PACKAGE.

.ANALYSIS AND UPPER LEVELS...

A 960S STACKED LOW CENTER SOUTH OF THE AK PEN MOVES TO NEAR KODIAK
ISLAND TONIGHT...THEN BECOMES STATIONARY OVER THE GULF MON BEFORE
DRIFTING SOUTH AND WEAKENING MON NIGHT/TUE. THE FRONTAL TROUGH
ASSOCIATED WITH THIS FEATURE LIES ACROSS THE AK PEN AND IS RAPIDLY
MOVING NORTH ACROSS KODIAK ISLAND. THE WESTERN PORTION MOVES OVER
BRISTOL BAY AND WEAKENS TONIGHT. THE GULF PORTION IMPACTS THE NORTH
GULF COAST TONIGHT...THEN MOVES INLAND AND WEAKENS MON. THE BARRIER
JET ALONG THE NORTH GULF COAST SHOULD INTENSIFY INTO THE EARLY
EVENING HOURS THEN DIMINISH OVERNIGHT. OUT WEST...UNSETTLED WEATHER
CONDITIONS WITH SEVERAL WEAKENING FEATURES INFLUENCE THE AREA. OTHER
THAN THE LOW SOUTH OF THE AK PEN...A SERIES OF WEAK WAVES ARE
PRODUCING VIGOROUS RAIN AND SNOW SHOWERS ACROSS THE WESTERN AND
CENTRAL ALEUTIANS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
THE MAIN FEATURE THROUGH MON WILL BE THE LOW CENTER SOUTH OF THE AK
PEN AND ITS ASSOCIATED FRONTAL TROUGH. IT LOOKS LIKE THE THE COASTS
WILL RECEIVE THE MAJORITY OF THE PRECIPITATION WITH MOST SEA LEVEL
LOCATIONS RECEIVING A MIX OF RAIN AND SNOW. INLAND AREAS WILL
GENERALLY BE DOWN-SLOPED...BUT SOME SPILL OVER SNOW IS POSSIBLE AS
THE FRONTAL TROUGH LIFTS NORTH AND THE LOW MOVES INTO THE NORTHERN
GULF MON. CONDITIONS WILL BECOME SOMEWHAT DRIER MON NIGHT/TUE AS THE
LOW DRIFTS SOUTH AND THE RIDGE BUILDS IN FROM THE WEST.

SOUTHWEST ALASKA/ALASKA PENINSULA...
LOW CLOUDS AND FOG WILL CONTINUE TO BREAK UP ACROSS THE SW MAINLAND
WITH INCREASED NORTHERLY FLOW. A WEAKENING OCCLUDED FRONT WILL BRING
SOME SNOW ACROSS THE SW MAINLAND THROUGH TONIGHT AND BE FOLLOWED BY
DRIER CONDITIONS ON MON. PATCHY FOG ALSO TO BECOME A CONCERN AGAIN
MON NIGHT AS THE RIDGE BUILDS EAST. GUSTY NORTHERLY WINDS WITH SNOW
SHOWERS WILL CONTINUE INTO MON ACROSS THE AK PEN.

BERING SEA AND ALEUTIANS...
AREAS OF SCATTERED RAIN AND SNOW SHOWERS WILL CONTINUE TO IMPACT THE
ALEUTIAN CHAIN TONIGHT BEFORE DIMINISHING ON MONDAY AS HIGH PRESSURE
BUILDS OVER THE AREA. LATE MONDAY INTO TUESDAY...A STRONG FRONT WILL
TRACK FROM WEST TO EAST...WITH RAIN AND GALE TO STORM FORCE WINDS
IMPACTING MUCH OF THE REGION.

.LONG TERM FORECAST...

WEDNESDAY AND BEYOND...ANOTHER BROAD UPPER LOW WILL PARK ITSELF OVER
THE WESTERN BERING SEA. A POWERFUL 200 KNOT EAST ASIAN JET STREAM
WILL ONCE AGAIN ESTABLISH ITSELF OVER THE NORTH PACIFIC...WHICH WILL
ALLOW FOR NUMEROUS STORM SYSTEMS TO FORM ALONG IT. THE FIRST SYSTEM
WILL PUSH INTO SOUTHERN ALASKA WEDNESDAY AND THURSDAY WITH ANOTHER
LATE WEEK INTO SATURDAY. TEMPERATURES SHOULD MODERATE CLOSER TO
CLIMATOLOGICAL AVERAGES HEADING INTO THE WEEKEND.

THE PROGRESSIVE FLOW PATTERN WILL CONTINUE INTO NEXT WEEK...WITH THE
POTENTIAL FOR A VERY WET AND STORMY PATTERN AS A LARGE UPPER LEVEL
RIDGE BUILDS ACROSS THE EASTERN PACIFIC...WITH NUMEROUS STORMS
TRANSLATING OVER TOP THE RIDGE AXIS.

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

RMC JAN 13