Storm Warning 66, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
254 PM AKST TUE DEC 29 2015

.SHORT TERM...ACTIVE WEATHER PATTERN CONTINUES. WE HAVE A BREAK IN
THE WEATHER TODAY BEFORE THE NEXT FRONT MOVES INTO THE FORECAST
AREA TONIGHT INTO WEDNESDAY.

AS OF TUESDAY AFTERNOON, THERE IS A HIGH OVER INTERIOR BRITISH
COLUMBIA, AND A DEVELOPING LOW MOVING INTO CENTRAL GULF OVERNIGHT.
WATER VAPOR IMAGERY SHOWS A CLEAR DRY SLOT COMING INTO THE BACK
SIDE OF THIS DEVELOPING CYCLONE, WHICH IS INDICATIVE OF FURTHER
INTENSIFICATION OF THIS CYCLONE. A WELL DEVELOPED WEATHER FRONT
ASSOCIATED WITH THIS STRONG LOW IS FORECASTED TO MOVE INTO THE GULF
OF ALASKA TONIGHT, BRINGING IN STORM FORCE WINDS AND HIGH SEAS OF
20 FT OR GREATER INTO THE OUTER COAST. BY WEDNESDAY THIS STORM
FORCE FRONT WILL MOVE INTO THE EASTERN GULF AND SLOW DOWN ITS
EASTWARD PROGRESSION AND SLOWLY WEAKEN. BY WEDNESDAY AFTERNOON,
THERE WILL BE SMALL CRAFT ADVISORY LEVEL WINDS IN SOUTHERN LYNN
CANAL, CROSS SOUND, SOUTHERN CHATHAM STRAIT, SUMNER STRAIT, AND
CLARENCE STRAIT. GUSTY WINDS WILL ALSO BE FOUND ON LAND AREAS ALONG
THE OUTER COAST.

PRECIPITATION WILL MOVE ALONG THE WEATHER FRONT. HEAVY RAIN WILL
SPREAD INTO YAKUTAT AREA ON WEDNESDAY MORNING. AROUND ONE INCH OF
RAINFALL EXPECTED IN YAKUTAT AREA. BY WEDNESDAY AFTERNOON, MENTION
CHANCE OF RAIN FOR GUSTAVUS, ELFIN COVE, AND HAINES. PRECIPITATION
WILL BE HAVING A TOUGH TIME TO SPREAD FURTHER INLAND, AS THE FRONT
STALLS OVER EASTERN GULF OF ALASKA. PRECIPITATION TYPE SHOULD BE
ALL RAIN EXCEPT FOR HIGHER ELEVATIONS OF KLONDIKE AND HAINES
HIGHWAYS. SNOW LEVEL WILL BE ABOVE 2000 FEET NEAR YAKUTAT, AROUND
1000 TO 1500 FEET ELSEWHERE.

MOSTLY CLEAR SKIES EXPECTED TONIGHT FOR SOUTHERN PANHANDLE. A FEW
CLEAR BREAKS WILL ALSO DEVELOP ELSEWHERE. WITH LIGHT WINDS AND
REMNANT LOW LEVEL MOISTURE, THINK THAT THERE WILL BE FOG POTENTIAL
TONIGHT INTO TOMORROW MORNING, ESPECIALLY FOR SOUTHERN PANHANDLE
AREA INCLUDING ANGOON, PETERSBURG, WRANGELL, KETCHIKAN, AND
KLAWOCK. PATCHY FOG EXPECTED IN HOONAH, GUSTAVUS, AND JUNEAU.
CLOUDS ASSOCIATED WITH THE WEATHER FRONT WILL SPREAD INTO THE
PANHANDLE DURING THE DAY ON WEDNESDAY.

FORECAST CONFIDENCE IS ABOUT AVERAGE. MADE LITTLE OR NO CHANGES TO
THE FORECAST PACKAGE. USES ECMWF TO ADJUST THE RAINFALL AMOUNTS.

.LONG TERM...STALLED GALE FORCE FRONT WILL BE ORIENTED N-S OVER
THE GULF AT THE START OF THE LONG TERM PERIOD...WITH A WARM
CONVEYOR BELT CHARACTERIZED BY PW VALUES NEAR 2 SD SPREADING N
ALONG THE FRONT AND ACROSS AKZ017. THIS MOISTURE COMBINED WITH
LOW-LEVEL ELYS ALONG THE COAST/ENHANCED CONVERGENCE AND
OROGRAPHIC ASCENT IS FORECAST TO YIELD A MULTI-INCH RAINFALL EVENT
FROM YAKUTAT WWD WED NIGHT AND THU /HI-RES WRF GUIDANCE SHOWS 2
INCHES PER 6 HRS AT 06Z THU/. DUE TO THE EXPECTED POSITION OF
THE HIGHEST PRECIP TOTALS...HYDRO ISSUES FOR THE SITUK RIVER ARE
NOT ANTICIPATED ATTM.

PROGRESSIVE UPPER-LEVEL SHORTWAVE TROUGH MOVES ACROSS THE NERN
GULF AND NRN PANHANDLE BY 00Z FRI...WHICH WILL SHUNT THE FRONT
EWD TOWARD THE COAST OF THE CNTRL/SRN PANHANDLE...AFTER WHICH IT
IS FORECAST TO WASH OUT THU NIGHT. SURFACE PRESSURE GRADIENT WILL
TIGHTEN OVER THE SRN HALF OF THE PANHANDLE AS THE FRONT
APPROACHES...RESULTING IN SMALL CRAFT WINDS /POSSIBLE GALE FOR
CLARENCE STRAIT/ OVER THE CNTRL/SRN INNER CHANNELS...AND GUSTS
APPROACHING STRONG WIND CRITERIA FOR AKZ027 /AND PERHAPS 28/.

THE NEXT FRONTAL SYSTEM TO IMPACT THE REGION WILL MOVE NE ACROSS
THE GULF FRI EVENING...AND THEN ADVANCE ONSHORE OVER THE
PANHANDLE BY LATE FRI NIGHT. THIS FRONT IS EXPECTED TO YIELD A
HIGHER PROBABILITY FOR HEAVY RAINFALL OVER THE CNTRL/SRN PANHANDLE
FRI NIGHT THROUGH SAT. AFTER THIS FRONT EXITS...RESIDUAL MOIST
SWLY FLOW WILL CONTINUE TO SUPPORT RAIN OVER THE PANHANDLE THROUGH
SUN. HOWEVER...MODEL TRENDS SHOW UPPER HEIGHTS AMPLIFYING NWWD
ACROSS THE REGION HEADING INTO EARLY NEXT WEEK...WHICH SIGNALS THE
POTENTIAL FOR DRIER WEATHER. CURRENT FORECAST REFLECTS THIS TREND
WITH LOWER POP AND QPF MON-WED.

INHERITED PRESSURE GRIDS WERE LEFT UNCHANGED THROUGH SAT...THEN
NUDGED TOWARD WPC FROM 12Z SUN ONWARD. WINDS WERE TRENDED UPWARD
OVER THE SRN MARINE AND LAND ZONES WED NIGHT-FRI NIGHT. REMAINDER
OF THE INHERITED GRIDS WERE UPDATED WITH AN ENSEMBLE BLEND WERE
NECESSARY.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING FOR PKZ052.
         GALE WARNING FOR PKZ041>043-051.
         SMALL CRAFT ADVISORY FOR PKZ013-022-033-035-036.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ053.

&&

RCL/GARNER

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