Gale Warning 242, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
340 PM AKDT FRI MAR 13 2009

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN EXCELLENT AGREEMENT...SO MAINLY USED THE GFS
FOR THE SYNOPTIC PATTERN AND USED THE NAM IN AREAS WHERE ITS ENHANCED
RESOLUTION PROVED USEFUL...SUCH AS THROUGH CHANNELED TERRAIN.

.ANALYSIS AND UPPER LEVELS...

A STRONG ANTICYCLONICALLY CURVED JET IS LOCATED OVER THE SOUTHERN
BERING SEA AND ALEUTIAN CHAIN.  THIS FEATURE IS BEGINNING TO AID IN
THE DIGGING OF AN UPPER LOW OVER THE GULF...BRINGING A PATTERN CHANGE
FOR THE WEEKEND AND BEYOND.  WEAK RIDGING ALOFT HAS DEVELOPED EAST OF
THE KAMCHATKA PENINSULA AND EXTENDS NORTHWARD INTO EASTERN SIBERIA.
A STRONG UPPER TROUGH LOCATED OVER FAR NORTHERN AND CENTRAL CANADA
CONTINUES TO RAPIDLY RETROGRADE TOWARDS THE ALCAN BORDER FROM THE
EAST AND WILL BECOME A KEY WEATHER PLAYER IN REINFORCING THE COLD
WEATHER FOR SOUTHCENTRAL LATE THIS WEEKEND INTO EARLY NEXT WEEK.

AT THE SURFACE...LOW PRESSURE IS LOCATED NEAR PRINCE WILLIAM SOUND IN
ASSOCIATION WITH A DEVELOPING UPPER LEVEL LOW JUST TO ITS SOUTHEAST.
WESTERLY WINDS ON THE BACKSIDE OF THIS LOW COMBINED WITH A SUBTLE
SHORTWAVE MOVING SOUTHEASTWARD ACROSS SOUTHERN ALASKA ARE PRODUCING
LIGHT SNOW SHOWERS ALONG AND TO THE WEST OF THE CHUGACH AND KENAI
MOUNTAINS.  OTHERWISE...THERE IS A RAPIDLY WEAKENING LOW IN THE
CENTRAL BERING SEA WHICH WILL HAVE LITTLE IF ANY SIGNIFICANT IMPACT
ON THE WEATHER.

.SHORT TERM FORECAST...

WEST OF THE ALASKA RANGE...THE WEAK RIDGING CURRENTLY JUST EAST OF
THE KAMCHATKA PENINSULA RAPIDLY BUILDS NORTHWARD AND STRENGTHENS THIS
WEEKEND AND THEN BECOMES NEARLY STATIONARY FROM THE CENTRAL ALEUTIANS
NORTHWARD INTO FAR EASTERN SIBERIA BY SUNDAY NIGHT.  AS THIS RIDGE
BUILDS A STATIONARY UPPER LOW OVER EASTERN SIBERIA CURRENTLY WILL BE
PUSHED SOUTHEASTWARD AND WILL MOVE RAPIDLY ACROSS SOUTHWEST
ALASKA...FOLLOWED ON ITS HEELS BY THE RETROGRADING LOW FROM NORTHERN
CANADA WHICH WILL AID IN STRENGTHENING A POWERFUL NORTHERLY JET OVER
THE EASTERN BERING SEA...BRISTOL BAY...AND INTO THE FAR SOUTHWESTERN
GULF OF ALASKA AS THE WEEKEND PROGRESSES INTO EARLY NEXT WEEK.
THUS...EXPECT AN UPTICK IN WINDS THROUGH THE WEEKEND...ESPECIALLY IN
EXPOSED LOCATIONS NEAR THE COASTLINE AND THROUGH CHANNELED TERRAIN IN
THE ALEUTIAN RANGE AND AKPEN...AND SCATTERED SNOW SHOWERS ACROSS
SOUTHWEST ALASKA AND THE AKPEN.  ALSO...EXPECT TEMPERATURES TO DROP
AS STRONG NORTHERLY FLOW USHERS IN AN AIRMASS FROM THE ARCTIC AND
NORTHERN INTERIOR OF THE STATE. IN THE WESTERN AND CENTRAL
ALEUTIANS...AN UPPER SHORTWAVE WILL TRY TO UNDERCUT THE BUILDING
RIDGE AND WILL LIKELY BRING A CHANCE OF SHOWERS FOR THE LAST HALF OF
THE WEEKEND.

SOUTH AND EAST OF THE ALASKA RANGE...AFTER TONIGHTS WEAK SYSTEM
MOVES THROUGH SOUTHCENTRAL BRINGING A CHANCE OF LIGHT SNOW...EXPECT
THE PATTERN CHANGE TO TAKE FULL FORCE WITH CLEARING SKIES THROUGH THE
WEEKEND AND A RETURN TO COLD TEMPERATURES INTO EARLY NEXT WEEK.  AS
SURFACE HIGH PRESSURE BUILDS ACROSS THE NORTHERN HALF OF THE STATE
AND LOW PRESSURE STRENGTHENS IN THE GULF OF ALASKA...EXPECT OUTFLOW
WINDS THROUGH CHANNELED TERRAIN TO INCREASE AND BECOME QUITE
STRONG...AND LIKELY PERSIST THROUGH EARLY NEXT WEEK.

.LONG TERM FORECAST...
IT APPEARS THE PATTERN CHANGE WILL STICK WITH US THROUGH ALL OF NEXT
WEEK...SO EXPECT COLD...DRY...AND WINDY CONDITIONS (ESPECIALLY
THROUGH CHANNELED TERRAIN) FOR SOUTHCENTRAL ALASKA.  FOR THE
AKPEN...STRONG NORTHERLY FLOW WILL ALSO CONTRIBUTE TO THE DEVELOPMENT
OF SHOWERY ACTIVITY THROUGH THE EXTENDED PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...130 132 160 165 170 175 176 179 180
         STORM WARNING...150 155
         HVY FRZG SPRY WARNING...121 129 130 138 140 150 160 165 179
                                 180 185
FIRE WEATHER...NONE.

CC MAR 09