Storm Warning 259, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
510 AM AKDT SAT OCT 31 2009

.MODEL DISCUSSION...

MODELS REMAIN IN GENERALLY GOOD AGREEMENT IN THE SHORT TERM...THOUGH
THERE ARE SOME DIFFERENCES IN THE PLACEMENT OF A WEAK LOW THAT
DEVELOPS IN THE GULF OF ALASKA TODAY AND REMAINS NEARLY STATIONARY
BEFORE HEADING EAST BY LATE SUNDAY TOWARDS THE PANHANDLE. IN THE
EXTENDED...MODEL CONSISTENCY HAS AGAIN GONE OUT THE PROVERBIAL
WINDOW...THOUGH THEY GENERALLY AGREE ON A SIGNIFICANT WEATHER SYSTEM
HEADING EAST ACROSS THE BERING SEA THE EARLY TO MIDDLE PART OF NEXT
WEEK...AND THEN AFFECTING THE SOUTHERN MAINLAND BY THE MIDDLE TO END
OF THE WEEK.

.ANALYSIS AND UPPER LEVELS...

A WEAK 995 MB LOW IS DEVELOPING IN THE CENTRAL GULF THIS MORNING
ALONG A PRESSURE TROUGH LEFT OVER FROM THE LOW THAT MOVED INLAND OVER
THE PANHANDLE YESTERDAY. A CLOSED UPPER LOW REMAINS OVER THE GULF
REGION...AND THESE FEATURES WILL CONTINUE TO REMAIN NEARLY STATIONARY
OVER THE NORTHERN GULF THROUGH THE WEEKEND. A HIGHLY AMPLIFIED UPPER
LEVEL AND SURFACE RIDGE RESIDE FROM THE CHUCHKI SEA SOUTH ACROSS THE
EASTERN BERING SEA AND ACROSS THE EASTERN ALEUTIANS. EVEN SAINT PAUL
IS ENJOYING WEAK WINDS AND A PARTLY CLOUDY MORNING. TO THE WEST...THE
FIRST IN A PARADE OF DISTURBANCES IS MAKING ITS WAY EAST WITH A FRONT
MOVING FROM THE WESTERN ALEUTIANS TODAY AND INTO THE CENTRAL
ALEUTIANS TONIGHT. WEAK LOW PRESSURE WILL LIKELY DEVELOP NEAR THE
CENTRAL ALEUTIANS TONIGHT BEFORE SLIDING SOUTHEAST INTO THE NORTH
PACIFIC OCEAN BY SUNDAY AFTERNOON AS THE RIDGE REFUSES TO YIELD
EASILY.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

GUSTY WINDS CONTINUE TO BE THE MAIN FOCUS OF THIS FORECAST PACKAGE.
MATANUSKA VALLEY GAP WINDS HAVE BEEN STAYING RATHER STRONG THROUGH
THE NIGHT...AND LATEST NAM MODEL GUIDANCE INDICATES THAT THE HIGH
WIND WARNING WILL NEED TO EXTENDED A FEW MORE HOURS INTO THE LATE
MORNING PERIOD. THE OBSERVATIONS THUS FAR SUPPORT THIS AS PALMER
AIRPORT HAS CONTINUED TO GUST UP ABOVE 60 MPH UP TO THE ORIGINAL
EXPIRATION TIME. A RELATIVELY STRONGER PRESSURE GRADIENT BETWEEN
TALKEETNA AND ANCHORAGE HAS HELPED TO BEND THESE GUSTY WINDS INTO
MOST OF ANCHORAGE AS WELL (ESPECIALLY THE WEST SIDE)...BUT GUIDANCE
IS SUPPORTIVE OF DIMINISHING THESE WINDS OVER THE NEXT COUPLE OF
HOURS BEFORE BECOMING MUCH WEAKER BY THE AFTERNOON.

FOR THE EASTERN PRINCE WILLIAM SOUND REGION...WINDS HAVE COME DOWN
SIGNIFICANTLY OVER THE PAST FEW HOURS AND WITH A WEAKENING
NORTH-SOUTH PRESSURE GRADIENT WE SEE NO REASON TO CONTINUE THE HIGH
WIND WARNING. AS WE HEAD INTO THE EVENING PERIOD...IT IS POSSIBLE AS
WARM ADVECTION MOVES OVER THE CORDOVA AREA AND THE UPPER LOW SWINGS
BACK TO THE WEST TOWARDS THE WESTERN PRINCE WILLIAM SOUND AREA THAT A
FEW SNOW SHOWERS COULD OCCUR. OTHERWISE...CONDITIONS WILL REMAIN
SUNNY WITH SOME HAZE NEAR AREAS OF STRONG WINDS THIS
MORNING...FOLLOWED BY A GENERAL DIMINISHING TREND IN THE WINDS
THROUGH THE AFTERNOON HOURS OVER ALL OF SOUTHCENTRAL AS THE TROUGH IN
THE GULF WEAKENS...THUS RELAXING THE NORTH-SOUTH PRESSURE GRADIENT
ACROSS THE AREA.

SOUTHWEST ALASKA...

COLD ADVECTION CONTINUES OVER THE REGION AS HIGH PRESSURE AT THE
SURFACE SLOWLY WORKS ITS WAY OVER THE DELTA REGION OVER THE NEXT
COUPLE OF DAYS. THIS WILL RESULT IN A GRADUAL DIMINISHING OF WINDS
TODAY THROUGH THE WEEKEND AS THE PRESSURE GRADIENT BETWEEN THE LOW IN
THE GULF AND THE HIGH MOVING OVERHEAD WEAKENS. THE NORTHERLY JET THAT
REMAINS ALONG AND JUST WEST OF THE ALASKA RANGE WILL MOVE SOUTHEAST
INTO THE GULF AND HELP TO MOVE THE UPPER RIDGE NORTH AND EASTWARD
OVER THE INTERIOR OF THE STATE BY THE END OF THE WEEKEND.

BERING SEA/ALEUTIANS/ALASKA PENINSULA...

THINGS HAVE NOT CHANGED MUCH IN THE SHORT TERM OUT WEST. A MODERATE
STRENGTH FRONT ASSOCIATED WITH A LOW NEAR THE KAMCHATKA PENINSULA
WILL WORK ITS WAY WEST TO EAST FROM THE WESTERN ALEUTIANS INTO THE
CENTRAL ALEUTIANS TONIGHT. THIS WILL BRING A PERIOD OF WINDS REACHING
SMALL CRAFT ADVISORY LEVELS THROUGH SUNDAY...BEFORE THE FRONT WASHES
OUT AND A WEAK LOW THAT DEVELOPS ALONG THE FRONT MOVES SOUTH INTO THE
PACIFIC OCEAN. THE NEXT SYSTEM ON ITS HEELS WILL ENTER THE SOUTHWEST
BERING AROUND SUNDAY MIDDAY WITH A GALE FORCE FRONT THAT WILL RACE
EASTWARD. BY SUNDAY NIGHT...STORM FORCE WINDS IN THE COLD ADVECTION
REGION TO THE SOUTH OF THE SURFACE LOW WILL BEGIN TO AFFECT THE
WESTERN ALEUTIANS AND THEN THE SOUTHERN BERING SEA SUNDAY NIGHT
THROUGH EARLY MONDAY BEFORE WINDS WEAKEN TO GALE FORCE.

.LONG TERM FORECAST...

BEYOND MONDAY...IT APPEARS THE PATTERN WILL BE MUCH MORE PROGRESSIVE
THAN IN THE PAST WEEK. THERE ARE STILL STRONG INDICATIONS THAT A
LARGE PARENT LOW OVER THE EASTERN ASIA MAINLAND WILL EJECT ITSELF
ACROSS THE BERING SEA TUESDAY AFTERNOON THROUGH THURSDAY. THIS SHOULD
HELP TO BRING MUCH MORE UNSETTLED WEATHER TO THE AREA OF
RESPONSIBILITY TOWARDS THE MIDDLE TO LATTER PART OF THE COMING WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING...111
MARINE...GALE WARNING...130 140 176
FIRE WEATHER...NONE.

CC OCT 09