Small Craft Advisory 598, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT FRI AUG 9 2013

.MODEL DISCUSSION...
MODEL INITIALIZATIONS ON THE SYNOPTIC FEATURES WERE OK THIS MORNING.
NOTABLE DIFFERENCES OCCUR AT THE UPPER LEVELS. THE THE GFS/ECMWF
BRING A WELL DEFINED SHORT WAVE FROM THE GULF TO OVER SOUTHCENTRAL
ALASKA SAT AFTERNOON. THE NAM IS ABOUT 6 HRS SLOWER WITH THIS
FEATURE. THIS WAS ALSO THE TREND ON THE 06Z RUN. THE TIMING OF
FRONTAL PRECIPITATION INTO THE GULF SEEMS TO BE RELATIVELY CLOSE.
SURFACE PRESSURE CENTERS BECOME SOMEWHAT MORE DIFFICULT TO COORDINATE
IN THE GULF/SOUTHCENTRAL AS THEY BECOME PROGRESSIVELY WEAKER WITH
TIME. OUT WEST...MOST SEEM TO HANDLE THE WEAKENING LOW NEAR THE DELTA
OK AND ARE COMING INTO BETTER AGREEMENT ON THE HANDLING OF A LOW
MOVING NORTH TOWARD THE ALEUTIANS SUN.

.ANALYSIS AND UPPER LEVELS...
THIS MORNINGS WATER IMAGERY SHOWS A SHORT WAVING NORTH ACROSS
SOUTHCENTRAL AND A SECONDARY WAVE MOVING OVER KODIAK ISLAND. A RATHER
BROAD BAND OF MOISTURE IS ALSO STREAMING NORTH ACROSS THE GULF. THERE
IS ALSO SIGNIFICANT DRYING IN THE UPPER LEVELS BEHIND THE WAVE NEAR
KODIAK. THE STACKED UPPER CENTER SHOWS UP NICELY NEAR NUNIVAK ISLAND
AS WELL AS THE NEXT SHORT WAVE PUSHING SOUTH ACROSS THE EASTERN
BERING SEA.

THE DRYING BEHIND THE WAVE TOWARD KODIAK IS PUSHING EASTWARD SOME AND
HAS HELPED CHANGE THE ORIENTATION OF THE SURFACE FRONT WHICH HAS
SHIFTED NORTH AND EAST. THE RESULT HAS BEEN A REDUCTION IN THE
PRECIPITATION ACROSS COOK INLET AND THE WESTERN KENAI WHILE
CONTINUING WIDESPREAD RAIN ALONG THE GULF AND SUSITNA VALLEY.
PRECIPITATION WILL BECOME SOMEWHAT MORE WIDESPREAD AGAIN ON SAT AS
THE NEXT WAVE ROUNDS THE BASE OF THE TROUGH AND HEADS NORTH TOWARD
SOUTHCENTRAL.

THE STACKED LOW OVER NUNIVAK ISLAND LOOKS LIKE ITL WILL FINALLY MAKE
SOME HEADWAY NORTH AND EAST LATE SUNDAY AS A SHARPENING TROUGH OVER
THE BERING SEA COMES IN PHASE WITH SHORT WAVE MOVING TOWARD THE
ALEUTIANS. WEAK RIDGING BETWEEN THE TWO SYSTEMS WILL MOVE OVER THE
EASTERN BERING SEA SUN/SUN NIGHT.

.SHORT TERM FORECAST...

.SOUTHCENTRAL...
THE FRONTAL TROUGH OVER THE GULF WILL CONTINUE TO SLOWLY MOVE EAST
THROUGH SAT. RAIN AND SHOWERS ARE EXPECTED TO DIMINISH SOME ACROSS
THE AREA AFTER THE PASSAGE OF THE NEXT WAVE SAT. PRESSURE GRADIENTS
AND RESULTANT GAP FLOWS SHOULD WEAKEN SOME INLAND OVERNIGHT.
HOWEVER...BARRIER JET CONDITIONS WITH THE ADVANCING FRONTAL SYSTEM
WILL KEEP STRONG WINDS ALONG THE EASTERN GULF INTO SAT MORNING. GAP
FLOWS WILL ALSO INCREASE AGAIN ACROSS COPPER RIVER SAT. WINDS WILL BE
MUCH LITTLE LIGHTER ACROSS THE REGION AS GRADIENTS RELAX SAT NIGHT
AND SUN.

SOUTHWEST ALASKA...SHOWERS AND AREAS OF LIGHT RAIN WILL CONTINUE INTO
SUNT WITH THE PROXIMITY OF THE UPPER LOW CENTER NEAR NUNIVAK ISLAND.
CONDITIONS WILL BECOME MUCH MORE STABLE SUN NIGHT INTO MON WITH A
BUILDING UPPER RIDGE. THIS WILL INCREASE THE THREAT OF LOW CLOUDS AND
FOG ACROSS THE REGION...ESPECIALLY ALONG THE COASTS.

BERING SEA AND ALEUTIANS...RIDGING SPREADING ACROSS THE REGION WILL
BRING INCREASED STABILITY WITH LOW CLOUDS AND FOG THROUGH THE
WEEKEND.

.LONG TERM FORECAST...
THERE WILL BE A SHIFT IN THE PATTERN NEXT WEEK WITH THE MAIN UPPER
LOW BEING OVER THE WESTERN BERING INSTEAD OF THE EASTERN
BERING/SOUTHWEST MAINLAND COAST. THERE IS STILL A LOT OF UNCERTAINTY
DURING THIS TIME SO WE KEPT THE FORECAST FAIRLY GENERAL FOR NOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 120.
FIRE WEATHER...NONE.

RMC AUG 13