Gale Warning 216, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
235 PM AKDT WED APR 6 2011

.SHORT TERM...ISOLATED THUNDERSTORMS SHOULD OCCUR IN PUBLIC ZONE
17 AND ALONG THE OUTER COAST INTO ZONE 22 LATE THIS AFTERNOON AND
INTO THIS EVENING. OTHER THAN THESE ISOLATED THUNDERSTORMS THE
CHANGES TO THE SHORT RANGE FORECAST ARE SMALL. 18Z THU AN
OCCLUSION WILL EXTEND SSE FM PAWD THAT WILL MOVE NE PAST PAMD ABT
00Z. THIS OCFNT IS ASSOCD WITH GALE FORCE WINDS SPREADING INTO
OUR AREA OF RESPONSIBILITY THU. BOTH THE GFS AND NAM MODELS WERE
USED.

500H TROUGH ALOFT EXTENDS SSE FM OVER PABR T0 PAFA TO PACV AT
THIS TIME. THIS TROUGH ALOFT WILL MOVE E AND WEAKEN BEFORE
REACHING A PAJN TO PASI LINE TONIGHT. ISOLATED THUNDERSTORMS
SHOULD OCCUR IN THE ZONE 17 AND ALONG THE OUTER COAST INTO ZONE 22
LATE THIS AFTERNOON AND INTO THIS EVENING. THE 12Z PAYA RAOB, THE
SFC TEMPERATURES TO OCCURRING THIS AFTERNOON, AND THE DIFFLUENCE
OF THE UPPER LEVEL FLOW DO SUPPORT THUNDERSTORMS, HOWEVER THE
CONVECTIVE AVAILABLE POTENTIAL ENERGY IS NOT HIGH AND THIS LIMITS
HOW STRONG DEEP CONVECTION CAN BE.

THE OCFNT MENTIONED ABOVE IS A STRONG FEATURE AND THE UPPER LEVEL
SUPPORT WILL, BEGINNING THU, GENERATE STRONG PRESSURE FALLS IN
SOUTHERN YUKON TRRTY AND THE NORTHERN PANHANDLE. NOTE THAT WIND
INCREASES WILL CONTINUE THROUGH THE HAND OFF FROM THE THE SHORT
RANGE FORECAST TO THE LONG RANGE, I.E. FROM THURSDAY AFTERNOON TO
THURSDAY EVENING. THIS TREND OF FURTHER WIND INCREASES WILL BE
ESPECIALLY TRUE FOR THE PANHANDLE N OF FREDERICK SOUND. PLEASE SEE
THE LONG RANGE SECTION BELOW.

&&

.LONG TERM...A STRONG OCCLUDED FRONT WILL PUSH THROUGH SOUTHEAST
ALASKA THURSDAY NIGHT WITH A SECONDARY TROUGH MOVING THROUGH ON
FRIDAY. A VERTICALLY STACKED LOW WILL SET UP OVER THE NORTHERN
GULF BY FRIDAY NIGHT WITH FAIRLY DEEP ONSHORE SOUTHWEST FLOW AND
WILL ROTATE A SERIES OF TROUGHS INTO SOUTHEAST ALASKA OVER THE
WEEKEND. BY MONDAY ENERGY SHIFTS TO SOUTHERN GULF WHICH TURNS FLOW
OFFSHORE FOR NORTHERN WHILE REMAINING ONSHORE FOR SOUTHERN.

EXPECT SMCR TO GALE FORCE WINDS WITH OCCLUDED FRONT THURSDAY
NIGHT FOR INSIDE WATERS. WILL START OFF WITH A STRONG PRESSURE GRADIENT
(-18 MB PAHN-CYDB) BETWEEN RIDGE TO SE AND LEE TROUGH ACROSS
SOUTHERN YUKON. THIS WEAKENS OVERNIGHT. GALES IN THE COASTAL
WATERS ALSO DROP OFF IN THE EVENING. RAIN WILL BE ON THE INCREASE
ACROSS NORTHERN HALF AND WILL SPREAD TO SOUTHERN HALF BY FRIDAY
MORNING. THERE STILL IS THE POSSIBILITY THAT IT MAY START OUT AS
SNOW FOR THE HAINES AREA BUT WITH MODERATE SLY WILL GO TO ALL
RAIN. AMOUNTS WILL BE OVER AN INCH IN THE WETTER LOCATIONS AND
PROBABLY APPROACHING 1 INCH ELSEWHERE.

A SECOND ROUND OF RAIN IS EXPECTED TO MOVE ONSHORE FRIDAY WITH
SECONDARY TROUGH WITH AMOUNTS EQUALLY AS PLENTIFUL. STILL HAVE
FAVORABLE SE GRADIENTS THROUGH INNER CHANNELS AND WILL BE LOCALLY
BREEZY WITH SMCR CONTINUING.

CAA BEGINS IN ERNEST FRIDAY NIGHT WITH ATMO BECOMING MORE UNSTABLE
SO WILL SWITCH PRECIP OVER TO SHOWERS. BY SATURDAY NIGHT TEMPS WILL
COOL AND BE MARGINAL FOR SNOW SHOWERS NORTHERN HALF BUT DONT SEE
ANY ACCUMS. AS ENERGY SHIFTS TO SOUTHERN GULF POPS DROP OFF ACROSS
THE NORTH BUT STAY LIKELY FOR SOUTHERN AREAS.

MODELS IN GOOD AGREEMENT THROUGH THE WEEKEND BEFORE TIMING AND
POSITIONAL DIFFERENCES START. USED GFS FRESHEN GRIDS THROUGH DAY 4
THEN OPTED TO MAKE NO CHANGES BEYOND.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ051-052.
         SMALL CRAFT ADVISORY FOR PKZ011>013-043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-041-042.

&&

JBT/MM