Small Craft Advisory 808, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT SUN SEP 30 2007

.MODEL DISCUSSION...
POSITIONS OF THE LOW THIS MORNING WERE INITIALIZED WELL.
HOWEVER...THE WAVE MOVING NORTH THROUGH THE GULF WAS DEPICTED SLOWER
THAN REALITY. THEREFORE...SHOWERS HAVE BEEN DIMINISHING QUICKER THAN
GUIDANCE SUGGESTED.

VERY GOOD AGREEMENT BETWEEN MODELS THROUGH TUESDAY AFTERNOON. A LOW
ENTERS THE WESTERN ALEUTIANS TUESDAY NIGHT. THE MODELS DISAGREE ON
THE TIMING AND POSITION OF THE LOW. THE STRENGTH IS SIMILAR BETWEEN
MODELS HOWEVER. THE GFS...ITS ENSEMBLES AND THE 18Z RUN OF THE NAM
ALL SAY THE LOW WILL BE FARTHER SOUTH. THIS DIFFERS FROM LAST NIGHTS
00Z GFS AND THE EURO MODELS. THE UNCERTAINTY IS BASED UPON THE
AMPLITUDE OF THE THE TROUGH MOVING THROUGH THE BERING. THE GFS DIG IT
THE FARTHEST SOUTH WHILE THE OTHER SWING IT FASTER EAST.
HOWEVER...THE 12Z ECMWF SWUNG CLOSER TO THE 12Z GFS SOLUTION. RIGHT
NOW...WE MOVED CLOSER TO THE 12Z GFS SOLUTION TO MOVE THE LOW FASTER
TO THE EAST AND BIT FARTHER SOUTH.

.ANALYSIS...
THE MAIN LOW IS THE LARGE STACKED LOW OVER THE CENTRAL BERING.
NUMEROUS SHORT WAVE TROUGHS ROTATING AROUND THIS LOW WITH ONE MOVING
THROUGH THE SOUTHWEST AND SOUTH CENTRAL AREAS THIS MORNING. AS
MENTIONED EARLIER...MODELS A LITTLE SLOW ON THIS FEATURE. AT THE
SURFACE...THIS IS DEPICTED BY AN OCCLUDED FRONT. THE WAVE WILL BE
STRETCHED AND WEAKENED OVER THE NORTHERN GULF. BEFORE THAT...ENOUGH
GRADIENT BUILD UP ALONG THE COAST FOR MODERATE EASTERLY WINDS FROM
CORDOVA INTO TURNAGAIN ARM THIS AFTERNOON AND EVENING. SHOWERS AND
STRONG WEST TO SOUTHWEST WINDS BEHIND THE FRONT IN THE SOUTHEAST
BERING. THIS HAS LED TO THE HIGH SURF ADVISORY FOR THE SOUTHWEST
COAST. ANOTHER WAVE IS ANTICIPATED THIS EVENING ALONG THE WEST COAST.

.UPPER LEVELS...
LARGE UPPER LOW OVER THE NORTHERN BERING WITH A FEW SHORT WAVE
TROUGHS ROTATING AROUND THIS LOW. A STRONG JET JUST SOUTH OF THE
ALEUTIAN CHAIN PUSHING THE WAVES AROUND THE LOW A BIT FASTER THAN
GUIDANCE SUGGESTED. A PORTION OF THE UPPER LOW MOVES OVER THE
MAINLAND TONIGHT AND TOMORROW WITH A PORTION IN THE BERING STRAIT.
THIS LEAVES A LARGE SURFACE LOW OVER THE ENTIRE MAINLAND. THE CLOSED
LOW NEAR THE BERING STRAIT PUSHES TO THE SOUTHEAST TUESDAY AS A RIDGE
BUILDS IN THE BERING. THIS USHERS IN COLDER AIR OVER THE MAINLAND AS
WELL. A CLOSE LOW THEN MOVES TO THE KAMCHATKA PENINSULA WITH A TROUGH
EXTENDING TO THE NORTH PACIFIC. THIS TROUGH PHASES WITH A SHORT WAVE
MOVING OFF JAPAN TUESDAY NIGHT SOUTH OF SHEMYA. THIS IS WHERE THE
UNCERTAINTY STARTS. OTHER MODELS ARE A BIT FARTHER NORTH WITH THE
DEVELOPMENT OF THE LOW IN THE SOUTHERN BERING WEDNESDAY NIGHT. THE
LOW THEN FLOWS EAST QUICKLY INTO THE GULF BY FRIDAY AS IT BREAKS
UNDER THE RIDGE IN THE BERING. THE RIDGE BUILDS BEHIND THIS LOW
FRIDAY. THE LOW THEN SITS IN THE GULF THROUGH NEXT WEEKEND WITH A
NORTHWEST FLOW THROUGH THE EASTERN BERING.

.SHORT TERM FORECAST...
ALEUTIANS AND SOUTHWEST ALASKA...
LARGE LOW OVER THE NORTH CENTRAL BERING WITH GALE FORCE WINDS THROUGH
MUCH OF THE SOUTHERN BERING. THIS IS BRINGING A LARGE FETCH FOR WAVE
CREATION OVER THE SOUTHEAST BERING. COMBINED WITH HIGH TIDE THIS
AFTERNOON...A HIGH SURF ADVISORY IS IN EFFECT. RAIN AND SHOWERS
ENCIRCLE THIS LOW THROUGHOUT THE BERING AND SOUTHWEST ALASKA THIS
AFTERNOON. THE LOW MOVES INLAND TONIGHT NEAR THE KUSKOKWIM DELTA AND
THE FLOW REMAINS RATHER STRONG FROM THE WEST FOR THE SOUTHERN BERING.
MODERATE WINDS WILL BE BEHIND THIS SYSTEM FROM THE NORTHWEST AS WELL.
THE LOW CROSSES INTO SOUTH CENTRAL MONDAY WITH A GOOD SHORT WAVE
TROUGH MOVING ACROSS THE AKPEN. COMBINED WITH HIGH PRESSURE BUILDING
IN THE WESTERN BERING CREATING A GOOD SURFACE PRESSURE
GRADIENT...THIS WILL LIKELY INCREASE THE WINDS TO NEAR 60 MPH GUSTS.
IN ADDITION...A HIGH SURF ADVISORY MAY BE NEEDED AGAIN TOMORROW FOR
WESTERLY FACING SHORES IN SOUTHWEST ALASKA. HIGH PRESSURE BUILDS
CONTINUALLY IN THE BERING THROUGH WEDNESDAY WITH A STRONG NORTHWEST
COLD FLOW THROUGH THE EASTERN BERING. THIS WILL CONTINUE THE STRONG
WINDS THROUGH THE AKPEN AND EASTERN BERING. SHOWERS WILL LIKELY
CONTINUE BUT BE LESS IN COVERAGE ON WEDNESDAY FOR SOUTHWEST ALASKA
AND THE EASTERN ALEUTIANS. MOST PRECIP WILL END OVER THE REMAINDER
MONDAY NIGHT UNTIL THE LOW PUSHES TO THE WESTERN ALEUTIANS FROM THE
NORTH PACIFIC WEDNESDAY WITH GALE FORCE WINDS AND MODERATE TO HEAVY
PRECIP.

SOUTH CENTRAL ALASKA...
A FRONT ALONG THE COAST SUPPORTED BY AN UPPER LEVEL WAVE BRINGING
RAIN TO MOST OF SOUTH CENTRAL. A RIDGE DEVELOPED AHEAD OF THE FRONT
AND HAS CREATED SOME STRONGER WINDS NEAR THE NORTHERN GULF COAST INTO
THE SOUND. THESE WINDS WILL DIMINISH THIS EVENING AS THE FRONT SWINGS
INLAND. RAIN WILL ALSO TURN TO MORE SHOWERY WEATHER AT THIS POINT AS
WELL. A LOW DEVELOPS IN THE NORTHERN GULF COAST AS ANOTHER WAVE MOVES
THROUGH TONIGHT. THIS LOW WILL DISSIPATE INLAND TOMORROW BUT A TROUGH
OF LOW PRESSURE WILL REMAIN IN THE GULF AS THE UPPER LOW MOVES OVER
SOUTH CENTRAL. WITH A BIG LOW IN THE BERING MOVING INTO THE MAINLAND
MONDAY AND TUESDAY AND MANY WAVES ROTATING AROUND...INSTABILITY
SHOWERS ARE POSSIBLE THROUGH TUESDAY. THE FLOW THEN TURNS MORE
NORTHWEST WITH COOLER AIR FILTERING INTO THE AREA. THE AIR MASS WILL
DRY SLOWLY THROUGH TUESDAY WITH COLDER AIR CONTINUING TO MOVE INTO
SOUTH CENTRAL ALASKA. ONLY ISOLATED MOUNTAIN SNOW SHOWERS ARE
EXPECTED BY WEDNESDAY.

.LONG TERM FORECAST...A LOW MOVES THROUGH THE SOUTHERN BERING
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT WITH STRONG WINDS AND MODERATE
PRECIP. STORM FORCE WINDS ARE DEFINITELY POSSIBLE WITH THIS LOW AS IT
DIGS TO THE MID 970S THURSDAY. THE LOW MOVES TO THE GULF FRIDAY WITH
RAIN MAINLY ALONG THE COASTAL AREAS. GALE TO STORM FORCE WINDS ARE
ALSO POSSIBLE IN THE GULF. THE LOW GRADUALLY WEAKENS THROUGH THE
WEEKEND. NOT MUCH PRECIPITATION OUTSIDE OF THE VICINITY OF THIS LOW
THROUGH THE PERIOD EXCEPT ISOLATED SNOW SHOWERS IN SOUTH CENTRAL
WEDNESDAY NIGHT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH SURF ADVISORY 155 AND 161
MARINE...GALE 132 150 155 160 165 170 172 179
FIRE WEATHER...NONE

JN SEP 07