Gale Warning 313, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
332 PM AKDT SAT APR 17 2010

.ANALYSIS AND UPPER LEVELS...
AN ELONGATED UPPER LEVEL LOW STRETCHES FROM THE NORTHERN BERING AND
DIGS ACROSS THE ALEUTIAN ISLANDS AND INTO THE NORTH PACIFIC. AN UPPER
LEVEL RIDGE CONTINUES TO BUILD FROM WESTERN CANADA INTO MAINLAND
ALASKA.  MEANWHILE...A BROAD WEAK RIDGE IS LOCATED ACROSS THE NORTH
PACIFIC SOUTHWEST OF THE WESTERN ALEUTIANS. THE RIDGE OVER THE
MAINLAND IS BUILDING WESTWARD WHILE THE NORTH PACIFIC RIDGE IS MOVING
EAST. AS A RESULT...THE UPPER LEVEL LOW IS BECOMING DISCONNECTED FROM
ITS NORTH POLE POTENTIAL VORTICITY SUPPORT AND WEAKENING.

.AT THE SURFACE...A 976 MB ELONGATED LOW IS CENTERED 200 MILES SOUTH
OF KODIAK ISLAND. AN ASSOCIATED TROUGH THAT HAS BEEN BRINGING RAIN
AND SNOW TO KODIAK ISLAND AND SOUTH AND EAST PORTIONS OF THE KENAI
PENINSULA. THIS TROUGH STRETCHES INTO THE EASTERN BRISTOL BAY AND
KUSKOKWIM VALLEY REGION AND PROGRESSING WESTWARD. SURFACE HIGH
PRESSURE IS BUILDING ACROSS EAST MAINLAND ALASKA HOWEVER CLOUDS
PERSIST ACROSS MUCH OF THE STATE. NO STRONG SURFACE RIDGING EXISTS
UNDER THE UPPER LEVEL RIDGE OVER THE WESTERN NORTH PACIFIC.

.MODEL DISCUSSION...MODELS APPEAR TO BE CAPTURING THE DYNAMICS OF THE
UPPER LEVEL LOW AS IT CONTINUES TO DIG INTO THE NORTH PACIFIC THIS
MORNING. HOWEVER...IN THE SHORT TERM FORECAST MODELS ARE SHOWING MUCH
MORE DISAGREEMENT IN RESOLVING THE EVOLUTION OF THE SURFACE LOW SOUTH
OF KODIAK. THE CURRENT PATTERN FAVORS THE DEVELOPMENT OF ELONGATED
LOWS AT THE SURFACE...WHICH MAY BE RESOLVED AS ONE LOW OR AS COUPLED
BARBELL LOWS DEPENDING ON THE MODEL.  THEREFORE...THERE IS SOME
UNCERTAINTY IN THE POSITION OF LOWS OVER THE NEXT FEW DAYS.  THE
NAM IS THE FAVORED SOLUTION FOR THE SHORT TERM WITH THE STRONGER
DEVELOPMENT OF A TRIPLE POINT LOW THAT ROTATES INTO THE GULF OVER THE
NEXT SEVERAL DAYS. HPC GUIDANCE WAS RELIED UPON FOR THE LONG TERM.

.SHORT TERM FORECAST...THE CHANCE FOR STEADY PRECIPITATION ALONG THE
SOUTHCENTRAL COAST WILL DECREASE THIS EVENING AS A SHORTWAVE MOVES
AWAY FROM THE REGION. THE NEXT CHANCE FOR STEADY PRECIPITATION WILL
OCCUR SUNDAY AFTERNOON AS THE NEXT FRONT APPROACHES THE COAST.
DOWNSLOPING SHOULD LIMIT THE PRECIPITATION OVER THE ANCHORAGE BOWL
AND WESTERN KENAI PENINSULA.

.SOUTHWEST... THE SHORTWAVE ASSOCIATED WITH THE LOW SOUTH OF KODIAK
WILL PROGRESS WESTWARD ACROSS THE BRISTOL BAY AND KUSKOKWIM VALLEY
AND DELTA REGIONS. SNOW AND RAIN ARE EXPECTED ACROSS THESE REGIONS
THIS AFTERNOON THROUGH SUNDAY MORNING ALTHOUGH NO ACCUMULATIONS ARE
EXPECTED. THE SHORTWAVE WILL CONTINUE TO MOVE WESTWARD SUNDAY AND
BRING THE POSSIBILITY OF PRECIPITATION TO THE ALASKA PENINSULA.
STRONG WINDS ARE POSSIBLE ACROSS THE ALASKA PENINSULA AS THIS
SHORTWAVE PROGRESSES OVERNIGHT. THE REGION WILL THEN DRY OUT OVER THE
NEXT FEW DAYS AS THE LOW SOUTH OF KODIAK MOVES TO THE SOUTHEAST AND
WEAKENS.

.BERING SEA/ALEUTIANS...ONLY SCATTERED SHOWERS ARE EXPECTED ACROSS
THE ALEUTIANS OVER THE NEXT FEW DAYS. BY EARLY MONDAY MORNING A 984
MB LOW PRESSURE WILL APPROACH THE WESTERN AND CENTRAL ALEUTIANS
BRINGING THE POSSIBILITY OF STEADIER PRECIPITATION AND GALE FORCE
WINDS.

.LONG TERM FORECAST...AN ACTIVE WEATHER PATTERN WILL REMAIN IN THE
REGION OVER THE NEXT WEEK WITH LOWS MOVING ACROSS THE ALEUTIAN
ISLANDS AND INTO THE GULF. MODELS SUGGEST THAT AN UPPER LEVEL RIDGE
WILL GENERALLY BE OVER THE MAINLAND WHICH SHOULD LIMIT PRECIPITATION
OVER THE INTERIOR OVER THE NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...132
            GALE WARNING...120 129 130 136 137 138 150 155 165 170
                           171.
FIRE WEATHER...NONE.

ELN APR 10