Small Craft Advisory 471, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKDT TUE JUN 9 2009

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER LEVELS...A RIDGE REMAINS IN PLACE OVER THE GULF OF
ALASKA AND EASTERN MAINLAND. A HIGH AMPLITUDE TROUGH IS STILL OVER
THE BERING...WITH A LARGE CUT-OFF LOW SOUTH OF THE ALEUTIANS. A
ROBUST SHORTWAVE OVER NORTON SOUND IS LIFTING NORTHWARD. SHORTWAVE
RIDGING IS BUILDING OVER THE AKPEN AND BRISTOL BAY.

AT THE SURFACE...HIGH PRESSURE EXTENDS FROM THE GULF OF ALASKA INTO
THE SOUTHERN MAINLAND. A LARGE LOW COMPLEX SOUTH OF THE CENTRAL
ALEUTIANS IS EVIDENT ON SATELLITE IMAGERY. THE THERMAL TROUGH AXIS IS
CENTERED OVER THE CENTRAL INTERIOR.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH WEDNESDAY...BUT BEGIN TO DIVERGE
SIGNIFICANTLY THEREAFTER. MAIN POINT OF CONTENTION REGARDS THE
POSITIONING OF THE LOW CENTER OVER THE BERING...AS WELL AS TIMING OF
WAVES ROTATING AROUND THE LOW COMPLEX. LITTLE CHANGE WAS DONE TO THE
EXISTING FORECAST THIS MORNING...WITH A FOCUS ON THE GFS FOR THE
SHORT TERM.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
PLEASANT WEATHER WILL CONTINUE ACROSS MOST OF THE AREA THROUGH
THURSDAY...AS UPPER RIDGING AND SURFACE HIGH PRESSURE REMAIN IN
CONTROL. THE THERMAL TROUGH WILL LEAD TO AN INCREASED THREAT OF
AFTERNOON SHOWERS ALONG THE COPPER RIVER BASIN OVER THE NEXT SEVERAL
DAYS. ELSEWHERE...AFTERNOON SEA BREEZES WILL CONTINUE TO AFFECT
COASTAL AREAS UNDER WEAK SYNOPTIC FLOW. PATCHY NIGHTTIME AND MORNING
FOG WILL FORM ALONG THE COAST...WITH KODIAK ISLAND AND PRINCE WILLIAM
SOUND BEING OF PRIMARY CONCERN.

.SOUTHWEST...
ISOLATED SHOWERS OVER THE KUSKOKWIM DELTA WILL BE COMING TO AN END
THIS MORNING AS THE SHORTWAVE LIFTS OUT OF THE AREA. SURFACE HIGH
PRESSURE AND UPPER RIDGING WILL LEAD TO GENERALLY FAIR WEATHER ACROSS
THE REGION THROUGH THURSDAY. SCATTERED SHOWERS CANNOT BE RULED OUT
ACROSS THE AKPEN...WHERE SOUTHERLY FLOW AHEAD OF THE LOW COMPLEX WILL
PERSIST. OTHERWISE...PATCHY FOG WILL IMPACT PARTS OF BRISTOL BAY AND
THE LOWER KUSKOKWIM THROUGH WEDNESDAY.

.BERING SEA AND ALEUTIANS...
THE LARGE LOW COMPLEX SOUTHWEST OF ADAK WILL KEEP LOW
CEILINGS...RAIN...AND PATCHY FOG OVER THE ISLANDS THROUGH THE NEXT
SEVERAL DAYS. THE COMPLEX WILL BEGIN SHIFTING TOWARDS THE WESTERN
ALEUTIANS BY LATE WEDNESDAY...ALTHOUGH VARIOUS WAVES ROTATING AROUND
THE LOW WILL KEEP CONDITIONS UNSETTLED THROUGHOUT THE ISLAND CHAIN.

.LONG TERM FORECAST...
AS AFOREMENTIONED...MODELS ARE HAVING SOME PROBLEMS COMING TO A
COMMON SOLUTION IN THE EXTENDED. CONFIDENCE IS HIGH IN THE RIDGE OVER
THE GULF BREAKING DOWN BY THE END OF THE WEEK...WHILE A LARGE CUT-OFF
LOW REMAINS OVER THE ALEUTIANS. THE THERMAL TROUGH IS ALSO EXPECTED
TO REMAIN ENTRENCHED THROUGH THE END OF THE WEEK. AS A
RESULT...EXPECT GENERALLY UNSETTLED WEATHER OVER THE BERING AND
ALEUTIANS...WITH WARMER AND DRIER CONDITIONS OVER THE MAINLAND. THE
THERMAL TROUGH WILL ALSO LEAD TO ISOLATED DIURNAL CONVECTION OVER
AREAS OF ENHANCED TERRAIN.

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

NRH JUN 09