Small Craft Advisory 442, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTED
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT SAT MAY 30 2009

.ANALYSIS AND UPPER LEVELS...
A PATTERN CHANGE IS OCCURRING ACROSS THE STATE TODAY. THE COLD UPPER
LEVEL LOW WHICH HAD BEEN PARKED NEAR THE SEWARD PENINSULA IS LIFTING
BACK NORTH INTO THE ARCTIC. A HIGH PRESSURE RIDGE IS AMPLIFYING OVER
THE EASTERN GULF OF ALASKA AND INTO THE YUKON WHILE A STRONG
SOUTHERLY JET STREAM IS MOVING NORTH TOWARD THE ALASKA PENINSULA.

AS THE JET STREAM WORKS NORTH INTO THE AKPEN/SOUTHWEST
MAINLAND...THE RESIDUAL COLD AIR FROM THE CENTRAL/NORTHERN BERING
AND YUKON/KUSKOKWIM DELTA WILL ERODE...AND RAIN AND WIND WILL
OVERSPREAD THE REGION FROM THE CENTRAL BERING INTO THE SOUTHWEST
MAINLAND FOR SOME TIME TO COME.

.MODEL DISCUSSION...
MODELS ARE STRUGGLING A BIT MORE TODAY IN THE SHORT TERM OVER THE
WEST THAN THEY HAD BEEN. MODELS HAVE NOT HANDLED THE PRESENT
SHORTWAVE MOVING THROUGH THE SOUTHERN BERING TOO WELL...AND THE RUN
TO RUN MODEL CONSISTENCY WITH THE TIMING OF SYSTEMS OUT WEST HAS
FALLEN APART. STILL...MOST 12Z MODEL RUNS WITH THE EXCEPTION OF THE
NAM AGREE WITH EACH OTHER...SO WILL TREND FORECASTS TOWARD THIS
SOLUTION WHILE STILL ATTEMPTING NOT TO GET TOO CUTE WITH THE EXACT
TIMING OF FEATURES BEYOND THE FIRST PERIOD OR TWO. OUT IN THE
EXTENDED...MODELS AGREE WELL ON THE LARGE SCALE STRONG OMEGA BLOCK
WITH THE CENTER/HIGH PRESSURE PORTION OF THE OMEGA BLOCK BEING
CENTERED OVER THE EASTERN GULF OF ALASKA...BUT DISAGREE SOME WITH
INDIVDUAL LOW PRESSURE SYSTEM TRACKS OUT WEST ON THE WEST LEG OF THE
OMEGA BLOCK.

.SHORT TERM FORECAST...
SOUTHCENTRAL SOUTH AND EAST OF THE ALASKA RANGE...
SHORTWAVE IN MOIST SOUTHWEST FLOW TO MOVE THROUGH SOUTHCENTRAL
TONIGHT...BRINGING WIDESPREAD RAIN TO ALL BUT PERHAPS THE MIDDLE OF
THE COPPER RIVER BASIN. THEN ON SUNDAY THE RIDGE OVER THE EASTERN
GULF REALLY AMPLIFIES AND BUILDS NORTH AND NORTHWEST A
LITTLE...BRINGING AN END TO THE RAIN IN THE AFTERNOON OVER MOST
AREAS. BREEZY SOUTHERLY WINDS WILL PERSIST OVER MOST AREAS
HOWEVER...AND WILL NEED TO CONSIDER THE COPPER RIVER BASIN FOR A
POSSIBLE RED FLAG WARNING. THE EASTERN GULF HIGH PRESSURE WILL
CONTINUE TO AMPLIFY AND BUILD NORTH TOWARD THE YUKON/ALASKA BORDER
THROUGH TUESDAY. HOWEVER...THAT LEAVES SOUTHCENTRAL ON THE DIRTY
SIDE OF THE RIDGE WITH ONSHORE FLOW PERSISTING. STILL...TEMPERATURES
WILL GRADUALLY REBOUND AND SOME DRYING WILL OCCUR...THE MORE THE
FURTHER EAST AND FURTHER INLAND YOU GO. RAIN FROM SUNDAY NIGHT
THROUGH TUESDAY SHOULD REMAIN ALONG AND WEST OF A LINE FROM THE
WESTERN SUSITNA VALLEY TO COOK INLET TO KODIAK...BUT WE WILL NEED TO
KEEP A CLOSE EYE ON THINGS AS A SUBTLE SHIFT IN THE MODELS COULD
MEAN A BIG DIFFERENCE FOR THE BIG POPULATION CENTERS OF
SOUTHCENTRAL.

SOUTHWEST MAINLAND WEST OF THE ALASKA/ALEUTIAN RANGE...
RAINY AND WINDY CONDITIONS WILL PERSIST THROUGH AT LEAST TUESDAY
OVER THE SOUTHWEST MAINLAND AS NUMEROUS SHORTWAVES MOVE THROUGH IN
SOUTHERLY FLOW...RIDING THE STRONG SOUTHERLY JET STREAM OVER THE
AREA.

BERING SEA/ALEUTIANS/AKPEN...
AS MENTIONED IN THE MODEL DISCUSSION...MODEL RUN TO RUN CONSISTENCY
HAS BEEN LESS THAN STELLAR OUT WEST. NOT A LOT OF TRUST IN THE
TIMING OF SYSTEMS RIGHT OFF THE BAT...AS THE NEXT OF A MULTITUDE OF
SYSTEMS APPROACHING THE AREA FROM THE NORTH PACIFIC SEEMS TO BE
DEVELOPING A CLOSED CIRCULATION...AT LEAST AT MID LEVELS...EARLIER
THAN THE MODELS HAD INDICATED. BUT THERE IS CONFIDENCE ON VERY MOIST
SOUTH TO SOUTHEAST FLOW OVER THE REGION FOR AT LEAST THE NEXT
SEVERAL DAYS WITH LITTLE MORE THAN A SIX HOUR BREAK BETWEEN SYSTEMS.
THE WESTERN ALEUTIANS SHOULD REMAIN GENERALLY DRY AND TO THE WEST OF
MOST OF THE SYSTEMS ROTATING NORTH THEN WEST AROUND THE MEAN LOW
CENTERED SOUTH OF THE ALEUTIANS. THE PRIBILOFS HAVE ACTUALLY GOTTEN
SOME SNOW TODAY...BUT THE REMNANT COLD AIR FROM THE PRIBILOFS NORTH
WILL QUICKLY BE REPLACED BY WARM AIR TONIGHT WITH PRECIP TYPE
BECOMING ALL RAIN.

.LONG TERM FORECAST...
HIGH CONFIDENCE IN THE OVERALL PATTERN PERSISTING THROUGH ABOUT
FRIDAY...WITH THE OMEGA BLOCK CENTERED OVER SOUTHEAST ALASKA OR THE
EASTERN GULF AND WET CONDITIONS PERSISTING FROM THE SOUTHWEST
MAINLAND INTO THE CENTRAL BERING/ALEUTIANS. THE TRICKY PARTS WILL
CONTINUE TO BE THE TIMING OF INDIVIDUAL SYSTEMS OUT WEST...AND
WHETHER OR NOT THE RIDGE INCHES EAST ENOUGH TO ALLOW SOUTHCENTRAL TO
GET BACK INTO THE RAIN. ECMWF HAS GENERALLY BEEN SHIFTING THE
RIDGE/CENTER OF THE OMEGA BLOCK EAST A LITTLE MORE THAN THE
GFS...AND THE GFS HAS BEEN MUCH STRONGER WITH A LOW MOVING INTO THE
EASTERN BERING THURSDAY. NOT SURE WHICH MODEL TO TRUST OUT IN THE
EXTENDED AT THIS POINT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING ZONES 150 155 160 175 413.
FIRE WEATHER...CONTEMPLATING RED FLAG WARNING OR FIRE WEATHER WATCH
               FOR 141.

FOISY MAY 09