Small Craft Advisory 580, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
130 PM AKDT TUE JUL 22 2008

.ANALYSIS AND UPPER LEVELS...ANCHOR LOW IS NEARLY STATIONARY OVER
THE BERING STRAIT. WATER VAPOR IMAGERY SHOWS MULTIPLE SHORT-WAVES
EMBEDDED WITHIN THE CYCLONIC FLOW. ONE OF THE STRONGER SHORT-WAVES
EXITED SOUTHCENTRAL THIS MORNING AND IS HEADING NORTHWARD ACROSS
THE INTERIOR. SHOWER ACTIVITY HAS DIMINISHED...BUT CONTINUES
PRIMARILY OVER EASTERN PRINCE WILLIAM SOUND AND OVER THE MOUNTAINS.
ANOTHER SHORT-WAVE IS TRACKING SOUTHEASTWARD ACROSS THE KUSKOKWIM
DELTA TO BRISTOL BAY. RAIN HAS OVERSPREAD BRISTOL BAY AND IS MOVING
ACROSS THE ALASKA PENINSULA TO KODIAK ISLAND AND SOUTHERN COOK INLET.

AN UPPER SHORT-WAVE/WEAK SURFACE LOW ARE LOCATED SOUTHWEST OF THE
WESTERN ALEUTIANS. WITH A STRONG RIDGE TO THE SOUTHEAST AND THE
UPPER LOW DROPPING DOWN FROM THE BERING STRAIT...THIS SYSTEM IS
MOVING VERY SLOWLY TOWARD THE ALEUTIANS. LASTLY...A WEAK SURFACE
LOW LOCATED SOUTH OF THE ALASKA PENINSULA IS TRACKING SOUTHEASTWARD
AWAY FROM THE REGION.

.MODEL DISCUSSION...MODELS INITIALIZED WELL. HOWEVER...THERE
CONTINUES TO BE PROBLEMS WITH RUN-TO-RUN CONSISTENCY...NAMELY WITH
HANDLING OF THE GULF LOW ON THURSDAY. GFS IS BY FAR THE DEEPEST
SOLUTION...BUT RUN-TO-RUN CONSISTENCY IS TERRIBLE AND THE ENSEMBLE
MEAN IS ABOUT 10 MILLIBARS WEAKER. PREFER THE ECMWF WHICH SHOWS THE
MOST CONSISTENCY. ONLY MINOR ADJUSTMENTS WILL BE MADE IN THE
SHORT-TERM. ECMWF AND GFS SOLUTIONS DIVERGE SIGNIFICANTLY BEYOND
60 HOURS...SO WILL STICK WITH CURRENT FORECAST.

.SHORT TERM FORECAST...

SOUTHERN MAINLAND...SHORT-WAVES WILL ROTATE FROM SOUTHWEST ALASKA
NORTHEASTWARD ACROSS SOUTHCENTRAL TONIGHT AND WEDNESDAY WHILE THE
UPPER LOW DROPS FROM THE BERING STRAIT ACROSS SOUTHWEST ALASKA
WEDNESDAY AND INTO THE GULF THURSDAY. SOUTHCENTRAL AND THE GULF
WILL SEE THE BRUNT OF THE RAIN TONIGHT THROUGH THURSDAY UNDER
SOUTHWEST FLOW ALOFT. SOUTHWEST ALASKA WILL SEE PERIODS OF
RAIN/SHOWERS BUT IT WILL BE SHORTER LIVED WITH DRIER AIR MOVING
IN BEHIND THE UPPER LOW WEDNESDAY NIGHT INTO THURSDAY. AS THE COLD
UPPER CORE MOVES OVERHEAD ON WEDNESDAY MID TO UPPER LEVELS WILL
DESTABILIZE. THIS MAY BE ENOUGH TO PRODUCE AN ISOLATED
THUNDERSTORM...MAINLY OVER THE KILBUCK AND AHKLUN MOUNTAINS OF
SOUTHWEST ALASKA. WESTERN SOUTHCENTRAL SHOULD ALSO SEE SOME DRYING
LATE THURSDAY AS THE GULF LOW TRACKS EASTWARD AND FLOW BACKS TO
THE NORTH BEHIND THE SYSTEM. HOWEVER...THE THREAT WILL THEN BE
SHORT-WAVE ROTATING IN FROM THE EAST. BASED ON CURRENT TRACK OF
SYSTEM LOOKS LIKE PRINCE WILLIAM SOUND TO COPPER BASIN WILL REMAIN
WET INTO SATURDAY WHILE THE COOK INLET REGION LOOKS DRY FOR FRIDAY
AND SATURDAY.

BERING SEA/ALEUTIANS...THE WEAK LOW/SHORT-WAVE SOUTHWEST OF WESTERN
ALEUTIANS WILL TRACK RIGHT ALONG THE ALEUTIANS (OVER TOP OF THE
PACIFIC RIDGE) TONIGHT THROUGH THURSDAY NIGHT AND THEN SOUTHEASTWARD
INTO THE PACIFIC FRIDAY. MAIN IMPACT WILL BE RAIN AND FOG. HIGH
PRESSURE WILL BUILD OVER THE EASTERN BERING WEDNESDAY AND
THURSDAY...HELPING TO MAINTAIN WIDESPREAD STRATUS AND/OR FOG ACROSS
THE REGION.

.LONG TERM FORECAST...THE CURRENT COOL AND WET PATTERN WILL PERSIST
THROUGH THE EXTENDED FORECAST PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...ASHFALL ADVISORY 185.
MARINE...ASHFALL ADVISORY 170.
FIRE WEATHER...NONE.

SEB JUL 08