Small Craft Advisory 628, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM AKDT MON AUG 18 2008

.ANALYSIS AND UPPER LEVELS...
STRONG VERTICALLY STACKED LOW OVER THE WESTERN GULF OF ALASKA MOVING
ESSENTIALLY EASTWARD. CYCLONIC FLOW AT UPPER LEVELS OVER ALL OF
SOUTHERN ALASKA. RIDGE AT THE SURFACE AND ALOFT OVER THE CENTRAL
BERING SEA. THE MAIN JET STREAM SCRAPES THE ALEUTIANS...BUT IS
ESSENTIALLY SOUTH OF THE AREA.

.MODEL DISCUSSION...
GOOD MODEL AGREEMENT THROUGH 60 HOURS. STUCK MAINLY WITH THE 00Z
AND/OR 12Z GFS FOR THE AFTERNOON PACKAGE...WITH A LITTLE 12Z NAM AND
ECMWF SPRINKLED IN FOR GOOD MEASURE. DIFFERENCES FROM 60 TO 120
HOURS ARE MAINLY IN THE DETAILS...BUT ENOUGH MODEL DIVERGENCE TO
LOWER CONFIDENCE. PREFERENCE FOR THIS PERIOD WAS SLIGHTLY TOWARD THE
ECMWF.

.SHORT TERM FORECAST...
GULF LOW STILL PRODUCING STORM FORCE WINDS THROUGH TONIGHT THEN
MOVING EAST AND SOUTH OF THE AREA WITH THE LOW BY TUESDAY AFTERNOON.
PLENTY OF RAIN IN KODIAK FROM THIS SYSTEM...AND POSSIBLY THE
SOUTHERN KENAI PENINSULA. SHOWERS EXPECTED INLAND THIS EVENING AND
EVEN SOME THUNDERSTORMS. THE BEST INSTABILITY IS GENERALLY NORTH OF
A LINE RUNNING FROM GLENNALLEN THROUGH MCGRATH. SOME SUPPRESSION OF
CONVECTION OVER MUCH OF SOUTH CENTRAL ALASKA DUE TO HIGH CLOUDS AND
SOME DOWNWARD MOTION FROM THE GULF LOW.

ON TUESDAY MOST OF THE SHOWERS WILL BE ALONG THE BERING SEA COAST
DUE TO A RESIDUAL TROUGH OVER BRISTOL BAY. SOME WARMING ALOFT OVER
THE KUSKOKWIM VALLEY AND SOUTH CENTRAL ALASKA WILL KEEP SHOWERS TO A
MINIMUM.

.LONG TERM FORECAST...
THE BRISTOL BAY LOW WILL REMAIN NEARLY STATIONARY INTO THE WEEKEND
WHILE INCREASING IN STRENGTH AND SIZE ALLOWING SHOWER ACTIVITY TO
INCREASE AGAIN OVER SOUTHER ALASKA.

BY FRIDAY AND INTO THE WEEKEND THE MODELS ARE NOT IN TOTAL AGREEMENT
ON THE TIMING OF SYSTEMS...BUT ALL AGREE ON KEEPING THE MEAN TROUGH
POSITION OVER SOUTHWEST ALASKA FOR CONTINUED SHOWERS IN THE CYCLONIC
FLOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING 132 150.
         GALE WARNING 120 130 138.
FIRE WEATHER...NONE.

LUDWIG AUG 08