Area Forecast Discussion
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FXAK67 PAJK 192245
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
245 PM AKDT SUN APR 19 2015

.SHORT TERM...A WEAKENING FRONT CONTINUES TO MAKE SLOW PROGRESS TO
THE EAST OVER SOUTHEAST ALASKA THIS AFTERNOON. FARTHER SOUTH ALONG
THE FRONTAL BOUNDARY, A DEVELOPING WAVE IS MOVING NORTH. THIS WAVE
WILL RE-INVIGORATE PRECIPITATION TONIGHT AND PRODUCE HEAVY RAIN AT
TIMES OVER MUCH OF THE CENTRAL PANHANDLE. 24 HOUR FORECAST STORM
TOTALS GENERALLY RANGING FROM 1.3 INCHES OVER THE CENTRAL
PANHANDLE TO AS MUCH AS 2.15 INCHES IN THE JUNEAU AREA. THE USUAL
WATERWAYS SUBJECT TO FLASHY BEHAVIOR DURING HEAVY RAIN, MONTANA
CREEK AND JORDAN CREEK, ARE BEING WATCHED CLOSELY. CURRENTLY, BOTH
ARE EXPECTED TO REMAIN WITHIN THEIR BANKS. AN SPS ISSUED LAST
NIGHT CONCERNING FORECAST RAIN AMOUNTS REMAINS IN EFFECT. SNOW
LEVELS SUFFICIENTLY HIGH ENOUGH THAT EVEN WHITE PASS IS EXPECTED
TO REMAIN IN RAIN TONIGHT WITHOUT SWITCHING OVER TO SNOW. THUS
HIGHER ELEVATIONS WILL SEE SNOW MELT ASSOCIATED WITH THIS RAIN ON
WHAT LITTLE SNOW PACK DOES REMAIN AT ALTITUDE.

POST FRONTAL WINDS ALONG THE OUTER COAST ARE NOW BELOW GALE FORCE
AND EXPECTED TO CONTINUE TO SLOWLY DIMINISH OVERNIGHT. SMALL CRAFT
ADVISORIES FOR SOME OF THE INNER CHANNELS THIS EVENING INCLUDE
NORTHERN LYNN CANAL, WHERE IT HAS BEEN QUITE WINDY ALL DAY, AS
WELL AS FOR THE PORTION OF STEPHENS PASSAGE ON THE SOUTH SIDE OF
DOUGLAS ISLAND WHERE WINDS HAVE BEEN AROUND 30 KTS OUT OF THE EAST
ALL DAY. ELSEWHERE, CLARENCE STRAIT IS LIKELY STILL BLOWING
SOUTHEAST AT 25 KTS OR SO AND WILL CONTINUE TO DO SO FOR MUCH OF
THE NIGHT TONIGHT BEFORE FINALLY CALMING DOWN TOMORROW. FORECAST
INCLUDES A SHIFT FROM SOUTHEASTERLY TO NORTHWESTERLY WINDS FOR
THE NORTH-SOUTH CHANNELS BY TOMORROW AFTERNOON, BUT SMALL CRAFT
WINDS ARE FORECAST ONLY FOR NORTHERN LYNN CANAL TOMORROW
AFTERNOON. ON THE OUTSIDE, SMALL CRAFT WINDS WILL RELAX BELOW 25
KTS LATE TONIGHT, BUT SEA STATES WILL REMAIN HIGH WITH A WELL
DEVELOPED SOUTHWESTERLY SWELL OF 10 FEET OR HIGH THROUGH TOMORROW
AFTERNOON.

MODELS IN GOOD AGREEMENT FOR THE SHORT TERM FORECAST PERIOD. USED
A BLEND OF GFS, GEM, AND ECMWF FOR UPDATES TO PRESSURE AND WIND
DIRECTION. NAM USED AS A FOUNDATION FOR WIND GRIDS. POP AND QPF
UPDATED USING GEM, ECMWF, AND GFS. VERY LITTLE CHANGE TO EXISTING
TEMPERATURE GRIDS. OVERALL FORECAST CONFIDENCE IS AVERAGE.

.LONG TERM...MODELS REMAIN IN FAIR AGREEMENT THROUGH THE MID WEEK
WITH AN UPPER LEVEL LOW NEAR KODIAK EARLY TUESDAY NIGHT DRIFTS
SOUTHEAST ACROSS THE GULF. THE ASSOCIATED SURFACE LOW WILL
CONTINUE TO PUSH THE RIDGE OF HIGH PRESSURE EAST ACROSS SOUTHEAST
ALASKA...THEN FRONTAL PASSAGE GRADUALLY ENTERS INTO THE EASTERN
GULF EARLY WEDNESDAY AND MOVES ONSHORE OVER THE PANHANDLE.
REFRESHED THE INHERITED FORECAST WITH THE 12Z RUN ECMWF THROUGH
WEDNESDAY NIGHT FOR ITS GOOD CONSISTENCY.

THE WEAKENING FRONTAL BOUNDARY OVER THE PANHANDLE ON MONDAY NIGHT
WILL CONTINUE TO DISSIPATE AS A RIDGE OF HIGH PRESSURE CONTINUES
TO BUILD OVER THE CENTRAL GULF ON TUESDAY. AS THE GENERAL FLOW
PATTERN SWITCHES FROM ONSHORE TO OFFSHORE...CLOUDS WILL BEGIN
THINNING OUT WITH DECREASING POPS LATE MONDAY NIGHT INTO TUESDAY
ACROSS SOUTHEAST ALASKA...YIELDING GENERALLY DRY WEATHER TUESDAY
NIGHT AND WEDNESDAY. THIS WILL ALLOW OVERNIGHT TEMPERATURES COOL
DOWN AROUND FREEZING ACROSS THE NORTHERN AREAS.

AHEAD OF THE NEXT FRONTAL PASSAGE MOVING INTO THE EASTERN GULF
EARLY WEDNESDAY...SOUTHEASTERLY GALE FORCE WINDS WILL BEGIN
AFFECTING THE OUTER WATERS WITH SEAS BUILDING TO 14 TO 16 FEET. AS
THE FRONTAL BOUNDARY MOVES ONSHORE OVER THE PANHANDLE...WINDS WILL
DECREASE TO SMALL CRAFT LEVEL ON THURSDAY WITH SEAS SUBSIDING TO
AROUND 10 FEET BY FRIDAY. EAST-WEST ORIENTED INNER CHANNELS AND
NEAR OCEAN ENTRANCES...EXPECT SMALL CRAFT LEVEL WINDS WEDNESDAY
AND THURSDAY. MODEL DIFFERENCES BECOME LARGER BY LATE THURSDAY AND
USED THE WPC ENSEMBLE SOLUTIONS...UTILIZING HEAVIER WEIGHT OF THE
ECMWF ENSEMBLE MEANS...FOR THE REMAINING LONG TERM PERIODS.

&&

.AVIATION...LOW LEVEL JET ASSOCIATED WITH THE APPROACHING WAVE
HAVE PROMPTED THE INCLUSION OF WIND SHEAR IN THE TAFS FOR THE
SOUTHERN PANHANDLE. CEILINGS GENERALLY MARGINAL VMC TO IMC FOR THE
24 HOUR TAF CYCLE. VISIBILITIES EXPECTED TO DECREASE TO MARGINAL
VMC OR EVEN IMC AT TIMES IN HEAVY RAIN. ICING NOT EXPECTED TO BE
AN ISSUE ON APPROACH OR DEPARTURE BELOW 5000 FEET FOR NORTHERN
PANHANDLE AND 6000 FEET FOR SOUTHERN PANHANDLE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-031-033-035-036-041>043-051-
     052.

&&

$$

FRITSCH/AHN

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