Small Craft Advisory 774, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTED
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKDT TUE OCT 7 2008

CORRECTED FOR WARNINGS.

.MODEL DISCUSSION...
IN THE SHORT TERM THE MODELS ARE IN GOOD AGREEMENT AGAIN.  NAM
CONTINUES TO BE BETTER AT RESOLVING THE INDIVIDUAL SHORTWAVES MOVING
THROUGH THE REGION ALTHOUGH THE GFS IS JUST FINE WITH THE SYNOPTIC
LEVEL FEATURES.  FOR THAT REASON THE NAM WAS USED FOR THE 24 HOUR
FORECAST.  AFTER ABOUT 48 HOURS THERE ARE STILL SOME DIFFERENCES IN
THE MODELS ON THE LOW MOVING INTO THE CENTRAL ALEUTIANS. THIS
MORNINGS GFS SOLUTION DIFFERS FROM YESTERDAYS 00Z SOLUTION BUT SHOWS
GOOD CONSISTENCY WITH THE 12Z AND 18Z RUNS.  THE NEW SOLUTION SHOWS
THE LOW MOVING INTO THE CENTRAL ALEUTIANS AND THEN RETROGRADING
SLIGHTLY BEFORE MOVING EASTWARD TOWARD THE MAINLAND.  YESTERDAYS 12Z
ECMWF DID NOT AGREE WITH THIS SOLUTION AND PUSHED THE LOW UP THE WEST
COAST MORE QUICKLY...HOWEVER THE NEW RUN HAS TRENDED TOWARD THE GFS.
GIVEN THIS TREND AND THE GFS CONSISTENCY IT WAS CHOSEN FOR THE MID
RANGE AND EXTENDED FORECAST.  ALSO OF NOTE IS THE FACT THAT THE GFS
IS A MUCH STRONGER SOLUTION THAN THE OTHER THREE MODELS. WITH THE
UPPER LEVEL SUPPORT THIS SOLUTION DOES NOT SEEM UNLIKELY AND THE GFS
HAS BEEN CONSISTENT ON THE STRENGTH FOR SEVERAL DAYS SO THE FORECAST
WENT WITH THIS SOLUTION ALTHOUGH IT SEEMS TO BE AN OUTLIER.

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL TROUGH IS BEGINNING ITS SHIFT EASTWARD TODAY BUT THIS
MORNING STILL LINGERS OVER THE CENTRAL MAINLAND.  AT THE SURFACE A
LOW HAS MOVED INTO PRINCE WILLIAM SOUND AND IS BRINGING A STRONG BAND
OF MOISTURE INTO THE EASTERN ZONES.  AS THIS LOW MOVES EASTWARD THE
COLD AIR WILL ADVECT IN BEHIND IT AND ENHANCE THE SNOWSHOWERS.  WITH
THE EASTWARD SHIFT OF THE PATTERN THE UPPER LEVEL RIDGE WILL MOVE
OVER THE MAINLAND AND A STRONGER UPPER LEVEL LOW WILL MOVE OVER THE
ALEUTIANS...PROVIDING UPPER LEVEL SUPPORT FOR A NEW SURFACE LOW
FORECAST TO MOVE INTO THE ALEUTIANS ON WEDNESDAY AFTERNOON.  THIS
WILL CAUSE THE SURFACE LOW TO RETROGRADE WESTWARD AND
STRENGTHEN...BECOMING THE FIRST SIGNIFICANT STORM OF THE SEASON.

.SHORT TERM FORECAST...
EAST OF THE ALASKA RANGE...A STRONG SHORTWAVE THAT TURNED INTO A
CLOSED SURFACE LOW HAS MOVED INTO PRINCE WILLIAM SOUND AND BROUGHT
MUCH OF THE SOUTHCENTRAL AREA THE FIRST SNOW OF THE SEASON THIS
MORNING.  AS THE SURFACE LOW LINGERS IN PRINCE WILLIAM SOUND PERIODS
OF SNOW WILL CONTINUE FOR THE SOUTHCENTRAL REGION TODAY.  TEMPS ARE
STILL PRETTY WARM...BOTH ON THE GROUND AND ALOFT...SO THE SNOW WILL
BE PRETTY HEAVY AND WILL COMPACT AND MELT REDUCING THE ACCUMULATION.
NOT MUCH MOISTURE FROM THIS SHORTWAVE IS EXPECTED TO MAKE IT ACROSS
THE CHUGACH RANGE AND INTO THE COPPER RIVER BASIN BUT THE AREA COULD
SEE SOME SHOWERS.  AS THE LOW MOVES EASTWARD TOMORROW THE SNOW WILL
TAPER OFF AND THERE WILL BE A BRIEF RESPITE BEFORE THE LOW IN THE
ALEUTIANS BEGINS TO AFFECT THE EASTERN DOMAIN.  GALE WARNING WINDS
WILL BEGIN TO SHOW UP IN THE MARINES ON THURSDAY AND STRONG WINDS ARE
EXPECTED FOR TURNAGAIN ARM THURSDAY NIGHT AS THE REGION EXPERIENCES
ITS FIRST CHINOOK EVENT OF THE SEASON.

WEST OF THE ALASKA RANGE...CALM WEATHER FOR THE WESTERN ZONES TODAY
WILL NOT LAST LONG AS THAT NEXT BIG LOW MOVES UP TOMORROW AFTERNOON.
IN THE MEANTIME WINDS WILL DECREASE AND SHOWERS WILL DIMINISH AS THE
SHORTWAVE RIDGE MOVES OVERHEAD.  ONCE THE LOW MOVES INTO THE CENTRAL
ALEUTIANS THE EFFECTS DEPEND HIGHLY ON ITS TRACK.  AS THE WARM FRONT
MOVES THROUGH THE EASTERN ALEUTIANS AND WESTERN AK PEN AND INTO THE
EASTERN BERING GALE FORCE WINDS CAN BE EXPECTED IN MOST OF THE
MARINES WITH STRONG WIND HEADLINES FOR THE PRIBILOFS...UNALASKA...AND
THE WESTERN AK PEN.  THESE WINDS WILL MOVE OFF ONTO THE MAINLAND AS
THE LOW STARTS TO SHIFT EASTWARD BEGINNING THURSDAY.

.LONG TERM FORECAST...
THE STRONG LOW IN THE ALEUTIANS IS FORECAST TO MOVE UP THE ALEUTIANS
AND ONTO THE WEST COAST NEAR KING SALMON ON FRIDAY NIGHT.  THE COLD
AIR ADVECTION BEHIND THIS SYSTEM IS STRONG AND MAY BRING STORM FORCE
WINDS TO THE ALEUTIANS AT THE END OF THE WEEK.  MEANWHILE THE
MAINLAND CAN EXPECT TO SEE A BIG WARM UP...WITH A MELT OF ALL THE
SNOW AND A SIGNIFICANT CHINOOK EVENT FOR THE EAST IN PARTICULAR.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 170 172 185 179
FIRE WEATHER...NONE

LEWF OCT 08