Small Craft Advisory 712, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT TUE SEP 6 2005

.DISCUSSION...
THE LONGWAVE PATTERN HAS SHIFTED SLIGHTLY SINCE YESTERDAY MORNING.
TODAY THE LONGWAVE TROUGH HAS MOVED EASTWARD AND IS NOW CENTERED OVER
THE WESTERN MAINLAND INSTEAD OF THE WEST TO CENTRAL BERING.  WATER
VAPOR IMAGERY AND 300MB ANALYSIS SHOW THAT THE JET AXIS HAS BECOME
MORE EAST TO WEST IN NATURE.  THIS SHOULD HELP SYSTEMS PROGRESS
RAPIDLY THROUGH THE FORECAST REGION ALTHOUGH THE PLACEMENT OF THE
LONGWAVE TROUGH MEANS THE WEATHER WILL CONTINUE TO BE RAINY FOR THE
NEXT COUPLE OF DAYS.

THE LOW PRESSURE SYSTEM THAT MOVED ONSHORE NEAR NUNIVAK ISLAND
YESTERDAY IS STILL THE MAIN SOURCE OF WEATHER TODAY.  THE JET IS
PUSHING THE FRONT THROUGH THE REGION AT A GOOD RATE.  HOWEVER
SOUTHWEST FLOW AND PLENTY OF MOISTURE MEANS HEAVY RAINS FOR THE
SOUTHCENTRAL REGION AS THE FRONT MOVES THROUGH.  RADAR IS SHOWING
STRONG ECHOES THIS MORNING OVER THE KENAI PENINSULA THE MATSU VALLEY
AND MOVING UP INTO PRINCE WILLIAM SOUND. BEHIND THE FRONT THE
PRECIPITATION SHOULD BE MOSTLY SHOWERY WHICH IS EVIDENCED BY THE
SPOTTY PRECIP IN THE BRISTOL BAY AND BERING COASTAL REGIONS.  THE LOW
PRESSURE CENTER ITSELF IS NOT MOVING QUITE AS RAPIDLY SINCE IT IS
ALIGNED WITH THE LONGWAVE TROUGH.  THIS LOW CENTER WILL KEEP
INSTABILITY ACROSS THE SOUTHERN PORTION OF THE MAINLAND THROUGH
WEDNESDAY MORNING.  EXPECT SHOWERS FOR MOST OF THE EASTERN AND
WESTERN ZONES THROUGH THE NEXT 24 HOURS.  WATCH FOR FOG ON WEDNESDAY
MORNING ALONG THE BERING COAST AS PLENTY OF MOISTURE WILL BE
AVAILABLE AND STABILITY WILL BE INCREASING.

ALONG THE ALEUTIANS A RIDGE IS BUILDING IN BEHIND THE LOW.  THE
EASTERN ALEUTIANS AND AK PENINSULA ARE UNDERNEATH THE DRY SLOT ALOFT
BUT SINCE THERE IS NO LACK OF LOW LEVEL MOISTURE SPOTTY SHOWERS ARE
STILL FORMING WITH THE WEAK INSTABILITY ALOFT.  IN THE WESTERN
ALEUTIANS CONDITIONS ARE MORE STABLE UNDERNEATH THE RIDGE SO LOW
STRATUS IS MORE PERVASIVE.  AS THE RIDGE MOVES EASTWARD THE SHOWERS
WILL AS WELL AND BY TOMORROW MORNING THE ENTIRE ALEUTIAN CHAIN SHOULD
BE SHOWER FREE FOR THE MOST PART.

MODEL DISCUSSION...MODELS SEEM TO BE IN GOOD AGREEMENT FOR THE NEXT
48 HOURS AGAIN TODAY.  USE THE GFS OUT WEST AND ETA IN THE EAST FOR A
GOOD COMBINATION.  AS FOR BEYOND 48 HOURS...YESTERDAY GFS WAS
TRENDING MUCH STRONGER THAN THE UKMET WHEN BRINGING THE NEXT LOW UP
TOWARD THE CENTRAL ALEUTIANS.  TODAY IT HAS ADJUSTED AND THE SOLUTION
IS CLOSER BUT STILL STRONGER THAN THE UKMET.  THIS IS AN INDICATION
THAT YESTERDAYS THEORY WAS CORRECT...THE UKMET SOLUTION WAS CLOSER TO
ACTUALITY BUT PERHAPS A LITTLE WEAK.  AS GFS CONTINUES TO CORRECT
ITSELF IT WILL PROBABLY TAKE THE MIDDLE GROUND AND PROVIDE THE BEST
SOLUTION IN THE END.

EXTENDED FORECAST...STILL EXPECTING HIGH PRESSURE WILL BUILD IN OVER
THE MAINLAND.  THE NEXT LOW PRESSURE SYSTEM SHOULD MOVE NORTHWARD
THROUGH THE ALEUTIANS AND MAKE ITS WAY UP THE WEST COAST ON FRIDAY.
IT LOOKS LIKE THE FRONTAL SYSTEM  WILL MAKE ITS WAY OVER THE TOP OF
THE RIDGE AND WILL BRING RAIN TO THE SOUTHCENTRAL REGION ON FRIDAY
AFTERNOON.  BY SATURDAY THIS SYSTEM WILL MOVE OUT OF THE AREA AND
GOOD WEATHER SHOULD PREVAIL FOR EVERY WHERE EXCEPT THE ALEUTIANS OVER
THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...NONE

LEW SEP 05