Small Craft Advisory 941, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
245 PM AKST TUE NOV 17 2009

.ANALYSIS AND UPPER LEVELS...A COLD WEATHER PATTERN REMAINS IN PLACE
WITH A BROAD UPPER TROUGH LOCATED OVER MAINLAND AND THE GULF OF
ALASKA. AN UPPER LEVEL RIDGE IS BUILDING OVER EASTERN SIBERIA AND
WILL EXTEND SOUTHWARD INTO THE CENTRAL BERING SEA. THIS AMPLIFYING
RIDGE WILL PLAY A ROLE IN THE STRONG LOW THAT WILL DEVELOP LATER
TONIGHT AND WEDNESDAY MORNING. AT THE SURFACE...SEVERAL POTENT MESO
LOWS ARE ROTATING AROUND THE BROAD CYCLONIC CIRCULATION IN THE
NORTHERN GULF.

.MODEL DISCUSSION...MODELS ARE IN FAIR AGREEMENT THROUGH THE SHORT
TERM. THE HIGH RESOLUTION NAM AND LOCAL WRF ARE HANDLING THE MESO
LOWS BETTER THAN THE GFS OR EUROPEAN BUT AS FOR SYNOPTIC FEATURES NO
REAL DIFFERENCES UNTIL 84 HOURS. ON FRIDAY...A WAVE WILL DEVELOP
ALONG THE JET AND MOVE ACROSS THE ALEUTIANS FRIDAY NIGHT AND
SATURDAY. THE GFS SEEMS TO BE THE OUTLIER IN THE TIMING...IT BEING A
BIT TOO FAST...SO WILL BE WEIGHTING THE MIDTERM FORECAST HEAVIER
TOWARD THE ECMWF.

.SHORT TERM FORECAST...
SOUTHCENTRAL AND GULF OF ALASKA...THE PRESSURE GRADIENT BETWEEN THE
COLD ARCTIC AIRMASS OVER THE MAINLAND AND THE GULF OF ALASKA LOW IS
RESULTING IN GUSTY WINDS THROUGH CHANNELED TERRAIN. WIND CHILL
ADVISORIES FOR THE NORTHERN SUSITNA VALLEY AND THOMPSON PASS WILL BE
EXTENDED THROUGH THURSDAY MORNING...WHEN THE GRADIENT WILL FINALLY
RELAX AND WINDS WILL DIMINISH ACROSS THE AREA. UNTIL THEN...THE MAIN
LOW IN THE EASTERN GULF WILL RETROGRADE BACK TOWARD THE KENAI
PENINSULA AND THEN SOUTH AGAIN...JUST EAST OF KODIAK ISLAND. THIS
TRACK WILL ENSURE THAT THE GRADIENT STAYS STRONG ENOUGH TO SUPPORT
STRONG WINDS THROUGH THE CHANNELED AREAS INCLUDING PASSAGE CANAL AND
RESURRECTION BAY. OTHERWISE...MOSTLY CLEAR SKIES WILL PREVAIL WITH
AREAS OF LOW CLOUDS AND ICE CRYSTALS.

ON FRIDAY...A TRIPLE POINT LOW WILL DEVELOP ALONG A FRONTAL BOUNDARY
NEAR KODIAK ISLAND AS SOUTHWESTERLY FLOW ALOFT FILTERS ACROSS THE
REGION. THIS WILL HELP TEMPERATURES REBOUND TO MORE CLIMATOLOGICAL
NORMAL READINGS...AND ALSO RETURN SOME MID AND HIGH LEVEL CLOUDS. AT
THIS TIME...THE NEXT BEST CHANCE OF SNOW FOR THE ANCHORAGE AREA WILL
BE THIS WEEKEND.

SOUTHWEST ALASKA...NO SIGNIFICANT CHANGES FROM THE FORECAST IN
SOUTHWEST ALASKA. ON FRIDAY...THE REMNANTS OF THE FRONT APPROACH THE
BRISTOL BAY COAST AND KUSKOKWIM DELTA...BRINGING BREEZY CONDITIONS
AND THE CHANCE OF SNOW BACK TO THE REGION. THE ARCTIC AIRMASS OVER
THE NORTHERN INTERIOR WILL LIMIT HOW FAR ONSHORE THE SYSTEM WILL
PROGRESS.

BERING SEA/ALEUTIANS...MOST ACTIVE WEATHER IS OUT WEST. A WEAKENING
FRONTAL BOUNDARY HAS BROUGHT SEVERAL INCHES OF SNOW TO THE EASTERN
ALEUTIANS OVERNIGHT AND THIS MORNING. THIS FRONT WILL CONTINUE TO
WEAKEN AS THE RIDGE BUILDS OVERHEAD TONIGHT. A NORTH PACIFIC LOW IS
IN ITS EARLY STAGES OF DEVELOPMENT EAST OF JAPAN. THIS LOW WILL
RAPIDLY DEEPEN TO 947 MB NORTHWEST OF SHEMYA WHILE ITS ASSOCIATED
FRONTAL BOUNDARY PUSHES EAST THROUGH THE WESTERN AND CENTRAL
ALEUTIANS. THIS SYSTEM WITH THE ASSISTANCE OF AN INCREASINGLY
AMPLIFIED JET WILL TAP INTO TROPICAL MOISTURE AND THE COLD ARCTIC
AIRMASS OVER EASTERN SIBERIA. THIS COMBINATION WILL LIKELY PRODUCE 65
KT WINDS OVER A SUBSTANTIAL PORTION OF THE NORTH PACIFIC AND WESTERN
BERING. A HIGH WIND WATCH IS IN EFFECT FOR THE WESTERN ALEUTIANS FOR
GUSTS AS HIGH AS 80 MPH POSSIBLE BEGINNING WEDNESDAY EVENING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH 191
MARINE...HURRICANE FORCE 170
         STORMS 175 185
         GALES 120 128 129 130 132 150 150 155 160 165 170 172 179
         HEAVY FREEZING SPRAY 129 130 140 150 160 165 180
FIRE WEATHER...NONE

AB NOV 09