Small Craft Advisory 845, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT SAT SEP 16 2006

.DISCUSSION...
MODELS...INITIAL PRECIP FIELD ALONG THE NORTHERN GULF COAST NOT
HANDLED WELL BY THE NAM/WRF THIS MORNING. OTHERWISE...MODELS HAVE
INITIALIZED WELL THIS MORNING. 12Z GFS SEEMS TO BE THE OUTLIER THIS
MORNING. ECMWF...NAM...CANADIAN...UKMET ALONG WITH THE 00Z AND 12Z
ENSEMBLES ALL PUSH FOR A SLOWER EVOLUTION OF THE CURRENT NORTH
PACIFIC LOW SOUTH OF SHEMYA ACROSS THE EASTERN ALEUTIANS.

UPPER LEVELS...OVERALL...THE MEAN TROUGH NEAR 160W TO MOVE OVER THE
MAINLAND BY TUESDAY. THE MODELS DO NOT DIFFER TOO MUCH EXCEPT WITH
THE SPEED AND STRENGTH OF THE WAVE MOVING ACROSS THE EASTERN
ALEUTIANS ON MONDAY. 12Z GFS WANTS TO MOVE IT QUICKLY INTO THE GULF
WHEREAS THE OTHER MODELS HOLD BACK ON THE LOW TO REMAIN OVER THE
ALASKA PENINSULA A BIT LONGER. THIS IS POSSIBLY DUE TO THE FACT A
SHORT WAVE TROUGH WILL BE DIGGING INTO THE BERING NEAR 180 TO AMPLIFY
RIDGE A BIT IN THE GULF IMPEDING THE PROGRESS OF THE LOW. THE
ECMWF...CANADIAN...AND UKMET ARE EVEN MORE SOLD ON THIS PROGRESSION.
THEREFORE...WILL LEAN AWAY FROM 12Z GFS. HAVE MOSTLY STUCK WITH 00Z
GFS RUN. IN THE MEANTIME...THE WEAK TROUGH OVER THE WEST COAST OF
ALASKA TO DISSIPATE AS THE LOW IN THE SOUTHERN GULF MOVES EAST. RIDGE
OF HIGH PRESSURE TO REMAIN OVER THE EASTERN INTERIOR. SHORT WAVE
TROUGH MOVING OUT OF THE NORTH PACIFIC TO MERGE WITH TROUGH
DEVELOPING OVER THE BERING SEA. THE DEVELOPING TROUGH OVER THE BERING
SEA IS A RESULT OF A SHORT WAVE MOVING OUT OF THE POLAR REGION. THE
TWO MERGE ON SUNDAY NEAR 170W. THE TROUGH TO BECOME NEGATIVELY TILTED
BY MONDAY AFTERNOON AS THE SOUTHERN WAVE TO MOVE THROUGH AS A CLOSED
LOW DEVELOPS NEAR SAINT LAWRENCE ISLAND. ANOTHER SHORT WAVE MOVING
SOUTH IN THE WESTERN BERING TO CARVE THE TROUGH FARTHER TUESDAY. BY
THIS TIME...THE JET ASSOCIATED WITH THE ALASKA PENINSULA LOW TO SLIDE
EAST AND ALLOW THE SURFACE LOW TO FILL. THE WAVE IN THE WESTERN
BERING CONTINUES TO DIG THE TROUGH OVER THE CENTRAL BERING WEDNESDAY.
THE LOW OVER THE WESTERN GULF TO PUSH INLAND. THE BERING LONG WAVE
TROUGH TO EVENTUALLY SWING OVER THE MAINLAND LATER IN THE WEEK WITH A
RIDGE OVER THE BERING. A STRONG LOW TO MOVE INTO THE WESTERN BERING
SATURDAY.

SURFACE WEST OF THE ALASKA RANGE...WEAK TROUGH ALONG THE WEST COAST
DISSIPATING THIS EVENING. ISOLATED SHOWERS OVER MUCH OF THE AREA
THROUGH TONIGHT. A RELATIVELY STRONG PRESSURE GRADIENT IS PRESENT IN
THE EASTERN AND CENTRAL ALEUTIANS DUE TO THE TROUGH ALONG THE COAST
AND HIGH PRESSURE OVER THE WESTERN BERING. STRONG WINDS TO DISSIPATE
TONIGHT AS THE TROUGH DISSIPATES. BIG STORY IS THE LOW MOVING OUT OF
THE NORTHERN PACIFIC TO THE CENTRAL ALEUTIANS TOMORROW AND THEN TO
THE ALASKA PENINSULA MONDAY. AS THE LOW MAKES ITS WAY TO THE CENTRAL
ALEUTIAN TOMORROW AFTERNOON...HEAVY PRECIPITATION TO ARRIVE AS WELL
AS STRONG WINDS. WRAP AROUND WINDS WILL BE STRONG AS WELL. WHEN THE
LOW MOVES TO THE EASTERN ALEUTIAN CHAIN SUNDAY NIGHT...THE NORTH
WINDS BEHIND IT WILL INCREASE TO POSSIBLE HIGH WIND CRITERIA DUE TO
THE STRONG BAROCLINIC ZONE WRAPPED IN THIS LOW. THESE WINDS TO WEAKEN
OVER THE DAY TUESDAY AS THE LOW FILLS A BIT WHEN IT MOVES TO THE
ALASKA PENINSULA. THE LOW WILL FILL FURTHER AS IT COLLAPSES BACK TO
THE UPPER LOW OVER THE EASTERN BERING/BRISTOL BAY TUESDAY AND
WEDNESDAY. A FRONT WILL PUSH NORTH THROUGH THE GULF AT THIS TIME. A
COUPLE OF WAVES ROTATING SOUTH ACROSS THE BERING TO BRING ENHANCED
NORTHERLY WINDS AND COLD AIR ADVECTION MONDAY AND TUESDAY. LOW TO
WRAP IN THE BERING WITH PLENTY OF SHOWER ACTIVITY THROUGH THURSDAY. A
STRONG FRONT TO MOVE INTO THE WESTERN BERING FRIDAY AND INTO THE
CENTRAL BERING SATURDAY. THE LOW ASSOCIATED WITH THE FRONT WILL MOVE
TO SHEMYA SATURDAY.

SURFACE EAST OF THE ALASKA RANGE...WEAKENING FRONT ALONG THE NORTH
GULF COAST TO BE PUSHED AWAY WITH RIDGING INLAND. THIS IS CREATING
SOME STRONG WINDS THROUGH GAPS THIS AFTERNOON AND WILL DISSIPATE THIS
EVENING AS IT PULLS AWAY FROM THE COAST. IN ADDITION...THE LOW
PULLING ACROSS THE SOUTHERN GULF TO HELP PULL TO PRECIP BAND SOUTH AS
WELL. GRADIENT WRINGING THE GULF TO REMAIN MODERATE WITH SMALL CRAFT
WINDS AND SEAS TO REMAIN THROUGH TOMORROW MORNING BEFORE THE LOW
WEAKENS AND MOVES NEAR CHARLOTTE ISLANDS. HIGH PRESSURE OVER THE
INLAND AREA TOMORROW...TO RESULT IN MAINLY DRY DAYS INTO MONDAY. THE
LOW MOVING UP THE ALEUTIAN CHAIN TO BRING STRONGER WINDS TO THE
WESTERN GULF MONDAY AFTERNOON WITH A FRONT REACHING KODIAK ISLAND.
THE FRONT TO MAKE TO THE NORTHERN GULF COAST MONDAY NIGHT WITH STRONG
WINDS. THE MAIN LOW TO REMAIN NEAR BRISTOL BAY WITH A FRONT ALONG THE
COAST INTO WEDNESDAY. THE FRONT TO DISSIPATE WEDNESDAY NIGHT INTO
THURSDAY. HOWEVER...AREA IS UNDER A BROAD TROUGH AT THIS TIME WITH
SCATTERED PRECIPITATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH ZONE 185
MARINE...GALE 170 171 172
FIRE WEATHER...NONE

JN SEP 06