Small Craft Advisory 308, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT SUN APR 1 2007

.DISCUSSION...

THE UPPER LEVEL PATTERN THIS MORNING CONSISTS OF A STRONG UPPER RIDGE
ANCHORED OVER THE GULF OF ALASKA AND STRETCHING NORTH ACROSS MUCH OF
MAINLAND ALASKA. A POWERFUL UPPER LOW AND ASSOCIATED SURFACE LOW
UNDERNEATH DOMINATE THE FAR WESTERN ALEUTIANS WITH A REFLECTED RIDGE
JUST DOWNSTREAM FROM THIS LOW OVER THE NORTHWESTERN BERING SEA. A
WEAKENING UPPER TROUGH IS LOCATED EQUATORWARD OF THIS RIDGE BETWEEN
THE MAIN UPPER LOW AND THE RIDGING OVER THE MAINLAND. AT THE
SURFACE...THE MAIN FEATURE OF NOTE IS THE STRONG VERTICALLY STACKED
LOW WEST OF ATTU. THE FRONTAL SYSTEM ASSOCIATED WITH THIS LOW IS
MARCHING EAST INTO THE CENTRAL ALEUTIANS THIS MORNING...ALTHOUGH THE
FRONT IS ALREADY APPEARING TO WEAKEN PER IR SATELLITE IMAGERY. WARM
ADVECTION/SOUTHERLY FLOW IN COMBINATION WITH THE ADVANCING/AMPLIFYING
UPPER RIDGE OVER THE EASTERN/CENTRAL BERING ARE BRINGING PLENTY OF
LOW CLOUDS AND FOG TO COASTAL PORTIONS OF SOUTHWESTERN ALASKA THIS
MORNING. FARTHER EAST...THE REST OF THE FORECAST AREA IS GENERALLY
CALM WITH LIGHT WINDS UNDER THE MAIN UPPER LEVEL/SURFACE RIDGE WITH
AREAS OF MAINLY HIGH CLOUDS MOVING ACROSS THE AREA FROM THE REMNANTS
OF THE PREVIOUS MAJOR STORM THAT MOVED ACROSS THE BERING A FEW DAYS
AGO IN CONJUNCTION WITH A WEAK UPPER TROUGH CENTERED SOUTH OF
UNALASKA.

MODELS CONTINUE TO DISPLAY ROBUST CONSISTENCY FROM MODEL TO MODEL AND
FROM RUN TO RUN...NECESSITATING MAINLY MINOR CHANGES TO THE GRIDS
THIS MORNING.

FOR THE WEST...A POWERFUL JET...ALREADY SHOWING UP IN IR IMAGERY
COMING OFF OF JAPAN...IS PROGGED TO STREAK ACROSS THE PACIFIC AROUND
45N...ALLOWING FOR THE DEVELOPMENT OF A POWERFUL UPPER/SURFACE LOW IN
THE SOUTHERN GULF OF ALASKA BY LATE TUESDAY NIGHT. THE LARGE LOW WEST
OF THE ALEUTIANS RETREATS WEST INTO SIBERIA WHILE CONTINUED SOUTHERLY
FLOW IN COMBINATION WITH THE INTERACTIONS WITH THE OLD FRONTAL
BOUNDARY AND THE TRAIN OF LOWS MOVING SOUTH OF THE ALEUTIANS IN
ASSOCIATION WITH THE JET WILL ALLOW FOR A GENERALLY WET PATTERN OVER
MUCH OF THE BERING SEA REGION THROUGH MUCH OF THE COMING WEEK. LOW
CLOUDS AND FOG LOOK TO CONTINUE ALONG COASTAL SOUTHWESTERN ALASKA
UNTIL MONDAY AT WHICH TIME THE SURFACE FLOW ACROSS THAT REGION TURNS
EASTERLY AND OFFSHORE IN RESPONSE TO THE AFOREMENTIONED DEVELOPING
LOWS SOUTH OF THE ALEUTIANS.

FOR SOUTHCENTRAL ALASKA...RIDGING ACROSS THE REGION WILL GRADUALLY
WEAKEN DURING THE EARLY PART OF NEXT WEEK AS THE TOP HALF OF THE
RIDGE IS PUSHED EAST INTO NORTHERN CANADA BY A STRONG SHORTWAVE THAT
DROPS ACROSS THE NORTHERN HALF OF ALASKA OUT OF THE ARCTIC. THIS
SHORTWAVE DEVELOPS INTO AN UPPER LOW THAT DROPS INTO CENTRAL ALASKA
AND BACK INTO THE BERING...BRINGING SOME MID AND UPPER LEVEL MOISTURE
ACROSS SOUTHCENTRAL...RESULTING IN INCREASED CLOUDS BY MONDAY
NIGHT...ALTHOUGH THE LACK OF LOW LEVEL MOISTURE SHOULD PRECLUDE THE
DEVELOPMENT OF ANY PRECIP. DRY WEATHER CONTINUES THROUGH MIDWEEK
UNDER A REORIENTED EAST-WEST RIDGE CAUSED BY THE LARGE LOW IN THE
SOUTHERN GULF...BRINGING A DECREASE IN CLOUDS ACROSS MUCH OF THE
REGION BY THURSDAY. THE POTENTIAL FOR WET WEATHER...PARTICULARLY
ALONG THE COAST INCREASES SUBSTANTIALLY BY FRIDAY THOUGH AS THIS
STRONG LOW DRIFTS NORTH WITH ITS ATTENDANT MOISTURE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 170 172 175 176 185
FIRE WEATHER...NONE.

WOOD APR 07