Weather Service Report


496 
FXAK67 PAJK 272316
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
316 PM AKDT WED AUG 27 2014

.SHORT TERM...AN UNSTABLE AIR MASS LIES OVER THE PANHANDLE IN THE
WAKE OF YESTERDAY EVENING'S SYSTEM THAT EXITED INTO NORTHERN BC.
A FEW SHOWERS HAVE PROGRESSED EASTWARD ACROSS THE SOUTHERN
PANHANDLE. TO THE NORTH ONSHORE FLOW COUPLED WITH SOME AFTERNOON
HEATING HAVE HELPED SCATTERED SHOWERS REDEVELOP. HOWEVER, AS THE
NEXT BIG SYSTEM PREPARES TO JUMP ACROSS THE ALASKA PENINSULA FROM
BRISTOL BAY INTO THE GULF OF ALASKA, SOME OF THE SCATTERED SHOWERS
OVER THE NORTH MAY HAVE DEVELOPED FROM A WEAK POORLY DEFINED WAVE
RIDING OVER THE RIDGE AHEAD. THESE SHOWERS WILL PERSIST OVERNIGHT
AND SLOWLY MORPH INTO A STRATIFORM CHARACTER INTO THURSDAY
MORNING AS THE ATMOSPHERE STABILIZES AHEAD OF A WEAK WARM FRONT.

YAKUTAT WILL SEE RAIN DEVELOP OVERNIGHT. CANNOT RULE OUT A
SCATTERED SHOWER EARLY THIS EVENING, BUT DID NOT INCLUDE THIS IN
THE ZONE AS THE MAIN POINT WILL BE THE COVERAGE OF RAIN EXPANDING
THROUGH THE NIGHT. THE RAIN WILL EXTEND SOUTHEASTWARD PARTICULARLY
ALONG THE PANHANDLE COASTLINE. MODELS ARE MAINLY SHOWING SOME
INTERIOR PENETRATION AS WELL INTO THURSDAY AFTERNOON, BUT QPF IS
LESS THAN A TENTH OF AN INCH. A SOUTHEAST COMPONENT TO 700 MB FLOW
WILL KEEP RAINFALL AMOUNTS VERY LIGHT HERE WHICH IS COMMONLY WHAT
OUR MODELS STRUGGLE WITH. THUS ADDED A DESCRIPTOR HERE...LIGHT...
ALL THE WAY SOUTH TO PRINCE OF WALES AND NORTH TO JUNEAU/SKAGWAY.

KEPT PATCHY FOG FOR MUCH OF THE PANHANDLE FOR LATE TONIGHT AS
SATURATED CLOUDY AREAS WILL LIKELY REFORM IN THE SHALLOW SURFACE
LAYER. HOWEVER AS BOUNDARY LAYER WINDS INCREASE IN RESPONSE TO THE
SYSTEM ENTERING THE CENTRAL GULF...LIMITED MORNING FOG TO AREAS
SOUTH AND EAST OF JUNEAU/KAKE. COULD BE SOME BREAKS SOMETIME
TONIGHT TO FAVOR FOG DEVELOPMENT, BUT JUST ENOUGH CLOUDS SHOULD
KEEP AREAL COVERAGE DOWN. 

AS THE CORE OF THE LOW MOVES TO THE CENTRAL GULF...THE INSTABILITY
WILL INCREASE OVER MARINE ZONE 310. THUS WE INTRODUCED A SLIGHT
CHANCE OF THUNDERSTORMS FOR THURSDAY AFTERNOON.

NAM/ECWMF USED TO STRENGTHEN WINDS OVER THE GULF AS SMALL CRAFT
WILL DEVELOP OVER ZONE 52 TONIGHT AND SPREAD ALL THE WAY SOUTHEAST
TO 41 THURSDAY AFTERNOON. THINK CROSS SOUND WILL REMAIN BELOW
SMALL CRAFT AS THE ORIENTATION AND 850 WINDS ARE MAINLY FROM THE
SOUTH/SOUTHEAST SO 20 KT SHOULD SUFFICE HERE THURSDAY. FORECAST
CONFIDENCE GOOD OVERALL...MUCH BETTER THAN YESTERDAY. 

.LONG TERM...A MINOR SHORTWAVE DROPPING INTO THE UPPER LEVEL
TROUGH WILL DEEPEN THE TROUGH AND INCREASE INSTABILITY OVER THE
CENTRAL GULF. FCST SOUNDINGS SHOW FAVORABLE CAPE AND LIMITED CIN
WITH THE COLD POOL ALOFT. GFS AND NAM BOTH PROG LI/S OF -1 TO -2
SO INCLUDED SCHC TSTMS OVER THE GULF AND SOUTHERN PANHANDLE THU
NIGHT INTO FRI AS THE SHORTWAVE MOVES ACROSS THE REGION. THIS
STORM WILL ALSO RESULT IN INCREASING WINDS OVER THE MARINE ZONES.
SMALL CRAFT ADVISORIES WILL LIKELY PERSIST ALONG THE COASTAL ZONES
INTO FRI WITH WINDS INCREASING TO ADVISORY LEVELS OVER MUCH OF THE
INSIDE WATERS THU NIGHT INTO FRI.

SHOWERS WILL SLOWLY DIMINISH FRI INTO SAT AS THE UPPER LOW
WEAKENS AND MOVES INLAND. HIGHLY ZONAL FLOW WILL BEGIN TO RIDGE
SAT AS ANOTHER UPPER LOW MOVES INTO THE WESTERN GULF. THIS WILL
WORK TO RELAX THE PRESSURE GRADIENT ALLOWING WINDS AND SEAS TO
DIMINISH. OVERALL...SAT WILL BE DRIER BUT CANNOT RULE OUT SPOTTY
SHOWERS...SO KEPT A CHANCE OF SHOWERS.

THE PRESSURE GRADIENT WILL TIGHTEN AND PRECIPITATION CHANCES WILL
INCREASE SUN AS A SURFACE LOW MOVES ACROSS THE GULF AND INTO THE
PANHANDLE. MODELS IN GOOD AGREEMENT WITH ANOTHER LOW MOVING
ACROSS THE GULF AND IMPACTING THE PANHANDLE EARLY NEXT WEEK. MODEL
SOLUTIONS DIVERGE IN STRENGTH OF THIS FEATURE AS IT MOVES INLAND
WED AND UPPER RIDGING BEGINS TO EXPAND OVER THE REGION...BUT
TRENDED FORECAST TOWARDS DRIER WEATHER USING A FORECAST BLENDED
TOWARDS WPC/EC.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ041>043-051-052. 
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ053. 

&&

$$

JWA/BC

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