Small Craft Advisory 568, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKDT SAT AUG 13 2011

.ANALYSIS AND UPPER LEVELS...
A STRONG UPPER RIDGE REMAINS OVER THE EASTERN BERING SEA BUT IT IS
STARTING TO WEAKEN. AN UPPER LOW HAS MOVED INTO NORTHWEST ALASKA AND
HAS INTENSIFIED THE UPPER TROUGH OVER THE NORTHERN AND EASTERN
MAINLAND. THE SURFACE PATTERN IS VERY SIMILAR TO THE UPPER SYSTEMS
WITH A RIDGE OVER THE EASTERN BERING AND A TROUGH WITH MANY MINOR
LOWS OVER THE NORTHERN AND EASTERN ALASKA. MOST OF THE SOUTHERN
MAINLAND REMAINS CLOUDY WITH AREAS OF SHOWERS OVER THE SOUTHCENTRAL
ALASKA AND SOUTHWEST INTERIOR. LOW CLOUDS AND FOG COVER THE
ALEUTIANS, BERING SEA AND THE SOUTHWEST COASTAL SECTIONS.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THOUGH THE NAM IS PREFERRED OVER THE GFS
OVER THE GULF BECAUSE IT APPEARS TO HANDLE THE SURFACE WINDS ALONG
THE COAST BETTER. THE COLD UPPER LOW OVER NORTHWEST ALASKA WILL MOVE
INTO THE NORTHERN SUSITNA VALLEY SUNDAY AFTERNOON THEN INTO THE
NORTHERN GULF OF ALASKA MONDAY. A TROUGH EXTENDING TO THE WEST OF THE
LOW WILL MOVE SOUTH INTO THE BERING SEA AND WILL WEAKEN THE RIDGE AS
IT IS DISPLACED INTO THE WESTERN BERING MONDAY. AT THE SURFACE...THE
BROAD TROUGH OVER THE NORTHERN AND EASTERN INTERIOR WILL SPREAD SOUTH
AND WEST TO THE REST OF MAINLAND ALASKA TONIGHT. A WEAK LOW WILL
DEVELOP OVER THE KENAI PENINSULA SUNDAY MORNING AND WILL GRADUALLY
STRENGTHEN AS IT MOVES INTO THE NORTHEAST GULF MONDAY AFTERNOON.

.SHORT TERM FORECAST...
.SOUTHCENTRAL ALASKA...CLOUDS AND SCATTERED SHOWERS WILL CONTINUE
THROUGH TONIGHT AND AREAS OF RAIN DEVELOP LATE TONIGHT THROUGH SUNDAY
NIGHT AS THE UPPER LOW MOVES THROUGH THE REGION. RAIN WILL CHANGE TO
SCATTERED SHOWERS MONDAY. AREAS OF GUSTY WEST WINDS WILL DEVELOP
AROUND KODIAK ISLAND TONIGHT THROUGH SUNDAY NIGHT.

.SOUTHWEST ALASKA...AREAS OF RAIN OVER NORTHWEST ALASKA WILL SPREAD
SOUTH INTO THE KUSKOKWIM VALLEY AND KUSKOKWIM DELTA TONIGHT AND
BECOME SCATTERED SHOWERS SUNDAY AFTERNOON THROUGH MONDAY. AREAS OF
LOW CLOUDS AND FOG WILL PERSIST ALONG THE COAST THROUGH TONIGHT BUT
WILL IMPROVE SUNDAY AND MONDAY.

.BERING SEA AND ALEUTIANS...THE SURFACE RIDGE OVER THE EASTERN BERING
WILL BEGIN TO BREAK DOWN SUNDAY EVENING AS A WEAK TROUGH MOVES INTO
THE CENTRAL BERING. THIS WILL PRODUCE MORE UNSTABLE CONDITIONS WHICH
WILL REDUCE THE FOG AND PRODUCE MORE SHOWERS.

.LONG TERM FORECAST...
THE MID RANGE MODELS ARE IN FAIRLY GOOD AGREEMENT. A BROAD UPPER
TROUGH WILL REMAIN OVER MAINLAND ALASKA THROUGH WEDNESDAY. A UPPER
LOW DEVELOPING OVER THE KAMCHATKA PENINSULA MONDAY NIGHT WILL DRIFT
INTO THE CENTRAL BERING WEDNESDAY NIGHT. THIS PATTERN WILL KEEP THE
CLOUDS AND SHOWERS OVER THE SOUTHERN MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

NM AUG 11