Gale Warning 613, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
525 AM AKDT SAT SEP 25 2010

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER-LVLS A BROAD TROUGH ENVELOPS MAINLAND AK SOUTH THROUGH
THE GULF OF AK AND INTO THE NORTH PACIFIC. ACROSS THE NORTHERN BERING
AN UPPER-HIGH IS PINCHED OFF NEAR SAINT LAWRENCE ISLAND. A 150 KT JET
MAX IS ROUNDING THE BASE OF THE TROUGH AND RUSHING UP INTO THE AK
PANHANDLE. A 190 KT JET MAX IS TRAVERSING SOUTH OVER THE WESTERN
ALEUTIANS AND WILL REINFORCE THE TROUGH. THESE FEATURES ARE WELL
DEPICTED IN WATER VAPOR SATELLITE IMAGERY. AT THE SURFACE...A LOW
ABOUT 300 NM SOUTH OF MIDDLETON ISLAND IN THE GULF OF AK IS MOVING
NORTH AND SLOWLY FILLING. RAIN SHOWERS ASSOCIATED WITH THIS SYSTEM
BRUSHES PRINCE WILLIAM SOUND...THE KENAI PENINSULA AND KODIAK ISLAND.
FURTHER WEST...A COMPACT BUT STRONG LOW IS PASSING SAFELY SOUTH OF
THE CENTRAL ALEUTIAN CHAIN AND A WEAK TROUGH LINGERS OVER THE FAR
WESTERN ALEUTIANS. SURFACE RIDGING POKES INTO SOUTHCENTRAL AK FROM
THE WEST ASSOCIATED WITH THE AFOREMENTIONED UPPER HIGH IN THE
NORTHERN BERING. AS A RESULT...DRY NORTHERLY FLOW PERSISTS OVER THE
SOUTHERN INTERIOR WITH RATHER WINDY CONDITIONS.

.MODEL DISCUSSION...
MODELS ACCEPTABLY CAPTURE THE MAJOR WEATHER FEATURES IN THE AOR. THE
SURFACE LOW OVER THE GULF OF AK WILL APPROACH MIDDLETON ISLAND
THROUGH SATURDAY AND WEAKEN OVERNIGHT BEFORE DISSIPATING SUNDAY
MORNING. MODELS DO NOT DEPICT THE SURFACE LOW MOVING MUCH FURTHER
NORTH THAN MIDDLETON ISLAND. THE NAM WAS AN OUTLIER...WEAKENING THE
SYSTEM SLOWER AND TRACKING IT FURTHER EAST...MORE TOWARDS CORDOVA.
ALL MODELS DO DRAG THE RESIDUAL UPPER-LOW NORTHEAST AND ASHORE
EASTERN PRINCE WILLIAM SOUND ON SUNDAY. THE NAM DID NOT INITIALIZE
WELL...SO TRENDED MORE TOWARDS THE GFS SOLUTION. OUT WEST...A
TROPICAL SYSTEM EAST OF JAPAN LOOKS TO APPROACH THE FAR WESTERN
ALEUTIANS SUNDAY NIGHT. MODELS HAVE BEEN CONSISTENT IN SHOWING THIS
SYSTEM WILL YIELD STORM-FORCE WINDS OR HIGHER AS IT ROTATES INTO THE
AOR. FURTHERMORE...MODELS TRACK THE SYSTEM SIMILARLY THROUGH THE
ALEUTIAN CHAIN NEXT WEEK AND INTO THE SOUTHERN GULF OF AK BY LATE
NEXT WEEK. MODELS ARE NOT PERFORMING WELL WITH REGARDS TO
TEMPERATURES ACROSS THE AOR. THE PERSISTENT STRONG WINDS ARE MIXING
OUT THE LOWER ATMOSPHERE AND NOT ALLOWING FOR GOOD RADIATIONAL
COOLING DESPITE VERY LOW DEWPOINTS. AS SUCH TEMPERATURE FORECASTS
HAVE BEEN TRENDED HIGHER THAN THE MODEL GUIDANCE.

MODELS GENERALLY AGREE WITH THIS DEVELOPMENT. THE COMPACT LOW SOUTH
OF THE ALEUTIAN CHAIN WILL MOVE INTO THE NORTH PACIFIC THROUGH
SUNDAY...AND EVENTUALLY ROTATE NORTH INTO THE GULF OF AK...BUT
ASSOCIATED WEATHER LOOKS TO LARGELY BE OVER THE EASTERN PORTION OF
THE GULF AND TOWARDS SE AK.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
THE SHOWERS (MIXING WITH SNOW AT HIGHER ELEVATIONS) BRUSHING THE
KENAI PENINSULA AND KODIAK ISLAND WILL DIMINISH THROUGH SATURDAY. THE
RESIDUAL UPPER-LOW IN THE GULF WILL DRIFT NORTHEAST AND BRING MORE
WIDESPREAD PRECIPITATION ON SUNDAY FOR EASTERN PRINCE WILLIAM SOUND
AND THE COPPER RIVER BASIN. COOLER TEMPERATURES AT HIGHER ELEVATIONS
WILL ENABLE SNOW TO MIX IN WITH THE RAIN. ACROSS THE ANCHORAGE BOWL
AND MAT-SU VALLEY...CONDITIONS LOOK TO REMAIN GENERALLY DRY...THOUGH
A SQUEEZED PRESSURE GRADIENT WILL CONTINUE TO SUPPORT BREEZY
CONDITIONS THROUGH TONIGHT...ALBEIT WEAKER THAN YESTERDAY. AS
MENTIONED...THE LOW IN THE GULF WILL WEAKEN...AND ALLOW FOR WINDS TO
DIMINISH TEMPORARILY LATE TONIGHT AND SUNDAY. HOWEVER THE LOW PASSING
SOUTH OF THE CENTRAL ALEUTIANS THIS MORNING WILL ROTATE UP INTO THE
EASTERN GULF ON MONDAY...AND ONCE AGAIN SQUEEZE THE GRADIENT TO YIELD
BREEZY/BLUSTERY CONDITIONS INTO EARLY NEXT WEEK.

.SOUTHWEST...
THE SOUTHWEST MAINLAND WILL BE CHARACTERIZED BY ABUNDANT SUNSHINE AND
DRY WEATHER THE NEXT SEVERAL DAYS. THE PRESSURE GRADIENT WILL REMAIN
STRONG...WITH STIFF NORTHERLY WINDS PERSISTING AND KEEPING CONDITIONS
RATHER CHILLY/BRISK INTO EARLY NEXT WEEK.

.BERING SEA/ALEUTIANS...
A STRONG LOW NEAR JAPAN WILL APPROACH THE WESTERN BERING ON
SUNDAY...AND TRACK INTO THE CENTRAL BERING ON MONDAY. LOOK FOR
WIDESPREAD RAIN TO BE ACCOMPANIED BY STORM-FORCE AND POSSIBLE
HURRICANE FORCE WINDS PARTICULARLY OVER THE WESTERN AND CENTRAL
ALEUTIAN CHAIN.

.LONG TERM FORECAST...
FORECAST CHALLENGES NEXT WEEK WILL LARGELY FOCUS ON THE LOW THAT
TRACKS ACROSS THE BERING. DECENT MODEL AGREEMENT IN TERMS OF THE
TRACK AND SCOPE OF SIGNIFICANT WEATHER ASSOCIATED WITH IT. THE COLDER
AIRMASS IN NORTHERN AK SLOWLY BEGINS TO SLIP SOUTH THROUGH NEXT WEEK
AS WELL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...351 411 414 120 130 132 138 140 150 160 165 170 175
                176 180
FIRE WEATHER...NONE

JAM SEP 10