Small Craft Advisory 646, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT MON AUG 26 2013

.MODEL DISCUSSION...

EXCEPT FOR THE GEM...MODELS OVERALL ARE IN FAIR AGREEMENT THROUGH WED
AFTERNOON. THE POSITIONING OF THE SURFACE CENTER BEYOND THIS BECOMES
MORE PROBLEMATIC AS SOLUTIONS BEGIN TO DIVERGE AS THE UPPER TROUGH
DIGS OVER THE GULF. THE NAM APPEARS TO BE THE BEST COMPROMISE THROUGH
THE REMAINDER OF THE SHORT RANGE. THOUGH THE SURFACE AND UPPER AIR
PATTERNS DIVERGE...THE PRECIPITATION PATTERNS ARE IN SOMEWHAT
AGREEMENT THROUGH WED AFTERNOON.

.ANALYSIS AND UPPER LEVELS...
.500 MB...A WEAK TROUGH ASSOCIATED WITH A WEAKENING FRONTAL BOUNDARY
EXTENDS SE ACROSS WESTERN ALASKA TO THE SOUTHERN GULF. THIS TROUGH
LIFTS ACROSS SOUTHCENTRAL TUE. A FAIRLY VIGOROUS WAVE OVER THE
EASTERN BERING SEA DIVES SOUTH OF THE GULF TONIGHT. A LOW OVER
EASTERN RUSSIA MOVES TO OVER THE SEWARD PENINSULA TUE NIGHT THE OVER
THE KOBUK VALLEY WED AFTERNOON. A SHORT WAVE ASSOCIATED WITH THIS
CENTER MOVES INTO SOUTHCENTRAL TUE AFTERNOON AND SETS UP W TO SW
FLOW. THE TROUGH ASSOCIATED WITH THE LOW CENTER OVER NW ALASKA DIGS
SOUTH ALONG 157W TUE NIGHT AS A WAVE DROPPING SOUTH ACROSS THE
EASTERN BERING SEA PHASES WITH A WAVE MOVING EAST ACROSS THE SOUTHERN
BERING. THIS SETS UP BROAD SWLY FLOW ACROSS SOUTHCENTRAL AND THE GULF
AND NW FLOW ACROSS THE EASTERN BERING SEA/EAST ALEUTIANS...AND AK PEN
WHICH HOLDS THROUGH WED AFTERNOON.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
A WEAK FRONTAL BOUNDARY MOVES EAST ACROSS THE REGION TUE. THIS
FEATURE IN COMBINATION WITH A DIGGING TROUGH ALOFT WILL LIKELY
PROVIDE SOME RAIN OR SHOWERS TUE. CONDITIONS WILL BECOME SOMEWHAT
WETTER ON WED AS THE UPPER TROUGH SETS UP MOIST SW FLOW ACROSS THE
GULF AND SOUTHCENTRAL. WINDS FOR THE MOST PART WILL BE RELATIVELY
LIGHT ACROSS SOUTHCENTRAL TONIGHT AND TUE. WINDS INCREASE SOME ACROSS
THE GULF WITH THE APPROACH OF THE LOW CENTER AND ASSOCIATED FRONT TUE
NIGHT AND WED.

SOUTHWEST ALASKA/AK PEN...
THE GFS HANDLES THE RAIN MOVING EAST ACROSS THE AK PEN TONIGHT. RAIN
SHOULD DIMINISH THIS EVENING AS THE WAVE MOVES SE. THE WEAK FRONTAL
BOUNDARY MOVES ACROSS THE SW MAINLAND OVERNIGHT. WEAK RIDING ON THE
BACKSIDE WILL BRING LOW CLOUDS AND PATCHY FOG ACROSS THE COASTAL
AREAS AND NEAR INLAND AREAS TONIGHT. INCREASED CHANCES OF
RAIN...ASSOCIATED WITH A WAVE MOVING ACROSS THE BERING SEA...SPREADS
TO THE AK PEN LATE TUE AFTERNOON AND TO BRISTOL BAY LATE TUE NIGHT.
RAIN WILL CONTINUE EAST ON WED...HOWEVER...THE PROXIMITY OF THE UPPER
TROUGH WILL HOLD THE THREAT OF SHOWERS OVER THE REGION THROUGH WED
EVENING. THE SW MAINLAND SHOULD EXPERIENCE DRYING WITH THE ONSET OF
NORTHERLY FLOW WED NIGHT/THU.

BERING SEA AND ALEUTIANS...
A DEVELOPING LOW MOVES TO THE WESTERN ALEUTIANS TONIGHT AND TO THE
EASTERN ALEUTIANS TUE NIGHT. EXPECT STRONG SW FLOW IN ADVANCE OF THIS
CENTER AND BRISK NW FLOW ON THE BACKSIDE. ALSO EXPECTED RAIN AS THIS
SYSTEM PASSES THROUGH. RIDGING BUILDS IN THE WAKE OF THIS SYSTEM ON
TUE AND HOLDS OVER THE BERING SEA THROUGH WED...SO EXPECT AREAS OF
LOW CLOUDS AND FOG TO BE RELATIVELY WIDESPREAD. A WEAK WAVE SKIRTS
THE ALEUTIANS WED.

.LONG TERM FORECAST...
GUIDANCE WANTS TO CONTINUE THE CURRENT PROGRESSIVE PATTERN INTO THE
EXTENDED PERIOD WITH THE ACTIVE JET OVER THE ALEUTIANS. INDIVIDUAL
SOLUTIONS CONCERNING SPECIFIC SYSTEMS ARE GOING TO BE HARD TO COME
BY WITH SUCH A PROGRESSIVE PATTERN. LOOK FOR MORE GENERAL TROUGHING
OVER THE BERING SEA WITH ACTIVE JET OVER THE ALEUTIANS AND A MOIST
SOUTHWEST FLOW EXTENDING ONTO THE MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...172 AND 175.
FIRE WEATHER...NONE

RMC AUG 13