Small Craft Advisory 461, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1245 PM AKDT SAT JUN 6 2009

.ANALYSIS AND UPPER LEVELS...HIGH AMPLITUDE TROUGH OVER THE BERING
AND RIDGE OVER THE GULF AND EASTERN ALASKA REMAIN IN PLACE. A
SHORT-WAVE TROUGH IS MOVING NORTH-NORTHEAST ACROSS SOUTHWEST ALASKA
THIS MORNING PRODUCING RAIN ALONG THE KUSKOKWIM DELTA AND SHOWERS
INLAND. AREAS OF STRATUS AND STRATO-CU SETTLED IN OVER MUCH OF
SOUTHCENTRAL OVERNIGHT AND IS HOLDING FIRMLY IN PLACE OVER NORTHERN
COOK INLET AND THE MAT-SU. THE 12Z ANCHORAGE SOUNDING SHOWS A STEEP
INVERSION FROM 830 MB TO 780 MB...WHICH IS PREVENT VERTICAL MIXING
NEEDED TO HELP DISSIPATE THE CLOUDS. THE SUN WILL HELP ERODE THE
CLOUDS FROM THE EDGES...BUT IT WILL TAKE QUITE A WHILE TO GET RID
OF ALL THE CLOUDS. A SURFACE HIGH IS BUILDING NORTHWARD ACROSS
BRISTOL BAY AND THE KUSKOKWIM VALLEY INTO THE INTERIOR. THIS HAS
SET UP NORTHERLY FLOW ACROSS SOUTHCENTRAL WHICH IS NOW RESULTING
IN FORMATION OF A LEE SIDE TROUGH OVER THE NORTHERN GULF...WHICH
IN TURN PROVIDES A POSITIVE FEEDBACK OF TIGHTER PRESSURE GRADIENT
AND STRONGER WINDS. THE STRENGTH OF THESE OFFSHORE WINDS WILL LIMIT
OR PREVENT SEA BREEZE FORMATION THIS AFTERNOON ALONG THE NORTH GULF
COAST AND PRINCE WILLIAM SOUND. THE WEATHER OUT WEST REMAINS ACTIVE
WITH A SERIES OF LOWS MOVING THROUGH THE BERING SEA TROUGH. AS ONE
LIFTS NORTHWARD OVER THE NORTHERN BERING ANOTHER IS DROPPING INTO
THE BACK SIDE OF THE TROUGH TOWARD THE WESTERN ALEUTIANS. A
SHORT-WAVE ROUNDING THE BOTTOM OF THE TROUGH IS PUSHING A SURFACE
LOW NORTHWARD TOWARD THE EASTERN ALEUTIANS AND SOUTHERN ALASKA
PENINSULA.

.MODEL DISCUSSION...DIFFERENCES IN MODEL SOLUTIONS LIE WITH THE
DETAILS OF LOW POSITIONS AND TRACKS...BUT THEY ARE ALL GROUPED
IN A FAIRLY SMALL AREA. THERE IS ALSO GOOD RUN-TO-RUN CONSISTENCY.
THEREFORE...WILL STICK CLOSE TO EXISTING FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE UPPER SHORT-WAVE OVER SOUTHWEST ALASKA
WILL CLIP THE SUSITNA VALLEY THIS AFTERNOON BEFORE HEADING TI
INTERIOR ALASKA. THIS WILL TRIGGER A FEW SHOWERS NORTH OF TALKEETNA.
THE PASSAGE OF THE SHORT-WAVE AND SHIFTING OF FLOW TO WEST TO
NORTHWEST WILL HELP BREAK UP THE CLOUDS SITTING OVER ANCHORAGE
AND MAT-SU REGION. SO EXPECT MOSTLY SUNNY SKIES TO DEVELOP BY
THIS EVENING. UPPER LEVEL SHORT-WAVE RIDGE WILL THEN BUILD OVERHEAD
SUNDAY WHILE SURFACE HIGH CONTINUES TO BUILD OVER INTERIOR ALASKA
AND SURFACE TROUGH BECOMES MORE WELL DEFINED ALONG THE NORTH GULF
COAST. THE NORTH TO EAST SYNOPTIC FLOW WILL ADVECT MUCH WARMER AIR
INTO THE REGION AND HELP TO FIGHT OFF SEA BREEZES...SO EXPECT
WIDESPREAD TEMPERATURES IN THE 60S AND 70S ON SUNDAY. ANOTHER
SHORT-WAVE TROUGH STEMMING FROM THE QUASI-PERMANENT ALEUTIAN LOW
WILL MOVE INTO SOUTHCENTRAL MONDAY BRINGING A FEW CLOUDS AND
SHOWERS...BUT IT WILL MOVE QUICKLY THROUGH ALLOWING THE RIDGE
TO BUILD BACK IN BY LATE TUESDAY. SO ITS LOOKING LIKE A GENERALLY
DRY AND WARM WEEK.

SOUTHWEST ALASKA...THE SHORT-WAVE OVER SOUTHWEST ALASKA WILL
EXIT THIS AFTERNOON AND EVENING AND SHORT-WAVE UPPER RIDGE WILL
BUILD IN. THIS WILL PRODUCE CLEARING SKIES OVER MOST OF BRISTOL
BAY AND THE LOWER KUSKOKWIM. CLOUDS WILL REMAIN ALONG THE PERIPHERY
OF THE RIDGE OVER THE KUSKOKWIM DELTA. ON SUNDAY THE SURFACE HIGH
WILL MOVE NORTH OF THE REGION AND LOW LEVEL FLOW WILL SHIFT TO
NORTHERLY TO EASTERLY. THIS WILL ADVECT IN WARMER AIR...PRODUCE
DRY OFFSHORE FLOW...AND HELP CLEAR OUT SOME OF THE CLOUDS OVER THE
KUSKOKWIM DELTA. THEREFORE...EXPECT A PARTLY CLOUDY TO MOSTLY SUNNY
DAY ACROSS SOUTHWEST ALASKA WITH MUCH WARMER TEMPERATURES IN THE
60S TO AROUND 70. THIS WILL BE SHORT-LIVED HOWEVER...AS THE NEXT
TROUGH SWINGS THROUGH ON MONDAY...BRINGING CLOUDS AND SHOWERS. AS
THE PROGRESSION OF TROUGH/RIDGES CONTINUES...UPPER RIDGE WILL BUILD
BACK IN LATE TUESDAY AND WEDNESDAY.

BERING SEA/ALEUTIANS...THE PACIFIC SYSTEM HEADED FOR THE EASTERN
ALEUTIANS/SOUTHERN ALASKA PENINSULA HAS DECENT JET SUPPORT AND IS
TAPPING INTO TROPICAL MOISTURE. THEREFORE...EXPECT THIS TO BE A
SOAKER. IT WILL RAPIDLY DISSIPATE AS IT MOVES ACROSS THE ALASKA
PENINSULA INTO BRISTOL BAY SUNDAY NIGHT WITH THE JET SUPPORT MOVING
OFF TO THE EAST. THE LOW DROPPING INTO THE BACK SIDE OF THE UPPER
TROUGH WILL EVOLVE INTO A VERY LARGE COMPLEX LOW AS IT SETTLES
INTO THE BOTTOM OF THE TROUGH MONDAY. DETAILS OF PARTICULAR LOWS
IS HARD TO PINPOINT...BUT WEATHER WILL REMAIN UNSETTLED ALONG THE
ALEUTIAN CHAIN.

.LONG TERM FORECAST...LONG-WAVE PATTERN LOOKS LIKE IT WILL REMAIN
UNCHANGED THROUGH THE END OF NEXT WEEK WITH LARGE CUT-OFF LOW ALONG
THE ALEUTIANS AND RIDGE OVER THE NORTHEAST PACIFIC AND NORTHWARD TO
MAINLAND ALASKA. SO LOOK FOR MORE OF THE SAME...WITH GENERALLY DRY
AND WARM CONDITIONS OVER SOUTHCENTRAL TRANSITIONING ACROSS SOUTHWEST
ALASKA TO CLOUDY AND WET CONDITIONS ALONG THE ALEUTIANS AND SOUTHERN
ALASKA PENINSULA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 155.
FIRE WEATHER...NONE.

SEB JUN 09