Area Forecast Discussion - Southeastern


FXAK67 PAJK 180132
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
432 PM AKST WED DEC 17 2014
.SHORT TERM...QUIET DAY ACROSS THE PANHANDLE WITH MOSTLY CLOUDY TO
PARTLY CLOUDY SKIES BEING THE RULE OF THE DAY. ONLY MAJOR FEATURE
SHOWING UP RIGHT NOW IS A WEAK LOW AND ASSOCIATED FRONTAL BAND
OVER THE SE GULF. MOST OF THE PRECIP AND WIND IS STILL OFFSHORE
ACCORDING TO RADAR BUT THAT SHOULD MOVE INTO THE SOUTHERN OUTER
COAST LATER THIS AFTERNOON AND EVENING. HIGHEST WINDS WITH IT ARE
AROUND 25 KT AT DIXON ENTRANCE WEST BUOY AT THIS TIME. ELSEWHERE,
RATHER NICE DAY WITH WINDS MOSTLY LESS THAN 20 KT.

INTO TONIGHT AND TOMORROW, THE WEAK FRONT WILL LINGER ALONG THE
SOUTHERN OUTER COAST THROUGH TOMORROW BEFORE IT IS ABSORBED BY THE
STORM FORCE FRONT ADVANCING ACROSS THE GULF. THAT STORM FORCE
FRONT IS THE MAIN FOCUS FOR THE FORECAST MOSTLY FOR THE GULF
TONIGHT AND FOR THE REST OF THE AREA BY TOMORROW. FOR THE GULF,
WINDS TONIGHT WILL BE INCREASING TO MIN GALE BY LATE TONIGHT.
THEY WILL CONTINUE TO INCREASE INTO TOMORROW UP TO STORM FORCE FOR
THE EASTERN GULF AS THE MAIN FRONT APPROACHES THE COAST AND A BIT
OF BARRIER JET INFLUENCES START TO SHOW UP. FOR THE SOUTHERN
PANHANDLE THINGS WILL GET REALLY WINDY ON THU AS 850 MB WINDS RAMP
UP TO 60 TO 65 KT. ZONE 27 LOOKS LIKE IT IS IN LINE FOR ANOTHER
HIGH WIND WARNING (GUSTS TO 60 MPH) FOR THU AS A RESULT WHILE
ZONES 23 AND 28 SHOULD JUST SEE HIGH STRONG WIND CRITERIA (GUSTS
UP TO 50 MPH) AS THE FRONT WEAKENS SLIGHTLY AS IT MOVES EAST.
FARTHER NORTH, NORTHERLY PRESSURE GRADIENT NORTH OF THE FRONT WILL
BE INCREASING RESULTING IN HIGHER NORTHERLY WINDS IN THE NORTHERN
PANHANDLE. LYNN CANAL IN PARTICULAR MAY REACH GALE FORCE THU
AFTERNOON AS JUNEAU TO SKAGWAY GRADIENT REACHES NEARLY 4 MB. THE
OTHER AREA TO WATCH IS DOWNTOWN JUNEAU AND DOUGLAS AS THERE IS 30
TO 40 KT CROSS BARRIER FLOW FORECAST TO START UP ON THU. THE
PROBLEM IS THERE IS A CRITICAL LEVEL AT AROUND 600 MB BUT IT IS
NOT THAT WELL DEFINED BY A WIND SHIFT. THERE IS ALSO LITTLE IF ANY
COLD AIR AROUND TO FORM A SOLID INVERSION ABOVE RIDGE TOP. SO I AM
GOING FOR SOME 15 TO 25 KT WINDS THU IN DOWNTOWN JUNEAU AND
DOUGLAS WITH GUSTS REMAINING BELOW STRONG WIND CRITERIA.

COMPLICATING THINGS IS THE TRIPLE POINT LOW THAT FORMS ALONG THE
FRONT SW OF HAIDA GWAII LATE TONIGHT THAT WILL FOCUS THE WINDS
ALONG THE COAST. SHORT RANGE MODELS ARE GOING BACK AND FORTH ON
THAT FEATURE AS TO WHETHER OR NOT IT WILL BE A CLOSED LOW OR JUST
A OPEN WAVE AND HOW FAR ALONG THE FRONT IT WILL BE SITUATED. NAM
IS JUST A BIT FURTHER EAST THEN THE REST WHILE GFS WAS THE
FARTHEST WEST. ECMWF WAS IN THE MIDDLE ON ITS 0Z RUN BUT THE NEW
12Z RUN HAS ALMOST GOTTEN RID OF THE FEATURE COMPLETELY. IN THE
END LEANED TOWARD THE 0Z EC FOR PRESSURE AND GFS FOR WIND SPEED
GUIDANCE. THIS KEPT A SLIGHTLY WEAKER VERSION OF THE LOW IN PLACE
THAT EVENTUALLY WEAKENS TO AN OPEN WAVE IN THE CENTRAL GULF BY THU
AFTERNOON.

AS FOR PRECIP, NORTHERLY WINDS AHEAD OF THE FRONT AND SOME BREAKS
IN THE CLOUD COVER WILL CAUSE TEMPERATURES TO DIP BELOW FREEZING
TONIGHT IN THE NORTHERN PANHANDLE. AS A RESULT, THERE IS A HIGHER
POSSIBILITY OF SNOW FOR THE NORTHERN PANHANDLE TONIGHT AND
TOMORROW. HOWEVER, DURING THE LOWEST TEMPS, THE POPS AND QPF WILL
BE AT THEIR LOWEST AS WELL. WHEN THE HEAVIER PRECIP STARTS UP THU
AFTERNOON THE PRECIP MAY START OUT AS SNOW BUT WARM AIR ADVECTION
ASSOCIATED WITH THE FRONT AS WELL AS A LITTLE AFTERNOON WARMING
WILL CAUSE THINGS TO QUICKLY CHANGE OVER TO RAIN SO LITTLE SNOW
ACCUMULATION IS EXPECTED. HAINES, SKAGWAY, AND HYDER HAVE THE BEST
CONDITIONS FOR SNOW BUT THE PRECIP DOES NOT QUITE REACH THEM BY
THU EVENING FOR THERE TO BE ANY LARGE ACCUMULATIONS AT THOSE
LOCATIONS. REST OF THE PANHANDLE HAS WARM ENOUGH TEMPS FOR RAIN
AND THE WARM AIR ADVECTION WITH THE FRONT WILL ENSURE THAT IT
STAYS RAIN. THE SOUTHERN PANHANDLE WILL SEE THE HIGHEST RAINFALL
AMOUNTS THROUGH THU AFTERNOON WITH AROUND A HALF AN INCH.
.LONG TERM...ACTIVE WEATHER PATTERN CONTINUES THROUGH THE
WEEKEND. REMAINING MILD AND WET, THEN POTENTIALLY A WEATHER
PATTERN CHANGE FOR NEXT WEEK.

 WINDY CONDITIONS WILL PERSIST FOR THE OUTER COAST AND THE
COASTAL AREAS OF SOUTHERN PANHANDLE. FOR FIRST PART OF THURSDAY
NIGHT, THERE WILL BE A BREAK IN THE WIND AFTER THE WIND EVENT ON
THURSDAY DAYTIME. THE BREAK, HOWEVER WILL BE BRIEF. ANOTHER
WEATHER FRONT WILL MOVE THROUGH THE AREA EARLY FRIDAY MORNING, AND
WINDS ON THE OUTSIDE WATERS WILL INCREASE TO GALE FORCE LEVEL
EARLY FRIDAY. THE GALE FORCE WINDS WILL CONTINUE THROUGH FRIDAY.
THERE WILL BE ANOTHER BRIEF BREAK LATER FRIDAY, BEFORE WINDS
INCREASE FURTHER ON FRIDAY NIGHT.

ON FRIDAY NIGHT, A STRONG WEATHER FRONT WILL MOVE THROUGH THE
AREA, DO EXPECT WINDS ON THE OUTSIDE TO PICK UP TO AT LEAST 45 KT.
THERE ARE STILL UNCERTAINTIES IN THE PATH AND INTENSITY OF THIS
STRONG WEATHER SYSTEM. HOWEVER, THIS WEATHER SYSTEM IS FAIRLY
POWERFUL. WITH A JET STREAK OF UP TO 200 KT, THERE ARE A LOT OF
UPPER LEVEL ENERGIES ASSOCIATED WITH THIS WEATHER SYSTEM. WITH THE
ORIENTATION OF THE JET STREAK FROM SOUTHWEST TO NORTHEAST AIMING
TOWARDS COAST OF BC, DO EXPECT AREAS OF FAVORED CYCLOGENESIS TO BE
OFF THE COAST OF HAIDA GWAII. THE MAIN UPPER LOW WILL BE LOCATED
IN THE WESTERN GULF, WITH IMPULSES OF DISTURBANCES SPINNING UP IN
THE NORTHEAST PACIFIC OCEAN THEN HEADING NORTH TOWARDS THE
PANHANDLE. MAIN THEME OF THIS PATTERN WILL BE EPISODES OF STRONG
WINDS, ABOVE NORMAL TEMPERATURES, AND CONTINUED ONSHORE FLOW
PROVIDING AMPLE MOISTURE TO THE REGION.

 PRECIPITATION WILL BE MOSTLY RAIN FOR THE SOUTHERN AND CENTRAL
PANHANDLE. FOR THE NORTHERN PANHANDLE, INCLUDING SKAGWAY, HAINES,
AND LYNN CANAL, DO EXPECT SNOW POTENTIAL FOR THESE LOCATIONS. FOR
JUNEAU AREA, THERE WILL BE POTENTIAL FOR WET SNOW MIXING IN WITH
RAIN ON THURSDAY NIGHT. HOWEVER, SNOW ACCUMULATION SHOULD BE LESS
THAN 1 INCH. PRECIPITATION TYPE WILL BE VERY TRICKY TO FORECAST,
AS TEMPERATURES WILL HOVER AROUND THE FREEZING MARK FOR THE
CENTRAL PANHANDLE THURSDAY NIGHT.

FORECAST CONFIDENCE REMAINS BELOW AVERAGE. NUMERICAL MODELS ARE
STILL TRYING TO RESOLVE THE PATH OF INDIVIDUAL DISTURBANCES
SPINNING AROUND THE MAIN LOW OVER THE WESTERN GULF OF ALASKA.
MODELS ARE ALSO STRUGGLING WITH RUN-TO-RUN INCONSISTENCIES.
PRECIPITATION TYPE IS ALSO A VERY TRICKY FORECAST ISSUE. USES AN
ENSEMBLE OF ECMWF/GEM/GFS/NAM TO UPDATE THE FORECAST PACKAGE
THROUGH SATURDAY, THEN TRANSITION INTO WPC GUIDANCE THROUGH NEXT
WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 6 AM TO 6 PM AKST THURSDAY FOR AKZ027.
         STRONG WIND FROM 3 AM AKST THURSDAY THROUGH LATE TONIGHT FOR 
     AKZ027.
         STRONG WIND FROM THURSDAY MORNING THROUGH THURSDAY AFTERNOON FOR 
     AKZ023-028.
MARINE...STORM WARNING FOR PKZ041-042. 
         GALE WARNING FOR PKZ012-022-033-036-043-051-052. 
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-031-032-034-035. 

&&

$$

EAL/RCL

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