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FXAK67 PAJK 311506
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
606 AM AKST SAT JAN 31 2015

.SHORT TERM...WINDY CONDITIONS HAVE ALREADY STARTED UP ACROSS THE
NORTHERN PANHANDLE THIS MORNING IN RESPONSE TO THE COLD AIR MASS
THAT HAS SETTLED IN THE SOUTHERN YUKON. LYNN CANAL HAS BEEN SOLID
GALE MOST OF THE NIGHT WITH ELDRED ROCK AND LITTLE ISLAND
REPORTING SUSTAINED 40 TO 45 KT WINDS WITH GUSTS EASILY UP TO 60
KT. STEPHENS PASSAGE IS EVEN GETTING IN ON THE ACT WITH 25 KT WINDS
RECORDED AT FIVE FINGERS LIGHTHOUSE. SAR WIND RETRIEVALS FROM LAST
EVENING CONFIRM THE HIGHER WINDS IN THESE AREAS WITH SOME HIGHER
WINDS JUST STARTING TO SHOW UP IN CROSS SOUND AND CHATHAM STRAIT
AT THAT TIME. DESPITE ALL THIS WIND THERE STILL MANAGED TO BE
SOME LOW CLOUDS AND FOG AROUND THE PANHANDLE OVERNIGHT. WRANGELL
AND GUSTAVUS BOTH HAVE REPORTED LOWER VISIBILITIES DUE TO FOG
OVERNIGHT AND JUNEAU AND PETERSBURG REPORTED LOW CEILINGS.
SPORT NIGHTTIME MICROPHYSICS IMAGES OVERNIGHT REVEALED A RATHER
DECENT AREA OF KUPREANOF AND KUIU ISLANDS COVERED IN LOW CLOUDS
WITH SOME SCATTERED AREAS OF LOW CLOUDS AND FOG IN VARIOUS OTHER
PLACES (MOSTLY VALLEYS). THESE IMAGES REVEAL THAT THE AREA OF
COVERAGE HAS STEADILY BEEN DECREASING THROUGH THE NIGHT ESPECIALLY
IN THE NORTHERN PANHANDLE. THE REMAINING LOW CLOUDS AND FOG SHOULD
CONTINUE TO RAPIDLY DIMINISH THROUGH THE MORNING AS THE COLD DRY
OUTFLOW STRENGTHENS.

MAIN CONCERN THROUGH THE NEXT 24 HOURS IS THE STRONG OUTFLOW WINDS
ACROSS THE NORTHERN PANHANDLE. CROSS COAST MOUNTAIN PRESSURE
GRADIENTS ARE ALREADY REACHING 15 MB WITH THE SKAGWAY TO JUNEAU
GRADIENT CURRENTLY AT AROUND 7 MB. THESE GRADIENTS ARE EXPECTED TO
CONTINUE TO STRENGTHEN THROUGH TONIGHT. AS A RESULT GUSTY WINDS
ARE EXPECTED OUT OF THE USUAL OUTFLOW AREA. STRONG WIND HEADLINES
ARE UP FOR SKAGWAY AND HAINES (NEAR LYNN CANAL) ALONG WITH THE
HYDER ZONE FOR LATER TONIGHT NEAR CHANNELED TERRAIN. GALE WARNINGS
ARE ALSO UP FOR MOST OF THE NORTHERN INNER CHANNELS WITH A STORM
WARNING FOR NORTHERN LYNN CANAL. THE SKAGWAY WINDS ALSO INCLUDE A
WIND CHILL ADVISORY FOR WHITE PASS FOR TONIGHT AND EARLY SUNDAY AS
THE COLD TEMPERATURES AND HIGH WINDS PRODUCE WIND CHILLS OF 30
BELOW ZERO TONIGHT.

OF PARTICULAR CONCERN IS DOWNTOWN JUNEAU AND DOUGLAS WHERE
ANOTHER MOUNTAIN WAVE EVENT IS EXPECTED TO START SATURDAY. CROSS
BARRIER FLOW IS EXPECTED TO REACH 45 TO 55 MPH BY LATE TONIGHT.
THAT COMBINED WITH AN INVERSION ABOVE RIDGE TOP AND A DECENTLY
DEFINED CRITICAL LEVEL DEVELOPING AROUND 500 MB THIS AFTERNOON AND
EVENING ARE EXPECTED TO THROW WIND GUSTS TO 60 MPH AT DOWNTOWN
JUNEAU AND DOUGLAS STARTING THIS EVENING. AS SUCH A HIGH WIND
WARNING HAS REPLACED THE HIGH WIND WATCH THAT WAS IN EFFECT.

MEANWHILE THE SOUTHERN PANHANDLE AND SOUTHERN GULF WILL BE DEALING
WITH A WEAKENING FRONT AS IT SLOWLY PUSHES NORTHWARD. THIS FRONT
WILL HAVE AN EXTREMELY HARD TIME TRYING TO MAKE ANY PROGRESS
NORTHWARD DUE TO THE STRONG RIDGE OVER THE NORTHERN PANHANDLE AND
YUKON. IT DOES NOT HELP THAT IT IS MOVING INTO AN AREA OF DIFLUENT
FLOW ALOFT EITHER. AS SUCH THIS FRONT WILL NOT GET ANY FARTHER
NORTH THEN THE EXTREME SOUTHERN PANHANDLE AND GULF. CLOUDS FROM
THIS FRONT WILL LIKELY REACH THE CENTRAL PANHANDLE BY TONIGHT BUT
THE ASSOCIATED RAIN BANDS WILL ONLY REACH INTO ZONES 27, 28, AND MAYBE
29 BY LATE TONIGHT. OTHERWISE THE ONLY EFFECTS WILL BE SMALL CRAFT
EASTERLY WINDS ACROSS THE SOUTHERN HALF OF THE GULF.

SHORT RANGE MODELS WERE IN GOOD AGREEMENT. BUT DID DISPLAY SOME
DETAIL ISSUES. THE GEM GLOBAL MODELS WAS THE MODEL OF CHOICE FOR
THE PRESSURE GRADIENTS ALONG THE COAST MOUNTAINS AS ALL THE REST
WERE NOT STRONG ENOUGH COMPARED TO CURRENT OBSERVATIONS. FOR
WINDS PREFERRED THE NAM AND VARIOUS HI-RES MODELS PARTICULARLY FOR
THE JETS OF OUTFLOW COMING OUT OF SOUTHERN CHATHAM, CROSS SOUND,
AND THE PASSES EAST OF YAKUTAT.

.LONG TERM...STRONG NORTHERLY OUTFLOW WILL BE THE PREDOMINANT
FEATURE THROUGH THE EXTENDED PERIOD. CONDITIONS STATED ABOVE WILL
CONTINUE INTO MONDAY MORNING...WITH POTENTIALLY SLIGHTLY STRONGER
GUSTS ON SUNDAY. A COL IN THE PRESSURE FIELD AT 500MB WILL KEEP
THE CRITICAL LEVEL IN PLACE FOR THE MOUNTAIN WAVE EVENT (TAKU
WINDS). SURFACE HIGH PRESSURE WILL HOLD IN THE YUKON THROUGH
SUNDAY THEN WEAKEN SLIGHTLY ON MONDAY AND START TO SHIFT SOUTH
INTO B.C. MONDAY NIGHT. AS THIS HAPPENS WINDS WILL START TO
EASE...BUT NOT FOR LONG.

THE OCCLUDED FRONT WILL STILL BE OVER THE SOUTHERN PANHANDLE ON
SUNDAY MORNING AND REMAIN THERE THROUGH THE DAY...BUT PRECIP
SHOULD STAY SOUTH OF FREDERICK SOUND ACCORDING TO ALL MODELS. THIS
SHOULD BE MAINLY RAIN...BUT SOME SNOW IS POSSIBLE. SIGNIFICANT
ACCUMULATIONS ARE NOT EXPECTED SINCE THE AREA WILL BE UNDER
OFFSHORE FLOW AND MOST OF THE ENERGY WITH THE FRONT WILL BE TO THE
SOUTH. PRECIP WILL DISSIPATE DURING THE DAY MONDAY.

BOTH THE GFS AND ECMWF HAVE PRECIP DEVELOPING OVER THE PANHANDLE
ON WEDNESDAY...ALTHOUGH THE 06Z GFS HAD LESS. COULD BE DUE TO A SHORT
WAVE PASSING OVER...BUT MODELS LOOK WEAK WITH THAT FEATURE...SO
HARD TO TELL WHAT WOULD BE CAUSING IT. HAVE LIMITED POPS TO CHANCE
BECAUSE OF THIS UNCERTAINTY.

WEAK UPPER LEVEL FLOW CONTINUES THROUGH MID WEEK THEN AN UPPER LEVEL
TROUGH PASSES OVER THE NORTHERN PANHANDLE THURSDAY. MORE UPPER
LEVEL TROUGHS DIG INTO THE GULF RESULTING IN A RETURN TO ONSHORE
FLOW FOR THE END OF NEXT WEEK. AT THE SURFACE A BIG TROUGH/FRONT
REACHES THE SOUTHERN PANHANDLE ON THURSDAY AND SPREADS NORTH
THROUGH FRIDAY. MEANWHILE HIGH PRESSURE REBUILDS OVER THE YUKON
RESULTING IN STRONG NORTH OUTFLOW WINDS AGAIN. THE OVERRUNNING OF
THE FRONTAL PRECIP FROM THE SOUTH AND THE COLDER NORTH WIND COULD
CAUSE SOME SNOW. WILL NEED TO KEEP AN EYE ON THIS POTENTIAL FOR
LATE NEXT WEEK.

THE ECMWF AND NAM WERE PREFERRED IN THE MID RANGE DUE TO THEIR
GOOD HANDLING FOR OUTFLOW PRESSURE/WINDS. THE ECMWF AND GFS HAD A
SIMILAR IDEA FOR DECREASING TEMPERATURES FOR THE END OF NEXT WEEK
WITH ANOTHER NORTHERLY OUTFLOW EVENT. THIS WAS A BIG CHANGE AND IF
THE PATTERN HOLDS TEMPS MAY NEED TO BE LOWERED EVEN MORE. FORECAST
CONFIDENCE IS AVERAGE.


&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO 6 AM AKST MONDAY
     FOR AKZ025.
         STRONG WIND THROUGH LATE SUNDAY NIGHT FOR AKZ018-019.
         WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO NOON AKST SUNDAY
     FOR AKZ018.
         STRONG WIND FROM THIS EVENING THROUGH LATE TONIGHT FOR AKZ029.
MARINE...STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031-032-034-035-041-043.
         SMALL CRAFT ADVISORY FOR PKZ033-042-051-053.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

&&

$$

EAL/FERRIN

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