Small Craft Advisory 810, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
225 PM AKDT MON OCT 5 2009

.ANALYSIS AND UPPER LEVELS...
AT THE UPPER LEVELS...UPPER PORTION OF THE LONG WAVE TROUGH CUT OFF
AND IS RACING EAST ACROSS SOUTHCENTRAL ALASKA. RIDGING TAKING PLACE
OVER THE CENTRAL AND EASTERN BERING SEA IN ITS WAKE WHILE ANOTHER
LONGWAVE UPPER TROUGH IS SITTING OVER EASTERN SIBERIA AND THE
KAMCHATKA PENINSULA.

AT THE SURFACE...MID LEVEL AND SURFACE REFLECTION OF A POTENT
SHORTWAVE THAT MOVED THROUGH THE CENTRAL GULF OVERNIGHT WAS HIDDEN BY
THE PLUME OF MOISTURE STREAMING NORTHEAST ACROSS THE REGION. THE LOW
WAS MUCH STRONGER THAN ANTICIPATED...RESULTING IN MORE WIDESPREAD
COVERAGE OF RAIN OVERNIGHT AND THIS MORNING FROM THE KENAI PENINSULA
TO THE COPPER RIVER BASIN. WHILE THIS LOW DEPARTS...HIGH PRESSURE
BUILDS OVER THE EASTERN BERING SEA AND WILL QUICKLY SPREAD INLAND
TONIGHT.

.MODEL DISCUSSION...
EXCELLENT AGREEMENT IN THE MODELS OUT EAST. MAIN DIFFERENCES ARE
EVIDENT WITH THE CUTOFF LOW WELL SOUTH OF THE ALEUTIAN CHAIN AS IT
DEEPENS AND MOVES NORTH INTO THE CENTRAL BERING SEA TUESDAY. GFS AND
UKMET SHOW A VERY SIMILAR PATH WHILE THE NAM FOLLOWS A MORE EAST
TRACK AND THE ECMWF IS TO THE WEST. THE LATEST GFS/UKMET SOLUTION IS
IN AGREEMENT WITH THE INHERITED FORECAST SO NO CHANGES WERE MADE TO
THE ONGOING FORECAST. THE MODELS VARY ON THE NEXT STRONG LOW TO MOVE
INTO THE PICTURE WEDNESDAY NIGHT AND THURSDAY. AT THIS TIME...NOT
ENOUGH CONFIDENCE IN ANY OF THE SOLUTIONS TO STRAY FROM OUR CURRENT
FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
RAIN ENDED THIS MORNING ALTHOUGH THE WESTERLY FLOW IS BUTTING UP
AGAINST THE TALKEETNAS AND CHUGACH MOUNTAINS RESULTING IN MARGINAL
CEILINGS LASTING A BIT LONGER THAN ANTICIPATED. CLEARING IS CURRENTLY
CONFINED TO THE WESTERN HALF OF THE SUSITNA AND COPPER RIVER VALLEYS.
EVENTUALLY...WILL SEE MORE CLEARING AS THE TROUGH AXIS MOVES EAST AND
HIGH PRESSURE BUILDS OVERNIGHT. THE ABUNDANT MOISTURE AT THE SURFACE
FROM THE RECENT RAIN COUPLED WITH ANY CLEARING WILL RESULT IN AREAS
OF FOG OVERNIGHT. LOW CLOUDS AND FOG WILL DISSIPATE IN THE MORNING AS
THE RIDGE BUILDS QUICKLY OVERHEAD...BUT HIGH CLOUDS WILL AGAIN INVADE
FROM THE SOUTH AS A FRONT ASSOCIATED WITH THE AFOREMENTIONED NORTH
PACIFIC LOW MOVES INTO THE WESTERN GULF. RAIN WILL SPREAD NORTH FROM
KODIAK TUESDAY MORNING AND REACH THE ANCHORAGE BOWL BY TUESDAY
EVENING. ABNORMALLY WARM AIR ASSOCIATED WITH A DEEP SUBTROPICAL
CONNECTION WILL STREAM NORTH ACROSS THE STATE THROUGH THE REMAINDER
OF THE WEEK.

SOUTHWEST ALASKA...GRADUAL CLEARING TAKING PLACE AS THE INFLUENCE OF
THE RIDGE SPREADS INLAND. A FEW SHOWERS ARE STILL PRESENT BUT WITH
THE CLEARING TAKING PLACE OVERNIGHT...EXPECT FOG TO DEVELOP OVER MUCH
OF THE REGION. RAIN AND STRONG WINDS ASSOCIATED WITH THE FRONTAL
BOUNDARY MOVE NORTH AND WILL AFFECT THE SOUTHWEST INTERIOR BY TUESDAY
AFTERNOON. WINDS...ESPECIALLY THROUGH THE GAPS OF THE ALEUTIAN RANGE
ON THE ALASKA PENINSULA...COULD REACH AS HIGH AS 55 MPH. THERE WILL
BE A BRIEF BREAK LATE TUESDAY NIGHT AND WEDNESDAY MORNING BEFORE THE
NEXT FRONTAL BOUNDARY MOVES INLAND SPREADING RAIN AND WIND FROM
BRISTOL BAY TO THE UPPER KUSKOKWIM VALLEY. THE ACTIVE PATTERN WILL
CONTINUE THROUGH THE REST OF THE WEEK WITH THE MEAN TROUGH AXIS
MAKING LITTLE OR NO PROGRESS.

BERING SEA/ALEUTIANS...STRONG WINDS ARE THE BIGGEST STORY OUT WEST
ASSOCIATED WITH THE MULTIPLE LOWS DEVELOPING SOUTH OF THE CHAIN AND
WEAKENING AS THEY MOVE INTO THE CENTRAL BERING SEA. MAXIMUM GALES ARE
POSTED FOR ALMOST EVERY MARINE ZONE. GUSTS TO 55 MPH THROUGH
CHANNELED TERRAIN OF THE ALEUTIAN CHAIN CERTAINLY WITHIN REACH.
UNCERTAINTY REMAINS CONCERNING THE EXACT TRACK OF THE LOWS DURING THE
WEEK BUT FEEL CONFIDENT EACH STORM WILL BRING STRONG GALE FORCE WINDS
AND HEAVY DOWNPOURS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...132 155 160 165 170 171 172 175 176 179 180
185.
FIRE WEATHER...NONE.

AB OCT 09