Small Craft Advisory 599, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
337 AM AKDT WED JUL 30 2008

.ANALYSIS AND UPPER LEVELS...
A STRONG VERTICALLY STACKED UPPER LEVEL LOW IS POSITIONED OVER THE
ARCTIC NORTH OF BARROW THIS MORNING. STRONG UPPER LEVEL NORTHWEST
FLOW DOMINATES THE MAINLAND TO THE SOUTH OF THE ARCTIC LOW. AN
EMBEDDED SURFACE COLD FRONT IS MOVING SOUTH THROUGH THE CENTRAL
INTERIOR...WITH AIR COLD ENOUGH BEHIND THE FRONT FOR SNOW IN BARROW.
WIDESPREAD RAIN WITH THE FRONT IS PRESENT THIS MORNING ON THE NORTH
AND WEST SIDE OF THE ALASKA RANGE...WITH ONLY SOME LIGHT RAIN BEING
ABLE TO SNEAK OVER THE ALASKA RANGE INTO SOUTHCENTRAL.

THE BERING SEA AND ALEUTIANS ARE DOMINATED BY LIGHT FLOW ALOFT AND
AT THE SURFACE. HIGH PRESSURE IS PRESENT OVER THE EASTERN
BERING/ALEUTIANS WITH A STATIONARY...WEAK VERTICALLY STACKED LOW
JUST NORTH OF ADAK. LOW CLOUDS AND FOG DOMINATE THE
BERING/ALEUTIANS.

.MODEL DISCUSSION...
MODELS ARE DOING AN OKAY JOB...AT LEAST A LITTLE BETTER THAN THEY
HAD BEEN DOING. THE DAY CREW WENT MOSTLY WITH THE 12Z GFS THROUGH
THE EXTENDED...AND THANKFULLY THE 0Z GFS CAME IN SIMILAR TO THE 12Z
GFS...SO MINOR CHANGES ARE BEING MADE TO THE FORECAST. ECMWF HAS
BEEN LESS CONSISTENT RUN TO RUN. WHEN LOOKING AT ALL THE GFS
ENSEMBLE MEMBERS FOR THE PRESENT WEAK GULF LOW AND THE LOW TO AFFECT
THE WESTERN/CENTRAL ALEUTIANS BEGINNING FRIDAY...OPERATIONAL GFS
STILL SEEMS TO BE ON THE EDGE OF THE ENVELOPE OF SOLUTIONS...SO GFS
ENSEMBLE MEAN IS PROBABLY THE BEST SOLUTION.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
THE COLD FRONT WHICH HAS BROUGHT COPIOUS RAINFALL TO THE NORTH SIDE
OF THE ALASKA RANGE WILL CROSS THE RANGE TODAY. HOWEVER...BECAUSE OF
DOWNSLOPING...ONLY AREAS OF LIGHT RAIN ARE EXPECTED OVER
SOUTHCENTRAL WITH THE COLD FRONT FALLING APART AS WELL. THE RAIN
WILL TAPER OFF FOR MOST AREAS BY TONIGHT. UPPER LEVEL NORTHWEST FLOW
WILL PERSIST THROUGH FRIDAY TO THE SOUTH OF THE ARCTIC LOW...BUT
MOST SYSTEMS WILL ONLY GRAZE NORTHERN SOUTHCENTRAL. MOST AREAS WILL
BE DRY TONIGHT THROUGH FRIDAY AND WARM COMPARED TO THE TEMPERATURES
SEEN MOST OF THE SUMMER.

SOUTHWEST MAINLAND...
WEST TO NORTHWEST FLOW TO PERSIST OVER THE SOUTHWEST MAINLAND
THROUGH FRIDAY. AREAS OF RAIN WILL PERSIST INTO TONIGHT MAINLY OVER
THE KUSKOKWIM VALLEY. OTHERWISE...DRY THROUGH FRIDAY. HOWEVER...LOW
CLOUDS WILL BE TOUGH TO SHAKE IN SOME AREAS...ESPECIALLY THE
KUSKOKWIM DELTA...DUE TO ONSHORE FLOW.

BERING SEA/ALEUTIANS...
ABUNDANT LOW CLOUDS AND FOG TO PERSIST OVER THE BERING/ALEUTIANS
THROUGH FRIDAY DUE TO LIGHT FLOW AND LARGE SCALE HIGH PRESSURE. WEAK
LOW PRESSURE WILL BE PRESENT THROUGH TONIGHT JUST NORTH OF
ADAK...WITH A SOMEWHAT MORE SIGNIFICANT LOW TO BEGIN TO AFFECT THE
WESTERN/CENTRAL ALEUTIANS FROM THE SOUTHWEST BEGINNING FRIDAY.

.LONG TERM FORECAST...
A BRIEF RETURN TO WET CONDITIONS IS POSSIBLE THIS WEEKEND OVER
THE SOUTHERN MAINLAND...AS A SYSTEM MOVES THROUGH FROM WEST TO EAST
WITH RAIN CHANCES AND WETTER LOW LEVEL SOUTHERLY FLOW OVER
SOUTHCENTRAL. HOWEVER...THE DRY NORTHWEST FLOW SHOULD RESUME LATE
SUNDAY INTO NEXT WEEK AS THE RIDGE OF HIGH PRESSURE IN THE EASTERN
BERING AMPLIFIES.

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

FOISY JUL 08