Small Craft Advisory 655, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
110 PM AKDT SUN AUG 31 2008

.ANALYSIS AND UPPER LEVELS...A STRONG VERTICALLY STACKED LOW JUST
SOUTH OF KODIAK ISLAND IS THE PRIMARY WEATHER PRODUCER TODAY. THE
SURFACE PRESSURE BOTTOMED OUT AROUND 970 MB EARLY THIS MORNING AND
IS NOW SLOWLY RISING AS THE LOW TRACKS SLOWLY TOWARD KODIAK ISLAND.
QUIKSCAT WINDS SHOW WIDESPREAD GALES NEAR THE LOW CENTER AND
EXTENDING OUT ALONG THE OCCLUSION ACROSS THE KODIAK ISLAND WATERS.
THERE IS ALSO AN AREA OF STORM FORCE WINDS SOUTHEAST OF THE LOW
CENTER WHICH WAS CONFIRMED BY BUOY 46066 WHICH RECORDED A GUST TO
58 KT AND A SIGNIFICANT WAVE HEIGHT OF 26 FT EARLIER THIS MORNING.
THIS VERY SIGNIFICANT WAVE TRAIN IS MOVING NORTHWARD ACROSS
THE WESTERN GULF. RIDGING ALONG THE NORTH GULF COAST COMBINED WITH
STRONGER WINDS APPROACHING SOUTHCENTRAL AHEAD OF THE OCCLUSION ARE
PRODUCING STRONG WINDS THROUGH THE USUAL EAST-WEST GAPS IN THE
COASTAL MOUNTAINS. RADAR IMAGERY SHOWS THE FRONTAL RAIN BAND
APPROACHING THE NORTH GULF COAST WHILE ANOTHER BAND MOVES WESTWARD
ACROSS BRISTOL BAY. THE EAST SIDE OF KODIAK ISLAND HAS BEEN OBSERVING
MODERATE TO HEAVY RAIN ALL MORNING WITH 0.75 INCHES OF RAIN MEASURED
FROM 12Z AND 18Z.

ASIDE FROM THIS MAJOR STORM...A WEAK SURFACE LOW SOUTH OF THE
ALEUTIANS IS TRACKING EASTWARD WITH LITTLE IMPACT ON THE ALEUTIANS.
OTHERWISE FAIRLY QUIET CONDITIONS BETWEEN THE TWO LOWS.

.MODEL DISCUSSION...ALL MODELS INITIALIZED TOO WEAK WITH THE CENTRAL
PRESSURE OF THE LOW SOUTH OF KODIAK THIS MORNING...BUT AS MENTIONED
ABOVE MODELS ARE VERIFYING WELL WITH THE WIND FORECAST. MODELS
CONTINUE TO AGREE WITH MOVEMENT OF LOW OVER KODIAK ISLAND...BUT
THEN THE ECMWF/NAM MOVE THE LOW WESTWARD TO BRISTOL BAY WHILE THE
UKMET/GFS WEAKEN IT OVER KODIAK ISLAND. THINK THE MORE LIKELY
SOLUTION IS A WEAKENING SURFACE LOW REMAINING OVER KODIAK ISLAND
AND A SECONDARY VERY WEAK LOW FORMING IN BRISTOL BAY AS THE UPPER
LOW DRIFTS BACK WESTWARD. SINCE WIND SPEEDS IN THE VICINITY WILL BE
FAIRLY LIGHT AT THIS POINT THE ONLY IMPACT WILL BE ON WIND DIRECTION.

THERE ARE ALSO DIFFERENCES IN THE TRACK OF THE LOW SOUTH OF THE
ALEUTIANS AS IT APPROACHES KODIAK ISLAND MONDAY NIGHT AND TUESDAY.
THE NAM IS AN OUTLIER AND THE OTHER THREE MODELS ARE IN THE
BALLPARK...SO WILL STICK WITH THE GFS SOLUTION WHICH HAS BEEN
REASONABLY CONSISTENT. FOR THE SAME REASONS WILL ALSO USE GFS OUT
WEST WITH LOW DROPPING ACROSS THE WESTERN BERING.

.SHORT TERM FORECAST...

SOUTHCENTRAL...WINDS WILL CONTINUE TO INCREASE ALONG THE NORTH GULF
COAST TONIGHT AS THE OCCLUSION APPROACHES. AS THE SURFACE RIDGE IS
PUSHED NORTHWARD THE ORIENTATION OF THE ISOBARS WILL SHIFT FROM
NORTH/SOUTH TO NORTHWEST/SOUTHEAST. THUS...WESTERN TURNAGAIN ARM
WINDS SHOULD DIMINISH SOME...WHILE PORTAGE VALLEY AND EASTERN
TURNAGAIN ARM WINDS REMAIN STRONG AS THEY RECEIVE THE BRUNT OF THE
FRONTAL WINDS. GALES WILL ALSO SPREAD TO THE COASTLINE WITH STRONGER
GUSTS THROUGH CHANNELED AREAS. WINDS WILL QUICKLY DIMINISH ACROSS
THE REGION DURING THE DAY MONDAY AS THE LOW WEAKENS OVER KODIAK
ISLAND. RAIN...HEAVY AT TIMES...WILL REMAIN MAINLY ALONG THE COAST.
DOWNSLOPING WINDS WILL LIMIT PRECIPITATION ON LEE SIDE OF THE COASTAL
RANGE TO A FEW SPRINKLES OR SHOWERS. THERE WILL BE LITTLE TO NO BREAK
IN RAIN ALONG THE COAST AS THE NEXT LOW MOVES TO KODIAK ISLAND LATE
TUESDAY. THIS LOW DOES LOOK LIKE IT WILL TRACK FARTHER
NORTH...HEADING INLAND OVER SOUTHWEST ALASKA. THEREFORE...EXPECT
ANOTHER ROUND OF TURNAGAIN ARM WINDS...BUT ALSO A CHANCE OF RAIN
ACROSS THE ENTIRE REGION MID WEEK AS THE UPPER FLOW BECOMES
SOUTHERLY.

SOUTHWEST...BANDS OF RAIN OR SHOWERS ALONG WITH GUSTY WINDS WILL
PERSIST THROUGH MONDAY NIGHT ACROSS BRISTOL BAY AS UPPER LEVEL
WAVES AND MOISTURE FROM THE LOW ROTATE WESTWARD FROM THE KODIAK
LOW. DONT EXPECT MORE THAN A FEW SHOWERS TO MAKE IT NORTH AND
WEST TO THE KUSKOKWIM DELTA AND KUSKOKWIM VALLEY.  MORE RAIN WILL
OVERSPREAD THE REGION TUESDAY THROUGH WEDNESDAY AS THE NEXT LOW
TAKES A TRACK OVER SOUTHWEST ALASKA.

BERING SEA/ALEUTIANS...THE BERING SEA WILL REMAIN IN THE CENTER OF
THE UPPER TROUGH AWAY FROM THE MAJOR SYSTEMS DEVELOPING AND TRACKING
ALONG THE TROUGH EDGES. THUS GENERALLY QUIET CONDITIONS WILL PERSIST
ACROSS THE REGION.

.LONG TERM FORECAST...LOW CONFIDENCE IN THE EXTENDED FORECAST
PERIOD AS UPPER LEVELS ARE IN TRANSITION. THE END RESULT OF
MAINTAINING A MEAN TROUGH OVER THE ALASKA REGION IS THE SAME.
THIS JUST LOOKS LIKE A SHORT PERIOD OF TRANSITIONING SHORT-WAVE
TROUGHS WHICH MAKES PLACEMENT OF PARTICULAR SYSTEMS DIFFICULT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 120 130 132 138 140 150.
FIRE WEATHER...NONE.

SEB AUG 08