Small Craft Advisory 633, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
240 PM ADT THU JUL 20 2006

.DISCUSSION...

NEARLY VERTICALLY STACKED LOW SPINNING SOUTH OF KODIAK ISLAND WITH
OCCLUDED FRONT EXTENDING ALONG KODIAK ISLAND AND THE NORTH GULF
COAST. THIS IS BRINGING RAIN AND GALE FORCE WINDS TO COASTAL
LOCATIONS. WINDS HAVE STARTED TO TREND DOWNWARD AS FRONT BEGINS
TO SHEAR APART. THIS TREND WILL CONTINUE THROUGH THE REST OF THE
DAY. SATELLITE IMAGERY SHOWS MID TO HIGH CLOUDS SPREADING INLAND
ACROSS SOUTHCENTRAL AND INTO THE BRISTOL BAY ZONE. ONE OF THE
FORECAST PROBLEMS OF THE DAY IS IDENTIFYING WHETHER ENOUGH MOISTURE
WILL MAKE IT INLAND TO PRODUCE AFTERNOON/EVENING SHOWERS. RADAR
SHOWS SOME ECHOES MAKING IT ACROSS THE COASTAL LAND...BUT DO TO
DRY CONDITIONS...AS PER 12Z SOUNDINGS...NOT MUCH OF THIS IS
REACHING THE GROUND AND WHERE IT IS REACHING THE GROUND IT IS
VERY LIGHT. WITH SOME WEAK RIDGING ALOFT ACROSS THE SOUTHERN
MAINLAND STABILITY INDICES ARE MARGINAL FOR CONVECTION AND MID/HIGH
CLOUDS SHOULD LIMIT DESTABILIZATION ACROSS MUCH OF SOUTHCENTRAL.
THEREFORE WILL STICK WITH FORECAST OF ISOLATED SHOWERS INLAND AND
REMOVE MENTION OF THUNDERSTORMS FROM SOUTHCENTRAL. AT 21Z THERE IS
INITIAL CUMULUS DEVELOPMENT OCCURRING ALONG THE
KUSKOKWIM/KILBUCK/AHKLUN MOUNTAINS. WITH FULL SUN IN THIS AREA AND
SLOWLY INCREASING MOISTURE THIS MAY BE THE AREA TO WATCH FOR SHOWERS
THIS AFTERNOON. IF THE MID LEVEL CAP CAN BE BROKEN THERE IS THE
POTENTIAL FOR ISOLATED THUNDERSTORMS AS WELL.

A RIDGE OVER THE CENTRAL BERING IS PROVIDING FAIRLY CALM CONDITIONS
ACROSS THE REGION. THERE IS THE USUAL STRATUS ACROSS MUCH OF THE
BERING WITH SOME BREAKS IN THE EASTERN BERING WHERE THERE IS A GOOD
NORTHERLY JET BETWEEN RIDGE AND GULF LOW. AS RIDGE SLIDES EASTWARD
TONIGHT MUCH OF THIS WILL FILL IN BRINGING CLOUDS AND FOG TO THE
NORTHERN AKPENN/EASTERN ALEUTIANS/WESTERN MAINLAND COAST. A FRONT
ASSOCIATED WITH A LOW NORTHWEST OF WESTERN ALEUTIANS IS CURRENTLY
MOVING INTO THE WESTERN ALEUTIANS BRINGING RAIN AND SMALL CRAFT
WINDS. THIS FRONT WILL MAKE SLOW PROGRESS EASTWARD AS LOW DRIFTS
TO THE NORTH TONIGHT AND FRIDAY.

GFS/NAM/UKMET MODEL SOLUTIONS SHOWING FAIR VERIFICATION WITH MAJOR
SYNOPTIC FEATURES AT THIS HOUR. HOWEVER...NAM SOLUTION DIVERGES
WIDELY STARTING AT ABOUT 48 HOURS. DUE TO RECENT INCONSISTENCY AND
BAD PERFORMANCE OF NAM AS WELL AS FAIR RUN-TO-RUN CONSISTENCY OF
GFS WILL GO WITH THE GFS SOLUTION. THERE WAS ALSO A NOTABLE
DIFFERENCE IN THE STRENGTH OF WINDS ALONG THE WESTERN ALEUTIANS
FRONT. BASED ON QUICKSCAT AND THE FEW LAND BASED OBS OUT THERE
GFS IS VERIFYING BETTER WITH WINDS.

LOW SOUTH OF KODIAK ISLAND WILL REMAIN SOUTH OF KODIAK ISLAND AND
SLOWLY WEAKEN. ONSHORE FLOW/WEAK SYNOPTIC LIFT WILL CONTINUE TO
PROVIDE RAIN ALONG THE GULF COAST THE NEXT COUPLE DAYS. INLAND
LOCATIONS WILL REMAIN PARTLY TO MOSTLY CLOUDY WITH ISOLATED TO
SCATTERED CONVECTION. GRADIENT ALONG THE NORTH GULF COAST WILL
TIGHTEN TONIGHT AND FRIDAY PRODUCING THE USUAL GAP WINDS ACROSS
SOUTHCENTRAL. THE RIDGE OUT WEST WILL GRADUALLY BREAK DOWN AS
UPPER LOW OVER FAR WESTERN BERING SLIDES EASTWARD AND SHORT-WAVES
ROTATING AROUND IT MOVE INTO RIDGE. THIS LOW WILL MOVE TO THE
AKPENN BY LATE IN THE WEEKEND SPREADING MOISTURE INTO SOUTHWEST
ALASKA AND KODIAK ISLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 120 138 150 155 175.
FIRE WEATHER...NONE.

SEB JUL 06