106 FXAK67 PAJK 301435 AFDAJK SOUTHEAST ALASKA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JUNEAU AK 535 AM AKST FRI JAN 30 2015 .SHORT TERM...LOW AMPLITUDE UPPER IMPULSE IS APPROACHING HAIDA GWAII EARLY THIS MORNING. THIS FEATURE AND ASSOCIATED AREA OF SURFACE LOW PRESSURE WILL EXIT E INTO BC DURING THE AFTERNOON...WITH UPPER RIDGING OCCURRING IN ITS WAKE OVER THE GULF. SHEARED OUT NRN STREAM TROUGH WILL THEN SLIDE SE ACROSS NWRN CANADA AND THE NRN PANHANDLE TONIGHT. MEANWHILE...UPPER-LEVEL SUBSIDENCE IS OCCURRING OVER THE SRN/CNTRL PANHANDLE THIS MORNING...AND WHEN COMBINED WITH A MOIST BOUNDARY LAYER /DUE TO RECENT RAIN AND MELTING SNOW/...IS AIDING IN FOG DEVELOPMENT...WHICH HAS BEEN LOCALLY DENSE OVER JUNEAU AS WELL AS PETERSBURG AND WRANGELL. FOG IS EXPECTED TO DISSIPATE BY MID TO LATE MORNING...WITH BREAKS IN LOW CLOUDS POSSIBLY YIELDING SUNSHINE FOR CNTRL/SRN AREAS THIS AFTERNOON. OVER THE NRN PANHANDLE...DEEPER MOISTURE WILL FAVOR GREATER CLOUD COVER DURING THE DAY...PARTICULARLY OVER YAKUTAT WHERE PERIODS OF LIGHT SNOW AND RAIN ARE EXPECTED THIS MORNING. ASCENT WILL DECREASE OVER THIS AREA GOING INTO TONIGHT...AND CLOUDS WILL EVENTUALLY DISSIPATE TOWARD THE END OF THE SHORT TERM PERIOD. THE END RESULT WILL BE A PRECIPITATION FREE CWA TOWARD 12-15Z SAT...AS WELL AS COLDER LOW TEMPERATURES. STRONG OFFSHORE ORIENTED SURFACE PRESSURE GRADIENT IS FORECAST TO DEVELOP TONIGHT...WHICH WILL FURTHER AID IN DRYING THE AIRMASS ACROSS THE PANHANDLE. OF GREATER CONCERN WILL BE STRENGTHENING NLY WINDS OVER THE NRN/CNTRL INSIDE WATERS...AND E-NELYS OVER CROSS SOUND AND ICY STRAIT. STORM FORCE WINDS ARE PROBABLE FOR NRN LYNN CANAL LATE TONIGHT...AND GALES ARE EXPECTED FOR SRN LYNN AND STEPHENS PASSAGE. A STRONG WIND HEADLINE HAS ALSO BEEN POSTED FOR SKAGWAY. FARTHER S OVER DOWNTOWN JUNEAU AND S DOUGLAS...MOUNTAIN WAVE DEVELOPMENT WILL BE IN IT/S INCIPIENT STAGE LATE TONIGHT...AND THUS...HAVE HELD OFF ON ISSUANCE OF STRONG WIND HEADLINE ATTM. HOWEVER...DAY SHIFT WILL NEED TO RE-EVALUATE THE START TIME FOR STRONG WINDS. NUDGED PRESSURE GRIDS TOWARD THE NAM AND ECMWF THIS AFTERNOON/EVENING...THEN CONTINUED WITH INHERITED FOR THE REMAINDER OF THE SHORT TERM. MODEL GUIDANCE CONTINUES TO SHOW POP/QPF DECREASING GOING INTO TONIGHT...WHICH SUPPORTS PREVIOUS FORECAST THINKING. .LONG TERM...BEGINNING OF THE LONG RANGE PERIOD SEES THE OUTFLOW WINDS STARTING TO GET INTO GEAR ON SAT. SURFACE PRESSURES ACROSS THE SOUTHERN YUKON WILL HAVE BALLOONED TO 1045 MB BY THIS POINT WITH CROSS COAST MOUNTAIN PRESSURE GRADIENTS REACHING 10 TO 15 MB. THE COLD ARCTIC AIR THAT WILL BE SPILLING OVER THE MOUNTAIN PASSES WILL ONLY ADD TO THE WINDS. AS USUAL, LYNN CANAL WILL LIKELY BE THE WINDIEST SPOT WITH STORM FORCE WINDS EXPECTED FOR MUCH OF THE WEEKEND. NOT TO BE OUTDONE, SKAGWAY, DISENCHANTMENT BAY, TAKU INLET, AND THE PASSES EAST OF YAKUTAT WILL ALSO BE GUSTING THROUGH OUT THE WEEKEND WITH GUSTS IN THE 40 TO 50 MPH RANGE. THE COLD OUTFLOW WILL ALSO PROMOTE THE POSSIBILITY OF A STRONG MOUNTAIN WAVE WIND EVENT FOR DOWNTOWN JUNEAU AND DOUGLAS THIS WEEKEND. CROSS BARRIER FLOW IS EXPECTED TO BE AROUND 35 TO 45 KT WITH THE HIGHEST FLOW EXPECTED SAT NIGHT. AN INVERSION ABOVE RIDGE TOP WILL ALSO BE IN PLACE WITH THE COLD OUTFLOW. THE LIMITING FACTOR MAY BE THE CRITICAL LEVEL. THE CRITICAL LEVEL ON MODEL SOUNDINGS IS RATHER WELL DEFINED WITH A CLEAR DIRECTION SHIFT. HOWEVER, IT IS RATHER LOW AT 700 MB TO START. THIS BECOMES MORE FAVORABLE BY SAT NIGHT AS IT RISES TO AROUND 400 TO 500 MB. CURRENTLY EXPECTING GUSTS IN EXCESS OF 55 MPH AT MOST SAT NIGHT. THE WINDS FALL APART AFTER THAT AS THE CRITICAL LEVEL GETS OBLITERATED BY GENERAL NE FLOW IN ALL LEVELS. MEANWHILE THE SOUTHERN THIRD OF THE PANHANDLE WILL BE DEALING WITH THE REASON THAT THE NORTHERLY PRESSURE GRADIENT WILL BE SO HIGH. A WEAKENING FRONT WILL BE TRYING TO PUSH NORTH SAT INTO SUN BUT WILL NOT MAKE MUCH PROGRESS DUE TO THE BLOCKING HIGH TO THE NORTH. WHAT IT WILL DO IS BRING SOME GALE FORCE WINDS TO THE GULF OVER THE WEEKEND AS WELL AS SOME PRECIP FOR THE SOUTHERN PANHANDLE. THE GALE FORCE WINDS WILL MAINLY BE RELEGATED TO THE OFFSHORE ZONE ON SAT AND WILL GRADUALLY DIMINISH TO SMALL CRAFT CRITERIA BY SUN AS THE FRONT FALLS APART UNDER THE DIFLUENT FLOW ALOFT AND THE DRY OUTFLOW WINDS AT THE SURFACE. ANY PRECIP WILL NOT GET THAT FAR NORTH FOR THE SAME REASON. SO ONLY HAVE LIKELY POPS AS FAR NORTH AS SUNMER STRAIT BY SUN. PRECIP AMOUNTS WILL BE LIGHT WITH THE FRONT FALLING APART. FARTHER OUT DRY WEATHER CONTINUES INTO AT LEAST MID WEEK BUT OUTFLOW WINDS DIMINISH AS THE YUKON HIGH SLIDES SOUTHEAST INTO CENTRAL BC TAKING MOST OF ITS COLD AIR WITH IT. THINGS START TO GET A BIT MURKY HERE AS SOME MODELS START TO BRING ANOTHER NORTHERN STREAM TROUGH OUT OF SIBERIA. HOW FAR EAST IT GETS IS UP FOR DEBATE ESPECIALLY AS IT STARTS TO INTERACT WITH THE SOUTHERN STREAM JET LATE WEEK WHICH SPINS UP A MORE SUBSTANTIAL STORM INTO THE EASTERN GULF FOR FRI. TIMING, STRENGTH AND STRUCTURE ARE ALL UP FOR DEBATE HERE SO FORECAST CONFIDENCE FALTERS PAST MID WEEK. LONG RANGE MODELS WERE IN DECENT AGREEMENT UP UNTIL EARLY TO MID NEXT WEEK. GENERALLY FAVORED THE NAM/ECMWF/GEM FOR UPDATES. MOST OF THE CHANGES WERE FOR SUN NIGHT INTO MON TO STRETCH OUT THE OUTFLOW WINDS A BIT LONGER AS SUGGESTED BY THE GUIDANCE. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...DENSE FOG ADVISORY UNTIL 10 AM AKST THIS MORNING FOR AKZ026. DENSE FOG ADVISORY UNTIL 6 AM AKST EARLY THIS MORNING FOR AKZ025. STRONG WIND FROM NOON AKST TODAY THROUGH LATE TONIGHT FOR AKZ018. MARINE...STORM WARNING FOR PKZ012. GALE WARNING FOR PKZ013-031. SMALL CRAFT ADVISORY FOR PKZ011-021-022-032-034-035-043-053. && $$ GARNER/EAL VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU