Gale Warning 472, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM AKDT MON JUN 14 2010

.ANALYSIS AND UPPER LEVELS...WE ARE IN THE MIDST OF A PATTERN
CHANGE WITH A DEEP TROUGH OVER THE BERING SWINGING EASTWARD TOWARD
THE MAINLAND WHILE THE RIDGE OVER MAINLAND ALASKA TRANSLATES
EASTWARD. THUS...MID TO UPPER LEVEL FLOW IS SHIFTING TO THE
SOUTHWEST...A VERY FAVORABLE DIRECTION FOR TRANSPORTING MOISTURE
ACROSS SOUTHWEST AND MOST OF SOUTHCENTRAL ALASKA. ALSO...WATER
VAPOR IMAGERY SHOWS SEVERAL SHORT-WAVES EMBEDDED WITHIN THE BERING
TROUGH...POISED TO ROTATE INTO MAINLAND ALASKA. AT THE SURFACE
A LARGE LOW OVER THE CENTRAL BERING IS LIFTING NORTHWARD WHILE
A WEAKENING FRONT MOVES ONSHORE OF SOUTHWEST ALASKA. RADAR IMAGERY
SHOWS DISTINCT AREAS OF RAIN ALONG THE FRONT (AS OPPOSED TO A
SINGLE BAND OF RAIN)...WHICH LIKELY LINE UP WITH INDIVIDUAL WAVES
ALOFT. THERE ARE ALSO GUSTY SOUTHEASTERLY WINDS...BUT WITH A DEEP
MOIST LAYER OF SOUTH/SOUTHWEST FLOW THERE IS LITTLE IN THE WAY OF
DOWNSLOPE DRYING GOING ON. A SURFACE RIDGE IS BUILDING OUT AHEAD
OF THE FRONT OVER SOUTHCENTRAL...SO SOUTHEASTERLIES ARE ALSO
BEGINNING TO PICK UP IN THE USUAL PLACES. AS IS THE CASE IN
SOUTHWEST ALASKA...THESE WINDS MAY DELAY THE RAIN A BIT AND KEEP
IT A BIT LIGHTER ON THE IMMEDIATE LEE OF THE MOUNTAINS...BUT RAIN
WILL DEFINITELY FALL.

.MODEL DISCUSSION...GENERALLY SPEAKING THE MODELS ARE IN GOOD
AGREEMENT THROUGH THE SHORT-TERM WITH EVOLUTION OF MAJOR SYNOPTIC
FEATURES. THERE ARE SOME SMALL DIFFERENCES IN TRACK OF BERING LOW
AS WELL AS IN LOCATION OF DEVELOPMENT OF A SECONDARY LOW NORTH OF
SAINT PAUL ISLAND ON TUESDAY...BUT THESE DIFFERENCES MAKE LITTLE
DIFFERENCE IN THE OPERATIONAL FORECASTS. MORE SIGNIFICANT ARE
DIFFERENCES IN PLACEMENT AND TIMING OF INDIVIDUAL VORTICITY MAXIMA
OR SHORT-WAVES IN THE UPPER LEVELS...WHICH PROVIDES A CHALLENGE
TO THE EXACT TIMING OF PRECIPITATION. BOTTOM LINE THOUGH IS THAT
WE ARE ENTERING A WET PATTERN FOR THE SOUTHERN MAINLAND (WITH THE
EXCEPTION OF THE COPPER BASIN) AND OCCASIONAL RAIN IS EXPECTED AS
THESE UPPER WAVES MOVE ACROSS THE REGION.

.SOUTHCENTRAL...AN  OCCLUDED FRONT AND UPPER LEVEL SHORTWAVES
ASSOCIATED WITH THE LOW OVER THE BERING WILL BE IMPACTING THE
SOUTHCENTRAL REGION OVER THE NEXT SEVERAL DAYS.  THE EDGE OF THE
PRECIPITATION WAS AT HOMER THIS MORNING...AND WILL APPROACH THE
ANCHORAGE REGION BY LATE THIS EVENING. ALTHOUGH THERE WILL BE SOME
DOWNSLOPING ALONG THE WESTERN KENAI AND ANCHORAGE BOWL...MOIST
SOUTHWESTERLY FLOW AT MID AND HIGH LEVELS SHOULD ALLOW SOME SHOWERS
TO REACH THE SURFACE. RAIN WILL BEGIN TO DIMINISH ACROSS THE REGION
BY TUESDAY AFTERNOON...HOWEVER...SHOWERS WILL LINGER ALONG PRINCE
WILLIAM SOUND EVEN AFTER THE FRONT PASSES DUE TO MOIST ONSHORE FLOW.

.SOUTHWEST...RAIN AND FOG CONTINUE TO IMPACT MUCH OF THE SOUTHWEST
FORECAST REGION AS AN OCCLUDED FRONT AND UPPER LEVEL SHORTWAVES
PROGRESS THROUGH. ALTHOUGH THE FRONT WILL EXIT THE REGION EARLY
TUESDAY...RAIN SHOWERS WILL STILL IMPACT REGIONS ALONG THE BERING AS
A SURFACE LOW LINGERS IN THE CENTRAL BERING. A SERIES OF UPPER LEVEL
SHORTWAVES AND WEAK SURFACE FRONTS WILL CONTINUE ROTATE AROUND THIS
LOW AND BRING OCCASIONAL RAIN TO THE REGION THROUGH THE END OF THE
WEEK

.ALEUTIANS...THE CHANCE FOR SHOWERS WILL CONTINUE ACROSS MUCH OF THE
REGION AS A LOW STALLS IN THE CENTER OF THE BERING OVER THE NEXT FEW
DAYS. A FRONT WILL BRING THE CHANCE FOR STEADIER RAIN AS IT MOVES
ACROSS THE CENTRAL ALEUTIANS TONIGHT AND THE EASTERN ALEUTIANS BY
TUESDAY MORNING.

.LONGTERM...MODELS INDICATE THAT COOL AND MOIST CONDITIONS WILL
PERSIST ACROSS MUCH OF THE FORECAST REGION OVER THE NEXT WEEK.
UPPER LEVEL LOWS WILL CONTINUE TO LINGER IN THE BERING AND
SOUTHWEST ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...155 170 172 175.
FIRE WEATHER...NONE.

SEB/ELN JUN 10