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FXAK67 PAJK 302345
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
345 PM AKDT THU OCT 30 2014

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWING A WEAKENING LOW
PRESSURE SYSTEM MOVING INTO THE NORTHERN AK GULF WITH A SECONDARY
CIRCULATION OVER HAIDA GWAII. THE NORTHERN AK GULF LOW PRODUCED
GALE FORCE WINDS OVER NIGHT WITH SOME LINGERING SMALL CRAFT WINDS
OVER PKZ51 AND 52. THIS LOW WILL LINGER OVER THE NORTHEASTERN GULF
THROUGH FRIDAY WHEN IT EVENTUALLY WEAKENS TO AN OPEN WAVE TROUGH.
WINDS AROUND THE LOW WILL CONTINUE TO DIMINISH THROUGH THE LATE
EVENING. THE HAIDA GWAII LOW WAS TRICKY TO FORECAST AS MANY MODELS
WERE NOT SHOWING THIS FEATURE AND WERE IN CONSENSUS THAT THE LOW
WOULD SHOW LITTLE DEVELOPMENT WITH REMNANTS MOVING EASTWARD INTO
BRITISH COLUMBIA. IN REALITY THE LOW DROPPED DOWN TO 992 MB
PRODUCING SOME 20 KT WINDS OVER PKZ41, 25 KT OVER CLARENCE STRAIT
AND A BRIEF PERIOD OF STRONG WINDS OVER ZONE 28. NOW EXPECT THE
LOW TO MOVE ALONG AN NORTHEAST TRACK INCREASING WINDS OVER ZONE 26
THIS EVENING THEN MOVING INTO BRITISH COLUMBIA. NORTHWESTERLY WINDS
ARE DROPPING OFF RAPIDLY BECOMING CALM AS THE LOW MOVES OVERLAND
THEN WILL SHIFT TO THE SOUTH AND PICK BACK UP ON THE BACK SIDE OF
THE LOW.

AS BOTH LOWS TRACK IN OPPOSITE DIRECTIONS THE CURRENT FRONTAL
BAND OVER THE PANHANDLE THAT IS PRODUCING MODERATE TO HEAVY RAINFALL
WILL ALSO SPLIT. SOUTHERN PANHANDLE PRECIP WILL DIMINISH AND
CHANGE TO SHOWERS BIT FASTER THAN THE NORTHERN AND CENTRAL REGIONS
WHICH WILL HAVE A SECONDARY WRAP AROUND THE NORTHERN GULF LOW
TONIGHT. COOLER AIR ALOFT WILL HAVE THE ENTIRE REGION UNDER A
CONVECTIVE ENVIRONMENT BY FRIDAY. WHILE THIS COOLER AIR MASS IS
MORE CONDUCIVE FOR THUNDER STORM ACTIVITY OVER THE AK GULF AND
CENTRAL PANHANDLE COAST WITH CAPE IN AROUND 300 J/KG AND LIFTED
INDEX NEAR -1C NOT EXPECTING TEMPS TO BE LOW ENOUGH FOR SNOW. THE
EXCEPTION AGAIN IS AT HIGHER ELEVATIONS AND SOME COLD POOLS
NORTHWEST OF HAINES. FOR FRIDAY AFTERNOON A FRONT EXTENDING FROM A
LOW MOVING INTO THE BERING SEA WILL BEGIN TO CROSS THE AK GULF.
THIS FRONT WILL MAINLY IMPACT THE REGION IN THE LONG TERM
FORECAST.

MODELS HAD SOME DIFFERENCES WITH THE POSITION OF THE LOW IN THE
NORTHERN GULF BUT A GENERAL MODEL BLEND STAYED IN LINE WITH THE
INHERITED GRIDS. MORE SPREAD WITH THE LOW TO THE SOUTH WITH BETTER
INITIALIZATION WITH THE ECMWF/NAM, BUT ALL MODEL MISSED THE ACTUAL FEATURE.
OVERALL LEFT GRIDS TO THE NORTH AS IS WITH NUDGE TO THE 12Z
NAM/ECMWF FOR WINDS OVER THE AK GULF AND MANUAL EDITING OF WINDS
OVER THE SOUTHERN PANHANDLE. FORECAST CONFIDENCE IS BELOW AVERAGE.

.LONG TERM...EXTENDED RANGE FORECAST BEGINS WITH A TRIPLE POINT
LOW FORMING JUST EAST OF KODIAK ALONG A WARM FRONTAL BOUNDARY THAT
EXTENDS EAST ACROSS THE NORTHERN GULF. TRIPLE LOW ITSELF DOES NOT
LOOK LIKE IT WILL LAST LONG, AS WHAT LITTLE UPPER LEVEL JET
SUPPORT IT INITIALLY HAS WILL PULL AWAY TO THE SOUTH. THE LOW
ROTATES BACK TO THE WEST EVENTUALLY BECOMING ABSORBED INTO THE
MUCH LARGER PARENT CIRCULATION WHICH, BY SUNDAY NIGHT, WILL
FEATURE MULTIPLE MID LEVEL CIRCULATIONS AND SHORT WAVES.

THE FRONT THAT EXTENDS EAST FROM THE TRIPLE POINT LOW WILL BEGIN TO
AFFECT SOUTHEAST ALASKA SATURDAY NIGHT AS SHOWERS TRANSITION BACK
TO STRATIFORM PRECIPITATION. EXCELLENT AGREEMENT TODAY BETWEEN
GFS, NAM, AND ECMWF ON THE TIMING OF THIS FRONT AND ITS MOVEMENT
ACROSS THE PANHANDLE WITH MODERATE RAIN BECOMING HEAVY AT TIMES.
A POST FRONTAL SHORT WAVE TROUGH THEN MOVES IN SATURDAY EVENING,
FOLLOWED BY ANOTHER ON SUNDAY EVENING.

HAVE A NARROW BAND OF GALE FORCE WINDS OVER THE EASTERN GULF IN
ADVANCE OF THE SATURDAY FRONT ON FRIDAY NIGHT. AT THIS POINT, IF
THERE ARE STRONG WINDS, IT LOOKS LIKE THEY WILL BE LIMITED TO THE
CENTRAL AND SOUTHERN OUTER COAST LATE FRIDAY NIGHT INTO EARLY
SATURDAY. SMALL CRAFT WINDS OVER SEVERAL OF THE INNER CHANNELS
WITH A 40 KT GALE BEING FORECAST FOR CLARENCE STRAIT. WINDS WILL
DIMINISH THROUGH THE AFTERNOON SATURDAY AND OVERNIGHT. A
LOW THAT WILL FORM WELL TO THE SOUTH AND WEST WILL RIDE UP ALONG
THE EXISTING COLD FRONTAL BOUNDARY AND ARRIVE OVER THE FAR SOUTHEASTERN
GULF LATE SUNDAY NIGHT. WINDS OVER THE SOUTHERN COASTAL MARINE
ZONES AND INNER CHANNELS WILL PICK UP TO 30 KTS OR SO IN THE
OVERNIGHT HOURS ON SUNDAY. CURRENT FORECAST HAS THIS LOW
RETROGRADING BACK TO THE NORTHWEST AS IT OCCLUDES ALONG THE OUTER
COAST AND WEAKENS RAPIDLY ON MONDAY.

LONG TERM AGREEMENT BETTER TODAY AND THE EARLY
PORTION OF THE EXTENDED RANGE FORECAST REMAINS ON TRACK. NO
CHANGES TO PRESSURE OR WIND THROUGH SATURDAY NIGHT. UPDATED SUNDAY
AND SUNDAY NIGHT WITH ECMWF. WPC THEREAFTER. UPDATES TO POP AND
QPF YIELDED LITTLE TO NO CHANGE THROUGH SUNDAY NIGHT. FORECAST
CONFIDENCE UPGRADED TO AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ036-043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

$$

PRB/FRITSCH

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