Area Forecast Discussion
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FXAK67 PAJK 262222
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
222 PM AKDT TUE MAY 26 2015

.SHORT TERM...UPPER TROF OVER THE GULF IS IN PROCESS OF CLOSING
OFF ALOFT. THE RESULTANT UPPER LOW WILL DRIFT E INTO THE PANHANDLE
LATE TONIGHT AND WED. HIGH PRESSURE WILL BUILD OVER THE GULF LATER
TONIGHT AND WED IN RESPONSE TO UPPER RIDGE BUILDING NWD INTO THAT
AREA. USED BLEND OF THE 12Z ECMWF/GEM/NAM MODELS FOR THE FORECAST
THROUGH WED.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL AND WINDS. RIGHT
NOW...THERE IS A BAND OF PRECIP JUST OFFSHORE THE CENTRAL COASTAL
AREA ASSOCIATED WITH MID-LEVEL FRONT AND PVA AHEAD OF UPPER TROF. SOME
PRECIP IS ALSO BREAKING OUT JUST AHEAD OF THIS BAND RIGHT ALONG
THE CENTRAL COAST. EXPECT THE PRECIP BAND TO SWING NE ACROSS MOST
OF THE NRN HALF OF THE PANHANDLE THIS EVENING...THEN SETTLE ALONG
THE COAST MTNS FROM PAPG-PAJN OVERNIGHT AS UPPER LOW MOVES ONSHORE.
THIS WILL GENERALLY PERSIST THRU MOST OF WED...BUT A DEVELOPING
PRECIP BAND OVER NRN BC WILL LIKELY DRIFT SWWD INTO THE N-CENTRAL
AREA LATE IN THE DAY. DID LIMIT POPS TO LIKELY THOUGH AS PRECIP
BAND MAY THIN OUT SOME AS IT COMES ASHORE INTO A SLIGHTLY DRIER
AIRMASS ALREADY IN THE AREA THIS EVENING...THEN PRECIP MAY BE MORE
SPOTTY IN NATURE LATER TONIGHT INTO WED. LONGEST PERIOD OF LIKELY
POPS WILL BE AROUND THE PAJN AREA WHERE BEST UPSLOPE AND LIFT WILL
PERSIST. SRN AREA LOOKS LIKE IT WILL ONLY SEE A FEW SPRINKLES
LATER TONIGHT AND WED...THUS KEPT POPS ON LOW SIDE THERE. THE PAYA
AREA WILL PROBABLY GET CLIPPED BY THE BAND MOVING ONSHORE EARLY
THIS EVENING...THEN PRECIP THREAT WILL DIMINISH THERE LATER
TONIGHT AND WED BUT NOT COMPLETELY DISAPPEAR.

AS FOR WINDS...THEY WILL BE ON THE INCREASE OVER THE GULF AS WEAK
TO MODERATE COLD ADVECTION AND BUILDING SFC HIGH WILL TIGHTEN
PRESSURE GRADIENT. EXPECT BAND OF SCA LEVEL W-NW WINDS WED OVER
THE NRN AND ERN GULF. SOME DIURNAL ENHANCEMENT TO THE WINDS WILL
BE OCCURRING THIS EVENING OVER THE INNER CHANNELS...WITH SCA
LEVEL S WINDS LIKELY FOR FAR NRN LYNN CANAL AND 15-20 KT IN MOST
OTHER INNER CHANNELS THIS EVENING. THEY WILL DIMINISH LATER IN THE
EVENING BEFORE STRONGER WINDS BEHIND FRONT ALOFT COME IN LATE
TONIGHT AND WED. WILL LIKELY SEE SCA LEVEL WLY WINDS IN CROSS
SOUND AND SLY WINDS IN NRN LYNN CANAL WED...WITH 15-20 KT OVER
MUCH OF THE REMAINING INNER CHANNELS.

OTHERWISE...MARINE LAYER WILL BE LIFTED BY THE APPROACHING FRONT
WHICH SHOULD RAISE CLOUD CEILINGS FOR THE EARLY EVENING...BUT THEY
WILL LOWER AGAIN OVERNIGHT TONIGHT. DO NOT THINK CLOUDS WILL BE AS
LOW HOWEVER AS BOUNDARY LAYER WILL BE DEEPER AND ALLOW FOR BETTER
MIXING.

.LONG TERM...MODELS REMAIN IN FAIR AGREEMENT FOR AN UPPER LEVEL
LOW OVER THE CENTRAL PANHANDLE WEDNESDAY NIGHT SLOWLY FILLS AND
DRIFTS SOUTHEASTWARD TO THE SOUTHERN BRITISH COLUMBIA THROUGH
FRIDAY EVENING. SURFACE HIGH PRESSURE WILL CONTINUE TO DOMINATE
ACROSS THE GULF AND AN INVERTED SURFACE TROUGH OF LOW PRESSURE
WILL PERSIST EAST OF THE COAST MOUNTAIN RANGE. A MID LEVEL FRONTAL
PASSAGE ASSOCIATED WITH THE UPPER LOW WILL CONTINUE TO DISORGANIZE
AS IT MOVES SOUTHEAST WEDNESDAY NIGHT INTO THURSDAY MORNING. THE
INVERTED SURFACE TROUGH WILL MAINTAIN LIKELY POPS OVER THE EAST
CENTRAL PANHANDLE WEDNESDAY NIGHT...THEN MOVE SOUTH TO THE
SOUTHERN BRITISH COLUMBIA BY THURSDAY AFTERNOON. REFRESHED THE
INHERITED FORECAST WITH THE ECMWF AND GEM FOR THEIR GOOD CONSENSUS
THROUGH FRIDAY EVENING.

DRY AND SEASONABLY WARM WEATHER WILL RETURN TO SOUTHEAST ALASKA
LATE THURSDAY AND CONTINUE THROUGH EARLY NEXT WEEK AS THE UPPER
RIDGE CONTINUES TO BUILD NORTH AND SURFACE HIGH ANCHORS OVER THE
GULF. MODEL DIFFERENCES BECOME LARGER OVER THE WEEKEND AN UPPER
LEVEL SHORTWAVE TROUGH DEVELOPS OVER THE NORTHERN CANADA AND
SLOWLY DIGGING SOUTHWESTWARD. USED THE WPC ENSEMBLE GUIDANCE FOR
THE REMAINING LONG TERM PERIODS. EXPECT INCREASING RAIN CHANCE
OVER THE NORTHERNMOST PANHANDLE AND ALONG THE COAST MOUNTAIN RANGE
FROM SUNDAY. NEAR SMALL CRAFT LEVEL WEST TO NORTHWEST WINDS WILL
AFFECT THE SOUTHERN OUTSIDE WATERS WEDNESDAY NIGHT AND AGAIN LATE
FRIDAY. NO SIGNIFICANT WINDS ARE EXPECTED ACROSS THE INNER
CHANNELS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-041>043-051-052.

&&

$$

RWT/AHN

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