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000
FXAK67 PAJK 301303
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
503 AM AKDT THU OCT 30 2014

.SHORT TERM...SHARP TROUGH ALOFT PREVAILS THROUGH THE PERIOD,
WHILE AT LOW LEVELS THE SCENARIO IS SOMEWHAT MORE COMPLEX AS USUAL.
RELAXING GRADIENTS TODAY THE WAKE OF THE EASTERN GULF LOW WILL LIKELY
RESTRICT SCAS TO OFFSHORE WATERS AND WINDS WILL GENERALLY DECREASE
AT LOW LEVELS WITH THE EXCEPTION OF THE FAR NORTHWEST WHICH WILL
SEE SOME LOCALIZED WINDS. THE LIGHTING ACTIVITY TONIGHT HAS BEEN
RESTRICTED TO SOUTH OF HAIDA GWAII BUT MODELS POSE THREAT TO THE
CENTRAL OFFSHORE AREAS FOR ISOLATED CONVECTION THIS AFTERNOON AND
TONIGHT AND ALSO THE THREAT WILL EXIST FOR WESTERN PORTIONS OF
CHICHAGOF AND BARANOF ISLANDS. THE MAIN CURRENT LOW...995ISH MB
WEST OF SITKA...DRIFTS NORTH AND WEST WHILE MAINTAINING ITS
STRENGTH. ALONG WITH THE SOUTHERLY LOW-LEVEL JET TRAILING OFF TO
THE SOUTHEAST ALONG THE PANHANDLE A MODERATE RAIN SCENARIO IS
LIKELY TODAY ESPECIALLY OVER COASTAL REGIONS THROUGHOUT. THIS
LATTER TROUGH IS MAINTAINED THROUGH THE PERIOD BUT THAT IS WHERE
MODEL SOLUTIONS DIFFER WITH THE NAM BEING THE OUTLIER BOTH IN
PRECIP AND WIND...THE TRAILING TROUGH IS STRONGER ON THAT MODEL
AND INCLUDES A SECONDARY LOW...LEADS TO MODERATE PRECIP OVER THE
NORTH FOR LATE TONIGHT/FRIDAY MORNING AND WIND INCREASES. WE AREN`T BUYING
THAT AS THE EC/GEM/GFS MODELS AGREE TO SIMPLY MAINTAIN THE TROUGH
AND PREDICT A SLOW NWWD DRIFT OF THE NORTHERN LOW WHILE INCREASING
ONSHORE MOIST FLOW INTO THE PANHANDLE IN THE 09-15Z PERIOD
FRIDAY...WITH NO SECONDARY LOW FORMATION. THUS WINDS ARE LIKELY TO
BE SUB-SCA LEVEL THROUGH MUCH OF THE INTERIOR CHANNELS AFTER WINDS
WEAKEN RAPIDLY TODAY. THEN AFTER ABOUT 06Z THE GRADIENT BEGINS TO
INCREASE FOR THE CENTRAL PANHANDLE AS SOUTHWESTERLY FLOW BEGINS TO
INCREASE SOUTH OF THE MAIN LOW AND ALSO IN RESPONSE TO A WNW UPPER
JET ENTERING THE CENTRAL GULF LATE. THIS PATTERN IS PROGRESSIVE AS
UPPER SHORTWAVE RIDGING IS EVIDENT OVER THE WESTERN GULF EARLY
FRI. THIS SCENARIO WILL LIKELY LEAD TO A WET FRIDAY FOR MOST
AREAS WITH POSSIBLE SCA WINDS FOR NORTH/CENTRAL CHANNELS. FOR GRIDS WENT
WITH A BLENDED EC/GEM/GFS APPROACH ON PRESSURE WIND AND PRECIP
FIELDS. THIS INCLUDES PRECIP PERSISTING THROUGH THE PERIOD OVER MOST OF
THEN NORTH BUT ABATING OVER THE SOUTH LATER TODAY. TEMPERATURES
CONTINUE TO BE WARM ENOUGH TO MAINTAIN RAIN AT LOW LEVELS OVER ALL
BUT THE NORTHERN FRINGES AND HYDER...WHERE A MIXED SCENARIO IS
LIKELY. MODEL CONFIDENCE...USING THE ENSEMBLES MENTIONED...IS
AVERAGE FOR THE SHORT-TERM.

.LONG TERM...THE FIRST IN A LONG SERIES OF SHORTWAVE TROUGHS IS
FORECAST TO MOVE ONSHORE ACROSS SERN AK DURING FRI. RESIDUAL
POCKET OF COLD MIDLEVEL TEMPERATURES WILL INITIALLY SUPPORT
SHOWERS...WITH A TRANSITION BACK TO STRATIFORM OVER THE GULF AS
WARMER MIDLEVEL TEMPERATURES SPREAD EWD. THIS WARMER AIRMASS WILL
BE ACCOMPANIED BY A FRONTAL BOUNDARY AT THE SURFACE...WHICH WILL
ADVANCE ENE ACROSS THE GULF FRI AFTERNOON...AND THEN MOVE ONSHORE
SAT MORNING. WIDESPREAD RAIN WILL BE PROBABLE ALONG/AHEAD OF THE
FRONT...WITH MODERATE TO HEAVY RATES POSSIBLE OVER THE SRN
PANHANDLE WHERE STRONGEST MOISTURE FLUX WILL BE PRESENT.

IN ADDITION TO THE RAIN...A 40-50 KT LOW-LEVEL SELY JET IS
FORECAST TO OCCUR IMMEDIATELY AHEAD OF THE FRONT. THIS FEATURE
WILL RESIDE OVER THE OUTSIDE WATERS FRI NIGHT...FAVORING GALE
FORCE WINDS. THE LLJ THEN MOVES ONSHORE LATE FRI NIGHT INTO SAT
MORNING...AIDING IN GALE FORCE WINDS FOR CLARENCE STRAIT...AND
POSSIBLE STRONG GUSTY WINDS FOR LAND ZONES 23 /SITKA/...27
/HYDABURG/...AND 28 /KETCHIKAN/. THE COMBINATION OF STRONG WINDS
AND LOCALLY HEAVY RAIN MAY INCREASE THE THREAT FOR MUDSLIDES.

UPPER TROUGHING PERSISTS OVER THE WRN/CNTRL GULF THROUGH THE
MIDDLE OF NEXT WEEK...WITH NUMEROUS EMBEDDED IMPULSES EJECTING ENEWD
ACROSS THE PANHANDLE...THE MOST VIGOROUS OF WHICH WILL POTENTIALLY
SPIN UP A SURFACE LOW OVER THE SERN GULF ON MON. IF THIS SCENARIO
DOES INDEED UNFOLD...THEN WINDS OVER THE SRN INSIDE WATERS WILL
REINTENSIFY TO SMALL CRAFT/GALE...AND ANOTHER PERIOD OF
MODERATE/HEAVY RAIN WILL BE POSSIBLE OVER THE SRN LAND AREAS.
HOWEVER...MODEL SPREAD IS LARGE FOR THE MON TIME PERIOD...THUS
CONFIDENCE IS NOT HIGH REGARDING WIND AND HEAVY PRECIP POTENTIAL.

IN GENERAL...MODELS SHOW MUCH IMPROVED CONSENSUS IN THE LARGE-
SCALE DETAILS THROUGHOUT THE LONG TERM PERIOD. THIS GIVES
CONFIDENCE IN THE LIKELIHOOD FOR AN EXTENDED PERIOD OF WET WEATHER
OVER SERN AK DUE TO NUMEROUS UPPER WAVES PASSING ACROSS THE
REGION. NO CHANGE WAS MADE TO PRESSURE GRIDS THROUGH 00Z MON.
THEREAFTER...BLENDED IN THE LATEST ECMWF...WHICH RESULTED IN A
DEAMPLIFICATION OF LOW PRESSURE IN THE SERN GULF SUN NIGHT INTO
MON. POP/QPF GRIDS WERE REFRESHED WITH THE GFS AND ECMWF.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ022-043.
         SMALL CRAFT ADVISORY FOR PKZ012-021-035-036-042-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-052.

&&

$$

WESLEY/GARNER

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