Small Craft Advisory 573, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
235 PM AKDT SUN SEP 25 2011

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
UNDER PARTLY CLOUDY SKIES WITH FARE WEATHER CU DEVELOPING FROM AN
UPPER TROF MOVING ACROSS THE AREA. THERE IS AN AREA OF ALTO-CU
FROM CROSS SOUND EASTWARD TO JUNEAU BUT ONCE THE SUN SETS THESE
CLOUDS WILL DISSIPATE LIKE THE REST OF THE CLOUDS OVER THE
NORTHERN TWO THIRDS OF THE PANHANDLE TO BE MOSTLY CLEAR. THERE
MAY BE SOME ISOLATED SHOWERS EARLY THIS EVENING OVER THE SOUTHERN
THIRD FROM THE UPPER LEVEL ENERGY MOVING OVER THE AREA THIS
EVENING. WINDS ACROSS THE AREA ARE IN THE PROCESS OF SWITCHING
FROM THE NORTH TO THE SOUTH AS A RIDGE OF HIGH PRESSURE BUILDS
OVER THE AREA AHEAD OF A DEVELOPING LOW DRIFTING NE OUT OF THE
NORTH PACIFIC. WINDS SPEEDS WILL BE LESS THAN 15 KT. THE RIDGE
WILL DRIFT NE INTO CANADA THROUGH LATE TONIGHT AND THE WINDS OVER
THE INNER CHANNELS WILL BACK AROUND TO THE NORTH EARLY MONDAY
MORNING.

 AS THE CLOUDS DISSIPATE THIS EVENING TEMPS WILL COOL INTO THE
LOWER 40S TO LOWER 30 OVER THE NORTHERN INNER CHANNELS. SO WITH
THAT SAID A FROST ADVY WILL BE ISSUED FOR ZONES 17,20,21 AND
25 WITH TEMPS FALLING BELOW 32 IN AREAS AWAY FROM THE WATER.

 THE BIGGEST WEATHER ISSUE IN THE SHORT TERM PERIOD WILL BE THE
LOW LIFTING OUT OF THE NORTH PACIFIC. THERE HAS BEEN GOOD MODEL
AGREEMENT BETWEEN THE NAM AND EC THAT THE LOW WILL DEEPEN TO
970MB BEFORE IT BEGINS TO FILL IN THE AFTERNOON SW OF HAIDA
GWAII. THIS LOW WILL SPREAD GALE FORCE WINDS OVER THE SE GULF
THROUGH MON FROM THE ESE WITH SMALL CRAFTS WINDS FROM THE NE OVER
THE REST OF THE EASTERN GULF. OVER THE INNER CHANNELS THE WINDS
WILL INCREASE FROM THE NORTH TO BE SMALL CRAFT THROUGH THE DAY
WITH HIGH GUSTS FROM THE EASTERLY GAPS ALONG THE COAST MOUNTAINS.
FURTHER SOUTH...THE WINDS WILL INCREASE TO GALES FROM THE OVER
SUMNER AND CLARENCE STRAIT BY THE AFTERNOON. OVERLAND WINDS WILL
INCREASE OVER THE FAR SOUTHERN AREAS THROUGH THE MORNING WITH ESE
WINDS 20 TO 30 WITH GUSTS TO 40 MPH WHILE THE CENTRAL PANHANDLE
WILL SEE MORE LOCALLY WINDY CONDITIONS IN EASTERLY EXPOSED AREAS.

 THE SCATTERED TO ISOLATED SHOWERS OVER THE SOUTHERN HALF OF THE
FORECAST AREA WILL DISSIPATE THROUGH TONIGHT AS THE WEAK UPPER
RIDGE MOVES OVER THE AREA AND STABILIZE THE ATMOSPHERE. STEADY
RAIN WILL DEVELOP THROUGH THE EARLY MORNING HOURS AS THE WEATHER
FRONT LIFTS NORTH WITH STRONG MID AND UPPER LEVEL DYNAMICS. THE
RAIN WILL PERSIST THROUGH THE DAY ONCE IT STARTS. THE NORTHERN
TWO THIRDS WILL REMAIN ON THE DRY SIDE AS THERE WILL BE
SIGNIFICANT EASTERLY DOWN SLOP AT ALL LEVELS.

&&

.LONG TERM...MODELA ARE IN GENERAL AGREEMENT WITH A GALE FORCE
LOW NEAR HAIDA GWAII MOVES OVER THE SOUTHERN PANHANDLE LATE MONDAY
NIGHT AND WEAKENS AS IT DRIFTS FARTHER NORTHEAST ON TUESDAY.
EXPECT STRONG WINDS ACROSS THE SOUTHERN AREAS WILL DIMINISH ON
MONDAY NIGHT AS THE LOW MOVES ONSHORE. CATEGORICAL POPS WILL
PREVAIL ACROSS THE SOUTHERN ZONES THROUGH TUESDAY. A WEAK RIDGE OF
HIGH PRESSURE WILL BUILD ACROSS THE EASTERN GULF AND SOUTHEAST
ALASKA UNTIL A DEVELOPING LOW IN THE WESTERN GULF LATE TUESDAY
MOVING OVER THE NORTH CENTRAL GULF THROUGH THURSDAY. THE LOW IN
THE NORTH CENTRAL GULF WILL BE ABSORBED BY ANOTHER DEVELOPING LOW
IN THE NORTHEAST PACIFIC MOVING INTO THE FAR SOUTHEAST GULF BY
THURSDAY NIGHT.

 THE NAM AND ECMWF MADE A BETTER CONSENSUS AND WERE USED TO
REFRESH THE INHERITED GRIDS THROUGH WEDNESDAY NIGHT. THE GFS HAS
BEEN SHOWING RUN-TO-RUN INCONSISTENCY. FOR THE SECOND HALF OF THE
WEEK...THE HPC OUTPUTS WERE USED. THE HPC WENT HEAVILY WITH THE
ECMWF AND ITS ENSEMBLE APPROACH. THIS SCENARIO BRINGS THE
DEVELOPING LOW IN THE NORTHEAST PACIFIC INTO THE FAR SOUTHEAST
GULF BY EARLY THURSDAY NIGHT THEN ACROSS THE SOUTHERN PANHANDLE
FRIDAY MORNING AND WEAKENS AS IT FARTHER DRIFTS
NORTHEAST...FOLLOWED BY A WEAK RIDGE OF HIGH PRESSURE BUILDS
ACROSS THE FORECAST DOMAIN THROUGH THE WEEKEND. CONTINUED ONSHORE
FLOW UNDERNEATH THE RIDGE WILL MAINTAIN THE FORECAST DOMAIN
GENERALLY WET WITH MOSTLY CLOUDY TO CLOUDY SKIES. ANOTHER
DEEPENING LOW IN THE WESTERN GULF FRIDAY NIGHT INTO THE WEEKEND
WILL GENERATE INCREASING EAST TO SOUTHEASTERLY PRESSURE GRADIENT
ACROSS THE COASTAL WATERS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM MONDAY MORNING THROUGH MONDAY AFTERNOON FOR
     AKZ027>029.
         FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM AKDT MONDAY FOR
     AKZ017-020-021-025.
MARINE...GALE WARNING FOR PKZ035-036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ011>013-022-031>034-043.

&&

ABJ/AHN