Small Craft Advisory 24, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
155 PM AKST WED JAN 6 2016

.SHORT TERM...ASIDE FROM INCREASING MID TO HIGH LEVEL CLOUDS AND
WEAKENING OUTFLOW WINDS THERE WILL BE LITTLE CHANGING WEATHERWISE
OVER THE NEXT 24 HOURS. AN EASTERLY WAVE OVER THE GULF IS
PRODUCING SCATTERED TO BROKEN CLOUD COVER OVER MUCH OF THE
PANHANDLE TODAY. THIS FEATURE WILL MOVE INTO THE NORTH CENTRAL
GULF BY LATE TONIGHT. ADDITIONAL WEAK IMPULSES EMBEDDED WITHIN THE
EAST-SOUTHEAST FLOW WILL CONTINUE TO BRING CLOUD COVER INTO THE
PANHANDLE THROUGH THURSDAY AFTERNOON. HOWEVER...EXPECT THE AREAL
EXTENT OF CLOUD COVER TO BE MORE WIDESPREAD ON THURSDAY WITH
LESS SUNSHINE THAN WE HAVE SEEN THE PAST FEW DAYS. LIGHT
PRECIPITATION WITH THESE DISTURBANCES IS EXPECTED TO REMAIN
OFFSHORE EXCEPT FOR SOME ISOLATED SHOWER ACTIVITY THURSDAY
AFTERNOON IN YAKUTAT.

WINDS WILL BE ON THE DIMINISHING TREND THROUGH THE NEXT 24 HOURS
AS THE PRESSURE GRADIENT ALONG THE COAST MOUNTAINS RELAXES.
PERSISTENT 45-50 MPH GUSTS IN SKAGWAY WILL GRADUALLY SUBSIDE AND
ARE EXPECTED TO FALL BELOW THE STRONG WIND CRITERIA OF 40 MPH
THURSDAY MORNING. WINDS ACROSS THE REMAINDER OF THE INNER CHANNELS
WILL BE 20 KT OR LOWER ON THURSDAY. TEMPERATURES WILL BE SIMILAR
TO THE PAST FEW DAYS WITH NO AIRMASS CHANGE. HOWEVER MORE CLOUD
COVER WILL RESULT IN OVERNIGHT LOWS BEING A FEW DEGREES WARMER
THAN WE HAVE BEEN EXPERIENCING.

USED THE 12Z NAM/00Z ECMWF FOR UPDATES TO THE INHERITED FORECAST.
CHANGES WERE MINIMAL. FORECASTER CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...PRIMARY UNCERTAINTY IN THE LONG TERM PERIOD IS HOW AN
UPPER-LEVEL RIDGE EVOLVES OVER THE W COAST OF N AMERICA. ECMWF
KEEPS THE RIDGE FIRMLY POSITIONED IMMEDIATELY ALONG THE
COAST...WHILE THE GFS SHIFTS THE RIDGE SLIGHTLY OFFSHORE DUE TO
THE MORE WLY EXPANSE OF A LARGE-SCALE UPPER-LEVEL CANADIAN
VORTEX/TROUGH. DIFFERENCES IN THE RIDGE POSITION SUBSEQUENTLY
IMPACT THE TIMING/EWD PROGRESSION OF A FRONTAL BOUNDARY FRI AND
SAT...WITH THE ECMWF BRINGING THE FRONT ONSHORE AROUND MIDDAY
SAT...AND THE GFS HOLDING THE FRONT OFFSHORE OVER THE GULF. THE
TIMING ISSUES BETWEEN THE ECMWF AND GFS IN FRONTAL SYSTEMS REMAINS
OUT OF PHASE THEREAFTER...THOUGH THE PROBABILITY OF PRECIPITATION
WILL BE ELEVATED...AND A MODERATING TREND IN TEMPERATURES IS
LIKELY. HOWEVER...DUE TO LARGE MODEL SPREAD...DETAILS IN THE LONG
TERM FORECAST ARE UNCERTAIN...WHICH PROMPTED A LOWERING/SMEARING
OF POP/QPF VALUES.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THROUGH LATE TONIGHT FOR AKZ018.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-031-034-041-042-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043-051.

&&

TPS/GARNER

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