Gale Warning 267, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKST SUN MAR 1 2009

.MODEL DISCUSSION...

THE GFS WAS USED FOR THE SHORT TERM PERIODS AS THE MODELS ARE IN
OVERALL GOOD AGREEMENT THROUGH MOST OF THE FORECAST PERIOD.  FOR THE
EXTENDED FORECAST...USED A BLEND OF HPC GUIDANCE AND THE 00Z EURO IN
HANDLING TRACK OF THE SYSTEM OUT WEST MID TO LATE WEEK.

.ANALYSIS AND UPPER LEVELS...

A STRONG UPPER TROUGH CONTINUES TO DIG INTO THE GULF OF ALASKA THIS
MORNING WITH AN ASSOCIATED 1007 MB SURFACE LOW PRODUCING
PRECIPITATION FROM PRINCE WILLIAM SOUND EASTWARD...AS WELL AS INTO
MUCH OF THE COPPER RIVER BASIN ALONG A FRONTAL ZONE.  THIS STRONG
UPPER TROUGH IS CURRENTLY SPLITTING FROM A 489 DM LOW AND ASSOCIATED
984 MB SURFACE LOW LOCATED IN THE ARCTIC SEA NORTH OF THE STATE.  AN
UPPER RIDGE CONTINUES TO BUILD ACROSS THE CENTRAL ALEUTIANS AND
BERING SEA FROM THE SOUTH...WITH SURFACE RIDGING IN CONTROL OF THE
NORTHERN AND EASTERN BERING...THE EASTERN ALEUTIANS AND AKPEN...AND
BEGINNING TO EXTEND INTO THE CENTRAL INTERIOR BETWEEN THE ARCTIC SEA
AND GULF OF ALASKA LOWS.  BETWEEN THE BUILDING RIDGE TO THE WEST AND
THE TROUGH OVER THE GULF OF ALASKA...AND AS SURFACE PRESSURE GRADIENT
INCREASES OVER THE WESTERN GULF...STRONG NORTHWESTERLY WINDS HAVE
BEEN BRINGING WINDY CONDITIONS TO SOUTHWEST ALASKA AND OUT OVER THE
WESTERN GULF AND BRISTOL BAY MARINE ZONES.

IN THE ALEUTIANS...A FRONT ASSOCIATED WITH A SERIES OF WEAK LOWS NEAR
AND WEST OF SHEMYA IS SITUATED ACROSS THE WESTERN AND CENTRAL
ALEUTIANS.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...WEAK HIGH PRESSURE WILL CONTINUE
TO BUILD ACROSS MOST OF THE STATE AS A TROUGH REMAINS ACROSS THE
NORTHERN GULF.  THIS WILL INCREASE THE PRESSURE GRADIENT AND ALLOW
FOR AN INCREASE IN OUTFLOW WINDS THROUGH CHANNELED
TERRAIN...ESPECIALLY ACROSS THE EASTERN KENAI PENINSULA WHERE STRONG
NORTHWESTERLY FLOW ALOFT WILL CONTRIBUTE IN BRINGING GUSTY WINDS
ALOFT TO THE SURFACE.  AS THE HIGH MOVES EASTWARD INTO
MONDAY...STRONGER WINDS SHOULD SHIFT EASTWARD TO THE COPPER RIVER
BASIN.  BY MONDAY NIGHT THE UPPER RIDGE IS FLATTENED BY AN
APPROACHING TROUGH MOVING ACROSS THE BERING STRAIT TOWARDS NORTHERN
ALASKA. INCREASED ZONAL FLOW ALOFT WILL LIKELY RESULT IN A FAST
MOVING LOW PRESSURE SYSTEM THAT ZIPS ACROSS KODIAK ISLAND AND INTO
THE NORTHERN GULF...BRINGING A CHANCE OF PRECIPITATION TO
SOUTHCENTRAL LATER IN THE DAY ON TUESDAY.

WEST OF THE ALASKA RANGE...THE FRONTAL ZONE ACROSS THE ALEUTIANS WILL
CONTINUE TO LIFT QUICKLY NORTH ACROSS THE BERING AND BEGIN TO AFFECT
THE AKPEN THIS EVENING.  STRONG WINDS TO GALE FORCE WILL THUS AFFECT
MOST OF THE BERING TODAY AND TONIGHT.  THIS SYSTEM WILL BEGIN TO
AFFECT SOUTHWEST ALASKA LATE SUNDAY NIGHT AS UPPER RIDGING MOVES
QUICKLY EASTWARD AND IS FLATTENED BY THIS APPROACHING
TROUGH...SETTING UP FAST ZONAL FLOW ALOFT.  WEAK HIGH PRESSURE ZIPS
ACROSS THE REGION TUESDAY AHEAD OF ANOTHER POTENTIAL WEATHER SYSTEM
FOR THE ALEUTIANS LATE TUESDAY THAT COULD BRING POTENTIALLY WINDY
CONDITIONS TO THE WESTERN BERING SEA.

.LONG TERM FORECAST...

USED A BLEND OF HPC GUIDANCE AND THE 00Z ECMWF FOR THE EXTENDED
PERIOD.  LOW PRESSURE AND ASSOCIATED FRONTAL ZONE MOVES EASTWARD INTO
THE WESTERN MAINLAND THURSDAY AS UPPER RIDGING MOVES TOWARDS THE
ALCAN BORDER.  THIS SHOULD RESULT IN MOSTLY UNSETTLED WEATHER FROM
MIDWEEK INTO THE WEEKEND FOR A MAJORITY OF THE STATE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...120 130 132 150 170 172 175 176 179 180 185
         HEAVY FREEZING SPRAY WARNING...121 129 141 185
FIRE WEATHER...NONE.

CC MAR 09