High Wind in Alaska, October 9 to 10, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
534 AM AKDT FRI OCT 9 2009

.ANALYSIS AND UPPER LEVELS...

A LARGE BLOCKING MID-LEVEL RIDGE CONTINUES TO REMAIN ENTRENCHED FROM
THE EASTERN GULF OF ALASKA NORTHWARD ACROSS THE EASTERN THIRD TO
ONE-HALF OF THE ALASKA MAINLAND...WITH A COUPLE OF POTENT MID-LEVEL
LOWS OVER THE SOUTHERN BERING SEA AND NORTH PACIFIC OCEAN. THE FIRST
SYSTEM IS SLOWLY WEAKENING WITH A 986 MB SURFACE LOW STACKED
UNDERNEATH ABOUT HALFWAY BETWEEN ATKA ISLAND AND THE PRIBILOFS. THE
SECOND LOW IS AN IMPRESSIVE LOOKING SYSTEM ON SATELLITE RAPIDLY
MOVING NORTH TOWARDS SOUTHWESTERN ALASKA AND THE ALASKA PENINSULA.
THIS FEATURE WILL PLAY A MAJOR ROLE ON THE WEATHER OVER THE NEXT 24
TO 36 HOURS WITH MANY SIGNIFICANT WEATHER IMPACTS IN THE FORM OF
WIND...RAIN...AND COASTAL FLOODING.

.MODEL DISCUSSION...

MODELS CONTINUE TO BE IN REASONABLE AGREEMENT ON THE EVOLUTION OF THE
MAJOR SYSTEM WHICH WILL AFFECT A LARGE PORTION OF OUR AREA OF
RESPONSIBILITY. THE 00Z GFS BEGAN TO SPEED UP THE PROGRESSION OF THE
LOW IN FAST SOUTHERLY FLOW ALOFT...AND THE 00Z EUROPEAN AND 06Z NAM
FOLLOWED SUIT. THEREFORE...THE ONLY REAL CHANGE IN THE THE GRIDS WAS
TO SPEED TIMING OF THE LOW AND ITS EFFECTS BY ABOUT 3 HOURS. THIS
WILL BRING AN EARLIER START TIME TO THE HIGH WIND WARNINGS ESPECIALLY
FOR THE BRISTOL BAY WATERS AND PUBLIC ZONES.

.SHORT TERM FORECAST...

THE MAIN PLAYER IN THE SHORT TERM CONTINUES TO BE THE STRONG LOW
MOVING NORTH FROM THE PACIFIC TOWARDS THE ALASKA PENINSULA. CROSSING
TIME OF THE SOUTHERN AKPEN IS FORECASTED AT AROUND 06Z THIS
EVENING...WITH THE LOW THEN CONTINUING NORTHWEST TO THE EAST OF THE
PRIBILOFS FRIDAY NIGHT INTO SATURDAY AND THEN SWINGING WELL WEST OF
SAINT MATTHEW ISLAND SATURDAY NIGHT INTO SUNDAY. AS MENTIONED
BEFORE...THE CONSENSUS OF THE MODELS OVER THE PAST TWELVE HOURS IS TO
SPEED PROGRESSION OF THIS LOW BY ABOUT 3 HOURS OVER PREVIOUS
FORECASTS. THIS MEANS AN EARLIER START TIME TO STORM WARNINGS IN THE
COASTAL WATERS SURROUNDING KODIAK ISLAND AND THE AKPEN THIS AFTERNOON
(INSTEAD OF EARLY THIS EVENING). AS WE HEAD INTO FRIDAY NIGHT AND
LATE SATURDAY MORNING...STRONG PRESSURE RISES IN THE WAKE OF THE LOW
SHOULD BE ABLE TO BRING A BRIEF PERIOD OF HIGH WINDS WITH GUSTS OF AT
LEAST 75 MPH TO THE SOUTHERN PART OF KODIAK ISLAND...THUS
NECESSITATING THE UPGRADE OF THE HIGH WIND WATCH TO A HIGH WIND
WARNING THERE. HIGH WIND CRITERIA WILL ALSO BE FELT IN GUSTS ALONG
CHANNELED TERRAIN OF THE ALASKA AND ALEUTIAN RANGES...AS WELL AS
ALONG THE IMMEDIATE COASTLINE OF THE BRISTOL BAY WATERS. IN
ADDITION...AS THE LOW PASSES BY WE EXPECT WINDS AND SEAS ON THE BACK
SIDE OF THE SYSTEM TO PICK UP ENOUGH TO CAUSE A STORM SURGE OF
SEVERAL FEET...THUS ALSO NECESSITATING THE ISSUANCE OF A COASTAL
FLOOD WATCH FOR AREAS ALONG THE COASTLINE OF THE KUSKOKWIM DELTA
ZONE.

THE HIGH WIND WATCH FOR TURNAGAIN ARM AND HIGHER ELEVATIONS OF THE
ANCHORAGE ZONE HAS BEEN UPGRADED TO A HIGH WIND WARNING...WITH
CONFIDENCE HIGH THAT AS THE FRONT ASSOCIATED WITH THE POTENT LOW OUT
WEST MOVES INTO SOUTHCENTRAL TONIGHT...THE EXISTING STRONG EAST-WEST
PRESSURE GRADIENT THROUGH TURNAGAIN ARM WILL BECOME TIGHTENED EVEN
MORE TO SUPPORT HIGH WIND CRITERIA. CONFIDENCE IS NOT QUITE AS HIGH
FOR EASTERN TURNAGAIN ARM AND PORTAGE VALLEY THAT THEY WILL REACH
HIGH WIND WARNING CRITERIA HOWEVER...AND WILL LEAVE IT TO THE
AFTERNOON CREW TO DECIDE WHETHER TO UPGRADE TO A WARNING.

.LONG TERM FORECAST...

VERY LITTLE TIME WAS SPENT ON THE EXTENDED FORECAST AS THE PRIMARY
FOCUS WAS ON THE SHORT TERM. CONFIDENCE IS BUILDING THAT A LARGE
UPPER RIDGE WILL TAKE HOLD OF THE MAINLAND...WITH NORTHERLY OFFSHORE
FLOW USHERING IN COOLER AND DRIER AIR INTO THE SOUTHERN HALF OF THE
STATE WITH MUCH MORE TRANQUIL AND PLEASANT WEATHER THAN THIS WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING...101 161 171
         HIGH WIND WATCH...125
         COASTAL FLOOD WATCH...155
MARINE...GALE WARNING...120 125 129 141 165 170 179
         STORM WARNING...130 132 138 140 150 155 160 180 185
FIRE WEATHER...NONE.

CC OCT 09