Small Craft Advisory 409, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT SUN MAY 17 2009

.ANALYSIS AND UPPER LEVELS...
AN UPPER LEVEL RIDGE EXTENDING FROM THE EASTERN BERING INTO THE
NORTHERN INTERIOR IS PROGRESSING EASTWARD. A DIGGING TROUGH AND
ASSOCIATED UPPER LOW OVER THE WESTERN BERING ARE BEGINNING TO
UNDERCUT THIS RIDGE.

AT THE SURFACE...CLEAR SKIES PREDOMINATE OVER THE MAJORITY OF
SOUTHCENTRAL WITH WEAK HIGH PRESSURE OVER THE NORTHERN GULF. A
FRONTAL BOUNDARY OVER THE EASTERN BERING AND ALEUTIANS IS MOVING EAST
TOWARDS THE AKPEN AND THE SOUTHWEST MAINLAND.

.MODEL DISCUSSION...
MODELS ARE IN SATISFACTORY AGREEMENT THROUGH 00Z WEDNESDAY.
CONFIDENCE CONTINUES TO BE HIGH CONCERNING THE UPPER RIDGE BECOMING
CUT-OFF OVER THE NORTHERN INTERIOR...AS THE DIGGING TROUGH CUTS OFF
OVER THE WESTERN GULF. THE GFS AND NAM SOLUTIONS WERE USED ONCE AGAIN
TO CONSTRUCT THE AFTERNOON FORECAST PACKAGE.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
MAJORITY OF SOUTHCENTRAL WILL BE DRY WITH GENERALLY FAIR WEATHER
TODAY AND TOMORROW AS WEAK HIGH PRESSURE AND UPPER RIDGING REMAIN IN
CONTROL. CLOUDS AND RAIN WILL BE OVERSPREADING KODIAK MONDAY AS THE
AFOREMENTIONED FRONTAL ZONE MOVES INTO THE AREA. EXPECTING FRONT TO
STALL AND DISSIPATE OVER THE WESTERN GULF...WITH SUBSEQUENT LOW
DEVELOPMENT NEAR KODIAK ISLAND MONDAY NIGHT. THIS WILL KEEP THE
THREAT OF PRECIPITATION CONFINED PRIMARILY TO KODIAK ISLAND AND
WESTERN COOK INLET.

.SOUTHWEST...
RAIN ASSOCIATED WITH THE FRONTAL ZONE WILL IMPACT SOUTHWEST ALASKA
THROUGH TUESDAY. EXPECT THE AKPEN AND BRISTOL BAY AREAS TO PICK UP
HIGHEST RAIN AMOUNTS...WITH MAINLY SCATTERED SHOWERS OVER THE LOWER
KUSKOKWIM VALLEY. AS COLDER AIR FILTERS IN BEHIND THE FRONT...SNOW
MAY MIX WITH RAIN OVER PORTIONS OF THE KUSKOKWIM DELTA AND AKPEN.

.BERING SEA AND ALEUTIANS...
RAIN AND SNOW SHOWERS WILL CONTINUE THROUGH THE NEXT SEVERAL DAYS AS
THE UPPER TROUGH AND DEVELOPING CUT-OFF LOW ADVANCE EASTWARD.
PERIODIC SHORTWAVES ROTATING AROUND THE LOW WILL ALSO ENHANCE
PRECIPITATION POTENTIAL.

.LONG TERM FORECAST...
MEDIUM RANGE MODELS CONTINUE TO SHOW A CUT-OFF LOW SETTING UP OVER
THE GULF WITH A WEAKENING RIDGE OVER INTERIOR ALASKA. THE THERMAL
TROUGH IS EXPECTED TO INTENSIFY WHILE REMAINING IN PLACE OVER THE
INTERIOR...RESULTING IN AN INCREASE IN MOISTURE AND INSTABILITY FOR
THE SOUTHERN MAINLAND. SHORTWAVES ROTATING AROUND THE LOW IN THE GULF
WILL ALSO NEED TO BE MONITORED...AS THESE COULD TRIGGER MORE
SIGNIFICANT PRECIPITATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...RED FLAG WARNING 111 141 145

NRH MAY 09