Gale Warning 171, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKST MON FEB 9 2009

.ANALYSIS AND UPPER LEVELS...
AT THE SURFACE...A TROUGH IS LOCATED OVER THE NORTHERN GULF OF
ALASKA. AN OCCLUDED FRONT IS DISSIPATING OVER THE EASTERN
ALEUTIANS...WITH A 993 MB TRIPLE POINT LOW FORMING SOUTH OF SAND
POINT. A 972 MB LOW IS 225 NM SOUTHWEST OF SHEMYA.

IN THE UPPER LEVELS...A COLD UPPER VORTEX OVER THE ARCTIC IS SINKING
SOUTHWARD TOWARD NORTHERN ALASKA. A TROUGH ASSOCIATED WITH THE VORTEX
EXTENDS THROUGH THE WESTERN MAINLAND AND INTO THE WESTERN GULF. WEAK
RIDGING EXISTS OVER THE EASTERN GULF OF ALASKA...WITH ANOTHER RIDGE
STRETCHING FROM THE WESTERN BERING SEA THROUGH THE CENTRAL ALEUTIANS.

.MODEL DISCUSSION...
SMALL DIFFERENCES EXIST IN MODEL SOLUTIONS THROUGH 12Z
WEDNESDAY...MAINLY REGARDING THE STRENGTH AND POSITION OF THE LOW
NEAR SHEMYA. DIFFERENCES ALSO ARISE WITH THE DEVELOPING TRIPLE POINT
LOW IN THE GULF TUE NIGHT. AFTER THIS TIME MODEL AGREEMENT IS POOR.
THE GFS/NAM SOLUTION WAS USED TO CONSTRUCT THE SHORT TERM FORECASTS
THROUGH 12Z WEDNESDAY DUE TO CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
THE SHORTWAVE RESPONSIBLE FOR BRINGING LIGHT SNOW TO THE ANCHORAGE
BOWL OVERNIGHT IS MOVING EASTWARD OVER PRINCE WILLIAM SOUND THIS
MORNING. THE OVERALL PATTERN ACROSS SOUTHCENTRAL WILL REMAIN LARGELY
UNCHANGED THROUGH TONIGHT...RESULTING IN LOW CLOUDS AND FOG
CONTINUING TO PLAGUE PARTS OF COOK INLET AND THE MATANUSKA VALLEY. A
BROAD AREA OF LOW PRESSURE IN THE NORTHERN GULF IS INCREASING SNOW
SHOWER ACTIVITY OVER COASTAL AREAS OF PRINCE WILLIAM SOUND...BUT
PRECIPITATION WILL BE DECREASING THROUGH THE DAY. CONDITIONS ACROSS
THE REST OF SOUTHCENTRAL WILL REMAIN QUIET UNTIL WEDNESDAY...WHEN
MOISTURE INCREASES AS A SHORTWAVE MOVES ACROSS THE AREA.

.SOUTHWEST...
SNOW SHOWERS ALONG THE ALASKA PENINSULA AND SOUTHERN BRISTOL BAY WILL
BE DECREASING TODAY AS THE LOW DEPARTS TO THE SOUTHEAST. OTHERWISE
ACROSS THE AREA CONDITIONS WILL REMAIN QUIET AND COLD...AS HIGH
PRESSURE BUILDS INTO THE KUSKOKWIM DELTA FROM THE NORTHWEST. BY LATE
TUESDAY AN APPROACHING FRONT WILL BRING AN INCREASING CHANCE OF SNOW
ACROSS THE AREA. ALSO...A LOW APPROACHING THE PENINSULA FROM THE
SOUTHWEST WILL BEGIN SPREADING SNOW INTO SOUTHERN AREAS ON WEDNESDAY.

.BERING SEA AND ALEUTIANS...
SNOW OVER THE EASTERN ALEUTIANS TODAY WILL BE DIMINISHING AS THE
STALLED FRONT DISSIPATES AND THE DEVELOPING TRIPLE POINT LOW DEPARTS
TO THE SOUTHEAST. BLIZZARD CONDITIONS IN THE PRIBILOFS HAVE COME TO
AN END...ALTHOUGH BLOWING SNOW WILL REMAIN A CONCERN OVER THE NEXT
SEVERAL DAYS AS WINDS REMAIN STRONG AHEAD OF THE NEXT FRONT. RAIN AND
SNOW WILL OVERSPREAD THE WESTERN AND CENTRAL ISLANDS TODAY INTO
TONIGHT AS THE NEXT WEATHER FRONT MOVES THROUGH. GALE FORCE WINDS ARE
EXPECTED AS THE FRONT MOVES ACROSS THE ISLANDS...WITH BLOWING SNOW
BECOMING A CONCERN ON TUESDAY AS COLD ADVECTION BEHIND THE FRONT
INCREASES. AT THIS TIME...THE LOW IS EXPECTED TO TRACK WEST OF
SHEMYA. THIS TRACK WILL RESULT IN BRISK SOUTHERLY FLOW WITH SCATTERED
SHOWERS AFTER THE FRONT HAS PASSED.

.LONG TERM FORECAST...
AS MENTIONED IN THE PREVIOUS DISCUSSION...EXPECT A LOW AMPLITUDE
PROGRESSIVE PATTERN OVER THE AREA THROUGH THE EXTENDED FORECAST
PERIOD. AS A RESULT...STORMS WILL TRACK QUICKLY FROM THE BERING SEA
INTO MAINLAND ALASKA. DUE TO THE LOW AMPLITUDE PATTERN WARMEST AIR
WILL REMAIN SOUTH OF THE FORECAST AREA...WITH SNOW BEING THE
PREDOMINANT PRECIPITATION TYPE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 172 175 176 179 185
         HEAVY FREEZING SPRAY 121 160 165 179
FIRE WEATHER...NONE

NRH FEB 09