Small Craft Advisory 778, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT FRI SEP 21 2007

.MODEL DISCUSSION...
MODELS HAVE COME TOGETHER ON A SOLUTION FOR THE SHORT TERM.  PREVIOUS
RUNS OF THE GFS INDICATED THAT MODEL WAS PUSHING A LOW FROM THE
NORTHERN PACIFIC INTO THE GULF OF ALASKA AT 60 HRS...THIS DIFFERED
SIGNIFICANTLY FROM THE NAM AND ECMWF PREVIOUS SOLUTIONS.  HOWEVER 00Z
RUNS TODAY INDICATE THAT ALL MODELS ARE ON TRACK WITH PUSHING THE LOW
JUST WEST OF KODIAK AT 60 HRS.

.ANALYSIS AND UPPER LEVELS...LONGWAVE TROUGH CURRENTLY MOVING
EASTWARD OVER WESTERN CANADA WITH A LONGWAVE RIDGE MOVING OVER THE AK
WEST COAST THIS MORNING.  THIS IS APPARENT ON SATELLITE WITH THE MAIN
LOW PRESSURE CENTER FAR OFF TO THE EAST IN THE PANHANDLE.  CONDITIONS
ARE FAIRLY UNSTABLE AS COOL TEMPERATURES ALOFT COMBINE WITH AFTERNOON
HEATING...IN THE SOUTHCENTRAL REGION THIS IS AUGMENTED BY SEVERAL
SHORTWAVES MOVING IN FROM THE WEST.  SOUTH OF THE ALEUTIANS A CIRRUS
SHIELD ASSOCIATED WITH THE NEXT MAJOR LOW PRESSURE SYSTEM IS JUST
BEGINNING TO APPEAR ON SATELLITE.  AS THIS SYSTEM MOVES NORTHWARD IT
WILL PUMP WARM AIR INTO THE WEAK RIDGE MOVING OVER THE MAIN PORTION
OF THE STATE THEREBY STRENGTHENING IT AND CAUSING THE LOW TO MOVE
MORE TOWARD THE WESTERN PORTION OF THE STATE...AS FORECAST BY THE
MODELS.

.SHORT TERM FORECAST...
EAST OF THE ALASKA RANGE...WITH THE RIDGE MOVING IN OVERHEAD AND
CLEARING SKIES FOG IS A PREVAILING PROBLEM THIS MORNING...IN
PARTICULAR FOR THE SOUTHCENTRAL REGION WHERE LAST NIGHTS SHOWERS
ADDED PLENTY OF AVAILABLE MOISTURE TO THE BOUNDARY LAYER.  AS THE
RIDGE MOVES IN THE GRADIENT BETWEEN IT AND THE LOW TO THE EAST WILL
TIGHTEN SLIGHTLY AND GUSTY NORTH TO NORTHWESTERLY WINDS CAN BE
EXPECTED...IN PARTICULAR THROUGH CHANNELED TERRAIN.  THIS WILL SAVE
SOME LOCATION FROM THE EARLY MORNING FOG.  AS MENTIONED IN THE
ANALYSIS UNSTABLE CONDITIONS CONTINUE THROUGHOUT THE REGION IN THE
AFTERNOON AS THE CLEARING SKIES WILL CAUSE AMPLE SURFACE HEATING.
EXPECT SHOWERS TO CONTINUE IN PARTICULAR OVER MOUNTAINOUS
REGIONS...WITH MIXED PRECIPITATION AT HIGHER ELEVATIONS. OVER THE
WEEKEND THE FRONT ASSOCIATED WITH THE LOW MOVING INTO THE ALEUTIANS
MAKES ITS WAY INTO THE EASTERN ZONES...STARTING WITH KODIAK ON
SATURDAY AND MOVING INTO THE SOUTHCENTRAL REGION ON SUNDAY.  EXPECT
INCREASED WINDS IN THE MARINE ZONES WITH POSSIBLE GALES BEGINNING
SUNDAY.

WEST OF THE ALASKA RANGE INCLUDING THE ALEUTIANS...CONDITIONS WILL
IMPROVE FOR THE MAINLAND TODAY AS THE AXIS OF THE RIDGE MOVES
OVERHEAD. ON SATURDAY THE ALASKA PENINSULA WILL BEGIN TO FEEL THE
EFFECTS OF THE LOW MOVING IN FROM THE NORTH PACIFIC.  THIS SYSTEM
WILL BRING GALE WINDS TO THE MARINES AND RAIN TO THE MAINLAND. WITH
THE LOW CENTER ITSELF REMAINING SOUTH OF THE AK PEN THE KUSKOKWIM
VALLEY AND DELTA WILL BE MARGINALLY AFFECTED BY THE FRONT.  IN THE
ALEUTIANS CONDITIONS ARE FAIRLY CALM THIS MORNING BUT GUSTY WINDS ARE
EXPECTED TO BEGIN FOR THE EASTERN ALEUTIANS THIS AFTERNOON AND
EVENING AS THE LOW APPROACHES.  EXPECT GALES IN THE MARINE ZONES
BEGINNING TONIGHT.  THE WESTERN ALEUTIANS WILL BE UNAFFECTED BY THIS
LOW...HOWEVER A SEPARATE AND STRONGER LOW WILL BRING A STRONGER FRONT
TO THE AREA SATURDAY MORNING.  THIS LOW IS TIGHTLY WRAPPED AND WINDS
IN THE WESTERN ALEUTIANS WILL BE STRONG SATURDAY NIGHT.

.LONG TERM FORECAST...
BY THE BEGINNING OF NEXT WEEK THE LOW CURRENTLY MOVING TOWARD THE
ALEUTIANS WILL PROGRESS INTO THE GULF OF ALASKA AND DISSIPATE AS IT
MOVES ONSHORE.  THE LOW MOVING NORTHWARD WEST OF THE WESTERN
ALEUTIANS WILL MOVE INTO THE BERING SEA...THIS PLACES THE UPPER LEVEL
AND LOW LEVEL JETS OVER THE ALEUTIANS...SO WINDY WEATHER WILL
CONTINUE THROUGH THE BEGINNING OF NEXT WEEK.  THIS ALSO BRINGS A MORE
SOUTHWESTERLY FLOW TO THE MAINLAND...SO ALL AREAS CAN EXPECT A WET
WEEK.

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

LEWF SEP 07