Area Forecast Discussion
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FXAK67 PAJK 301354
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
554 AM AKDT MON MAR 30 2015

.SHORT TERM...BROAD UPPER TROUGH EXTENDED SSE FROM NEAR KODIAK
ISLAND ACROSS THE NRN PAC DURING THE EARLY MORNING...WHILE
DOWNSTREAM RIDGE WAS AMPLIFYING OVER WRN CANADA. IN BETWEEN THESE
TWO FEATURES...A SHORTWAVE TROUGH WAS QUICKLY APPROACHING HAIDA
GWAII...WITH BAROCLINIC LEAF CLOUD STRUCTURE BLOSSOMING ALONG
ITS NRN PERIPHERY. SURFACE LOW PRESSURE HAS SUBSEQUENTLY DEEPENED
IN RESPONSE TO THE INCREASING ZONE OF ASCENT. MODEL GUIDANCE IS
COMING INTO BETTER CONSENSUS TRACKING THE LOW NWD FROM HAIDA GWAII
AT 18Z MON INTO THE SRN PANHANDLE BY 00Z TUE...AND THEN GRADUALLY
DISSIPATING IT THEREAFTER AS IT LIFTS INTO THE CNTRL PANHANDLE.
UPDATED PRESSURE GRIDS WITH A BLEND OF THE 00Z NAM/GEM/GFS.

PRESSURE GRADIENT WILL BECOME LOCALLY INTENSE OVER CLARENCE STRAIT
AND AKZ028 /KETCHIKAN/...AND WILL SUPPORT SLY GALE FORCE WINDS FOR
CLARENCE...AND STRONG WIND GUSTS TO 40 MPH OVER THE KETCHIKAN
VICINITY. GUSTS TO 35 MPH WILL ALSO BE POSSIBLE OVER AKZ027...AND
WLY SMALL CRAFT WINDS COULD OCCUR ALONG THE BACKSIDE OF THE LOW
OVER MARINE ZONES 41 AND 42. AS THE LOW TRACKS N...WINDS WILL
SLACKEN OVER THE S...BUT MAY BRIEFLY STRENGTHEN TO SMALL CRAFT
OVER FREDRICK SOUND AND STEPHENS PASSAGE. OVER DOWNTOWN JUNEAU AND
DOUGLAS...NE WINDS COULD GUST UP TO 35 MPH FOR A FEW HOURS DURING
THE AFTERNOON/EARLY EVENING AS 30-40 KT CROSS BARRIER FLOW PEAKS
IN ADVANCE OF THE SRN PANHANDLE LOW. ELSEWHERE WINDS ARE CURRENTLY
EXPECTED TO BE RELATIVELY WEAK...WITH THE EXCEPTION OF LYNN
CANAL...WHERE WINDS WILL FLIP TO N BY AFTERNOON...AND POSSIBLY
STRENGTHEN TO 25 KT BRIEFLY DURING THE EARLY TO MIDDLE NIGHT.

SUBTROPICAL MOISTURE PLUME WAS POINTED TOWARD VANCOUVER ISLAND BC
AT 09Z. PART OF THIS MOISTURE...CHARACTERIZED BY PW VALUES NEAR
0.6 INCH...IS FORECAST TO BECOME ENTRAINED INTO THE CYCLONE
MOVING N FROM HAIDA GWAII. AS THE LOW MOVES INTO THE SRN PANHANDLE
DURING THE AFTERNOON...RAIN CHANCES WILL BECOME MAXIMIZED FROM
KLAWOCK/HYDABURG E TO KETCHIKAN AS FOCUSED ZONE OF ENHANCED
ASCENT AND MOISTURE SPREADS INTO THE REGION. A PERIOD OF HEAVY
RAIN APPEARS PROBABLE FOR THESE AREAS AS A RESULT. HIGHEST POP
VALUES THEN SHIFT TOWARD PETERSBURG/WRANGELL DURING THE NIGHT.
MEANWHILE...LOW-LEVEL WINDS ARE FORECAST TO TAKE ON AN OFFSHORE
COMPONENT OVER THE CNTRL AND NRN PANHANDLE DURING THE AFTERNOON.
THIS WILL FAVOR CLEARING SKIES AND MILD HIGH TEMPERATURES /MID TO
UPPER 40S/. CLOUDS AND RAIN WILL THEN BECOME INCREASINGLY PROBABLE
DURING THE NIGHT AS THE WEAKENING LOW APPROACHES FROM THE S.

.LONG TERM...WHILE THE MOST EXCITING DYNAMICS SURROUND THE SYSTEM
PUSHING INTO THE PANHANDLE TODAY, THE PARENT UPPER LOW OVER THE
WESTERN GULF WILL SLOWLY CRAWL INTO OUR SIDE OF THE GULF TUESDAY
AND AFFECT SOUTHEAST`S WEATHER IN LESS IMPACTFUL WAYS.

AS THE JET HAS SLID WELL TO THE SOUTHEAST, LIGHT FLOW ALOFT WILL
HELP KEEP RESIDUAL MOISTURE IN PLACE FROM THE PREVIOUS SYSTEM
ACROSS THE PANHANDLE. THERMODYNAMIC PROFILES ARE COMPLEX ACROSS THE
PANHANDLE, BUT WE THINK THERE WILL BE A ZONE OF STABILITY IN THE
LOWER LEVELS ACROSS THE NORTHERN INTERIOR PANHANDLE INTO THE
NORTHEAST GULF, WITH GREATER CONVECTIVE POTENTIAL ELSEWHERE. AS
THE COLDER UPPER LOW ADVANCES EASTWARD, COLDER AIR SHOULD
DESTABILIZE THE ATMOSPHERE EVEN ACROSS YAKUTAT AND JUNEAU AND
SHOWERS WILL ENCOMPASS THE ENTIRE FORECAST AREA. AS THE UPPER
LOW, NOW AN OPEN TROUGH, MAKES IT JUST OFFSHORE OF CAPE DECISION
THOUGH, THE SOUTHERN ZONES WILL EXPERIENCE A PEAK IN SHOWER
ACTIVITY TUESDAY AFTERNOON/NIGHT JUST AS THE NORTHERN PANHANDLE
MAY SEE MORE QPF TUESDAY MORNING WITH MORE ONSHORE FLOW COMPONENT.
CAPE VALUES WILL BE GREAT OVER THE SOUTHERN PANHANDLE DURING THIS
TIME, AND THE POSSIBILITY OF THUNDERSTORM ACTIVITY WILL BE
EVALUATED CLOSER INTO THE PERIOD.

AS THE TROUGH AXIS SLIDES INTO CANADA BY WEDNESDAY AFTERNOON,
SHOWER ACTIVITY WILL DIMINISH AS AN UPPER LEVEL RIDGE HINDERS
CONVECTIVE ASCENT. THIS TRANSIENT RIDGE IS A DIRECT RESPONSE TO
THE NEXT SIGNIFICANT WEATHER MAKER ENTERING THE WESTERN GULF ON
WEDNESDAY. THIS SYSTEM`S ASSOCIATED FRONT WILL CAUSE WINDS TO
ACCELERATE TO SOLID SMALL CRAFT FOR MARINE ZONE 310 AS WELL AS THE
OUTSIDE WATER ZONES. WE ALSO RAISED WIND SPEEDS TO GALE FOR LATE
WEDNESDAY NIGHT IN ZONE 52. THIS REPRESENTS A DEFINITE CHANGE IN
THE FORECAST, AS ALL MODELS ARE BRINGING THE FRONT INTO BETTER
RESOLUTION. LIKEWISE THE INSIDE CHANNELS MAY SEE SOME BRIEF
ACCELERATIONS FROM THE SOUTH. RIGHT NOW, HAVE LIMITED THE RISE IN
SOME AREAS, ESPECIALLY OVER THE CENTRAL PANHANDLE. CONFIDENCE
GREATER TO THE SOUTH WHERE CLARENCE WILL ONCE AGAIN RISE TO 30 KT
LATE WEDNESDAY NIGHT. LOOK FOR THESE WINDSPEEDS TO RISE AS
CONFIDENCE GROWS, ESPECIALLY ACROSS THE CENTRAL PANHANDLE.

THIS SYSTEM WILL SPREAD RAIN ACROSS THE EASTERN GULF
AND LIKELY THE COASTAL ZONES LATE WEDNESDAY NIGHT, PUSHING INTO
THE GREATER PANHANDLE BY THURSDAY. A CHANCE OF A LITTLE SNOW IS
POSSIBLE WITH SOME COOLER AIR BEING PULLED ACROSS THE MOUNTAINS IN
RESPONSE TO THE LOW OVER THE NORTHERN PANHANDLE WEDNESDAY NIGHT
AND THURSDAY NIGHT, BUT DOUBTFUL THIS WILL BE VERY IMPACTFUL AS
POTENTIAL AMOUNTS AND LIKELIHOOD BARELY DESERVES MENTIONING.
PRECIPITATION WILL QUICKLY DIMINISH AS THE LOW SLIDES SOUTHEAST,
BUT WILL TAKE MORE TIME DISSIPATING FROM THE SOUTH DUE TO ITS
TRACK.

THE WEEKEND CONTINUES TO LOOK MAINLY DRY AND PERHAPS SLIGHTLY
COOLER THAN NORMAL AS A COOLER AND DRYER ZONAL FLOW DEVELOPS AND
DIRECTS SOME BERING SEA AIR INTO SOUTHEAST ALASKA.

GOOD MODEL AGREEMENT WITH FEATURES, THUS A BLEND OF GEM, GFS, AND
NAM WAS USED TO BROAD-BRUSH SUBTLE TIMING/INTENSITY DIFFERENCES.
CONFIDENCE AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH THIS EVENING
     FOR AKZ028.
MARINE...GALE WARNING FOR PKZ036.
         SMALL CRAFT ADVISORY FOR PKZ012-022-043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042-052.

&&

$$

GARNER/ADKINS

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