Small Craft Advisory 483, NWS Anchorage, AK

SOUTH CENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT THU JUL 14 2011

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT IN THE SHORT TERM WITH THE EXCEPTION OF
THE LOW MOVING INTO THE SOUTHERN BERING FRI AND SAT. BY SAT EVENING
SOLUTIONS RANGE FROM JUST WEST OF THE PRIBILOFS TO NORTH OF ATTU.  WE
WENT WITH THE GFS BASED ON CONTINUITY FROM THE PREVIOUS PACKAGE AND
THE GFS POSITION IS AN AVERAGE OF THE OTHER MODELS.
IN THE LONG TERM...MODELS AGREE IN BUILDING A RIDGE ALONG THE
SOUTHWEST COAST MON AND  WITH THE POSITION AND STRENGTH OF THE NEXT
LOW MOVING TO THE WESTERN ALEUTIANS MON.

.ANALYSIS AND UPPER LEVELS...
.UPPER LEVELS...A COLD CORE LOW LIES OVER ST LAWRENCE ISLAND. A
SHORTWAVE ROTATING AROUND THIS LOW IS MOVING OVER SOUTHWEST ALASKA
BRINGING RAIN AND LOW CLOUDS WEST OF THE ALASKA RANGE TODAY AND
TONIGHT. A SECOND WAVE IS MOVING SLOWLY ACROSS THE SOUTH CENTRAL.
THIS WAVE BROUGHT SHOWERS TO ANCHORAGE EARLIER TODAY.  SHOWERS WILL
END FROM THE WEST OVER THE COPPER RIVER BASIN TONIGHT AS THIS WAVE
MOVES OVER.  A SMALL SHORT WAVE WILL MOVE FROM THE EASTERN ALEUTIANS
TO THE SOUTHERN GULF OF ALASKA FRI.

.AT THE SURFACE...A SURFACE LOW LIES BENEATH THE UPPER LEVEL LOW IN
THE NORTH BERING. THE WESTERLY FLOW SOUTH OF THIS LOW IS BRINGING LOW
CLOUDS AND RAIN TO SOUTHWEST ALASKA. THE PRESSURE GRADIENT BETWEEN
THERMAL TROUGH OVER THE COPPER RIVER BASIN AND A WEAK RIDGE OVER THE
KUSKOKWIM VALLEY IS CAUSING GUSTY NORTH AND WEST WINDS OVER THE KENAI
PENINSULA INCLUDING RESURRECTION BAY AND WHITTIER.

.SHORT TERM FORECAST...
.SOUTH CENTRAL...SHOWERS WILL END FROM THE WEST OVER SOUTH CENTRAL AS
AN UPPER LEVEL WAVE MOVES ACROSS THE REGION. CONDITIONS SHOULD DRY
OUT TONIGHT AND STAY RELATIVELY DRY UNTIL A NEW SYSTEM APPROACHES FRI
NIGHT AND SAT. MEANWHILE SHOWERS WILL CONTINUE OVER THE COPPER RIVER
BASIN AS THE THERMAL TROUGH PERSISTS IN THE BASIN. ISOLATED
THUNDERSTORMS ARE LIKELY IN THE BASIN FRIDAY.

.SOUTHWEST MAINLAND...A SERIES OF UPPER LEVEL SHORTWAVES CONTINUE TO
MOVE THROUGH THE KUSKOKWIM DELTA REGION BRING RAIN. THESE WAVES WILL
WEAKEN AS THEY APPROACH BRISTOL BAY SO ONLY ISOLATED SHOWERS ARE
EXPECTED THERE. WITH THE UPPER LEVEL LOW IN PROXIMITY WEAK WAVES WILL
CONTINUE TO BRING RAIN TO THE SOUTHWEST MAINLAND OVER THE NEXT
SEVERAL DAYS.

.BERING AND ALEUTIANS...SURFACE RIDGING IS SUPPORTING FOG AND STRATUS
ACROSS MUCH OF THE SOUTHERN BERING. A WEAK LOW WILL DEVELOP AND
APPROACH THE EASTERN ALEUTIAN ISLANDS LATE TONIGHT BRINGING RAIN TO
THE CENTRAL AND THE EASTERN ALEUTIANS TONIGHT. A MORE IMPRESSIVE LOW
WILL FOLLOW QUICKLY ON ITS HEELS AND APPROACH SHEMYA BY FRIDAY
MORNING.

.LONG TERM FORECAST...
THE CURRENT PATTERN OF UPPER LEVEL RIDGING OVER
THE EASTERN NORTH PACIFIC AND LOWS IN THE BERING WILL CONTINUE
THROUGH MON. MODEL GUIDANCE RAPIDLY BECOMES UNCERTAIN AFTER MON NEXT
WEEK. THE CURRENT FORECAST SUPPORTS A RIDGE OF HIGH PRESSURE BUILDING
OVER WESTERN ALASKA THROUGH FRI NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 130 138 132 351
FIRE WEATHER...NONE.

RHH JUL 11