Small Craft Advisory 424, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT SAT MAY 23 2009

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER LEVELS...A CUT-OFF LOW CENTERED SOUTHEAST OF KODIAK
ISLAND IS DRIFTING SOUTHWARD. THE UPPER LOW IS EMBEDDED IN A BROAD
TROUGH ENCOMPASSING ALL OF MAINLAND ALASKA. UPPER LEVEL RIDGING OVER
THE WESTERN ALEUTIANS AND BERING SEA IS BUILDING EASTWARD.

AT THE SURFACE...HIGH PRESSURE IS BUILDING OVER THE BERING SEA AND
ALEUTIANS. A 1003 MB LOW IS CLEARLY EVIDENT ON SATELLITE
IMAGERY...CURRENTLY LOCATED SOUTHEAST OF KODIAK ISLAND.
ELSEWHERE...THE THERMAL TROUGH OVER INTERIOR ALASKA IS CENTERED NORTH
OF THE ALASKA RANGE.

.MODEL DISCUSSION...
MODELS ARE IN SATISFACTORY AGREEMENT THROUGH 00Z TUESDAY. DIFFERENCES
ARISE CONCERNING THE EVOLUTION OF THE LOW COMPLEX IN THE GULF AND THE
HIGH OVER THE BERING SEA. THE FORECAST THIS AFTERNOON WAS CONSTRUCTED
USING THE NAM AND GFS SOLUTIONS.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
STRONG WINDS AND WIDESPREAD RAIN ALONG COASTAL AREAS WILL CONTINUE
THROUGH TONIGHT AS THE AFOREMENTIONED LOW IN THE GULF IMPACTS THE
REGION. THE SURFACE LOW IS EXPECTED TO SLIP SOUTHWARD WHILE THE
THERMAL TROUGH WEAKENS SLIGHTLY...ALLOWING THE PRESSURE GRADIENT TO
GRADUALLY RELAX. AS A RESULT...WINDS AND PRECIP WILL BE DIMINISHING
AS WE HEAD INTO SUNDAY. A MORE TYPICAL SEA BREEZE PATTERN IS EXPECTED
TO RETURN TOMORROW AS A RESULT OF THE WEAKER SYNOPTIC FLOW. THE
THERMAL THROUGH AXIS WILL BE DRIFTING SOUTHWARD THROUGH
MONDAY...ACTING TO ENHANCE INSTABILITY SHOWERS AND THUNDERSTORMS OVER
SOUTHCENTRAL...PARTICULARLY OVER MOUNTAINOUS AREAS.
ELSEWHERE...EXPECT SHOWERS TO PERSIST ALONG COASTAL LOCATIONS UNDER
MOIST ONSHORE FLOW.

.SOUTHWEST...
PRIMARY CONCERN THROUGH MEMORIAL DAY WILL BE DIURNAL SHOWERS AND
THUNDERSTORMS AS THE AFOREMENTIONED THERMAL TROUGH INFLUENCES THE
AREA. MAIN THREAT FOR PRECIP WILL BE OVER NORTHERN PORTIONS OF
BRISTOL BAY...WESTERN KUSKOKWIM DELTA...AND THE LOWER KUSKOKWIM
VALLEY...WHERE INSTABILITY AND CONVECTIVE POTENTIAL IS HIGHEST.
ELSEWHERE THROUGH THE HOLIDAY WEEKEND GUSTY NORTHERLY FLOW ALONG THE
COAST WILL CONTINUE...WITH PESKY SHOWERS AND STRATUS AFFECTING THE
AKPEN.

.BERING SEA AND ALEUTIANS...
HIGH PRESSURE BUILDING OVER THE BERING MEANS FOG AND STRATUS WILL BE
THE MAIN CONCERN THROUGH MEMORIAL DAY. THE PRIBILOFS ARE EXPECTED TO
REMAIN MAINLY CLEAR WHEREAS THE WESTERN AND CENTRAL ISLANDS SHOULD
STAY IN THE CLOUDS. A FRONT APPROACHING FROM THE NORTH PACIFIC SUNDAY
NIGHT WILL SPREAD LIGHT RAIN AND GUSTY WINDS INTO THE WESTERN
ISLANDS.

.LONG TERM FORECAST...
THE LARGE SCALE PATTERN IS EXPECTED TO REMAIN RELATIVELY STAGNANT AS
WE HEAD INTO NEXT WEEK...WITH THE QUASI STATIONARY LOW COMPLEX IN THE
GULF AND HIGH PRESSURE OVER THE BERING SEA AND ALEUTIANS. THE THERMAL
TROUGH OVER THE INTERIOR WILL KEEP INSTABILITY AND MOISTURE ELEVATED
OVER THE SOUTHERN MAINLAND...WITH FOG AND STRATUS CONTINUING OVER THE
BERING SEA AND ALEUTIANS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...RED FLAG WARNING 111

NRH MAY 09