Small Craft Advisory 441, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT FRI MAY 29 2009

.ANALYSIS AND UPPER LEVELS...
ON THE LARGE SCALE...MEAN UPPER LOW PRESSURE ENCOMPASSES THE
STATE...EXTENDING FROM THE ALEUTIANS NORTHEAST INTO THE NORTHWEST
TERRITORIES OF CANADA. GETTING MORE DETAILED...THERE IS A COMPLEX
AREA OF LOW PRESSURE CENTERED JUST SOUTH OF THE WEST/CENTRAL
ALEUTIANS WITH AN OCCLUDED FRONT EXTENDING EAST ALONG THE CENTRAL
AND EASTERN ALEUTIANS TO THE AKPEN. OVER THE MAINLAND...TWO UPPER
LEVEL LOWS ARE PRESENT...ONE CENTERED OVER NORTON SOUND AND THE
OTHER OVER THE YUKON. SURFACE HIGH PRESSURE IS PRESENT OVER THE
NORTHERN BERING AND OVER THE SOUTHERN GULF OF ALASKA.

A PATTERN CHANGE IS IN STORE...WITH THE HIGH PRESSURE IN THE
SOUTHERN GULF OF ALASKA BUILDING NORTH INTO THE NORTHEAST GULF AND
YUKON. THE LOW PRESSURE COMPLEX CENTERED JUST SOUTH OF THE ALEUTIANS
WILL STRENGTHEN TO ENCOMPASS THE ENTIRE BERING...WITH A SOUTHERLY
JET ON THE EAST SIDE OF THE TROUGH BRINGING RAIN FURTHER NORTH INTO
THE WESTERN MAINLAND.

.MODEL DISCUSSION...
MODELS IN PRETTY GOOD AGREEMENT...ALTHOUGH THEY HAVE MADE A CHANGE
REGARDING THE RIDGE POSITION. THE MODELS ARE NOW KEEPING THE
BUILDING RIDGE A LITTLE FURTHER EAST INTO THE NORTHEAST GULF AND
YUKON FOR THE NEXT COUPLE DAYS...WHICH WOULD KEEP MOST OF THE
FORECAST AREA ON THE WET/WEST SIDE OF THE RIDGE. THE ECMWF FIRST HAD
THIS EASTWARD TREND WITH THE 12Z RUN YESTERDAY...AND BEGINNING WITH
THE 0Z MODEL RUNS LAST NIGHT...ALL OTHER MODELS HAVE LATCHED ON.

.SHORT TERM FORECAST...
SOUTHCENTRAL SOUTH AND EAST OF THE ALASKA RANGE...
THE UPPER LEVEL TROUGH AXIS WHICH HAS BEEN JUST UPSTREAM OF MAINLAND
SOUTHCENTRAL WILL FINALLY PUSH THROUGH LATE THIS AFTERNOON WITH
GENERALLY DRY CONDITIONS TONIGHT INTO SATURDAY MORNING. BEGINNING
SATURDAY AFTERNOON...STRONG HIGH PRESSURE WILL BUILD NORTH INTO THE
NORTHEAST GULF AND YUKON...WHILE A SOUTHERLY JET MOVES NORTH INTO
THE WESTERN GULF/SOUTHWEST MAINLAND BRINGING WITH IT ABUNDANT
RAINFALL. SOUTHCENTRAL WILL BE RIGHT IN BETWEEN THE HIGH AND LOW.
RIGHT NOW...IT LOOKS LIKE FROM LATE SATURDAY THROUGH MONDAY MOST OF
THE RAIN WILL BE FROM ANCHORAGE WEST...WITH GENERALLY DRY AND WARMER
CONDITIONS FURTHER EAST INTO THE COPPER RIVER BASIN. ALSO...EXPECT
INCREASING SOUTHERLY WINDS THROUGH THE WEEKEND...THE STRONGEST BEING
THROUGH CHANNELED TERRAIN.

SOUTHWEST MAINLAND...
LIGHT WEST TO NORTHWEST FLOW WILL QUICKLY BE REPLACED BY
MOIST...STRONG SOUTHERLY FLOW BEGINNING SATURDAY MORNING. EXPECT
WIDESPREAD RAIN AND WINDY CONDITIONS SATURDAY INTO AT LEAST EARLY
NEXT WEEK.

BERING SEA/ALEUTIANS...
MEAN LOW PRESSURE WILL RESIDE OVER THE ALEUTIANS FOR THE NEXT
SEVERAL DAYS...WITH SEVERAL INDIVIDUAL SURFACE LOWS ROTATING AROUND
THE MEAN UPPER LEVEL LOW. THE BERING/NORTH PACIFIC TROUGH WILL
AMPLIFY SATURDAY AND SUNDAY...BRINGING RAIN FURTHER NORTH TO THE
PRIBILOFS AND DRIER NORTHERLY FLOW TO THE WESTERN ALEUTIANS.

.LONG TERM FORECAST...
SOME MODEL DISAGREEMENT EXISTS REGARDING THE TRACK OF INDIVIDUAL
LOWS IN THE EXTENDED...BUT GENERALLY THE MODELS AGREE ON THE PATTERN
PERSISTING OF MEAN LOW PRESSURE IN THE BERING/ALEUTIANS ON THE WEST
LEG OF AN OMEGA BLOCK...AND HIGH PRESSURE OVER THE EASTERN GULF AND
YUKON.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING ZONES 150 155 172 175 413 414.
FIRE WEATHER...NONE.

FOISY MAY 09