Small Craft Advisory 927, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
130 PM ADT SAT NOV 3 2007

.ANALYSIS AND UPPER LEVELS...TROUGH CENTERED OVER THE NORTHERN GULF
AND SOUTHCENTRAL IS PROGRESSING EASTWARD TOWARD CANADA. THERE IS A
WEAK SURFACE LOW NEAR MIDDLETON ISLAND WITH SHOWERS ROTATING ACROSS
THE PRINCE WILLIAM SOUND REGION. ELSEWHERE ACROSS SOUTHCENTRAL
PRECIPITATION HAS MOSTLY ENDED WITH THE EXCEPTION OF A FEW SHOWERS.
SKIES CLEARED THIS MORNING OVER THE KENAI PENINSULA/COOK INLET
REGION AND FOG IS NOW FORMING. AS CLOUDS DECREASE THIS AFTERNOON
AND EVENING ACROSS THE REST OF SOUTHCENTRAL EXPECT A SIMILAR OUTCOME.
OUT OVER THE WESTERN BERING SATELLITE IMAGERY SHOWS A NEARLY
STATIONARY MATURE LOW WITH SURFACE FRONT EXTENDING ACROSS THE
NORTHERN BERING AND THEN SOUTHEASTWARD ACROSS THE EASTERN BERING
SEA AND SOUTHERN AKPEN. A SHORT-WAVE IN THE VICINITY OF 170W IS
BEING DRIVEN EASTWARD BY STRONG WESTERLY FLOW INTO THE BASE OF A
SHORT-WAVE RIDGE. THIS IS SERVING TO CUT OFF THE RIDGE AT ITS BASE.
THE SHORT-WAVE IS BEGINNING TO LIFT NORTHEASTWARD AS IT BUMPS UP
AGAINST THE RIDGE. THE BERING LOW AND FRONT ARE BOTH WEAKENING SO
WINDS ARE ON THE WAY DOWN ACROSS THE REGION. GALE FORCE WINDS ARE
STILL BEING OBSERVED ALONG THE FRONT AND IN THE VICINITY OF THE LOW.

.MODEL DISCUSSION...NAM IS A BIT OFF ON THE LOCATION OF THE BERING
SEA LOW. OTHERWISE MODELS INITIALIZED WELL AND ARE IN GOOD AGREEMENT
THROUGH ABOUT 36 HOURS (SUN AFTERNOON). SOLUTIONS THEN QUICKLY
DIVERGE AFTER THAT SO FORECAST CONFIDENCE GOES DOWN SIGNIFICANTLY
FARTHER OUT IN TIME. SPREAD IN GFS ENSEMBLE ALSO BECOMES RATHER
LARGE VERY QUICKLY. WITH PACIFIC LOW HEADED FOR THE GULF SUNDAY
NIGHT COORDINATED WITH JUNEAU TO TAKE A POSITION CLOSE TO THE NAM.
THE GFS HAS BEEN CONSISTENTLY FARTHEST SOUTH AND EAST WITH ITS TRACK
WHILE THE ECMWF HAS BEEN CONSISTENTLY FARTHEST NORTH AND WEST. THE
12Z ECMWF MADE A BIG JUMP TOWARD THE GFS AND IS NOW BETWEEN THE NAM
AND GFS ALONG WITH THE UKMET. SINCE THIS WILL BE A LARGE JUMP FROM
PREVIOUS FORECAST WILL STICK CLOSE TO THE NAM POSITION FOR NOW. WITH
OTHER SYSTEMS DEVELOPING IN MASSIVE CIRCULATION OUT WEST LITTLE
CHANGE WILL BE MADE DUE TO THE GREAT UNCERTAINTY IN LOCATION AND
DEPTH OF THESE SYSTEMS.

.SHORT TERM FORECAST...

SOUTHCENTRAL...PARTIAL CLEARING TONIGHT WILL ALLOW FOR DECENT
RADIATIONAL COOLING AND THE FORMATION OF FOG. WOULD EXPECT AT
LEAST ISOLATED AREAS OF DENSE FOG. CLOUDS WILL INCREASE OVER
WESTERN PORTIONS OF SOUTHCENTRAL AFTER MIDNIGHT AS THE FRONT
OVER THE BERING SEA APPROACHES. THE FRONT WILL STALL ALONG SHELIKOF
STRAIT/COOK INLET CORRIDOR SUNDAY AS SHORT-WAVES OVER EASTERN
BERING/SOUTHWEST ALASKA ROTATE NORTHWARD AND UPPER RIDGE BUILDS
UP A BIT OVER SOUTHCENTRAL. THIS WILL KEEP HIGHEST CHANCES OF
PRECIPITATION FROM KODIAK ISLAND TO COOK INLET AND THE ALASKA RANGE.
WEAK UPPER WAVES MOVING ACROSS GULF WILL ALSO BRING SHOWERS TO
THE NORTH GULF COAST. ELSEWHERE OVER SOUTHCENTRAL EXPECT JUST A
SMALL CHANCE OF SHOWERS. WITH COLD AIR NOW IN PLACE PRECIPITATION
FOR ALL BUT KODIAK ISLAND AND THE IMMEDIATE GULF COAST WILL BE IN
THE FORM OF SNOW. PRECIPITATION WILL GRADUALLY TAPER OFF SUNDAY
NIGHT AND MONDAY AS FRONT DISSIPATES AND UPPER LEVEL RIDGE
STRENGTHENS SLIGHTLY AHEAD OF NEXT SYSTEM. ALTHOUGH SOME UNCERTAINTY
EXISTS IN STRENGTH AND TRACK OF NEXT LOW COMING UP TOWARD KODIAK
ISLAND...PRECIPITATION AND WIND ARE LIKELY FOR THE GULF COASTAL
REGIONS HEADING THROUGH THE DAY TUESDAY.

SOUTHWEST ALASKA...THE FRONT WILL BEGIN TO IMPACT THE IMMEDIATE
COAST THIS AFTERNOON AND THEN MOVE INLAND TONIGHT INTO SUNDAY
MORNING. AIR MASS OVER SOUTHWEST ALASKA IS COLD ENOUGH FOR ALL SNOW.
HOWEVER THERE IS SLIGHTLY WARMER AIR RIGHT ALONG THE FRONT. STRONG
SURFACE WINDS ALONG THE FRONT WILL ALSO HELP TO PRODUCE ENOUGH MIXING
NEAR THE COAST TO WARM SURFACE TEMPERATURES ABOVE FREEZING.
THEREFORE..EXPECT PRECIPITATION TO MIX WITH OR CHANGE TO RAIN
BRIEFLY ALONG THE IMMEDIATE COAST. COLDER AIR BEHIND THE FRONT WILL
TREND PRECIPITATION QUICKLY BACK TOWARD ALL SNOW. A DRYING TREND
WILL TAKE PLACE SUNDAY NIGHT AND MONDAY AS A WEAK UPPER RIDGE BUILDS
OVERHEAD AHEAD OF THE NEXT SYSTEM TRACKING TOWARD KODIAK ISLAND.
THIS SYSTEM WILL LIKELY IMPACT BRISTOL BAY WITH PRECIPITATION AND
WIND ON TUESDAY WHILE AREAS TO THE NORTH WILL LIKELY REMAIN DRY.

BERING SEA/ALEUTIANS...SHOWERY WEATHER WILL PERSIST BEHIND THE FRONT.
ALTHOUGH COLDER AIR ALOFT HAS MOVED OVERHEAD THE MARINE LAYER IS
STILL QUITE WARM...SO PRECIPITATION TYPE WILL REMAIN MAINLY RAIN.
A LARGE COMPLEX CYCLONIC CIRCULATION WILL SET UP ACROSS THE BERING
SEA HEADING INTO THE NEW WEEK. MULTIPLE LOWS WILL BE EMBEDDED WITHIN
THE LARGER CIRCULATION...MAKING IT DIFFICULT TO PINPOINT THE LOCATION
AND STRENGTH OF THEM. BOTTOM LINE...EXPECT UNSETTLED WEATHER TO
PERSIST.

.LONG TERM FORECAST...WITH A LARGE CYCLONIC CIRCULATION OVER THE
REGION...EXPECT GENERALLY UNSETTLED WEATHER ACROSS THE ENTIRE
FORECAST AREA THROUGH THE END NEXT WEEK. WITH SOUTHCENTRAL ON THE
EAST SIDE OF THE CIRCULATION STORMS WILL LIKELY MOVE FROM SOUTH
TO NORTH ACROSS THE REGION...SO THE TYPICAL DOWNSLOPE AREAS WILL
LIKELY STAY MOSTLY DRY THROUGH THE PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 150 155 160 172 175 176.
FIRE WEATHER...NONE.

SEB NOV 07