Small Craft Advisory 896, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKST SUN NOV 16 2008

.ANALYSIS AND UPPER LEVELS...
A BROAD UPPER LEVEL TROUGH ENCOMPASSES THE STATE THIS
MORNING...ROUNDED OUT BY THE JET STREAM WHICH GOES SOUTHEAST FROM
THE KAMCHATKA PENINSULA TO THE WESTERN ALEUTIANS AND TO AROUND 30N
150W. THE JET THEN HEADS BACK NORTHEAST TOWARD THE QUEEN CHARLOTTE
ISLANDS OF BRITISH COLUMBIA.

THE STRONGEST FEATURE IN THE FORECAST AREA THIS MORNING IS A GALE
FORCE 993 MB LOW IN THE BERING NORTH OF ADAK AND SOUTHWEST OF SAINT
PAUL. THIS LOW IS MOVING SOUTHEAST ALONG THE EAST SIDE OF THE JET
STREAM AND WILL CROSS THE ALEUTIANS AROUND UMNAK ISLAND TONIGHT. THE
STRONGEST WINDS WITH THIS LOW ARE ON ITS WEST SIDE.

THE FEATURE IMPACTING THE MAJORITY OF THE POPULATION IS AN UPPER
LEVEL TROUGH WHICH EXTENDS FROM THE YUKON KUSKOKWIM DELTA SOUTHEAST
TO KODIAK THIS MORNING...MOVING NORTHEAST. A COUPLE OF WEAK EMBEDDED
SURFACE LOW PRESSURE SYSTEMS ARE LOCATED NEAR BETHEL AND OVER THE
NORTH END OF KODIAK ISLAND THIS MORNING...BOTH MOVING NORTHEAST AND
WEAKENING. ALL OF THIS IS BRINGING SNOW TO THE SOUTHERN MAINLAND
LAST NIGHT INTO TODAY...WITH RAIN MIXED IN FOR PLACES NEAR THE GULF
OF ALASKA.

.MODEL DISCUSSION...
MODELS ARE DOING OKAY OVERALL. GENERALLY PREFER THE ECMWF OVER THE
GFS WHERE DIFFERENCES ARISE. ONE ISSUE IN THE WESTERN ALEUTIANS IS A
LOW WHICH THE 0Z GFS TRIES TO MOVE EAST THROUGH THE RIDGE AROUND
TUESDAY. WE DISCOUNTED THE 0Z GFS AND KEPT WITH THE IDEA OF THE
ENERGY SPLITTING WHEN IT HITS THE RIDGE.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
AN UPPER LEVEL TROUGH IS MOVING NORTHEAST THROUGH SOUTHCENTRAL
TODAY...WITH AN EMBEDDED SURFACE LOW OVER THE NORTH END OF KODIAK
ISLAND MOVING TO SOUTH OF SEWARD THIS AFTERNOON AND DISSIPATING.
FAIRLY WIDESPREAD BUT MAINLY LIGHT SNOW IS TRANSLATING FROM
SOUTHWEST TO NORTHEAST WITH THIS SYSTEM TODAY. AN INCH OR TWO IS
EXPECTED FOR MOST AREAS...WITH HIGHER SNOWFALL AMOUNTS AROUND THE
NORTH EDGE OF PRINCE WILLIAM SOUND. SNOWFALL WILL TAPER OFF BY LATE
TONIGHT NEARLY EVERYWHERE AS HIGH PRESSURE BUILDS IN. COLD ADVECTION
WILL OCCUR MONDAY THROUGH WEDNESDAY WITH DRY OFFSHORE NORTHERLY FLOW.
LOOK FOR STEADILY FALLING TEMPERATURES AND LOCALLY GUSTY WINDS
THROUGH CHANNELED TERRAIN.

SOUTHWEST MAINLAND...
AN UPPER LEVEL TROUGH MOVING EAST THROUGH THE SOUTHWEST MAINLAND
WILL CONTINUE TO BRING SNOW TODAY ALONG THE ALEUTIAN AND ALASKA
RANGE AND OVER THE EASTERN PORTION OF THE KUSKOKWIM VALLEY. A FEW
SNOW SHOWERS WILL PERSIST NEAR THE YUKON KUSKOKWIM DELTA NEAR A WEAK
SURFACE LOW. HIGH PRESSURE BUILDS IN RAPIDLY TONIGHT...THEN THE FLOW
TRANSITIONS TO DRY OFFSHORE MONDAY THROUGH WEDNESDAY AS COLDER AIR
MOVES BACK IN.

BERING SEA/ALEUTIANS...
A GALE FORCE 993 MB LOW IN THE CENTRAL BERING THIS MORNING WILL MOVE
SOUTHEAST AND CROSS UMNAK ISLAND TONIGHT...THEN MOVE INTO THE NORTH
PACIFIC WELL SOUTH OF THE ALASKA PENINSULA. THE STRONGEST WINDS WITH
THIS LOW WILL CONTINUE TO BE ON ITS WEST SIDE. A FRONT EXTENDS OUT
AHEAD AND EAST OF THIS LOW AND IS BRINGING RAIN AND SNOW TO THE
EASTERN ALEUTIANS...AKPEN...AND PRIBILOFS TODAY. HOWEVER...THIS
FRONT WILL NOT MAKE IT TO THE WEST COAST DUE TO THE DEVELOPING
BLOCKING SURFACE HIGH PRESSURE OVER THE MAINLAND. AS THE LOW MOVES
OFF INTO THE NORTH PACIFIC...STRONG HIGH PRESSURE DEVELOPS OVER THE
NORTH CENTRAL BERING MONDAY THROUGH WEDNESDAY.

.LONG TERM FORECAST...
COLD SURFACE HIGH PRESSURE AND OFFSHORE FLOW WILL PERSIST OVER THE
MAINLAND PROBABLY INTO NEXT WEEKEND. THE HIGH PRESSURE IN THE BERING
ON WEDNESDAY SHOULD BREAK DOWN IN THE LATTER PART OF THE WEEK WITH
INCREASED STORMINESS AND WARMER TEMPERATURES. THE FORECAST FOR
SOUTHCENTRAL THURSDAY AND BEYOND WILL BE TRICKY...BECAUSE DESPITE
THERE BEING COLD OFFSHORE FLOW WITH SURFACE HIGH PRESSURE OVER THE
INTERIOR...THE MODELS ARE HINTING AT AN UPPER LEVEL LOW OVER THE
SOUTHWEST MAINLAND WHICH COULD ALLOW FOR SOME SORT OF WEAK SURFACE
LOW TO FORM AROUND PRINCE WILLIAM SOUND OR NORTHERN GULF...PERHAPS
BRINGING SOME SNOW TO AREAS NEAR THE GULF COAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING ZONES 130 172 175 176 185 411 412 413.
FIRE WEATHER...NONE.

FOISY NOV 08