Area Forecast Discussion
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FXAK67 PAJK 211612 CCA
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE JUNEAU AK
806 AM AKDT THU AUG 21 2014

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE FORECAST AREA
UNDER MOST CLEAR SKIES AND LIGHT WINDS. THERE ARE A FEW POCKETS OF
PATCHY FOG NEAR ANGOON AND KLAWOCK AND LOCALLY DENSE. THE FOG WILL
DISSIPATE THROUGH THE EARLY MORNING HOURS. SUNNY SKIES WILL
DOMINATE THE FORECAST AREA WITH DEEP NORTHWEST FLOW FROM A BUILDING
UPPER RIDGE OVER THE GULF. THE RIDGE WILL SLOWLY DRIFT TO THE EAST
THROUGH TODAY WITH SOME ONSHORE FLOW MOVING BACK INTO THE NORTHERN
AND EASTERN COASTAL AREA LATE TONIGHT. THERE IS AN AREA OF SEA
STRATUS OVER THE WESTERN GULF THAT WILL TRACK UNDER THE BUILDING
RIDGE AND DRIFT EAST TO BE OVER THE EASTERN GULF BY LATE TONIGHT.
THE REST OF THE FORECAST AREA WILL REMAIN TO BE MOSTLY CLEAR
THROUGH TONIGHT.

A INVERTED TROF THAT IS OVER THE PANHANDLE WILL KEEP THE WINDS
OVER THE INNER CHANNELS FROM THE NNW BUT THEY WILL BE GENERALLY
LESS THAN 10 KT. THERE WILL BE AN INCREASE IN WINDS OVER CLARENCE
STRAIT AND CROSS SOUND IN THE AFTERNOON TO 20 KT. THE NORTHWEST
WINDS ALONG THE COASTAL WATERS WILL SLOWLY DECREASE OVER THE
NORTHERN GULF BUT KEEP GOING OVER THE EASTERN GULF INTO TONIGHT.
THERE WILL BE SOME AFTERNOON SEA BREEZES OVER LAND AREAS BUT THEY
WILL DIMINISH IN THE EARLY EVENING HOURS AND BE LIGHT OVER MOST OF
THE AREA TONIGHT.

TEMPERATURES ACROSS THE AREA WILL RANGE FROM THE UPPER 60S TO MID
70S WITH ALL DAY SUNSHINE ALONG WITH 850MB TEMPS OF +10-12 AND
DOWNSLOPE WINDS. THE OVERNIGHT LOWS WILL BE CHILLY OVER THE INNER
CHANNELS RANGING FROM THE LOWER 40S INLAND TO THE LOWER 50S NEAR
THE WATER.

PATCHY FOG WILL DEVELOP NEAR ANGOON, KLAWOCK AND MAYBE NEAR CROSS
SOUND AND YAKUTAT FROM THE MARINE LAYER MOVING IN ALONG THE COAST.

THERE IS ABOVE AVERAGE FORECASTER CONFIDENCE THROUGH THE SHORT
TERM PERIOD AND WHERE CHANGES WERE MADE USED THE 06Z NAM.

.LONG TERM...THE UPPER LEVEL RIDGE STARTS TO FLATTEN ON FRIDAY
WITH FLOW BECOMING MORE ZONAL AND ONSHORE. THIS WILL INTRODUCE
SOME MORE CLOUD COVER HOWEVER THE RIDGE REMAINS OVER THE EASTERN
GULF THROUGH THE WEEKEND...JUST NOT AS STRONG.

THE FORECAST IS GENERALLY LOOKING DRIER FOR THE WEEKEND DUE TO THE
UPPER LEVEL RIDGE REMAINING IN THE GULF. THE SURFACE PATTERN HAS A
COUPLE WEAK FEATURES PASSING THROUGH THE HIGH AND WEAKENING AS
THEY APPROACH THE AREA...THUS STILL HAVE SOME SLIGHT CHANCE POPS
ON SATURDAY AND AT LEAST PARTLY CLOUDY SKIES. LESS CONFIDENT IN
THE CLOUD COVER FORECAST HOWEVER AS MID LEVEL VORTICITY PASSING
OVER MOST OF THE DAY COULD MEAN MORE CLOUDS THAN THIS.

ON SUNDAY A SURFACE LOW WILL MOVE INTO THE CENTRAL GULF AND CAUSE
MORE CLOUD COVER AND INCREASING POPS. THE ECMWF AND GEM ARE THE
FASTEST TO MOVE PRECIP IN WHILE THE GFS DELAYS IT UNTIL LATER
MONDAY. HAVE GONE WITH A MIDDLE OF THE ROAD SOLUTION OF A CHANCE OF
RAIN ALONG THE OUTER COAST SUNDAY THEN INCREASING TO RAIN LIKELY
SUNDAY NIGHT AND MONDAY FOR THE REST OF THE PANHANDLE.

AN UPPER LEVEL TROUGH WILL MOVE INTO THE WESTERN GULF ON MONDAY.
THERE ARE SOME TIMING DIFFERENCES BETWEEN MODELS WITH THIS FEATURE,
BUT ALL HAVE IT. AGAIN THE GEM IS THE FASTEST AND THE ECMWF AND GFS
LOOK QUITE CLOSE WHICH IS PROMISING. THE UPPER LEVEL LOW TRACKS
ACROSS THE NORTHERN GULF THROUGH TUESDAY AND WEAKENS TO A TROUGH.
THE UPPER LEVEL TROUGH THEN LOOKS TO PASS OVER THE PANHANDLE
SOMETIME WEDNESDAY. ALL THIS MEANS IS GREATER CHANCES OF PRECIP FOR
NEXT WEEK.

THE UPPER LEVEL PATTERN IS IN BETTER AGREEMENT THROUGH THE EXTENDED
ALTHOUGH THE MSLP AGREEMENT IS NOT AS GOOD. USED A BLEND OF THE
ECMWF AND GFS FOR MOST UPDATES IN THE SHORT/MID RANGE THEN KEPT THE
FORECAST LARGELY IN TACT WITH WPC PRESSURE FIELDS THAT WERE IN THERE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

$$

ABJ/FERRIN

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU








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