Area Forecast Discussion
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000
FXAK67 PAJK 010005
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
405 PM AKDT FRI OCT 31 2014

.SHORT TERM...SHORT WAVE MOVING OVER THE CENTRAL AND NORTHERN
PANHANDLE EXTENDING FORM THE CIRCULATION IN THE AK GULF OFF CAPE
FAIRWEATHER PRODUCING GUSTY WINDS AND MODERATE SHOWERS. CLEAR
BREAKS AND COLD TEMPERATURES OVER THE SOUTHERN PANHANDLE EARLY IN
THE DAY TRANSITIONED TO ADVANCING SHOWERS FROM THE SHORT WAVE.
SHOWERS ALONG THE PANHANDLE COAST PRODUCED ICE PELLETS IN THE
UNSTABLE ENVIRONMENT WITH A REPORT OF A WATER SPOUT NEAR MIDDLE
ISLAND THIS AFTERNOON. AS THE WAVE MOVES OVERLAND AND INTO BRITISH
COLUMBIA TONIGHT WINDS WILL BEGIN TO DROP OFF. THE NEXT ADVANCING
FRONT CURRENTLY MOVING INTO THE AK GULF WILL BEGIN TO MOVE
OVERLAND WITH 850 MB WINDS IN THE 40 TO 50 KT RANGE. SURFACE WINDS
OVER THE AK GULF WILL INCREASE ONCE AGAIN TO GALE FORCE THROUGH THE
EVENING WITH GALES DEVELOPING OVER THE INNER CHANNELS LATE
TONIGHT. SO ANY BREAKS IN WINDS OVER THE PANHANDLE WILL BE FAIRLY
SHORT LIVED. AS THE FRONT MOVES INLAND SUSTAINED WINDS WILL DROP
OFF THROUGH THE MORNING WITH SOME LINGERING HIGHER GUSTS. WARM AIR
ADVECTION WILL STABILIZE THE ATMOSPHERE WHICH WILL TRANSITIONED
THE SHOWERS TO MORE STEADY RAIN FALL AND MAY KEEP THE HIGHER WINDS
ALOFT FROM MIXING DOWN AND THUS KEEP THE INNER CHANNEL WINDS
LOWER. BLENDED TPW SATELLITE SHOWING CURRENT MOISTURE FEED INTO
THE FRONT OF 0.1 TO 0.2 INCHES WITH FORECAST SIX HOUR QPF AROUND
ONE QUARTER OF AN INCH. THUS EXPECTING SOME MODERATE RAIN BUT NO
EXCEPTIONALLY HEAVY PRECIP. SNOW LEVELS WILL RISE WITH THE
ADVANCING FRONT BUT FOR NOW MODEL SOUNDINGS KEEPING THEM AT OR
BELOW 3000 FT. PRECIPITATION WILL BE RAIN FOR MOST OF THE
PANHANDLE WITH THE EXCEPTION OF HIGHER ELEVATIONS AND ALONG THE
HAINES AND KLONDIKE HIGHWAYS. THE HAINES HIGHWAY WILL START OUT AS
SNOW LATE TONIGHT THEN TRANSITIONS TO RAIN THROUGH THE SATURDAY AS
WARM AIR MOVES IN ALOFT. THE KLONDIKE HIGHWAY WILL STAY SNOW
LONGER AND THUS HAVE ISSUES A WINTER WEATHER ADVISORY FOR SNOW
ACCUMULATIONS LATE TONIGHT INTO SATURDAY AFTERNOON OF 3 TO 5
INCHES. THE SNOW SHOULD BEGIN TO MIX WITH RAIN EVEN NEAR WHITE
PASS WITH THE WARM AIR ALONG THE FRONT. BEHIND THE FRONT COLD AIR
ALOFT IS MOVING IN AND RAIN WILL TRANSITION BACK TO SHOWERS OVER
THE AK GULF THROUGH SATURDAY. THE INSTABILITY WITH CAPE AROUND 300
J/KG AND LIFTED INDEX OF -1 TO -2 C IS ENOUGH TO WARRANT ADDING
SLIGHT CHANCE OF THUNDERSTORM OVER THE OFFSHORE WATER TOMORROW
AFTERNOON.

MODEL WERE IN GOOD AGREEMENT FOR SYNOPTIC SCALE FEATURES WITH SOME
OF THE COARSE MODELS BUT TOO BROAD BRUSH ON POPS. REFRESHED GRIDS
WITH 12Z NAM BUT CHANGES WERE VERY SMALL OVERALL. FORECAST
CONFIDENCE IS AVERAGE.

.LONG TERM...A TRIPLE POINT LOW CURRENTLY FORMING NEAR KODIAK WILL
HAVE BEGUN TO WEAKEN NEAR THE KENAI BY THE START OF THE EXTENDED
RANGE FORECAST PERIOD. AT THE SAME TIME, A PAIR OF FAIRLY STRONG
SHORT WAVES WILL HAVE ROTATED AROUND THE BASE OF THE PARENT LOW
LOCATED OVER BRISTOL BAY AND BE MOVING ACROSS THE NORTHERN GULF.
THESE TWO SHORT WAVES WILL REINFORCE PRECIPITATION ASSOCIATED WITH
THE FRONT CURRENTLY OVER THE CENTRAL GULF. NET RESULT IS
PRECIPITATION ACROSS SOUTHEAST ALASKA THROUGH THE WEEKEND.

WELL TO THE WEST AND SOUTH, A LOW IS FORMING ON THE COLD FRONTAL
BOUNDARY NEAR 40N AND 170W. THE LOW WILL MOVE NORTHEAST ALONG THE
FRONTAL BOUNDARY AS IT GAINS STRENGTH. MODEL SOLUTIONS FOR MONDAY
NIGHT RANGING FROM THE CENTRAL PANHANDLE TO SOUTH OF HECATE
STRAIT. GEM IS RUNNING THE DEEPEST AND FARTHEST NORTH WHILE NAM IS
THE WEAKEST AND FARTHEST SOUTH. TRACK AND INTENSITY HAVE A VERY
LARGE IMPACT ON THE FORECAST DUE TO THE PROXIMITY OF THE CENTER OF
CIRCULATION AND WHERE THE HEAVIEST RAINS WILL FALL. CURRENT SATELLITE
IMAGERY INDICATING UPWARDS OF 3 INCHES OF PRECIPITABLE WATER AND A
SOLID TROPICAL MOISTURE CONNECTION. CURRENT FORECAST MOST IN LINE
WITH THE NAM DEPICTION WHICH REPRESENTS THE SOUTHERLY OUTLIER AND KEEPS
THE BULK OF THE RAIN SOUTH OF THE PANHANDLE. SITUATION WILL HAVE TO
BE CLOSELY WATCHED FOR CHANGES IN THE TRACK OF THIS LOW OVER THE
NEXT 3 DAYS.

USED A BLEND OF ECMWF AND GFS FOR PRESSURE AND WIND EARLY ON,
FOLLOWED BY A NAM/GEM BLEND. WPC TUESDAY AND ONWARD. POP AND QPF
ADJUSTED USING CURRENT ECMWF AND GEM THROUGH MONDAY NIGHT.
REMAINDER OF THE FORECAST UNCHANGED. OVERALL FORECAST CONFIDENCE
IS AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 1 PM AKDT
     SATURDAY FOR AKZ018.
MARINE...GALE WARNING FOR PKZ022-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031>035-053.

&&

$$

PRB/FRITSCH

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