Gale Warning 432, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTED
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKDT FRI MAY 8 2009

.MODEL DISCUSSION...

NO MAJOR CHANGES TO THE FORECAST WERE NECESSARY FROM THE ONGOING
FORECAST...EXCEPT TO INCLUDE MENTION OF INSTABILITY SHOWERS OVER THE
HIGHER ELEVATIONS OF THE CHUGACH...TALKEETNA...AND ALASKA RANGES.
THE MEDIUM RANGE FORECAST HINGES ON THE EXTENT THAT THE HUGE RIDGE
THAT BUILDS OVER THE BERING SEA THIS WEEKEND REMAINS STATIONARY OR
SLOWLY RETROGRADES TO THE WEST.  GIVEN THE LARGE WAVELENGTH OF THE
ASSOCIATED RIDGE IN THE GLOBAL MODELS...WAS INCLINED TO GO WITH HPC
GUIDANCE FOR LATE NEXT WEEK IN RETROGRADING THE RIDGE AND ALLOWING
COLDER AIR TO SPILL ACROSS THE STATE WITH STRONG NORTHERLY FLOW
ALOFT.

.ANALYSIS AND UPPER LEVELS...

VISIBLE SATELLITE IMAGERY CONTINUES TO INDICATE THAT A SURFACE LOW
CO-LOCATED WITH A DEEP UPPER LOW RESIDES OVER THE CENTRAL GULF OF
ALASKA.  THIS FEATURE IS MOVING VERY SLOWLY SOUTH AND EAST TOWARDS
THE PANHANDLE.  CYCLONIC FLOW WITH THIS LOW PRESSURE SYSTEM EXTENDS
AS FAR NORTHWARD AS PRINCE WILLIAM SOUND AND THE WRANGELL - ST. ELIAS
NATIONAL PARK...WHERE LIGHT RAIN HAS BEEN FALLING AROUND THE CORDOVA
AREA THIS MORNING.  A BUILDING CUT-OFF HIGH IS LOCATED OVER THE
ALASKA PENINSULA AND BRISTOL BAY EXTENDING INTO FAR SOUTHWEST
ALASKA...WITH RIDGING ASSOCIATED WITH THIS HIGH BUILDING ACROSS THE
SOUTHEAST BERING AND INTO THE INTERIOR BEHIND THE UPPER LOW OVER THE
GULF.  OFFSHORE FLOW ON THE DOWNSTREAM SIDE OF THE RIDGE HAS KEPT THE
BRISTOL BAY REGION MOSTLY CLEAR...BUT THE RIDGE AXIS MOVING A BIT
FARTHER EAST TODAY IS BRINGING THE LOW STRATUS CLOSER TO THE WESTERN
CAPES.  A VERY WEAK SHORTWAVE OVER THE CENTRAL BERING SEA IS BRINGING
ONLY A FEW HIGH CLOUDS WITH SURFACE HIGH PRESSURE IN CONTROL OF THE
CENTRAL AND EASTERN BERING SEA PROVIDING FOR CONTINUED LOW STRATUS IN
WEAK WINDS OVER MOST AREAS.  ANOTHER DEEP UPPER LOW IS MOVING SOUTH
AND EAST AWAY FROM THE ALEUTIAN CHAIN WITH ASSOCIATED CLOUD COVER
CONTINUING TO AFFECT THE CENTRAL ALEUTIANS.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

THE MAIN FORECAST PROBLEMS TODAY AND SATURDAY WILL BE WATCHING WINDS
PICK UP DURING THE AFTERNOON HOURS TODAY AND SATURDAY AS THE THERMAL
TROUGH FROM THE COPPER RIVER BASIN TO THE LOWER SUSITNA RIVER VALLEY
SHARPENS AND CAUSES WINDS TO INCREASE THROUGH THE PASSES...INCLUDING
TURNAGAIN ARM.  IN ADDITION...THE SEA BREEZES ALONG THE COASTLINES
HAVE BEEN ACCOUNTED FOR AS WELL AS EARLY EVENING SHOWERS ALONG THE
HIGHER ELEVATIONS ACROSS SOUTHCENTRAL MUCH LIKE LAST EVENING...WITH
LESSER CHANCES THE FARTHER WEST ESPECIALLY SATURDAY GIVEN UPPER
RIDGING IMPINGING ACROSS THE SOUTHERN ALASKA RANGE.  A SHORTWAVE
PASSING TO THE NORTH AND EAST WILL HELP INITIATE SHOWERS ALONG THE
ALASKA RANGE IN FAR NORTHEAST PARTS OF ZONE 141 SATURDAY THROUGH
SATURDAY EVENING...FOLLOWED BY PARTIAL CLEARING AS NORTHERLY FLOW
IMPARTED BY THE STRENGTHENING RIDGE TO THE WEST CREATES A DOWNSLOPE
EFFECT.  AS THE WEEKEND COMES TO AN END A SHARP SURFACE TROUGH FORMS
ACROSS THE NORTHERN GULF WITH HIGH PRESSURE ACROSS THE INTERIOR.
WITH THE INCREASING PRESSURE GRADIENT AND STRONG NORTHERLY FLOW ALOFT
WILL CONTINUE TO WATCH FOR POSSIBILITY OF STRONG WINDS ESPECIALLY
THROUGH THE CHANNELED TERRAIN.

SOUTHWEST ALASKA/BERING...THE CUT-OFF HIGH APPEARS TO RESIDE OVER THE
DELTA COASTLINE AREA AND EXPANDS THROUGH THE BEGINNING OF NEXT WEEK
TO INCLUDE NEARLY ALL OF THE BERING SEA.  LOW STRATUS APPEARS TO
REMAIN A THREAT FOR MOST OF THE BERING UNDERNEATH THE SUBSIDENCE
INVERSION...WITH THE SOUTHWEST MAINLAND REMAINING MOSTLY CLEAR
EXCEPT FOR SOME STRATUS AND FOG NEAR THE COAST.  SOUTHERLY FLOW MAY
BEGIN TO INCREASE AS A LOW BEGINS TO IMPINGE AND/OR TRY TO SLIDE
UNDER THE RIDGE FROM THE WEST...BRINGING STRONG SOUTHERLY FLOW TO
THE WESTERN ALEUTIANS FOR THE SUNDAY/MONDAY TIME FRAME AND THE
POSSIBILITY OF SHOWERS. HOWEVER...THIS SYSTEM SHOULD NOT REACH AS
FAR EAST AS THE CENTRAL ALEUTIANS THROUGH MONDAY.  THE BIGGEST
CONCERN OVER LAND WILL BE FLOODING ISSUES ON THE KUSKOKWIM RIVER.

.LONG TERM FORECAST...

THE GEFS GLOBAL ENSEMBLE MODEL CONTINUES TO DEPICT STRONG CONFIDENCE
ON THE UPPER RIDGE EXPANDING THROUGH THE MIDDLE OF THE WEEK TO
ENCOMPASS MOST OF THE BERING SEA.  AS WE HEAD TOWARDS LATE WEEK NEXT
WEEK...WITH SUCH A LARGE RIDGE WE SHOULD SEE IT BEGIN TO RETROGRADE
WESTWARD...WHICH CHOULD ALLOW A LONGWAVE TROUGH TO IMPINGE ON THE
AREA FROM THE EAST AND CONTINUE THE STRONG NORTHERLY OR NORTHWESTERLY
FLOW ALOFT.  THUS...CONFIDENCE IS FAIRLY HIGH THAT WE SHOULD SEE
COOLER AND CONTINUED WINDY CONDITIONS FOR THE LATTER HALF OF NEXT
WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WARNING...141 155
MARINE...NONE.
FIRE WEATHER...NONE.

CC MAY 09