Small Craft Advisory 434, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
300 PM AKDT TUE JUL 31 2012

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWING LOW
PRESSURE SYSTEM TRACKING INTO THE SOUTHEAST AK GULF WITH THE
ASSOCIATED FRONT CURRENTLY PASSING OVER THE AK PANHANDLE. STEADY
PRECIPITATION OCCURRING OVER THE CENTRAL AND SOUTHERN PANHANDLE
WITH HEAVY PRECIPITATION TO THE SOUTH. RAIN FALL AMOUNTS UP TO
ONE INCH OR MORE HAVE BEEN REPORTED FROM THIS SYSTEM. THE
NORTHWESTERN PANHANDLE COAST HAS TRANSITIONED TO POST FRONTAL
SHOWER ACTIVITY. SOME CLEAR BREAKS OCCURRING OVER YAKUTAT AS
WINDS SHIFT TO OFFSHORE FLOW. AS THE FRONT CONTINUES TO TRACK
EAST RAIN WILL DIMINISH FROM NORTH TO SOUTH WHILE TRANSITIONING
TO SHOWERS...WHICH WILL BECOME SCATTERED TO ISOLATED WEDNESDAY
MORNING INTO THE AFTERNOON. WINDS OVER THE CENTRAL AND SOUTHERN
PANHANDLE STEADILY INCREASED THROUGH THE DAY WITH THE APPROACHING
FRONT. UPPER END SMALL CRAFT WINDS WERE REPORTED OVER THE
SOUTHERN INNER CHANNELS WITH BRIEF GALES FORCE WINDS OCCURRING
OVER THE SOUTHERN OUTER COAST. INLAND GUSTS UP TO 35 MPH WERE
REPORTED THIS AFTERNOON. WINDS WILL DIMINISH QUICKLY THIS EVENING
FOR THE CENTRAL PANHANDLE WHILE LINGERING A BIT LONGER TO THE
SOUTH.

 THE LOW IN THE SOUTHEAST GULF WILL WEAKEN TO AN OPEN WAVE TROUGH
THROUGH WEDNESDAY MORNING. A RIDGE OF HIGH PRESSURE WILL BUILD
OVER THE PANHANDLE WITH WINDS INCREASING OVER THE NORTHERN
PANHANDLE AS THE GRADIENT TIGHTENS. BY WEDNESDAY AFTERNOON NEXT
BAND OF PRECIP ASSOCIATED WITH A SYSTEM MOVING INTO THE WESTERN
GULF WILL BEGIN TO AFFECT THE NORTHWESTERN PANHANDLE.

 MODELS WERE IN GOOD AGREEMENT TODAY. OVERALL THE GFS AND NAM
INITIALIZATION WERE PREFERRED. MAIN DIFFERENCES WERE TIMING OF
PRECIP ENDING FOR THE NORTHERN AND CENTRAL PANHANDLE TONIGHT WITH
GFS DROPPING POPS A BIT FASTER THAN THE NAM AND ECMWF. BLENDED IN
SOME GFS AND NAM WITH INHERITED GRIDS. MAIN CHANGES WERE KEEPING
SOME SMALL CRAFT WINDS A BIT LONGER IN THE EVENING BUT OTHER WISE
DIFFERENCES WERE MINOR. FORECAST CONFIDENCE IS ABOVE AVERAGE.

 HYDROLOGY...WHILE HEAVY RAIN WILL CAUSE LOCAL STREAMS AND RIVER
TO RISE...ESPECIALLY OVER THE SOUTHERN PANHANDLE...NOT EXPECTING
THESE RISES TO BE SIGNIFICANT AS RIVERS ARE BELOW AND WILL REMAIN
BELOW ACTION STAGE.

&&

.LONG TERM...MODELS ARE IN GENERAL AGREEMENT THROUGH THE WEEKEND
WITH AN UPPER LEVEL RIDGE ACROSS THE EASTERN GULF AND SOUTHEAST
ALASKA WEDNESDAY NIGHT DRIFTS EAST INTO CANADA THROUGH THURSDAY
NIGHT AND A CLOSED UPPER LOW EMBEDDED WITHIN THE NEXT UPPER
SHORTWAVE TROUGH APPROACHING THE WESTERN GULF LATE THURSDAY INTO
EARLY FRIDAY. THIS UPPER SHORTWAVE TROUGH DRIFTS EAST ACROSS THE
NORTHERN PANHANDLE THROUGH THE WEEKEND. A WEAK SURFACE RIDGE OF
HIGH PRESSURE ACROSS THE FORECAST DOMAIN WILL FURTHER WEAKEN
THROUGH THURSDAY NIGHT AND THE RIDGE TOP WILL BECOME FLAT BY LATE
THURSDAY NIGHT...ALLOWING A FRONTAL PASSAGE DRIFTS EAST ACROSS THE
NORTHERN PANHANDLE. REFRESHED THE INHERITED FORECAST PACKAGE WITH
THE MOST CONSISTENT GFS SOLUTIONS THROUGH THE WEEKEND.

 CHANCE OF RAIN WILL REPLACE ISOLATED SHOWERS OVER THE NORTHERN
AREAS BY WEDNESDAY EVENING INTO LATE WEDNESDAY NIGHT. CATEGORICAL
POPS WILL BEGIN AFFECTING YAKUTAT AREA LATE WEDNESDAY
NIGHT...SPREADING SOUTHEAST TO THE CENTRAL PANHANDLE THROUGH
THURSDAY. EXPECT CHANCE POPS ACROSS THE SOUTHERN AREAS. RAIN CAN
BE HEAVY AT TIMES OVER THE NORTH CENTRAL PANHANDLE. NOT MUCH WINDS
WILL BE DRIVEN DUE TO THE MAIN FRONTAL PASSAGE AND THE PARENT LOW
PASSING NORTH OF THE AREA. HOWEVER...A WEAK EMBEDDED BARRIER JET
WILL SET SMALL CRAFT WINDS OVER THE NORTHERN OUTER WATERS AND
NORTHERN MOST INNER CHANNELS WEDNESDAY NIGHT INTO THURSDAY.

 MODEL DIFFERENCES BECOME LARGER EARLY NEXT WEEK AS A PACIFIC
HIGH BUILDS AND BREAKS INTO THE ALASKAN GULF. LEANED OVER THE HPC
APPROACH FOR THE REMAINING LONG TERM PERIODS. GENERALLY DRIER
WEATHER WITH NO SIGNIFICANT WINDS ARE EXPECTED THROUGH THE FIRST
HALF OF NEXT WEEK. ESPECIALLY SOUTHERN AREAS...FREQUENT SUNNY
BREAKS CAN BE GRANTED.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ042.
         SMALL CRAFT ADVISORY FOR PKZ012-022-031>036-041-043.

&&

PRB/AHN