Small Craft Advisory 673, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT THU AUG 25 2005

.DISCUSSION...
SATELLITE IMAGERY THIS MORNING SHOWS THAT THE PATTERN HAS SHIFTED
SLIGHTLY FROM THE PAST COUPLE OF DAYS.  THE LONG WAVE TROUGH HAS
MOVED TO THE EAST AND IS NOW POSITIONED OVER THE EASTERN PORTION OF
THE STATE.  MEANWHILE A SHORTWAVE RIDGE HAS MOVED OVER THE
SOUTHCENTRAL REGION WHILE ANOTHER LOW PRESSURE SYSTEM IS MOVING ONTO
THE WEST COAST. WATER VAPOR IMAGERY SHOWS THE JET HAS REPOSITIONED
ITSELF ON A WEST EAST AXIS.  THIS SHIFT IN THE LONGWAVE PATTERN
INDICATES THE NEXT SYSTEM WILL TAKE A SLIGHTLY DIFFERENT TRACK THAN
THE MOST RECENT SYSTEM.  UPPER AIR ANALYSIS SHOWS WEAK DYNAMICS
ASSOCIATED WITH THE LOW IN THE BERING.  THE 850MB CHART SHOWS SOME
TEMPERATURE ADVECTION BUT THE UPPER LEVEL TROUGHS AT 500MB AND 300MB
ARE MINOR INDICATING THAT THE SYSTEM WILL DOES NOT HAVE THE UPPER
LEVEL SUPPORT TO STRENGTHEN SIGNIFICANTLY OVER THE NEXT 24 HOURS.

IN SPITE OF THE LACK OF UPPER LEVEL SUPPORT THE GRADIENT AT THE
SURFACE IS TIGHT AND WINDS ASSOCIATED WITH THIS LOW ARE MODERATE.
ADVISORY LEVEL WINDS ARE EXPECTED IN THE MID AND EASTERN ALEUTIANS
DIMINISHING BY THURSDAY EVENING.  CONDITIONS SHOULD IMPROVE AS THE
SURFACE RIDGE MOVES OVERHEAD ALTHOUGH LOW CLOUDS ARE ALWAYS A PROBLEM
WITH STABLE CONDITIONS IN THE BERING.

FOR THE MAINLAND THE SYSTEM SHOULD MOVE THROUGH THE SOUTHERN SECTION
OF THE AK PENINSULA BRINGING RAIN TO BRISTOL BAY BUT HAVING LITTLE
EFFECT ON THE KUSKOKWIM VALLEY AND DELTA.  IN THE EASTERN ZONES
MORNING FOG IS A CONCERN AFTER SKIES HAVE SCATTERED OUT OVERNIGHT.
THE LOW PRESSURE SYSTEM WILL CONTINUE TO SKIRT THE SOUTHERN PORTION
OF THE STATE.  THE SOUTHERN TIP OF THE KENAI PENINSULA AND THE PRINCE
WILLIAM SOUND WILL SEE SOME SHOWERS BUT EXPECT IMPROVING CONDITIONS
NORTHWARD.

DISCUSSION...THE GFS HAS BEEN FORECASTING THE CHANGE IN THE LONGWAVE
PATTERN FOR TWO TO THREE DAYS SO IT IS TRENDING RATHER WELL.  ETA HAS
PICKED UP ON THIS TREND AND NOW SHOWS THE SAME SOLUTION FOR THE NEXT
WEEK SO THE MODELS ARE IN GOOD AGREEMENT TRACKWISE.  THE GFS IS
RUNNING SLIGHTLY STRONGER WITH THE SYSTEM BUT SEEMS TO BE VERIFYING
WITH CURRENT OBSERVATIONS.  OVERALL GFS LOOKS BEST.

EXTENDED FORECAST...THE RIDGE THAT IS CURRENTLY OVER THE NORTH
PACIFIC SHIFTS EASTWARD AND BEGINS TO AFFECT THE MAINLAND.  THIS WILL
BRING GOOD WEATHER TO MOST ZONES FOR THE WEEKEND.  AT THE END OF
PERIOD A LOW PRESSURE SYSTEM MAKES LANDFALL NEAR THE SEWARD
PENINSULA.  THIS SYSTEM IS FORECAST TO EVENTUALLY MOVE INTO THE GULF
OF ALASKA BY TUESDAY.

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

LEW AUG 05