Small Craft Advisory 417, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT THU MAY 21 2009

.MODEL DISCUSSION...MODEL INITIALIZATIONS ARE REASONABLE WITH THE NAM
SLIGHTLY BETTER ON POSITION OF LOW CENTER OVER THE SE GULF OF ALASKA.
FORECAST TRENDS ARE IN GENERAL AGREEMENT AND REASONABLE. THE
GFS/ECMWF HAVE CONVERGED TOWARD A COMMON SOLUTION WITH THE LOW THAT
ENTERS THE SW GULF TONIGHT. OVERALL...WILL LEAN WITH THE GFS AND MAKE
SOME SHORT TERM ADJUSTMENTS WITH NAM.

.UPPER LEVELS...BLOCKING PATTERN IS STILL FORECAST TO SET UP ACROSS
THE REGION OVER THE NEXT DAY OR SO AND HOLD INTO EARLY NEXT WEEK.
SATELLITE IMAGERY SHOWS UPPER CENTER HAS MOVED JUST SOUTH OF THE
WESTERN AK PEN THIS MORNING. THIS LOW IS STILL EXPECTED TO BECOME
CUT-OFF FROM THE WESTERLIES FRI AND SHOULD LINGER IN THE SOUTHERN
GULF THROUGH SAT...THEN DRIFT SLOWLY SOUTH AND WEAKEN INTO EARLY NEXT
WEEK. THE RIDGE OVER WESTERN CANADA BUILDS WEST AND SETS UP OVER THE
NORTHERN INTERIOR/ARCTIC OCEAN FRI AND WILL PERSIST THROUGH THE
WEEKEND. THE RIDGE WILL REBUILD OVER THE BERING SEA LATE FRI AFTER A
SHORT WAVE MOVES SE ACROSS THE BERING SEA. THIS RIDGE WILL LINK UP
WITH HIGH OVER THE NORTHERN MAINLAND FRI NIGHT/SAT.

.SHORT TERM FORECAST...
.EAST...WEAK LOW OVER THE EASTERN GULF THIS MORNING IS WORKING ITS
WAY TOWARD KODIAK. CENTER WILL LIKELY BRING SMALL CRAFT WINDS TO THE
NORTHERN COASTAL MARINE AREAS TONIGHT AND SPREAD RAIN/SHOWERS ALONG
COASTAL LOCALS/KODIAK ISLAND. GENERAL PATTERN WITH A THERMAL TROUGH
OVER THE INTERIOR WITH A RIDGE ALONG THE NORTH GULF COAST AND LOW IN
THE SOUTHERN GULF WILL PERSIST THROUGH THE WEEKEND. MESOSCALE WINDS
LIKELY TO BE STRONGEST OVER THE COPPER RIVER BASIN AND ACROSS
SOUTHCENTRAL TODAY WITH A COMBINATION OF STRONG ISALLOBARIC PRESSURE
RISES ACROSS THE NORTHERN GULF AND STRENGTHENING INTERIOR THERMAL
TROUGH. ALTHOUGH THE THERMAL TROUGH WILL STRENGTHEN SOME THIS
WEEKEND...THE NORTHERN GULF RIDGE SHOULD WEAKEN SOME...THE RESULTANT
AFTERNOON AND EVENING WINDS SHOULD SOMEWHAT LESS. CONDITIONS ACROSS
SOUTHCENTRAL AND THE COPPER RIVER BASIN WILL BECOME INCREASINGLY MORE
UNSTABLE OVER THE NEXT DAY OR SO WITH INTENSIFYING INTERIOR THERMAL
TROUGH. THAT SAID...STABILITY INDICES POINT TOWARD THUNDERSTORM
POTENTIAL ALONG THE ALASKA RANGE FOR THE COPPER RIVER BASIN/SUSITNA
VALLEY FRI. THUNDERSTORMS A LITTLE MORE WIDESPREAD AND INTRUDING INTO
THE NORTHERN MAT ON SAT.

.SOUTHWEST ALASKA...NOT BIG CHANGES HERE. THERMAL TROUGH STRENGTHENS
OVER THE INTERIOR. AFTERNOON AND EVENING CONVECTION WILL BECOME MORE
WIDESPREAD THROUGH THE WEEKEND. THUNDERSTORMS FORECAST FOR THE
KUSKOKWIM VALLY TODAY WILL SPREAD TO THE DELTA FRI AND INTERIOR
BRISTOL BAY ON SAT.

.BERING SEA/ALEUTIANS/AK PEN...WEAKENING FRONTAL TROUGH AND
ASSOCIATED WAVES MOVE ACROSS THE CENTRAL BERING SEA/EAST-CENTRAL
ALEUTIANS THROUGH FRI. HIGH PRESSURE BUILDS BACK OVER THE BERING SEA
SAT AND WILL PERSIST THROUGH THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE
FIRE WEATHER...RED FLAG ZONES 101 111 AND 141.

RMC MAY 09