Area Forecast Discussion
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FXAK67 PAJK 201409
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
609 AM AKDT WED AUG 20 2014

.SHORT TERM...THE LATEST SATELLITE IMAGERY FROM THE VIIRS FOG
PRODUCT SHOWS THE FORECAST AREA UNDER MOSTLY CLEAR SKIES BUT THERE
ARE SOME POCKETS OF FOG. THE MAIN AREAS OF FOG ARE IN THE ANGOON,
JUNEAU, PETERSBURG, WRANGELL, KLAWOCK AND YAKUTAT WITH VISIBILITIES
RANGING FROM 4 MILES TO ONE HALF OF A MILE. THE FOG WILL DISSIPATE
THROUGH THE MORNING HOURS. THERE IS AN AREA OF SEA STRATUS OVER
THE GULF THIS MORNING WHICH WILL REMAIN THERE THROUGH THE
AFTERNOON HOURS. THERE IS NOT MUCH WIND AROUND THE AREA THIS
MORNING WITH THE SPEEDS NO MORE THAN 10 KT FROM THE NORTH.

THERE IS AN UPPER TROF OVER THE SOUTHERN GULF THAT WILL SLIDE TO
THE SE THROUGH TODAY. THIS FEATURE MANY PUSH SOME CLOUDS OVER THE
SOUTHERN COASTAL AREAS BY THE AFTERNOON. THERE WILL ALSO BE SOME
CLOUDS FROM THE YUKON THAT WILL SLIDE SOUTH IN THE AFTERNOON FROM
CONVECTION. SOME SCATTERED SHOWERS MAY MOVE OVER WHITE PASS AND
INTO SKAGWAY AND HAINES IN THE AFTERNOON. THE REST OF THE FORECAST
AREA WILL REMAIN MOSTLY SUNNY AND PRECIP FREE.

INCREASED THE DAY TIME HIGH TEMPERATURES WITH MORE SUNSHINE AND
INCREASING DOWNSLOPING FROM EASTERLY MID LEVEL FLOW ALONG WITH
STRENGTHENING INVERTED TROF OVER THE PANHANDLE. SO WITH THAT SAID
HIGHS WILL RANGE FROM THE UPPER 60S TO LOWER 70S.

AS MENTIONED ABOVE THE WINDS WILL BE GENERALLY ON THE LIGHT SIDE
BUT THROUGH THE DAY THE NORTHWEST WINDS WILL INCREASE TO 10 TO 15
KT AS THE INVERTED TROF INCREASES FROM SOUTH TO NORTH. THE DAY
TIME HEATING WILL GENERATE SOUTH WINDS TO INCREASE NEAR 20 KT OVER
NORTHERN LYNN ALONG WITH SEA BREEZES FROM 10 TO 15 MPH NEAR HAINES
AND SKAGWAY.

THROUGH TONIGHT THE CLOUDS OVER THE FAR NORTHERN AREA FROM CANADA
WILL DISSIPATE AND THE REST OF THE AREA WILL REMAIN ON THE CLEAR
SIDE. THE SEA STRATUS OVER THE GULF WILL MOVE SOME TO THE EAST AND BE
ALONG THE COAST. AT THIS TIME THE THINKING IS THAT IT WILL NOT MOVE
INLAND WITH GENERAL SYNOPTIC SURFACE FLOW OVER THE GULF FROM THE
NORTHWEST AND MID LEVEL FLOW FROM THE EAST. FOG WILL DEVELOP OVER
THE USUAL AREAS OVER THE INNER CHANNELS. THE WINDS WILL ALSO
INCREASE TO BE 15 TO 20 KT FROM THE NORTHWEST SOUTH OF FREDRICK
SOUND WITH THE STRENGTHENING INVERTED TROF. THIS WIND WILL KEEP FOG
FROM FORMING NEAR THE KETCHIKAN AREA. THE REST OF THE AREA WILL
SEE LIGHT WINDS.

OVERALL THERE IS ABOVE AVERAGE FORECASTER CONFIDENCE IN THE
GENERAL TREND BUT LOWER CONFIDENCE ON CLOUD COVER. MODELS WERE IN
GOOD AGREEMENT WITH THE PATTEN BUT WHERE CHANGES WERE MADE USED THE
06Z NAM.

.LONG TERM...UPPER LEVEL PATTERN HAS THE RIDGE DISCUSSED ABOVE
BUILDING OVER THE EASTERN GULF THURSDAY THEN BECOMING BROADER AND
FLATTENING OUT FRIDAY AND INTO THE WEEKEND. THIS MEANS MORE ONSHORE
FLOW WITH INCREASING CLOUD COVER...AKA A DIRTY RIDGE DEVELOPING
INTO THE WEEKEND. THE SURFACE RIDGE TIPS OVER AT A SIMILAR TIME
AND ALLOWS A LOW TO MOVE INTO THE CENTRAL GULF SATURDAY.

IN THE MEAN TIME...THURSDAY LOOKS TO BE MOSTLY SUNNY ACROSS THE
REGION AND WARMER. 850 MB TEMPERATURES ARE PROGGED TO BE 8-12C WHICH
WOULD TRANSLATE TO A MAX POSSIBLE TEMPERATURE OF 70-77. HAVE NOT
GONE QUITE THAT WARM EVERYWHERE...ALTHOUGH MANY LOCATIONS DO HIT THE
70F MARK. AFTERNOON SEA BREEZES WILL MAKE LOCATIONS NEAR THE WATER A
FEW DEGREES COOLER THAN INLAND AREAS. WINDS WILL BE RELATIVELY LIGHT
BUT NWLY FLOW AROUND THE RIDGE WILL CAUSE PLACES WITH A NW SEA
BREEZE DIRECTION (WRANGELL, KETCHIKAN, ETC.) TO GET A BIT MORE WIND
IN THE AFTERNOON. THE OPPOSITE IS TRUE FOR PLACES WITH A NORMAL
SOUTHERLY SEA BREEZE, IE. NORTHERN LYNN CANAL WILL SEE NORTH WINDS
IN THE MORNING BECOME LIGHT AND VARIABLE IN THE AFTERNOON. HAVE LEFT
ISOLATED/SCATTERED SHOWERS IN THE FORECAST OVER THE HYDER AREA ON
THURS  AFTERNOON DUE TO MODEL CAPE BEING A BIT HIGHER. WILL WATCH
FOR CONVECTION TO MOVE WEST INTO THE AREA FROM B.C. IN THE
AFTERNOON. SATELLITE IMAGERY SHOWS A MARINE LAYER UNDER THE RIDGE IN
THE GULF THIS MORNING. HAVE KEPT MORE CLOUD COVER OVER THE GULF AND
NEAR THE IMMEDIATE COAST ON THURSDAY FOR THIS REASON. WILL WATCH THIS
FEATURE TO SEE IF IT EXPANDS MORE...BUT FLOW ON THURSDAY IS MORE
NORTHERLY/OFFSHORE WHICH WOULD KEEP IT OUT OVER THE GULF.

FRIDAY WILL BE SIMILAR TO THURSDAY EXCEPT FLOW WILL BACK MORE
ONSHORE AND CAUSE INCREASING CLOUDS. ALSO THIS WIND DIRECTION CHANGE
MAY CAUSE THE MARINE LAYER OF LOW CLOUDS OUT IN THE GULF TO BE
PUSHED INTO THE IMMEDIATE COASTAL AREAS SUCH AS CROSS SOUND FRIDAY
MORNING. HAVE KEPT MENTION OF FOG FOR THOSE PLACES TO ACCOUNT FOR
THIS POSSIBILITY HOWEVER THE MARINE LAYER MAY JUST BE A LOW CLOUD
DECK AND NOT TRUE FOG DOWN TO THE SURFACE.

SATURDAY A LOW WILL MOVE INTO THE CENTRAL GULF THEN SLOWLY SHIFT TO
THE NORTH CENTRAL GULF THROUGH SUNDAY NIGHT. THIS WILL RESULT IN
MORE CLOUD COVER OVER THE WEEKEND AND A CHANCE OF PRECIP...HOWEVER
MODELS HAVE BEEN FLIP FLOPPING WITH THIS FEATURE. THEREFORE FORECAST
CONFIDENCE OVER THE WEEKEND IS LOWER...AND LEANING MORE ON THE DRY
SIDE THAN THE WET SIDE.

MODELS COME BACK INTO BETTER AGREEMENT FOR THE START OF NEXT WEEK
WITH PRECIP BECOMING MORE LIKELY MONDAY. THIS COINCIDES WITH WHEN
THE UPPER LEVEL RIDGE FINALLY MOVES EAST AND ALLOWS A TROUGH TO MOVE
INTO THE WESTERN GULF WITH A RETURN TO A MORE PROGRESSIVE PATTERN.

&&

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

&&

$$

ABJ/FERRIN

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








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