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FXAK67 PAJK 302304
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
304 PM AKDT SAT APR 30 2016

.SHORT TERM...A STRONG OCCLUDED FRONT ALONG THE CENTRAL OUTER
COAST WILL MOVE INLAND AND STALL ACROSS THE S-CENTRAL PANHANDLE
SSW INTO THE SE GULF BY LATE EVENING. A LOW PRESSURE WAVE WILL
DEVELOP ALONG THE FRONT AND MOVE N TO JUST W OF HAIDA GWAII BY
LATE SUN AFTERNOON. USED BLEND OF THE 12Z GFS AND NAM TO HANDLE
THE FORECAST THROUGH SUN.

MAIN FORECAST CONCERNS ARE PRECIP POTENTIAL/AMOUNTS AND WINDS.
RIGHT NOW...RAIN IS FALLING OVER NEARLY THE ENTIRE PANHANDLE WITH
FRONT ALONG THE COAST. AS FRONT MOVES INLAND THIS EVENING...THE
STEADIER RAIN WILL TRANSITION TO SHOWERS OVER THE NW HALF OF THE
AREA AFTER FROPA. THE SERN HALF OF THE AREA WILL STAY ON THE E
SIDE OF THE FRONT AND REMAIN IN STEADIER PRECIP TONIGHT. AS THE
LOW PRESSURE WAVE MOVES N THOUGH...THE FRONT WILL SHIFT N AND
PRECIP WILL TRANSITION BACK TO STEADIER RAIN OVER MUCH OF THE N
THROUGH THE DAY.

THE RAIN MAY BE HEAVY AT TIMES ESPECIALLY OVER THE S. RAINFALL OF
1 TO 2.5 INCHES IS EXPECTED OVER THE S...AND MAY EXCEED 3 INCHES
IN SOME AREAS THROUGH SUN AFTERNOON. THE N WILL LIKELY GET UP TO 1
INCH OF ADDITIONAL RAIN WITH HIGHER AMOUNTS IN THE MTNS THROUGH
SUN AFTERNOON. THE IMPACTS OF THIS WILL BE DISCUSSED IN THE
HYDROLOGY SECTION.

RIGHT NOW...WINDS AHEAD OF THE FRONT ARE MOSTLY GALE FORCE OVER
THE FAR ERN GULF. THESE WINDS WILL DROP TO SCA LEVELS OR LESS THIS
EVENING AFTER FROPA. INNER CHANNELS WILL SEE WINDS UP TO GALE
FORCE DIMINISH TO SCA LEVELS OR LESS OVER THE AREA BY LATE EVENING
...EVEN AHEAD OF THE FRONT...AS IT WILL WEAKEN SOME. KEEPING IN
SOME STRONG WIND HEADLINES THRU EARLY THIS EVENING MAINLY OVER
THE ERN INNER CHANNELS AND SRN COAST. WINDS WILL INCREASE OVER THE
FAR SRN AREA SUN AS LOW PRESSURE WAVE MOVES CLOSER TO THE AREA
WHILE THE NRN AREA WINDS DECREASE FURTHER WITH WEAKENING PRESSURE
GRADIENT DURING THE DAY.

.LONG TERM...PARENT LOW ON THE WESTERN GULF WILL CONTINUE TO
WEAKEN SUNDAY EVENING. A LOW PRESSURE WAVE WILL DEVELOP IN THE E
PACIFIC THE TRACK N ALONG THE STALLED FRONT EXTENDING FROM THE
WESTERN GULF PARENT LOW. THE WAVE WILL MOVE INTO THE SE GULF
SUNDAY EVENING BECOMING AN OPEN WAVE TROUGH AS IT MOVES NORTH OVER
THE PANHANDLE THROUGH MONDAY. A HIGH PRESSURE RIDGE WILL BEGIN TO
BUILD BEHIND THE LOW PRESSURE WAVE THROUGH WEDNESDAY. MEANWHILE
THE NEXT MAJOR LOW PRESSURE SYSTEM MOVES OVER THE ALEUTIANS AND
THEN JUST SOUTH OF THE AK PENINSULA WEDNESDAY NIGHT INTO THURSDAY.
AS OF NOW EXPECT THE FRONTAL BOUNDARY ASSOCIATED WITH THIS LOW TO
CROSS INTO THE EASTERN GULF THURSDAY THEN OVER THE PANHANDLE
FRIDAY. HOWEVER STILL SOME MODEL SPREAD REGARDING THIS FEATURE AS
MODELS HAVING DIFFICULTY WITH SPRING PATTERN TRANSITION.

THE SUNDAY NIGHT WAVE WILL BRING ANOTHER ROUND OF HEAVY RAINFALL
AND BREEZY CONDITIONS, BUT NOT AS STRONG AS THE SYSTEM CURRENTLY
MOVING OVER THE AREA. VARIABLE WIND DIRECTIONS WITH THE PASSING
LOW THEN TRANSITIONS TO MOVE SOUTHERLY FLOW AS THE RIDGE BUILDS
IN. RAIN WILL DIMINISH OVER MOST OF THE PANHANDLE UNDER THE
BUILDING RIDGE. STILL SOME VORT MAX ON LEE SIDE OF RIDGE KEEPING
PRECIP ALONG THE COAST MOUNTAINS. EVEN WITH THE MODEL DIFFERENCES
HAVE BIT MORE CONFIDENCE ON THE NEXT FRONT REACHING THE E GULF
FRIDAY BRINGING MORE RAIN AND STRONGER WINDS. IN THE EXTENDED
RANGE GFS/GEM HAVE BEEN CONSISTENT RUN TO RUN AND WITH EACH OTHER
AND ECMWF AS AN OUTLIER HAS BEEN SHOWING MORE RUN TO RUN
VARIATION.

USED 12Z GFS/NAM WITH ONLY MINOR TIMING CHANGES ON WIND DIRECTION
COMPARED TO INHERITED FORECAST TO DAY 4. NEW WPC GUIDANCE STILL
IN LINE WITH PREVIOUS FORECAST TO DAY 8 SO FEW CHANGES MADE THERE.
FORECAST CONFIDENCE IS AVERAGE.


&&

.HYDROLOGY...SO FAR UP TO 1 INCH OF RAIN HAS FALLEN ACROSS THE
AREA THROUGH LATE THIS AFTERNOON AND MANY SMALLER STREAMS HAVE
BEGUN TO RISE. WITH THE ADDITIONAL RAINFALL AMOUNTS EXPECTED...AREA
RIVERS AND STREAMS WILL RISE FURTHER WITH THE BIGGEST RISES
EXPECTED OVER THE SRN PANHANDLE. NOT EXPECTING ANY FLOODING AT
THIS TIME HOWEVER AS WATER LEVELS WERE FAIRLY LOW TO START.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ025>028.
     STRONG WIND UNTIL 4 PM AKDT THIS AFTERNOON FOR AKZ017-021>024.
MARINE...STORM WARNING FOR PKZ052.
     GALE WARNING FOR PKZ022-033>036-041>043-051-053.
     SMALL CRAFT ADVISORY FOR PKZ011>013-021-031-032.
&&

$$

RWT/PRB

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