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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








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