Flood in Alaska, June 23 to 25, 2012

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
306 PM AKDT SAT JUN 23 2012

.SHORT TERM...AN AREA OF LOW PRESSURE OVER THE SOUTHERN
PANHANDLE THIS AFTERNOON HAS CAUSED WINDS TO SHIFT TO THE SOUTH
ABRUPTLY ONCE IT PASSES WITH WINDS GUSTING TO AROUND 40MPH AND
TEMPERATURES DROPPING NEARLY 20 DEGREES. THIS LOW WILL WEAKEN AS
IT LIFTS NORTH OVER THE REST OF THE PANHANDLE THROUGH THE
NIGHT...SO EXPECTING WINDS GUSTS OF ABOUT 20 TO 30 MPH OVER THE
CENTRAL AREAS. AGAIN THIS WILL BE SHORT-LIVED AND WITH NO
PRECIPITATION EXPECTED...HOWEVER TEMPERATURES WILL REMAIN DOWN AS
THEY FALL TO THEIR OVERNIGHT LOWS.

 SUNDAY THE RIDGE OF HIGH PRESSURE CURRENTLY OVER THE GULF WILL
BE PUSHED EAST OVER THE REGION BY THE NEXT SYSTEM MOVING INTO THE
GULF. THE RIDGE WILL CAUSE ANOTHER BURST OF SOUTHERLY WINDS
THROUGH THE INSIDE WATERS. HAVE GONE WITH SMALL CRAFT ADVISORIES
FOR CLARENCE STRAIT THIS EVENING AND AGAIN SUNDAY AFTERNOON. ALSO
HAVE SMALL CRAFT ADVISORIES SUNDAY AFTERNOON FOR SOUTHERN
CHATHAM...SUMNER...AND NORTHERN LYNN CANAL.

 MUCH OF THE DAY SUNDAY WILL BE PARTLY CLOUDY TO MOSTLY SUNNY
AGAIN WITH TEMPERATURES IN THE UPPER 70S TO AROUND 80F IN THE
NORTH. THE SOUTHERN AREAS WILL SEE MORE CLOUD COVER AND THUS
COOLER TEMPERATURES IN THE 60S. A MARINE LAYER IN THE GULF WILL
MOVE IN OVERNIGHT AND REMAIN ALONG THE COAST THROUGH SUNDAY AS
LOW LEVEL FLOW TURNS MORE ONSHORE. THIS WILL KEEP THOSE AREAS
COOLER AS WELL.

 MODELS WERE IN GOOD AGREEMENT IN THE SHORT TERM. TRENDED TOWARD
THE ECMWF AS IT INITIALIZED WELL THEN MORE OF MESO-SCALE MODELS
FOR UPDATES TODAY. FORECASTER CONFIDENCE IS AVERAGE.

 &&

 .LONG TERM...A RETURN TO TYPICAL SOUTHEAST AK WEATHER IN STORE
FOR THE EXTENDED FORECAST. PACIFIC HIGH PRESSURE RIDGE WILL BREAK
DOWN AS MID LEVEL LOW PRESSURE SYSTEM ORIGINATING IN THE BERING
SEA TRACKS SOUTHEASTWARD OVER THE ALEUTIANS AND INTO THE
NORTHWESTERN AK GULF SUNDAY NIGHT INTO MONDAY. THIS MID LEVEL LOW
IS EXPECTED TO REMAIN THE DOMINANT FEATURE IN THE GULF THROUGH
NEXT WEEKEND. AT THE SURFACE LOW PRESSURE TROUGH WITH EXTENDING
OCCLUDED FRONT WILL MOVE ACROSS THE GULF REACHING THE PANHANDLE
LATE SUNDAY NIGHT INTO EARLY MONDAY MORNING. RAIN WILL DEVELOP
THROUGH THE NIGHT WITH CATEGORICAL PRECIPITATION OVER THE
MAJORITY OF THE REGION. ASSOCIATED HIGH PRESSURE RIDGE OVER THE
PANHANDLE WILL KEEP WINDS SOUTHERLY WITH SMALL CRAFT WINDS OVER
NORTHERN AND SOUTHERN LYNN CANAL SUNDAY NIGHT INTO MONDAY BEFORE
THE PRESSURE GRADIENT WEAKENS. EXPECTING A SERIES OF WEAK SURFACE
SHORT WAVES TO MOVE UNDER THEN MID LEVEL LOW THROUGH THE WEEK.
THIS ALONG WITH ONSHORE FLOW WILL KEEP THE REGION CLOUDY AND WET
WITH MILD TEMPERATURES. HIGHS WILL MAINLY BE IN THE UPPER 50S AS
THE MID LEVEL LOW BRINGS IN COLDER AIR FROM NORTHERN REGIONS.

 MODELS WERE IN GOOD AGREEMENT THROUGH WEDNESDAY WITH THE TIMING
OF THE APPROACHING FRONT AND COLD AIR MASS MOVING IN. BEGIN TO
SEE MODELS DIVERGE BY WEDNESDAY WITH THE GFS MOVING A STRONGER
LOW ACROSS THE NORTH PACIFIC COMPARED TO THE ECMWF...THUS THE
ECMWF KEEPS THE AK GULF LOW A BIT STRONGER. DID SEE A BIT MORE
AGREEMENT BETWEEN THE GFS AND ECMWF WITH NEW MODELS RUNS AND
STARTING TO SEE MORE CONSISTENCY WITH THE GFS. USED A BLEND OF
GFS/ECMWF TO UPDATE GRIDS THROUGH DAY 4 THEN TRANSITIONED TO AN
GFS/EC/HPC BLEND FINALLY ALL HPC TOWARDS DAY 8.

 FORECAST CONFIDENCE IS ABOVE AVERAGE THROUGH MID WEEK DUE TO THE
GOOD MODEL AGREEMENT BUT THEN CONFIDENCE DROPS BELOW AVERAGE
THROUGH THE END OF THE WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...AREAL FLOOD ADVISORY UNTIL 5 AM AKDT MONDAY FOR AKZ019.
         AREAL FLOOD WARNING UNTIL 5 AM AKDT MONDAY FOR AKZ018.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-033-035-036.

&&

HANNON/PRB