Small Craft Advisory 299, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
230 PM AKDT SUN APR 3 2016

.SHORT TERM...A LOW WILL BE TRACKING NORTHWARD OVER THE EASTERN
GULF OF ALASKA SUNDAY NIGHT THAT WEAKENS INTO AN OPEN TROUGH
MONDAY MORNING. THE FRONTAL BAND OF THE LOW IS SLOWLY WORKING NORTH
OVER THE SOUTHERN PANHANDLE TONIGHT AND INTO THE CENTRAL PANHANDLE
ON MONDAY. A TRAILING TROUGH/FRONT WITH AN ORGANIZING TRIPLE
POINT FEATURE WILL BE MOVING NORTHEAST FROM THE PACIFIC TO BE NEAR
50/140 MONDAY AFTERNOON SPREADING RAIN INTO THE SOUTHERN GULF
MONDAY AFTERNOON.

PRECIPITABLE WATER SAMPLING BY SATELLITE SUGGESTING 0.5 TO 0.7
INCHES OF WATER AVAILABLE WITH THE FIRST FRONT BAND WHICH IS MORE
THAT 2 TIMES NORMAL FOR THIS TIME OF YEAR. THINK THAT THE SOUTHERN
PANHANDLE WILL SEE ABOUT A THIRD TO A HALF INCH OF RAIN TONIGHT
AND ROUGHLY A QUARTER TO A THIRD OF AN INCH FOR THE CENTRAL
PANHANDLE ON MONDAY. ENOUGH RAIN TO WET THE GROUND AND BUMP THE
RIVER AND STREAMS LEVELS SLIGHTLY WITH RUNOFF ALTHOUGH SHOULD NOT
LEAD TO FLOODING ISSUES AS THE FLOW LEVELS ARE LOW.

WINDS IN THE EASTERN GULF AND INNER CHANNELS AT 10 TO 20 KT
GENERALLY...WITH A FEW AREAS EXPECTED TO INCREASE TO SMALL CRAFT
WINDS NEAR THE FRONT AND DIMINISHING AS IT PASSES. AS THE LOW AND
FRONT MOVES NORTHWARD THERE IS AN INCREASE IN THE EASTERLY FLOW
AROUND JUNEAU AND THROUGH TAKU INLET. DOWNTOWN JUNEAU AND DOUGLAS
SHOULD SEE GUSTY WINDS TO 30 MPH LATE TONIGHT INTO EARLY MONDAY
MORNING BEFORE THE FLOW SHIFTS AND WINDS WEAKEN DURING THE DAY.
CROSS SOUND WILL ALSO SEE THE ENHANCED EASTERLY FLOW INTO THE GULF
TONIGHT INTO MONDAY AND WILL BE ISSUING A SMALL CRAFT FOR THAT
AREA.

.LONG TERM...LONG RANGE FORECAST CONTINUES TO LOOK WET THROUGH
LATE WEEK AS THE WEST COAST RIDGE REMAINS MOSTLY STATIONARY. THE
RESULTING SW FLOW DIRECTS AT LEAST TWO WAVES INTO THE PANHANDLE
TUE THROUGH THU. THEN THE PATTERN SLIGHTLY CHANGES FRI INTO SAT AS
THE WEST COAST RIDGE RETROGRADES WEST TO A POSITION OVER THE
EASTERN GULF AND PANHANDLE. THIS RESULTS IN A DRIER FORECAST FOR
NEXT WEEKEND AND EARLY THE FOLLOWING WEEK.

SOME RATHER SIGNIFICANT CHANGES WERE NEEDED OVER THE PREVIOUS
FORECAST AS MID RANGE MODELS SHUFFLE WAVE POSITIONS AND STRENGTHS
AROUND A BIT. FIRST MAJOR CHANGE CONCERNS THE WAVE COMING INTO THE
SE GULF ON TUE. A STRONGER 100 KT 500 MB JET STREAK WEST OF HAIDA
GWAII HAS CAUSED THIS FEATURE TO STRENGTHEN IN RECENT MODEL RUNS.
CURRENT FORECAST HAS A WEAK LOW DEVELOPING WEST OF HAIDA GWAII
EARLY TUE BEFORE IT MOVES NE INTO BARANOF ISLAND BY TUE AFTERNOON
(THOUGH STRENGTH OF THE FEATURE VARIES BETWEEN 1005 MB AND 998 MB
BETWEEN MODELS). MAIN CHANGES HERE, BESIDES A STRONGER FEATURE,
WERE AN INCREASE IN WINDS ACROSS THE SE GULF AND SOUTHERN
PANHANDLE WITH MIN GALES NOW EXPECTED IN CLARENCE STRAIT TUE AS
THIS FEATURE MOVES THROUGH.

SECOND CHANGE OF NOTE IS FOR THE LOW THAT IS HEADING TOWARD THE
NORTHERN GULF COAST ON WED INTO THU. MODEL AGREEMENT HAS GOTTEN
BETTER BUT DIFFERENCES REMAIN (GEM AND NAM FAVOR A WEAKER LOW
INTO CAPE EDGECOMBE WHILE THE GFS AND ECMWF FAVOR A STRONGER LOW
WITH A TRACK NORTH ALONG 140 W). CURRENT SCENARIOS ARE MUCH
SLOWER THEN THE PREVIOUS FORECAST AND FAVOR A LOW TRACK FURTHER
EAST. GENERALLY THE GFS AND ECMWF SCENARIO HAS BEEN RATHER
CONSISTENT RECENTLY SO DECIDED TO HEAD IN THAT DIRECTION FOR THE
NEW FORECAST. THE RESULTING CHANGES IN THE WIND FIELD SHOWED MIN
GALES FORMING IN THE EASTERN GULF AND SOUTHERN INNER CHANNELS WED
NIGHT. A ROBUST TROPICAL MOISTURE PLUME ACCOMPANYING THIS SYSTEM
WILL ALSO BRING SOME RATHER HEAVY RAINFALL TO THE PANHANDLE WED
NIGHT INTO THU WITH A FEW INCHES OF QPF EXPECTED IN ABOUT A 24
HOUR PERIOD. WE WILL CONTINUE TO REFINE THE FORECAST AS NEW MODEL
RUNS COME IN.

ONCE WE GET PAST THU, THE UPPER RIDGE SHIFT WEST AND BEGINS TO DRY
THE PANHANDLE OUT FOR THE WEEKEND. CURRENT LONG RANGE GUIDANCE
SUGGESTS THIS DRY PERIOD LASTING THROUGH THE WEEKEND AND INTO NEXT
MON, BUT HAVE DIFFERENT SCENARIOS ON WHEN AND HOW IT WILL END
NEXT WEEK. GENERALLY FAVORED WPC WITH ITS ENSEMBLE APPROACH FOR
EXTENDED RANGE UPDATES.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-031-036-041>043-051-052.
&&

BEZENEK/EAL

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