Small Craft Advisory 445, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT WED MAY 21 2008

.ANALYSIS AND UPPER LEVELS...
AT THE SURFACE THE LOW CURRENTLY NEAR DUTCH HARBOR IS WEAKENING AND
DRIFTING NORTHWEST. THE ASSOCIATED FRONT IS DISSIPATING TO A TROUGH
AND EXTENDS TO JUST SOUTH OF THE PRIBILOF ISLANDS TO NEAR NUNIVAK
ISLAND THEN SOUTHEAST ACROSS THE ALASKA PENINSULA TO SOUTHWEST KODIAK
ISLAND. THIS IS UNDER THE UPPER LOW THAT IS IN A LARGE DEEP UPPER
TROUGH THAT EXTENDS FROM THE CANADIAN ARCTIC SOUTHWEST TO ANOTHER
UPPER LOW OVER THE NORTH PACIFIC AROUND 45N 175W. A STRONG 200 KT JET
IS ASSOCIATED WITH THIS UPPER TROUGH. CURRENT SATELLITE IMAGERY SHOWS
THE NEXT STORM FORMING ABOUT 900 NM SOUTH OF COLD BAY IN THIS TROUGH
AND THAT IS EXPECTED TO IMPACT SOUTHWEST ALASKA THURSDAY NIGHT AND
FRIDAY. THE THERMAL TROUGH PERSISTS FROM THE KUSKOKWIM VALLEY
EAST TO THE COPPER RIVER BASIN AND WILL BE THE FOCUS FOR THIS
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. THE THUNDERSTORMS
HAVE ALREADY INITIATED IN THE COPPER RIVER BASIN THIS AFTERNOON.

.MODEL DISCUSSION...
THE MODELS ARE STILL ATTEMPTING TO RESOLVE THE FORECAST TRAJECTORY OF
THE MAJOR INCOMING NORTH PACIFIC STORM. SUCCESSIVE MODEL RUNS
CONTINUE TO MOVE THE LOW WEST AND WE STILL HAVE DOUBTS AS TO THE PATH
THIS STORM WILL TAKE. THE LATEST RUNS INDICATE IT CROSSING THE ALASKA
PENINSULA BETWEEN COLD BAY AND SAND POINT THOUGH WE FEEL THE STORM
WILL MOST LIKELY TRACK THROUGH FALSE PASS INTO THE BERING SEA. AS THE
STORM TRACKS NORTH THE ASSOCIATED FRONT WILL PUSH THROUGH SOUTH
CENTRAL AND SOUTHWEST ALASKA FRIDAY. A RIDGE OF HIGH PRESSURE WILL
BUILD BACK INTO THE GULF OF ALASKA TO PRINCE WILLIAM SOUND.

.SHORT TERM FORECAST...
CONVECTION HAS ALREADY BEGUN IN THE COPPER RIVER BASIN AND WE
ANTICIPATE THE CONVECTION TO INITIATE IN THE LATE AFTERNOON EARLY
EVENING OVER THE MATANUSKA AND SUSITNA VALLEY AREA. THE LATEST
SATELLITE LOOP SHOWS THE CUMULUS DEVELOPING IN THE KUSKOKWIM VALLEY
AND WE ANTICIPATE SOME ISOLATED THUNDERSTORMS AGAIN TONIGHT FOR THAT
REGION. THE INCOMING LOW LEVEL COOL AIR OVER SOUTHWEST ALASKA SHOULD
DAMPEN THE CONVECTIVE POTENTIAL FOR THE BRISTOL BAY AREA THIS
EVENING. EXPECT CLOUDY COOLER CONDITIONS OVER SOUTHWEST ALASKA
THURSDAY THOUGH THE NORTHEAST PORTION OF THE ZONE MAY BE ON THE
FRINGE OF THE CLOUD COVER AND STILL HOLD A POSSIBILITY OF LATE
AFTERNOON CONVECTION THURSDAY.

THE MARINE STRATUS IS OVER THE GULF FROM CAPE SUCKLING EAST AND IS
PUSHING EAST AS THE RIDGE IS PUSHED EAST IN ADVANCE OF THE NEXT
INCOMING STORM. EXPECT THE STRATUS TO PERSIST THROUGH THURSDAY UNTIL
THE RIDGE DOES MOVE OVER THE PANHANDLE.

ON THURSDAY NIGHT AND FRIDAY AS THE HIGH PRESSURE OVER THE
NORTHERN GULF GIVES WAY TO A STRONG WEATHER FRONT...EXPECT STRONG
GUSTY SOUTHEAST WIND AND HEAVIER RAINFALL ALONG THE COASTAL REGIONS.

BERING SEA/ALEUTIANS...
THE WEAK SLOW MOVING LOW PRESSURE NEAR DUTCH HARBOR IS PRODUCING
SHOWERS ACROSS THE ALASKA PENINSULA AND LIGHT SNOW AND RAIN OVER THE
PRIBILOF ISLANDS. EXPECT THE NORTH TO EAST FLOW TO PERSIST OVER THE
PRIBILOFS AND THUS A CONTINUATION OF THE WINTRY WEATHER THROUGH
TONIGHT. THE SECONDARY WRAPPED FRONT WITH THIS LOW IS PRODUCING GALE
FORCE WIND OVER THE WESTERN ALASKA PENINSULA WATERS THAT IS EXPECTED
TO DIMINISH BELOW GALE TONIGHT. THE NEXT STORM MOVING IN FRIDAY IS
EXPECTED TO PRODUCE GALE FORCE WINDS AND SIGNIFICANT PRECIPITATION
ACROSS THE ALASKA PENINSULA AND THE EASTERN BERING FRIDAY AFTERNOON
AND NIGHT...BRINGING WIDESPREAD GALES AND SIGNIFICANT PRECIPITATION
THANKS TO ITS STRONG DYNAMICS AND TAP OF MOISTURE FROM THE TROPICS.

.LONG TERM FORECAST...
ONCE THE STRONG LOW IN THE EASTERN BERING MOVES NORTH AND CLEARS THE
REGION AROUND SUNDAY...A FAIRLY BENIGN WEATHER PATTERN IS EXPECTED
TO SET UP WITH ZONAL WEST TO EAST FLOW AND HIGH PRESSURE SOMEWHERE
OVER THE GULF OF ALASKA OR NORTH PACIFIC SOUTH OF THE AKPEN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNINGS 132 150 155 .
FIRE WEATHER...NONE.

SAM / AB MAY 08