Area Forecast Discussion
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FXAK67 PAJK 211352
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
552 AM AKDT TUE OCT 21 2014

.SHORT TERM...WINDY AND WET SHORT RANGE FORECAST IN THE WORKS AS A
GALE FORCE LOW CHURNS ITS WAY INTO THE SE GULF TODAY. RIGHT NOW
THE LOW IS STILL DOWN BY 50N 140W WITH ITS FRONT EXTENDING E
ACROSS THE SOUTHERN GULF TO NORTHERN HAIDA GWAII. THE FORWARD RAIN
BANDS AND SOME GUSTY WINDS HAVE ALREADY REACHED THE SOUTHERN
PANHANDLE THIS MORNING WITH GUSTS AS HIGH AS 35 MPH RECORDED AT
KETCHIKAN AND HYDABURG WITH SOME LIGHT RAIN. FARTHER NORTH THE
THERE ARE A FEW EFFECTS OF THE FRONT ALREADY BEING SEEN. THE FIRST IS
AN INCREASE IN HIGH LEVEL CLOUD COVER STOPPING TEMPERATURES FROM FALLING
SIGNIFICANTLY OVERNIGHT AND STALLING ANY FOG FORMATION THIS
MORNING. THE OTHER EFFECT IS CHANGING THE OVERALL PRESSURE
GRADIENT ACROSS THE PANHANDLE TO NORTH CAUSING WIND DIRECTION
SHIFTS FROM SOUTH TO NORTH IN SOME INNER CHANNEL AREAS.

FOR TODAY AND TONIGHT THE MAIN STORY WILL BE THE FRONT THE LOW IN
THE GULF SENDS OVER THE PANHANDLE FOLLOWED BY THE SECOND WRAP THAT
WILL PLOW IN BEHIND THE MAIN FRONT. THE MAIN FRONT WILL HEAD NORTH
OVER THE PANHANDLE TODAY SPREADING WIND AND RAIN AS IT GOES. THE
LOW LEVEL JET ACCOMPANYING THE FRONT IS ON THE ORDER OF 50 TO 55
KT. STRONG WIND HEADLINES ARE UP FOR ZONES 23, 26, 27 AND 28 AS A
RESULT WITH GUSTS TO UP TO 45 MPH EXPECTED. GALES ARE ALSO UP FOR
THE SOUTHERN GULF AND SOUTHERN INNER CHANNELS FOR THE SAME REASON.
HIGHEST WINDS WILL BE AROUND MIDDAY DURING FRONTAL PASSAGE WITH A
SECOND HIGHER MAXIMA THIS AFTERNOON AND EVENING AS THE SECOND
WRAP COMES ASHORE. WINDS FINALLY BEGIN DIMINISHING LATE TONIGHT AS
THE LOW BEGINS TO DRIFT WEST INTO THE CENTRAL GULF TAKING ITS
FRONTS WITH IT.

FARTHER NORTH THE NORTHERLY PRESSURE GRADIENT WILL BE THE PROBLEM
CHILD FOR WINDS TODAY. LYNN CANAL HAS JUST FLIPPED TO THE NORTH
ABOUT A HOUR AGO. THOSE WINDS WILL INCREASE TO 30 KT THIS
AFTERNOON AS NORTHERLY PRESSURE GRADIENTS INCREASE IN RESPONSE TO
THE FRONT COMING NORTH. THE OTHER AREA TO WATCH TODAY WILL BE
DOWNTOWN JUNEAU AND DOUGLAS FOR A MILD PRE-FRONTAL TAKU EVENT. NOT
ENTIRELY CONFIDENT ON THIS FEATURE AS CROSS BARRIER FLOW IS NOT
EXPECTED TO BE THAT STRONG (AROUND 30 TO 40 KT) AND THE CRITICAL
LEVEL IS NOT VERY WELL DEFENDED (THERE IS NO WIND DIRECTION SHIFT
ALOFT MORE OF A WEAKNESS IN THE GENERAL E FLOW ALOFT). STILL GUSTS
UP TO 40 MPH ARE POSSIBLE STARTING AROUND MIDDAY AND CONTINUING
INTO EARLY EVENING BEFORE SE SYNOPTIC FLOW CUTS IT OFF AND FLIPS
WIND DIRECTION TO MORE PARALLEL BARRIER FLOW. A STRONG WIND
HEADLINE HAS BEEN ISSUED FOR THE DOWNTOWN JUNEAU AND DOUGLAS AREA
FOR TODAY AS A RESULT.

AS FOR RAIN, NOT EXPECTING TOO MUCH PRECIP OUT OF THIS ONE.
LIMITING FACTORS ARE THAT MAIN MOISTURE PLUME IS AIMED AT THE AREA
SOUTH OF HAIDA GWAII AND THE NORTHERLY FLOW FOR THE NORTHERN PART
OF THE PANHANDLE. QPF AMOUNTS ARE IN THE HALF TO ONE INCH RANGE
MAINLY FOR THE SOUTHERN PANHANDLE AND OUTER COAST WITH LESSER
AMOUNTS FARTHER NORTH DUE TO THE NORTHERLY AND EASTERLY
DOWNSLOPING WINDS. THE MENTION OF ISOLATED THUNDERSTORMS HAS ALSO
BEEN INCLUDED FOR THE GULF WATERS AS A POCKET OF COOLER UPPER
LEVEL AIR AS WELL AS THE VORTICITY ASSOCIATED WITH THE LOW
DESTABILIZE THE SOUTHERN GULF TODAY AND TONIGHT.

SHORT RANGE MODELS WERE IN DECENT AGREEMENT BUT DID DISPLAY SOME
DIFFERENCES IN LOW POSITION BY LATE TONIGHT. GFS SEEMED TO BE A
BIT OF AN OUTLIER AS IT CARRIED THE LOW A LITTLE FURTHER WEST LATE
TONIGHT THEN MOST OTHER MODELS. PLUS IT GENERALLY UNDER DID THE
PRESSURE GRADIENT ACROSS THE PANHANDLE. GENERALLY FAVORED THE NAM
AND ECMWF FOR FORECAST GUIDANCE.

.LONG TERM...GALE FORCE LOW CURRENTLY MOVING INTO THE SOUTHERN AK
GULF WILL HAVE PULLED TO THE WEST NEARING KODIAK ISLAND BY
WEDNESDAY. THE ASSOCIATED FRONT CROSSES MOVED THE NORTHERN
PANHANDLE MOVING TOWARDS PRINCE WILLIAM SOUND. THE LOW WILL DROP
SOUTHEASTWARD AGAIN WITH A SECONDARY CIRCULATION ROTATING TO THE
SOUTH OF THE MAIN LOW WILL BEGIN TO DEVELOP OFF THE WEST COAST OF
HAIDA GWAII THURSDAY. CURRENT MODEL RUNS INDICATE THE ENTIRE
SYSTEM WILL BE DRIVEN SOUTHWARD BY FRIDAY AS UPPER LEVEL RIDGE
ADVANCES INTO THE WESTERN GULF. A CLOSED UPPER LOW ORIGINATING
OFF KAMCHATKA WILL MOVE OVER THE RIDGE WITH A TROUGH EXTENDING
INTO THE GULF AND FLATTENING THE RIDGE OVER THE WEEKEND THEN
FORMED A CLOSED CIRCULATION OVER THE AK GULF BY THE START OF NEXT
WEEK. MEANWHILE THE REMNANTS OF TROPICAL STORM ANA WILL MOVE
NORTHWARD AND AT THIS TIME MODELS ARE HAVING DIFFICULTY
DETERMINING IF THIS FEATURE WILL BE INCORPORATED INTO THE WESTERLY
MID LATITUDE FLOW AND REACH THE AK GULF OR REMAIN SOUTH OF THE
MAIN FLOW AND MISS OUR AREA. THUS THERE HAS BEEN SIGNIFICANT RUN
TO RUN INCONSISTENCY AND MODEL SPREAD AND THUS LOW FORECAST
CONFIDENCE.

WHAT IS EXPECTED IS PRECIP AND WINDS TO DIMINISH AS THE FRONT MOVES
OVER THE NORTHERN PANHANDLE AND THE PRESSURE GRADIENT WEAKENS. THE
POSITION AND STRENGTH OF THE SECONDARY CIRCULATION OFF HAIDA GWAII
IS UNCERTAIN WITH THE NAM/GFS KEEPING THIS LOW SOUTH OFT THE AK
GULF RESULTING IN DRIER WEATHER WHILE THE ECMWF/GEM MOVE IT OFF
THE SOUTHERN PANHANDLE COAST AND THUS MOVE IN MORE PRECIP TO THE
REGION. AT THIS TIME WHILE THE NAM DID INITIALIZE WELL IT ALSO IS
CURRENTLY IN LINE WITH THE ECMWF AND THUS THE SPLIT BETWEEN THESE
MODELS TOWARD THE END OF THE WEEK DOES NOT WARRANT MUCH CONFIDENCE
IN EITHER SOLUTION. THERE IS ALSO LARGE MODEL DIFFERENCE WITH THE
TIMING OF THE UPPER LEVEL TROUGH MOVING INTO THE N AK GULF BY THE
WEEKEND AND THUS DIFFERENCES IN A POTENTIAL SURFACE CIRCULATION
FORMING IN THE NORTHERN GULF AND PRODUCING PRECIP OVER THE
PANHANDLE. AND AS MENTIONED ABOVE ANA REMNANTS MAY HI THE AK GULF
MONDAY AS INDICATED BY THE ECMWF OR KEEP TO THE SOUTH PER THE GFS.
HENCE KEEPING WITH AN ENSEMBLE SOLUTION OF MOSTLY CLOUDY WITH
CHANCE OF RAIN.

INITIALLY BLENDED IN SOME 00Z NAM WITH INHERITED GRIDS SINCE THE NAM
INITIALIZED WELL AND SEEMED TO BE IN LINE WITH AT LEAST ONE MODEL
THROUGH MID RANGE. KEEP WITH WPC ENSEMBLE SOLUTION FOR THE REST OF THE
EXTENDED RANGE FORECAST. FORECAST CONFIDENCE IS BELOW AVERAGE
INITIALLY AND THE DROPS BY THE WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH LATE TONIGHT
     FOR AKZ026.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ027.
         STRONG WIND FROM 10 AM AKDT THIS MORNING THROUGH THIS EVENING
     FOR AKZ025.
         STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH WEDNESDAY
     MORNING FOR AKZ023.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ028.
MARINE...GALE WARNING FOR PKZ022-033-035-036-041>043-051.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031-032-034-052.

&&

$$

EAL/PRB

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