Small Craft Advisory 583, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT WED JUL 23 2008

.MODEL DISCUSSION...
12Z GFS IS IN CLOSER AGREEMENT WITH THE ECMWF THAN IN THE PREVIOUS
RUN.  THE ECMWF HAS BEEN MORE CONSISTENT RUN TO RUN THAN THE GFS AND
HAS BEEN THE MODEL OF CHOICE.  THE NAM CONTINUES TO DIFFER FROM THE
OTHER MODELS WITH THE GULF LOW.  THE NAM SOLUTION HAS A STRONGER LOW
ABOUT 200 NM EAST OF THE OTHER MODELS BY FRI MORNING.  THE PLAN TODAY
IS TO STICK WITH THE ECMWF AND GFS SOLUTION.

.ANALYSIS AND UPPER LEVELS...
THE PREDOMINATE UPPER AIR FEATURE IS A COLD UPPER LOW CENTERED
OVER BETHEL AND DIGGING DOWN TOWARD THE GULF OF ALASKA. A STRONG
SHORTWAVE IN THE SUSITNA VALLEY CONTINUES TO PRODUCE WIDESPREAD RAIN
IN SOUTH CENTRAL ALASKA. THIS WAVE IS MOVING EAST TONIGHT AND
THURSDAY. A WEAK CIRCULATION OVER THE WESTERN ALEUTIANS IS MOVING
SLOWLY EAST.

.SHORT TERM FORECAST...
SOUTHWEST FLOW ALOFT AHEAD OF THE UPPER LOW WILL CONTINUE TO PUMP
MOISTURE INTO THE SOUTHERN MAINLAND. AS THE UPPER LOW MOVES TO KODIAK
ISLAND BY THURSDAY MORNING SHOWERS WILL END OVER THE SOUTHWEST
MAINLAND. DRIER AIR WILL MOVE OVER THE WEST COAST ON THU AS HIGH
PRESSURE BUILDS OVER THE EASTERN BERING. FURTHER WEST WEAK LOW WILL
PERSIST OVER THE WESTERN ALEUTIANS THROUGH THURSDAY THEN MOVE TO THE
EASTERN ALEUTIANS FRIDAY.  EXPECT OCCASIONAL RAIN FOG AND
LOW CLOUDS WITH THIS LOW. FOG AND LOW CLOUDS ARE EXPECTED TO PERSIST
OVER THE CENTRAL AND EASTERN BERING UNDER A RIDGE THROUGH FRIDAY.

THE WEAK LOW MOVING TO THE GULF FROM WESTERN ALASKA WILL COMBINE IN
THE CENTRAL GULF WITH ANOTHER WEAK LOW MOVING IN FROM SOUTH OF THE
GULF ON THURSDAY.  THIS LOW WILL REMAIN NEARLY STATIONARY THEN MOVE
SLOWLY TOWARD THE PANHANDLE THURSDAY NIGHT AND FRIDAY.  DRIER AND
WARMER WEATHER IS EXPECTED FOR SOUTH CENTRAL FRIDAY AS THIS LOW MOVES
EAST.

.LONG TERM FORECAST...
THERE IS STILL A LOT OF INCONSISTENCY IN THE MODELS FOR THE WEEKEND.
THERE WILL BE AN UPPER TROUGH EXTENDING FROM THE EASTERN GULF TO
ANOTHER UPPER LOW OVER NORTON SOUND DURING THE WEEKEND. THIS
INCREASES INSTABILITY AND THE CHANCE OF SHOWERS AND CLOUDS.  THE
POSSIBLE GOOD NEWS IS THAT SOUTH CENTRAL MAY BE IN A BREAK IN BETWEEN
THE TWO LOWS.  SINCE THE LOWS ARE WEAK AND THE GUIDANCE IS
INCONSISTENT IT IS TOO EARLY TO TELL WHICH WILL WIN OUT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...ASH FALL ADVISORY ZONE 185.
MARINE...GALE 120 132 150.
FIRE WEATHER...NONE.

RHH JUL 08