Small Craft Advisory 689, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT FRI AUG 24 2007

.ANALYSIS...
STACKED LOW PRESSURE SYSTEM OVER THE NORTHERN GULF WITH ANOTHER OVER
THE WESTERN BERING. A FRONT STRETCHES FROM THE NORTHWEST BERING LOW
TO THE EASTERN ALEUTIANS. HIGH PRESSURE IS IN BETWEEN THE TWO
SYSTEMS. WINDS ALONG THE FRONT ARE AROUND GALE FORCE BUT QUICKLY
DIMINISHING. THIS IS TRUE ALSO FOR THE WINDS ALONG THE NORTHERN GULF
WITH THE GULF LOW. STILL SEEING QUITE A BIT OF SHOWERS CIRCULATING
AROUND THE GULF LOW. A SECONDARY BAND AROUND THE LOW STRETCHES OVER
THE ALASKA AND ALEUTIAN RANGE. SHOWERS FARTHER INLAND HAVE DIMINISHED
QUITE RAPIDLY THIS MORNING AND EARLY AFTERNOON. SOME BREAKS IN CLOUDS
HAVE ALLOWED PLACES TO WARM. WITH THE SURFACE HEATING...LIKELY WILL
SEE SOME CONVECTIVE SHOWERS WITH A SLIGHT CHANCE OF THUNDERSTORMS
OVER THE HIGHER TERRAIN THIS AFTERNOON AND EVENING. WITH THE EASTERLY
FLOW MODERATE...SOME OF THESE SHOWERS WILL DRIFT OVER THE VALLEYS.
ONSHORE FLOW OVER THE YUKON AND KUSKOKWIM DELTAS KEEPING LOW TO MID
CLOUDS THERE. THE CLEARING OF CLOUD COVER TO HAPPEN OVER MUCH OF THE
INTERIOR OUTSIDE OF THE DELTAS. THEREFORE...WITH PLENTY OF RESIDUAL
LOW LEVEL MOISTURE FOG WILL BE LIKELY AGAIN TONIGHT.

.MODEL DISCUSSION AND UPPER LEVELS...
MODELS INITIALIZED WELL THIS MORNING WITH THE GFS PROBABLY THE BEST
INITIALIZED. AT THE UPPER LEVELS AND SURFACE SYNOPTICALLY...THE
MODELS ARE IN FAIRLY GOOD AGREEMENT TODAY ON THE PROGRESSION OF ALL
FEATURES THROUGH MID NEXT WEEK. THE DIFFERENCE COMES WITH THE SMALL
SCALE FEATURES.

THE UPPER LOW IN THE GULF TO MOVE INTO THE EASTER GULF SATURDAY AND
DISSIPATE OVER THE PANHANDLE SUNDAY. THE PUSH IS CREATED BY THE
NORTHWEST BERING LOW LEAVING ITS POSITION AND CROSSING THE CHAIN NEAR
DUTCH HARBOR SATURDAY NIGHT. THE LOW MOVES INTO THE WESTERN GULF
MONDAY. MEANWHILE...A RIDGE BUILDS OVER THE BERING. THE LOW SETS INTO
THE CENTRAL GULF BY THURSDAY WITH THE RIDGE REMAINING OVER THE
BERING. A COUPLE SHORT WAVE TROUGHS WILL MOVE THROUGH THE RIDGE NEXT
WEEK KNOCKING IT DOWN A BIT.

.SHORT TERM FORECAST...
ALEUTIAN AND BERING...
STRONG LOW NEAR 56N 165E WITH A FRONT STRETCHING FROM ITS CENTER TO
THE CENTRAL ALEUTIANS. MODERATE WINDS ALONG THIS FRONT NOW AS IT HAS
STRETCHED QUITE A BIT OVERNIGHT AND THROUGH TODAY. A STRONG JET
COUPLED WITH AN UPPER LEVEL WAVE TO SWING THE LOW OUT OF THE WESTERN
BERING TO THE CENTRAL BERING SATURDAY THEN CROSS INTO THE NORTHERN
PACIFIC SOUTH OF SAND POINT SUNDAY. RAIN TO ENCIRCLE THE LOW THROUGH
ITS PROGRESSION ACROSS THE BERING. THE LOW FULLY MOVES INTO THE GULF
MONDAY ALLOWING HIGH PRESSURE TO STRETCH OVER THE ENTIRE BERING.

WESTERN ALASKA...
SHOWERS WRAPPING AROUND THE LOW IN THE GULF STRETCHING OVER THE
MOUNTAINS OF ZONES 151 AND 161. SOME INSTABILITY AS WELL MAY LEAD TO
A FEW THUNDERSTORMS THIS AFTERNOON AND EVENING. ONSHORE FLOW LEAVING
LOW TO MID CLOUDS OVER THE YK DELTA. THE SHOWERS ASSOCIATED WITH THE
GULF LOW TO PULL OFF TONIGHT. HOWEVER...ENOUGH RESIDUAL MOISTURE AND
INSTABILITY FOR ISOLATED SHOWERS AND THUNDERSTORMS MAINLY OVER THE
HIGHER TERRAIN. THE FLOW IS LIGHT ALOFT...SO MOST WILL NOT MAKE IT
INTO THE VALLEYS. THE BERING LOW CROSSES NEAR COLD BAY SATURDAY NIGHT
WITH SOME INCREASE IN WIND ACROSS THE AKPEN. GALE FORCE WINS WILL BE
FELT ALONG THE AKPEN TO COLD BAY. THIS WILL ALSO BRING SOME MORE
DRYING INLAND WITH AN INCREASED EASTERLY FLOW. AS THE LOW WRAPS IN
THE GULF MONDAY...SOME SHOWERS TO FILTER OVER INTO WESTERN ALASKA.

SOUTH CENTRAL...
LOW NEAR MIDDLETON ISLAND STARTING TO PULL AWAY FROM THE COAST THIS
AFTERNOON. PLENTY OF SHOWERS AROUND THE LOW WITH MORE ISOLATED
ACTIVITY FARTHER INLAND. WINDS ARE DIMINISHING NEAR THE LOW AS IT
FILLS TODAY AND TONIGHT AND DRAG SOUTHEAST. THE BIG QUESTION IS
WHETHER SOUTH CENTRAL WILL EXPERIENCE A EASTERLY WAVE AROUND THIS
LOW. THERE IS A CHANCE OF THIS HAPPENING BEFORE THE RIDGE BUILDS IN
TOO MUCH. RIGHT NOW...BELIEVE A WEAK WAVE TO MOVE ACROSS THE COPPER
RIVER BASIN TOMORROW AND WEAKEN BEFORE REACHING THE SUSITNA VALLEY.
HOWEVER...ENOUGH INSTABILITY FROM THE AIR MASS AND THE WAVE FOR
SHOWERS TO DEVELOP OVER THE MOUNTAINS EAST OF ANCHORAGE...PALMER AND
TALKEETNA. THEREFORE...WILL HAVE MENTION OF SHOWERS IN THE FORECAST
FOR SATURDAY NIGHT. AFTER THIS...HIGH PRESSURE BUILDS OVER THE
INTERIOR ALLOWING ONLY ISOLATED MOUNTAIN SHOWERS SUNDAY.
MEANWHILE...THE BERING LOW CROSSES INTO THE WESTERN GULF SUNDAY FOR
GALE FORCE WINDS AROUND KODIAK AND INCREASING SHOWERS THERE AS WELL.
SHOWERS AND WINDS TO INCREASE OVER THE GULF SUNDAY NIGHT AS THE LOW
SITS OVER THE SOUTHERN GULF. SOME SHOWERS TO MAKE ITS WAY ONTO THE
NORTHERN COAST AS WELL.

.LONG TERM FORECAST...
A COUPLE UPPER LEVEL WAVES TO RUN ACROSS THE RIDGE IN THE BERING WITH
THE FIRST MOVING INTO THE AREA MONDAY NIGHT BRINGING SOME SHOWERS TO
THE WESTERN AND CENTRAL BERING. A STRONGER WAVE POSSIBLE
TUESDAY/WEDNESDAY FOR MORE ORGANIZED PRECIP TO THE WESTERN ALEUTIANS
THROUGH THURSDAY.

SHOWERS FROM THE GULF LOW TO REMAIN OVER WESTERN ALASKA THROUGH
TUESDAY. AFTER THAT...A SOMEWHAT DRY NORTHERLY FLOW AIR MASS OVER THE
AREA THROUGH THURSDAY. MAY SEE SOME INSTABILITY SHOWERS OVER THE
MOUNTAINS ONCE AGAIN.

THE LOW WEAKENS IN THE GULF TUESDAY THROUGH THURSDAY WITH SHOWERS
WRAPPING AROUND THE ENTIRE GULF. SOME SHOWERS TO SPRAY INTO THE
MAINLAND AS WELL AS SOME SHORT WAVE TROUGHS AROUND THE LOW ARE
POSSIBLE THROUGH THE PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...NONE

JN AUG 07