Small Craft Advisory 789, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT MON SEP 24 2007

.MODEL DISCUSSION...
MODELS IN GOOD AGREEMENT AGAIN TONIGHT.  THERE IS A SLIGHT VARIATION
WITH THE NAM AFTER 36 HOURS WHERE IT SHOWS THE LOW AS ABOUT 3 DEGREES
FURTHER WEST.  GIVEN THE LACK OF FORECAST IMPACT THIS IS NOT A MAJOR
FUNCTION.  GFS STILL THE MODEL OF CHOICE GIVEN ITS GOOD RUN TO RUN
CONSISTENCY.

.ANALYSIS AND UPPER LEVELS...
MAJOR FEATURE THIS MORNING IS A STACKED LOW PRESSURE SYSTEM IN THE
BERING SEA.  THE POLAR FRONT JET IS HIGHLY ZONAL IN NATURE...FLOWING
ACROSS THE NORTHERN PACIFIC THROUGH THE BOTTOM OF THE AOR.  AS
SHORTWAVE TROUGHS MOVE THROUGH THE JET THEY MOVE INTO THE GULF OF
ALASKA AND THEN DISSIPATE AS THEY LOSE MOST OF THEIR UPPER LEVEL
SUPPORT.  THE JET REFLECTS DOWN TO THE SURFACE AS STRONG WINDS AT
MOST LEVELS.  WITH THE SURFACE LOW IN THE NORTHERN BERING THE FLOW
OVER THE MAINLAND IS SOUTHWESTERLY AT ALL LEVELS WHICH MEANS WET
WEATHER FOR MOST OF THE FORECAST ZONES.

.SHORT TERM FORECAST...
EAST OF THE ALASKA RANGE...FIRST OF A SERIES OF SHORTWAVES MOVING
THROUGH THIS MORNING WILL BRING RAIN TO THE SOUTHCENTRAL REGION AND
MORE SHOWERY TYPE PRECIPITATION TO THE COPPER RIVER VALLEY LATER
TONIGHT. TEMPERATURES AT HIGHER ELEVATIONS IN THE COPPER RIVER VALLEY
ARE COLD ENOUGH THAT THERE WILL BE SOME SNOW BUT NO ACCUMULATION IS
EXPECTED. A QUICK BREAK WILL OCCUR BEFORE THE NEXT SHORTWAVE MOVES IN
EARLY TUESDAY MORNING AND THIS MAY ALLOW SOME FOG TO FORM AHEAD OF
THE FRONT. TUESDAY LOOKS TO BE MUCH OF A REPEAT OF TODAY.  WINDS
ASSOCIATED WITH THESE SHORTWAVES HAVE DECREASED SLIGHTLY SO ONLY
SMALL CRAFTS EXPECTED IN THE MARINES FOR THE SHORT TERM.

WEST OF THE ALASKA RANGE...WET WEATHER CONTINUES FOR THIS REGION AS
WELL.  PRECIPITATION WILL BE MORE SHOWERY THIS MORNING BEFORE THE
NEXT SHORTWAVE MOVES THROUGH...THIS IS EXPECTED TO MOVE ONSHORE THIS
AFTERNOON AND WILL BRING RAIN TO THE AK PEN AND THE MAINLAND. WINDS
ARE STRONGER BEHIND THE FRONT THAN AHEAD OF IT SO GALES ARE NOT
EXPECTED IN THE SHORT TERM FOR MARINES EAST OF DUTCH HARBOR...BUT ARE
IN THE FORECAST FOR THE CENTRAL AND WESTERN ALEUTIANS.

.LONG TERM FORECAST...
THE LONGWAVE PATTERN FINALLY BEGINS TO CHANGE WEDNESDAY NIGHT AND
THURSDAY WHEN A RIDGE MOVES INTO THE ALASKA REGION.  THIS WILL CLEAR
SKIES OVER THE MAINLAND BRIEFLY AND PERHAPS LET THINGS DRY OUT A
LITTLE.  HOWEVER ON THE HEELS OF THIS RIDGE IS ANOTHER MAJOR LOW
PRESSURE SYSTEM WHICH IS EXPECTED TO MOVE INTO THE BERING LATE
THURSDAY.  AT THIS POINT THE MODELS ARE FORECASTING IT TO MOVE INTO
THE GULF OF ALASKA BY NEXT WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALES 155 170 172 175 176 179
FIRE WEATHER...NONE

LEWF SEP 07