Small Craft Advisory 433, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT TUE MAY 26 2009

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL LOW OVER THE GULF OF ALASKA REMAINS
STATIONARY...ALTHOUGH IT IS BEGINNING TO WEAKEN. RIDGING REMAINS OVER
THE CENTRAL BERING...WITH A SMALL UPPER LOW NORTH OF SHEMYA. A ROBUST
TROUGH DROPPING SOUTHEAST OUT OF THE ARCTIC IS CURRENTLY OVER THE
BERING STRAIT.

AT THE SURFACE...THE LOW COMPLEX REMAINS OVER THE GULF OF ALASKA. A
THERMAL TROUGH EXTENDS OVER THE ALASKA AND ALEUTIANS RANGES. HIGH
PRESSURE IS OVER THE CENTRAL BERING...WITH A WEATHER FRONT AFFECTING
THE WESTERN ALEUTIANS. ELSEWHERE...A FRONT IS OVER NORTHWESTERN AK.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH FRIDAY. MAIN DIFFERENCES ARISE
CONCERNING THE DETAILS OF THE BERING SEA RIDGE BREAKING DOWN WITH THE
APPROACH OF A BROAD SURFACE LOW. DIFFERENCES ALSO EXIST WITH REGARDS
TO THE LOW COMPLEX IN THE GULF DISSIPATING...AS HIGH PRESSURE BUILDS
IN FROM THE EAST. THE GFS AND NAM WERE USED ONCE AGAIN FOR THE
AFTERNOON PACKAGE...WITH LITTLE CHANGE TO THE ONGOING FORECAST.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
THUNDERSTORMS ASSOCIATED WITH THE THERMAL TROUGH WILL BE WINDING DOWN
TONIGHT...ALTHOUGH ANOTHER ROUND OF CONVECTION WILL BE POSSIBLE
TOMORROW ALONG THE ALASKA RANGE AS THE TROUGH RETREATS NORTHWARD.
COOL AND MOIST SOUTHWEST FLOW WILL BE DEVELOPING WEDNESDAY...BRINGING
WIDESPREAD SHOWERS TO THE AREA THROUGH THURSDAY.

.SOUTHWEST...
THE THERMAL TROUGH RESPONSIBLE FOR TRIGGERING SHOWERS AND
THUNDERSTORMS THE PAST COUPLE OF DAYS WILL BEGIN TO RETREAT NORTHWARD
TONIGHT. SHOWERS WILL PERSIST THROUGH THURSDAY AS THE AFOREMENTIONED
TROUGH AND ACCOMPANYING SURFACE FRONT DROP SOUTH FROM THE ARCTIC.
SHOWERS WILL ALSO BE TRIGGERED AS THE FRONT OVER THE BERING SEA
SPREADS MOISTURE INLAND ON SOUTHWEST FLOW. HIGHEST CHANCE FOR SHOWERS
WILL BE OVER THE MOUNTAINS...BRISTOL BAY...AND THE AKPEN.

.BERING SEA AND ALEUTIANS...
RAIN AND GUSTY SOUTHERLY FLOW WILL AFFECT THE ISLANDS THROUGH
THURSDAY AS A FRONT MOVES ACROSS THE AREA. THIS FRONT IS EXPECTED TO
STALL AND GRADUALLY DISSIPATE OVER THE EASTERN ALEUTIANS THROUGH THE
END OF THE WEEK.

.LONG TERM FORECAST...
MODELS CONTINUE TO TREND AT A PATTERN CHANGE TOWARDS THE END OF THE
WEEK...WITH A TROUGH OVER THE BERING AND A RIDGE BUILDING OVER THE
GULF OF ALASKA. THEREFORE EXPECT WET AND UNSETTLED CONDITIONS OUT
WEST WITH WARMER AND DRIER CONDITIONS OVER THE SOUTHERN MAINLAND.

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

NRH MAY 09