Gale Warning 241, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1130 AM AKDT THU OCT 9 2008

.SHORT TERM...A RIDGE OF HIGH PRESSURE AT THE SURFACE OVER THE
EASTERN GULF AND SOUTHEAST ALASKA WILL CONTINUE MOVING OFF TO THE
EAST THROUGH TONIGHT AND BE OVER CENTRAL B.C. ON FRIDAY WHILE THE
UPPER LEVEL RIDGE DOES NOT MOVE ACROSS SOUTHEAST ALASKA UNTIL
FRIDAY. A 965 MB LOW CENTERED IN BRISTOL BAY WILL SLOWLY FILL AS
IT DRIFTS SOUTHEAST THROUGH FRIDAY. THE ASSOCIATED STRONG
OCCLUSION...JUST NOW ENTERING THE WESTERN GULF...WILL MOVE INTO
THE EASTERN GULF BY FRIDAY AFTERNOON AND WILL SPREAD GALE TO
STORM FORCE WINDS TO THE OFFSHORE AND COASTAL WATERS ON FRIDAY.

CLOUD COVER CONTINUING TO DECREASE ACROSS THE SOUTHERN ZONES
TODAY AND BECOMING PARTLY SUNNY THIS AFTERNOON WHILE MID AND HIGH
CLOUDS INCREASE ACROSS THE NORTHERN HALF. BIORKA ISLAND RADAR
STILL SHOWING SCATTERED OPEN CELLED SHOWERS MOVING ONSHORE
COASTAL AREAS SHOULD DISSIPATE THROUGH THE AFTERNOON AS FLOW GAIN
OFFSHORE COMPONENT. THE WARM SECTOR ASSOCIATED WITH APPROACHING
SYSTEM SPREADING ACROSS ZONE 17 TODAY WITH THE MIDDLETON ISLAND
RADAR SHOWING RAIN HAS ALREADY SPREAD TO AS FAR EAST AS ICY BAY.
EXPECT THIS RAIN TO CONTINUE EAST WITH RAIN DEVELOPING IN PAYA BY
LATE AFTERNOON. SE WINDS INCREASING TO SMCR LEVELS IN NORTHERN
COASTAL AND OFFSHORE AREAS THROUGH THE AFTERNOON. SOUTHERLY
PRESSURE GRADIENTS BETWEEN RIDGE OVER PANHANDLE AND FALLING
PRESSURE ACROSS SOUTHERN YUKON WILL INCREASE WINDS THROUGH
NORTHERN LYNN CANAL TO AT LEAST 20 KT THIS AFTERNOON AND 25 TO 30
KT TONIGHT.

STRONG OCCLUSION...UNDER 130 KT SW JET WITH LONG FETCH OF WARM
AND MOIST AIR...WILL MOVE INTO EASTERN GULF TONIGHT. EXPECT
WIDESPREAD GALE FORCE SE WINDS ACROSS THE EASTERN GULF WITH STORM
FORCE WINDS MOVING INTO OFFSHORE AND NORTH GULF COAST BY LATE
TONIGHT AS LOW LEVEL BARRIER JET DEVELOPS. STRONG SOUTHERLY WINDS
IN MID AND UPPER LEVELS IMPINGING ON TERRAIN COMBINED WITH WARM
AND MOIST ATMOSPHERE WILL BE CONDUCIVE TO HEAVY RAIN FOR PAYA
BEGINNING LATE TONIGHT AND CONTINUING THROUGH FRIDAY. CURRENT
MODEL RUNS SUGGESTING ALMOST 4 INCHES OF RAIN IN 18 HOURS
COMBINED WITH FREEZING LEVELS THAT RISE TO AROUND 8K FEET WILL
LIKELY LEAD TO HYDRO ISSUES FOR THE AREA. WILL COORDINATE WITH
RFC ON A COURSE OF ACTION LATER THIS AFTERNOON. WINDS ALSO
INCREASING ACROSS PAYA AREA TONIGHT AND EXPECT GUSTS TO INCREASE
TO AROUND 50 MPH LATE TONIGHT INTO EARLY FRIDAY.

RAIN WILL SPREAD ACROSS THE NORTHERN TWO THIRDS OF SOUTHEAST
ALASKA TONIGHT WITH A CHANCE FOR SOUTHERN ONE THIRD. EAST TO
SOUTHEAST WINDS WILL INCREASE THROUGH THE INNER CHANNELS AND
REACH SMCR LEVELS BY MORNING. WINDS INCREASE TO GALE FORCE FOR
CROSS SOUND AND SOUTHERN CHATHAM FRIDAY AFTERNOON WITH GUSTS TO
50 MPH REACHING THE NORTHERN TO THIRDS OF COAST WITH BREEZY
CONDITIONS THROUGH NORTHERN INNER CHANNELS WITH WINDY CONDITIONS
CONTINUING FOR PAGY.

.LONG TERM...MODELS IN DECENT AGREEMENT THRU SAT...THEN BEGIN TO
DIVERGE AFTERWARD. THE MAIN CONCERN WILL BE EARLY IN THE LONG
RANGE WHEN A STRONG OCCLUDED FRONT WILL MOVE SLOWLY EWD THRU THE
AREA FRI NIGHT AND SAT. THE TIMING ON THIS IS A BIT SLOWER THAN
PREVIOUSLY FORECAST...AND THAT MAKES SENSE GIVEN A BUILDING MID-
LEVEL RIDGE TO THE E OF THE AREA. WENT WITH THE 12Z GFS FOR
TONIGHT AND SAT. DUE TO THE MODEL DIFFERENCES BEYOND THEN...AND
WITH THE CURRENT GRIDS REPRESENTING A REASONABLE COMPROMISE OF
THOSE DIFFERENCES...DECIDED TO LEAVE THE SAT NIGHT PERIOD ONWARD
AS IS. THIS WAS COORDINATED WITH WFO PAFC FOR GOOD INTRAOFFICE
CONSISTENCY.

WITH THE STRONG FRONT MOVING IN...LOOKS LIKE A WIDESPREAD WIND
ADVISORY EVENT FOR THE AREA FRI NIGHT INTO EARLY SAT...WITH THE
FAR SERN AREA SEEING THEIR WINDS DROP OFF LAST. WITH THE INNER
CHANNEL AREAS NOT LIKELY SEEING ADVISORY LEVEL WINDS UNTIL THE
3RD PERIOD...WILL NOT ISSUE THOSE WIND ADVISORIES WITH THIS
PACKAGE. WILL CONTINUE ANY WIND ADVISORIES FROM THE SHORT RANGE
PERIOD...IF NEEDED.

GIVEN SLOW MOVEMENT OF FRONT AND VERY STRONG S-SSW FLOW IN THE
LOW-MID LEVELS...LOOKS LIKE A HEAVY RAIN EVENT IS IN STORE FOR
THE NW HALF OF THE AREA. THE HEAVIEST RAIN SHOULD BE IN THE PAYA
AREA...WHERE RAINFALL TOTALS OF 5 TO 7 INCHES ARE LIKELY BY
DAYBREAK SAT. FURTHER E...IN THE PAJN-PAEL CORRIDOR...RAINFALL OF
2 TO 4 INCHES IS LIKELY BY MIDDAY SAT...WITH THE HEAVIER AMOUNTS
OVER THE WEST END OF THAT AREA. THE SOUTHERN AREA WILL LIKELY SEE
1 TO 2 INCHES OF RAIN BY LATE SAT AFTERNOON. GIVEN THESE HEAVY
AMOUNTS...MAY HAVE SOME LOCAL DRAINAGE ISSUES WITH FALLING LEAVES
CLOGGING UP SOME OF THE STORM DRAINS AND OTHER DRAINAGES....AND
EVEN SOME MAIN STEM RIVERS COULD GET UP TO NEAR BANKFULL OR
SLIGHTLY ABOVE OVER THE NW HALF OF THE AREA GIVEN THE HEAVY
AMOUNTS OF RAIN EXPECTED.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FOR AKZ017 022 AND 023 FRIDAY
         ESF FOR AKZ017
MARINE...STORM PKZ310 AND 051-052 TONIGHT AND FOR PKZ042-043
         FRIDAY GALE WARNING PKZ022. SMALL CRAFT ADVISORY FOR
         PKZ022-033-041>043.

MM/RWT