Small Craft Advisory 1, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
400 PM AKST THU DEC 31 2015

.SHORT TERM...HIGHLY AMPLIFIED UPPER FLOW REGIME IS PRESENT ACROSS
THE REGION THU AFTERNOON DUE TO A BROAD CYCLONE POSITIONED OVER
THE WRN ALEUTIANS...AND A RIDGE EXTENDING N FROM THE NERN PAC
ACROSS BC. A SHORTWAVE TROUGH EMBEDDED BETWEEN THESE TWO FEATURES
IS IN THE PROCESS OF EJECTING NE FROM THE NERN GULF TO NWRN
CANADA...WHICH IS AIDING IN SHIFTING A GALE FORCE FRONT EWD TOWARD
THE CNTRL PANHANDLE COAST...WHERE IT WILL STALL/WASH OUT TONIGHT.
MEANWHILE...A 955 MB SURFACE CYCLONE WILL ADVANCE N TOWARD THE
WRN TIP OF THE AK PENINSULA THROUGH FRI...WHILE ITS ASSOCIATED
OCCLUDED FRONT ENTERS THE CNTRL GULF BY 00Z SAT.

FRONTAL PRECIPITATION BAND LOCATED FROM AKZ018 S TO THE SERN GULF
IS CONTRACTING AND SHOWING SIGNS OF DISORGANIZING /PER SATELLITE
IMAGERY/ AS IT MOVES PROGRESSIVELY CLOSER TO THE RIDGE OVER
BC. BY TONIGHT...LIGHT RAIN IS FORECAST TO BECOME MAINLY CONFINED
TO THE CNTRL/SRN PANHANDLE. FARTHER N...MOIST UPSLOPE FLOW OVER
THE KLONDIKE HIGHWAY...COMBINED WITH SURFACE TEMPERATURES NEAR
FREEZING...ARE AIDING IN POTENTIAL ADVISORY LEVEL SNOWFALL FROM
3-5 INCHES. HOWEVER...SNOWFALL RATES ARE EXPECTED TO QUICKLY
DIMINISH BY EARLY THU EVENING AS PREVIOUSLY MENTIONED S/W EXITS
INTO THE YUKON.

GOING INTO FRI...LOW-LEVEL SELYS STRENGTHEN ONCE AGAIN IN ADVANCE
OF THE NEXT FRONT...WHICH WILL REFOCUS GREATEST PRECIPITATION
PROBABILITIES OVER THE NRN PANHANDLE. GALES WILL ALSO REDEVELOP
OVER THE ENTIRE GULF...WHILE CONTINUING THROUGHOUT THE SHORT TERM
PERIOD OVER CLARENCE STRAIT /DUE TO PERSISTENTLY TIGHT PRESSURE
GRADIENT/. GUSTY CONDITIONS WILL ALSO BE POSSIBLE ACROSS PORTIONS
OF THE PANHANDLE TONIGHT...DESPITE FRONTOLYSIS. THERE IS SOME
CONCERN THAT LOCATIONS FROM SITKA TO HYDABURG COULD FLIRT WITH
STRONG WIND CRITERIA...AND GUSTS TO 40 MPH ARE NOT OUT OF THE
QUESTION IN JUNEAU THIS EVENING...GIVEN PEAK SPEEDS OF 80-90 KT
ARE STILL BEING OBSERVED AT SHEEP MOUNTAIN.

UPDATES TO INHERITED GRIDS WERE MADE USING AN ENSEMBLE APPROACH.

.LONG TERM...THE SOUTHERLY FLOW ALOFT OVER THE EASTERN GULF SHIFTS
TO A SOUTHWEST AND BACK TO SOUTHEASTERLY MONDAY. THROUGH THIS
PATTERN THERE ARE 2 OR 3 SHORT WAVE FEATURES OR CLOSED LOWS
MOVING ACROSS OR AWAY FOR THE GULF. A CLOSED LOW SOUTH OF THE
GULF MOVES OFF TOWARDS CALIFORNIA COAST. DURING MONDAY, ANOTHER
IMPULSE MOVES IN THE MAIN FLOW PATTER SOUTH OF THE GULF OF ALASKA
EXTENDING THE TROUGH SOUTHEASTWARDS WHILE HIGH PRESSURE OF BRITISH
COLUMBIA PERSISTS. THE SOUTHEAST FLOW WILL INHIBIT MUCH IN THE WAY
OF PRECIPITATION FROM REACHING SOUTHEAST UNTIL MIDWEEK.

SYSTEMS WILL BE MOVING RAPIDLY ACROSS THE NORTH PACIFIC AS A
GENERALLY CONSISTENT JET STREAM OF 140 TO 160+ WITH A CORE OR TWO
REACHING 180 KT MOVES ACROSS THE NORTH PACIFIC MOVING THE SYSTEMS
QUICKLY EAST. THE MAIN AND SOUTHERN STREAM JET FLOWS FROM JAPAN
TO THE BAJA OF MEXICO. THE NORTHERN STREAM SPLITS OFF
OCCASIONALLY AROUND 160W TURNING NORTH INTO THE WESTERN HALF OF
THE STATE.

RAIN AND SNOW THROUGH MUCH OF THE WEEKEND AND THEN THAT WILL TAPER
OFF FOR A COUPLE OF DAYS. WINDY CONDITIONS FRIDAY NIGHT FOR THE
OUTER COASTAL ZONES AND LOCALLY BREEZY ACROSS THE INSIDE WINDS
CALMING DOWN FOR SATURDAY.

USED WPC WHICH WAS AN ENSEMBLE APPROACH FOR THE EXTENDED TIME
FRAME THROUGH THE PREVIOUS FORECAST WAS RATHER CLOSE TO THIS
ALREADY. THROUGH THE MID RANGE THE MODELS WERE FAIRLY CLOSE
AGREEMENT AND THE CHANGES MADE TO THE FORECAST WERE SMALL.
CONFIDENCE IS GOOD TO THE WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ025-027.
         WINTER WEATHER ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR
     AKZ018.
MARINE...GALE WARNING FOR PKZ022-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-031>035-053.

&&

GARNER/BEZENEK

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