Area Forecast Discussion
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FXAK67 PAJK 272241
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
241 PM AKDT WED MAY 27 2015

.SHORT TERM...UPPER LOW OVER CENTRAL SE AK WILL DRIFT SE AND BE
JUST SE OF THE FAR SRN PANHANDLE BY LATE THU AFTERNOON. UPPER
RIDGE WILL BUILD OVER THE GULF AND YUKON AREA THRU THU. SFC HIGH
OVER AND JUST S OF THE GULF WILL SLOWLY STRENGTHEN THRU THU.
MODELS WERE FAIRLY CLOSE ON THE MAIN FEATURES...WITH SOME
DIFFERENCES NOTED ON THE SMALLER SCALE.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL...TEMPS...AND
WINDS. RIGHT NOW...THERE ARE SMALL BANDS OF PRECIP WRAPPING AROUND
THE UPPER LOW...MAINLY AFFECTING THE CENTRAL PANHANDLE AND
E-CENTRAL GULF. THINK THESE WILL DIMINISH SOME TONIGHT AS UPPER
LOW MOVES SE. THERE IS A DEVELOPING BAND OF CLOUDS THAT LIKELY
HAVE PRECIP WITH THEM JUST E OF THE NRN PANHANDLE...AND IT IS
BEGINNING TO TURN WWD INTO THE AREA. THIS BAND WILL CURVE SWWD AND
AFFECT THE NRN THIRD OF THE AREA TONIGHT...WITH GREATEST THREAT OF
PRECIP FROM THE JUNEAU AREA TO PAOH THROUGH THIS EVENING. THIS
BAND WILL CONTINUE SWD ALONG THE CENTRAL AND SRN OUTER COAST BUT
DIMINISH OVERNIGHT...WITH MAINLY CLOUDS AND A FEW SPRINKLES OR
SPOTTY LIGHT RAIN LEFT BY DAYBREAK. THEN...LOOKS LIKE ANOTHER
PRECIP BAND WILL DEVELOP OVER CENTRAL BC AND MOVE INTO THE HYDER
AREA THU. BOTH BANDS ARE ASSOCIATED WITH SHORTWAVES ROTATING
AROUND THE UPPER LOW AND ARE ENHANCED BY MID-LEVEL WARM ADVECTION.

AS FOR TEMPS...TOUGHEST PART OF FORECAST MAY BE THU. A MORE
OFFSHORE FLOW WILL HELP CLEAR THINGS OUT FROM THE N LATE TONIGHT
AND THU OVER THE N. THIS OFFSHORE FLOW LOOKS LIKE IT WILL GET TO
THE SFC...SO TEMPS ON THU SHOULD BE MUCH WARMER OVER THE NRN AREA.
MAY GET WELL INTO THE 70S OVER THE FAR N...WITH AROUND 70 IN THE
PAJN AREA...AND 65-70 AROUND PAGS AND PAOH. OF COURSE...LOCAL SEA
BREEZES MAY TRY TO SLOW THE WARM UP SOME BUT GIVEN SUPPORT FOR
NLY FLOW ALL THE WAY TO SFC...THEY WILL BE WEAKER THAN USUAL.

WINDS WILL GENERALLY WEAKEN SLIGHTLY BUT STILL HANG AROUND 20 KT
OVER MUCH OF THE ERN GULF. WINDS ON THE INNER CHANNELS WILL PEAK
EARLY THIS EVENING...WITH SCA LEVEL W-NW WINDS AROUND CROSS
SOUND AND SCA LEVEL S WINDS IN FAR N LYNN CANAL. MUCH OF THE
REMAINING INNER CHANNELS SHOULD START AROUND 15-20 KT. WINDS OVER
INNER CHANNELS SHOULD WEAKEN LATER THIS EVENING...BUT BEGIN TO
PICK UP SOME OVER THE NRN AREAS AS NLY GRADIENT INCREASES. DO NOT
EXPECT MORE THAN 15-20 KT THOUGH IN THE NLY FLOW. SRN INNER
CHANNELS WILL SEE WINDS PICK UP AGAIN THU...MAINLY DRIVEN BY
DIURNAL ENHANCEMENT AND SOME MIX DOWN OF STRONGER WINDS FROM
ALOFT.

OTHERWISE...AS WARMER AIR ALOFT MOVES INTO THE NRN GULF AND MARINE
INVERSION STRENGTHENS...LOW CLOUDS SHOULD REDEVELOP OVER THAT AREA
AND EVENTUALLY SPREAD SE ACROSS THE ERN GULF THU. THINK THERE IS
ENOUGH OF AN OFFSHORE FLOW FOR THE OUTER COAST TO ONLY HAVE A
SHORT PERIOD OF THESE LOW CLOUDS EARLY THU HOWEVER.

.LONG TERM...MODELS REMAIN IN FAIR AGREEMENT FOR THE UPPER LEVEL
LOW NEAR DIXON ENTRANCE THURSDAY NIGHT CONTINUES FILLING SLOWLY
AND MOVES A LITTLE EAST INTO BRITISH COLUMBIA THROUGH LATE
SATURDAY. SURFACE HIGH PRESSURE WILL ANCHOR OVER THE SOUTH CENTRAL
GULF AND AN INVERTED TROUGH OF LOW PRESSURE WILL REMAIN ACROSS THE
PANHANDLE. REFRESHED THE INHERITED FORECAST WITH THE ECMWF FOR ITS
GOOD CONSISTENCY FOR PRESSURE AND WIND FIELDS. USED THE SREF
GUIDANCE FOR POPS WITH ENSEMBLE APPROACH FOR QPF VALUES.

WEAKENING MID TO UPPER LEVEL VORTICITY WILL REMAIN OVER THE
SOUTHERN PANHANDLE THROUGH SATURDAY. CLOUDS WILL BEGIN DECREASING
THURSDAY NIGHT THEN GENERALLY DRY AND SEASONABLY WARM WEATHER
RETURN TO SOUTHEAST ALASKA THROUGH EARLY NEXT WEEK. BETWEEN THE
HIGH PRESSURE AND INVERTED TROUGH...SOME WEST TO NORTHWEST WINDS
WILL BE ENHANCED TO 15 TO 20 KNOTS.

WHILE SURFACE HIGH CONTINUES ANCHORING OVER THE GULF...AN UPPER
LEVEL SHORTWAVE TROUGH DEVELOPS ACROSS THE YUKON AND SPILLS UPPER
LEVEL DYNAMICS TO SOUTHWEST TO WEST LATE WEEKEND THROUGH MID WEEK
NEXT WEEK. MODELS DIVERT ON HANDLING THIS FEATURE AND USED THE WPC
ENSEMBLE GUIDANCE TO BRING CERTAIN PREDICTABLE UPPER FEATURES TO
THE NORTHERN PANHANDLE WITH INCREASING CLOUDS AND RAIN CHANCE FOR
THE NORTHERNMOST PANHANDLE BY MID WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-041>043-052.

&&

$$

RWT/AHN

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