Small Craft Advisory 575, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT SAT AUG 18 2012

.MODEL DISCUSSION...MODEL SYNOPTIC FIELD INITIALIZATIONS WERE
REASONABLE WITH THE EXCEPT OF GPF. A COMPARISON OF MODEL QPF FIELDS
WITH RADAR DATA IN SW ALASKA SHOWS THAT THE MODELS ACROSS THE BOARD
WERE LAGGING IN THE PROGRESSION OF THE RAIN. WITH THIS EXCEPTION...
MODEL FORECAST TRENDS WERE SIMILAR AND REASONABLE THROUGHOUT THE
SHORT TERM.

.ANALYSIS AND UPPER LEVELS...

THE CENTRAL FEATURE TODAY IS A LARGE UPPER LOW AND ASSOCIATED 980'S
SURFACE LOW NEAR NUNIVAK ISLAND. THE STACKED SYSTEM SLOWLY WEAKENS AS
IT MOVES TO OVER NORTON SOUND LATE TONIGHT AND THEN INLAND OVER THE
SEWARD PENINSULA SUN. THE OCCLUDED FRONT THIS AFTERNOON EXTENDED FROM
THE NORTH DELTA TO OVER CENTRAL BRISTOL BAY TO THE AK PEN. THE FRONT
WILL CONTINUE GENERALLY EASTWARD PROGRESSION TODAY TO OVER
SOUTHCENTRAL ALASKA AND GULF TONIGHT. NEXRAD RADARS SHOWED WIDESPREAD
RAIN OVER BRISTOL BAY WITH ECHOS MOVING INTO SOUTHERN COOK INLET THIS
AFTERNOON.

THE LONG WAVE PATTERN SUGGESTS UNSETTLED WEATHER WITH ABUNDANT CLOUD
COVER AND HIGH PROBABILITIES OF RAIN/SHOWERS ACROSS MUCH OF THE
MAINLAND INTO EARLY NEXT WEEK. THOUGH SW ALASKA WILL BRIEFLY COME
UNDER THE INFLUENCE OF AN UPPER RIDGE MON BEFORE THE NEXT WAVE BRINGS
IN MOISTURE ON TUE.

.SHORT TERM FORECAST...

SOUTHCENTRAL...
RAIN SPREADS NORTH AND EAST ACROSS SOUTHCENTRAL ALASKA AND THE GULF
THROUGH THIS EVENING. THE FRONT AND SLOW MOVING UPPER TROUGH TO THE
WEST WILL CONTINUE MOIST SOUTHWESTERLY FLOW ALOFT THROUGH MON. THE
NET RESULT WILL BE CLOUDY AND GENERALLY WET CONDITIONS. PRESSURE
GRADIENTS WILL INCREASE ACROSS THE SOUTHCENTRAL TODAY AND PRODUCE
BRISK GAP FLOWS ACROSS THE REGION. OF NOTE ARE GAP FLOWS THROUGH
TURNAGAIN ARM...KNIK RIVER VALLEY...AND ALONG THE COPPER RIVER. FLOWS
MAY DIMINISH BRIEFLY TONIGHT...THEN INCREASE AGAIN SUN.

SOUTHWEST ALASKA...
STEADY RAIN ASSOCIATED WITH THE FRONT THIS AFTERNOON WILL DIMINISH
SOME AS FRONT PUSHES TOWARD SOUTHCENTRAL ALASKA. HOWEVER...WESTERLY
FLOW AND PROXIMITY OF THE UPPER LOW WILL CONTINUE CLOUDY AND SOMEWHAT
WET CONDITIONS(RAIN/SHOWERS) THROUGH SUN. RIDGING LATE MON MAY BRING
A BRIEF BREAK IN RAIN BEFORE THE NEXT WAVE TUE. WINDS WILL SLOWLY
DIMINISH ACROSS THE REGION THROUGH SUN.

BERING SEA/ALEUTIANS...

GALES OVER THE EASTERN BERING THROUGH TONIGHT. BEHIND THE FRONTAL
SYSTEM AND UPPER LEVEL TROUGH OVER THE EASTERN BERING...HIGH PRESSURE
RIDGING CENTERED JUST SOUTH OF THE ALEUTIANS WILL TAKE HOLD AND BRING
A MOSTLY PRECIPITATION-FREE SUNDAY TO THE BERING SEA. FOG AND LOW
STRATUS WILL BE STILL WIDESPREAD HOWEVER.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 160 165 185 412 413
FIRE WEATHER...NONE.

RMC AUG 12