Small Craft Advisory 783, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
2 PM AKST WED NOV 30 2011
 .SHORT TERM...A STRONG RIDGE AT THE SURFACE AND ALOFT IS TILTED
ACROSS SOUTHERN SOUTHEAST ALASKA AND WILL MOVE OFF TO THE EAST
TONIGHT. A STRONG OCCLUDED FRONT ENTERING THE EASTERN GULF WILL
SLOWLY MOVE THROUGH SOUTHEAST ALASKA TONIGHT AND EXIT SOUTHEAST
CORNER OF THE PANHANDLE BY LATE THURSDAY MORNING. HIGH PRESSURE
BUILDS INTO THE CENTRAL GULF THURSDAY WITH STRONG WEST WINDS
ACROSS THE GULF.

A OCCLUDED FRONT...UNDER A 150 KT SW JET MAX RIDING NE ALONG BACK
SIDE OF THE UPPER RIDGE...WILL MOVE ACROSS SOUTHEAST ALASKA
TONIGHT AND EXITS THE SOUTHEAST CORNER AROUND NOON ON THURSDAY. A
65KT LOW LEVEL BARRIER JET IS FORECAST TO DEVELOP AHEAD OF WAVE
ALONG THE FRONT THIS AFTERNOON THAT WILL MOVE ACROSS INNER
CHANNELS TONIGHT. EXPECT SOME OF THIS TO WORK DOWN TO THE SURFACE
WITH PLENTY OF TURBULENT ENERGY. HAVE PUT OUT A HWA FOR GUSTS TO
60 MPH IN ZONES 17-19, 22, AND 25 FOR TONIGHT AND EXPECT TO
UPGRADE THIS TO A WARNING WITH AFTERNOON PACKAGE. OTHER ZONES WILL
SEE STRONG WINDS AS THE FRONT MOVES THROUGH.

THERE IS A LONG FETCH OF MOISTURE AND MODERATE WAA AHEAD OF THE FRONT.
MODERATE RAIN IN PAYA WILL BECOME HEAVY BY LATE AFTERNOON WITH
HEAVIER RAINS SPREADING ACROSS NORTHERN AREAS THIS EVENING AND
ACROSS SOUTHERN BY LATE TONIGHT. PAYA AND COASTAL SE ALASKA WILL
BE THE WETTEST SPOTS WHERE 4 INCHES IS POSSIBLE BEFORE ENDING
THURSDAY AFTERNOON. 1 TO 2 INCHES OF RAIN IS LIKELY FOR INNER
CHANNELS AND SOUTHERN. FREEZING LEVELS WILL BE ON THE RISE AND
EXPECTED TO CLIMB TO 3000 FEET FOR A SHORT WHILE IN THE NORTH AND
TO 5000 FEET IN THE SOUTH.

SINCE MANY AREAS STILL HAVE A DEEP SNOW PACK THE RAIN ON TOP OF
THE SNOW WILL CAUSE PROBLEMS WITH INCREASED SNOW LOADS, PONDING OF
WATER IN LOW LYING AREAS, AND WILL INCREASE THE THREAT OF AVALANCHES
AND MUD SLIDES. THINK BEST WAY TO ADDRESS THEIR COMBINED AFFECT
WILL BE IN AN SPS.

GOOD AGREEMENT BETWEEN MODELS IN THE SHORT TERM. NAM CONTINUES TO
BE TOO COLD WITH ITS TEMPERATURES SO WILL STAY CLOSER TO THE GFS
FOR GRIDS.

LONG TERM...
OVERALL PATTERN REMAINS PROGRESSIVE THIS MORNING WITH A MAJOR COLD UPR
LOW OVR KAMCHATKA...DEEP SHORTWAVE UPR TROF ALG 165W...AND A HIGH
AMPLITUDE UPR RIDGE ALG 135W (OVR THE PANHANDLE) WHICH WILL CLEARLY
MOVE E INTO B.C. & YUKON BY THIS EVENING. THIS SETS UP A VERY STRONG
SW FETCH ALOFT OVR ALL OF SEAK FOR WARM AND WET AND WIND. SW JET CORE
OVR PAYA. CHECK OUT WIND WSW 135KT 34K FT AT YAKUTAT 30/12Z RAOB. SEE
SHORT TERM ABOVE FOR THE IMMEDIATE PROBLEMS WITH THIS SETUP.

THE UPR TROF ALG 165W AT 30/12Z HAS WINTRY COLD AIR IN IT DOWN TO -36C
AT 500 HPA AND IS MOVING RAPIDLY WITH JET...WILL BE OVR YUKON
BY 00Z TRANSITION TIME AS A LOWER AMPLITUDE RIDGE BUILDS ALG 140W
TO GIVE US WESTERLIES ALF. MOST SIGNIFICANT FEATURE IN THE LONG TERM
IS THAT IN SPITE OF SHORT WAVES COMING INTO UPR RIDGE FROM SW...MEAN
POSITION OF UPR RDG WILL OSCILLATE OVR THE GULF OF ALASKA THRU THE
WEEKEND WHICH GIVES US WARM AIR AND PERIODS OF WET CONDITIONS THROUGH
THE WEEKEND. NEW SIGNAL IS THAT EARLY NEXT WEEK PATTERN CHANGES TO
STRONG ARCTIC HIGH PRESSURE OVER THE YUKON FOR OUR COLD DRY WINDY
PATTERN SAY BY TUE.

TIMING IS TRICKY SO CONFIDENCE ON THE DETAILS ONLY MODERATE THROUGH
SAT. MODERATE CONFIDENCE ON THE BIG PATTERN CHANGE NEXT WEEK WHICH
WILL BE FUN TO SEE IF IT COMES TRUE. USED 30/12Z AK-GFS-40 FOR MUCH OF
THIS FORECAST AND PREVIOUS SHIFTS GRIDS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH LATE TONIGHT
   FOR AKZ026.
   STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH THURSDAY
     AFTERNOON FOR AKZ027.
   STRONG WIND THROUGH LATE TONIGHT FOR AKZ020-021-024.
   HIGH WIND WARNING FROM 9 PM THIS EVENING TO 3 AM AKST THURSDAY
     FOR AKZ023-025.
    HIGH WIND WARNING UNTIL 3 AM AKST THURSDAY FOR AKZ018-019-022.
    STRONG WIND UNTIL 3 PM AKST THIS AFTERNOON FOR AKZ018-022.
    STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ023.
    STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH THURSDAY MORNING
     FOR AKZ028.
    HIGH WIND WARNING UNTIL MIDNIGHT AKST TONIGHT FOR AKZ017.
MARINE...GALE WARNING FOR PKZ011>013-021-022-031>036-041>043-051>053.
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