Gale Warning 268, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
325 PM AKDT THU OCT 2 2014

.SHORT TERM...SURFACE LOW PRESSURE LOCATED OVER THE SWRN GULF THIS
AFTERNOON IS DEEPENING/OCCLUDING AS A LOBE OF VORTICITY IN THE
MIDLEVELS ADVANCES NWD ACROSS THE CNTRL GULF. FRONTAL BOUNDARY
EXTENDS ESEWD FROM THE LOW...AND WILL ENTER THE SERN GULF AND SRN
PANHANDLE THIS EVENING...AND THEN MOVE N ACROSS THE ERN GULF AND
CNTRL COASTAL AREAS BY LATE TONIGHT. A 50-70 KT ESELY LOW-LEVEL
JET WILL SPREAD NWD WITH THE FRONT AND AID IN GENERATING GALE TO
LOCAL STORM FORCE WINDS OVER THE OUTSIDE WATERS AND FAVORED INNER
CHANNELS...WITH SMALL CRAFT WINDS EXPECTED ELSEWHERE /REF MARINE
DISCUSSION BELOW/. WIND GUSTS UP TO 45 MPH WILL ALSO BE POSSIBLE
FOR LAND ZONES 23 /SITKA/...27 /CRAIG AND KLAWOCK/...AND 28
/KETCHIKAN/ THIS EVENING AS THE LLJ PASSES ACROSS THE REGION.
STRONG LOW-LEVEL WAA OCCURRING ALONG THE FRONTAL BOUNDARY WILL
SPREAD FROM SRN TO NRN AREAS THROUGH TONIGHT AND YIELD WIDESPREAD
MODERATE TO LOCALLY HEAVY RAINFALL.

FRONTAL BOUNDARY DISSIPATES OVER THE CNTRL/SRN INLAND AREAS BY FRI
MORNING. MEANWHILE...LOW OVER THE GULF WILL CONTINUE TO OCCLUDE
AND ACCELERATE INTO THE NRN GULF. MODEL GUIDANCE SHOWS A STING JET
DEVELOPING ALONG THE SSERN FLANK OF THE SURFACE LOW...WHICH WILL
AID IN THE REDEVELOPMENT OF GALE WINDS OVER MARINE ZONE 310
SPREADING INTO MARINE ZONES 43..51...AND 52 BY FRI AFTERNOON. COOL
MIDLEVEL AIRMASS /-20 TO -22 C AT 500 MB/ WILL SPREAD NWD
ALONG/AHEAD OF THE OCCLUDED CYCLONE TONIGHT INTO FRI. AIRMASS
WILL DESTABILIZE AS A RESULT AND SUPPORT THE POTENTIAL FOR A FEW
THUNDERSTORMS...INITIALLY OVER MARINE ZONE 310...AND THEN
SPREADING TOWARD COASTAL AREAS INVOF YAKUTAT BY LATE FRI
AFTERNOON.

.LONG TERM...LOW SHOULD WEAKEN OVER THE NRN GULF FRI NIGHT WHILE
SECOND WRAP OF OCCLUDED FRONT MOVES NE THRU THE NRN AREA. ON
SAT...WEAK LOW SHOULD BE OVER THE NW GULF WHILE SFC RIDGING BUILDS
OVER SE AK. THINGS GET TRICKY FOR SAT NIGHT AND SUN. NORTHERN
STREAM UPPER TROF WILL DIG S INTO SW AK SAT AND REMAIN THERE WHILE
SRN STREAM SHORTWAVE MOVES NE TOWARD THE GULF. MODELS HANDLE THE
INTERACTION BETWEEN THE STREAMS DIFFERENTLY...THUS THEY HANDLE SFC
LOW DEVELOPMENT DIFFERENTLY. DECIDED AGAINST MAKING MUCH CHANGE TO
THE SAT NIGHT AND SUN PERIODS FOR THIS REASON. ONCE THE SYSTEM
GETS INTO THE NRN GULF BY SUN EVENING...IT SHOULD WEAKEN AND SHIFT
ESE EARLY NEXT WEEK. WILL NEED TO WATCH OUT FOR A POTENT OCCLUDED
FRONT FOR LATE NEXT WEEK...AS THE REMNANTS OF TYPHOON PHANFONE
WILL BE EMBEDDED WITH IT. USED 12Z GFS/NAM/GEM BLEND FOR FRI NIGHT
AND SAT...THEN USED WPC FOR THE MOST PART FOR LATE SUN NIGHT
ONWARD.

FOR FRI NIGHT...NRN AREA WILL SEE LOCALLY HEAVY RAIN AND STRONGER
WINDS AS SECOND WRAP OCCLUSION MOVES NE ACROSS THE AREA. SEE
HYDROLOGY SECTION BELOW FOR DETAILS ON POTENTIAL FLOODING. WINDS
COULD REACH STRONG WIND HEADLINE LEVELS OVER THE NRN AREAS...
ESPECIALLY BY LATE NIGHT IN THE PAGY AREA.

FOR SAT...AREA WILL BE IN DEEP LAYER ONSHORE FLOW BUT AIRMASS WILL
BE SOMEWHAT UNSTABLE SO WILL GO WITH SHOWER TERMINOLOGY FOR THEN.
MOST SHOWERS SHOULD BE OVER THE NW HALF OF THE AREA.

FOR SAT NIGHT/SUN...LOOKS LIKE MORE STEADIER PRECIP WILL MOVE IN
BUT DETAILS ON INTENSITY/AMOUNTS REMAIN SKETCHY DUE TO THE MODEL
DIFFERENCES HANDLING THE LOW DEVELOPMENT. ANOTHER COMPLICATION IS
LIKELIHOOD OF SPLIT BAROCLINIC BANDS...WHICH MAY LIMIT HOW MUCH
LOW LEVEL MOISTURE IS ADVECTED N INTO THE AREA AS THE MORE SERN
BAND WILL LIKELY STAY SE OF THE AREA...KEEPING THE HIGHER PRECIP
WATER STREAM FURTHER S. WILL BE A CLOSE CALL FOR THE SRN AREA
THOUGH...SO LATER SHIFTS WILL NEED TO WATCH THIS CLOSELY FOR
POTENTIAL HEAVY RAIN THERE.

FOR SUN NIGHT-TUE NIGHT...LOW SHOULD WEAKEN OVER THE NRN GULF SUN
NIGHT-MON THEN DRIFT ESE INTO THE SE GULF AND ACROSS THE SRN
PANHANDLE TUE-TUE NIGHT. WILL LIKELY SEE SOME DRYING FROM THE NW
BEGINNING LATER MON NIGHT OVER THE NE GULF COAST AND FAR NRN INNER
CHANNELS...AND REACHING THE SRN AREA BY LATE TUE NIGHT.

FOR LATE WEEK...THERE IS POTENTIAL FOR A STRONG FRONT TO AFFECT
THE AREA. THE MAIN LOW WILL LIKELY REMAIN OVER/NEAR THE ERN
ALEUTIANS WHILE THE OCCLUDED FRONT MOVES NE INTO THE GULF. ECMWF
AND GFS SUGGEST THIS FRONT WILL START AFFECTING THE GULF AREA
THU...AND AFFECT THE LAND AREAS STARTING THU NIGHT.

&&

.AVIATION...MODERATE TO HEAVY RAIN AND ASSOCIATED LOWERED CEILINGS
/AOB 3000 FT/ AND VISIBILITY RESTRICTION WILL SPREAD NNE ACROSS
THE PANHANDLE TONIGHT...INITIALLY OVER SRN AREAS SUCH AS
KETCHIKAN...WRANGELL AND SITKA DURING THE EVENING...THEN
JUNEAU...GUSTAVUS...AND YAKUTAT LATE TONIGHT INTO FRI MORNING.
WIND SHEAR AT 2000 FT FROM 35-45 KT IS ALSO FORECAST TO OCCUR THIS
EVENING/TONIGHT OVER THE SRN PANHANDLE AND YAKUTAT AS A SELY LOW-
LEVEL JET SPREADS N AHEAD OF A FRONTAL BOUNDARY.

&&

.MARINE...STORM FORCE WINDS ARE FORECAST TO EMANATE OUT OF CROSS
SOUND AND INTO MARINE ZONE 43 AS PRESSURE GRADIENT CONTINUES TO
TIGHTEN AHEAD OF AN APPROACHING FRONTAL BOUNDARY. STORM FORCE
WINDS ARE ALSO POSSIBLE NEAR LINCOLN ROCK IN CLARENCE STRAIT AS
40-60 KT LOW-LEVEL JET SPREADS ACROSS THE REGION. GALES WILL
CONTINUE OVER THE OUTER WATERS THROUGH THE EVENING...SPREADING S
TO N AS A FRONT ADVANCES NWD ACROSS THE GULF...WITH A SECOND ROUND
OF GALES DURING FRI AS OCCLUDED CYCLONE MOVES INTO THE NRN GULF. SEAS
WILL BUILD AOA 20 FEET BEHIND THE FRONTAL PASSAGE. ELSEWHERE...SMALL
CRAFT WINDS ARE FORECAST TO OCCUR ACROSS ALL OF THE INSIDE
CHANNELS...WITH THE EXCEPTION OF LYNN CANAL. GALE FORCE WINDS MAY
REACH NRN LYNN CANAL LATER FRI NIGHT ONCE SECOND WRAP OF OCCLUDED
FRONT MOVES PAST THEM AND LOW LEVEL RIDGING STARTS TO BUILD IN.

&&

.HYDROLOGY...FRONTAL BOUNDARY ADVANCING TOWARD THE SRN AND CENTRAL
PANHANDLE TONIGHT IS FORECAST TO GENERATE 1-3 INCHES OF
RAINFALL. STREAM AND CREEK WATER LEVELS WILL RISE AS A
RESULT...SUCH AS MONTANA CREEK IN JUNEAU...AND THE TAIYA RIVER
NEAR SKAGWAY. HOWEVER...FLOODING POTENTIAL WILL DEPEND UPON HOW
LONG HEAVY RAIN RATES PERSIST. THIS POTENTIAL WILL CONTINUE TO BE
EVALUATED AS THE RAIN EVENT EVOLVES. ELSEWHERE...AN UPPER
DISTURBANCE WILL ADVANCE INTO THE NRN GULF ON FRI. SYNOPTIC AND
OROGRAPHIC LIFT WILL SUBSEQUENTLY STRENGTHEN OVER ZONE 17
/VICINITY OF YAKUTAT/ AND FAVOR THE DEVELOPMENT OF HEAVY RAIN
SEPARATE FROM THE FRONTAL EPISODE OVER THE CNTRL/SRN PANHANDLE.
LOCALLY HEAVY RAIN WITH SECOND WRAP OF OCCLUDED FRONT MAY CAUSE
POTENTIAL FLOODING ISSUES OVER THE REMAINDER OF THE N FRI NIGHT AS
WELL.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ027.
         STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ023.
         STRONG WIND UNTIL 10 PM AKDT THIS EVENING FOR AKZ028.
MARINE...STORM WARNING FOR PKZ022-036-043.
         GALE WARNING FOR PKZ033-041-042-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011-021-031-032-034-035-053.

&&

GARNER/RWT

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU

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