Winter Storm Warning 16, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
511 PM AKST WED FEB 4 2015

.SHORT TERM...DEVELOPMENT OF STRONG OUTFLOW WINDS WILL BE THE
PRIMARY WEATHER STORY DURING THE SHORT TERM PERIOD. A 1035 MB HIGH
AND ASSOCIATED ARCTIC AIRMASS OVER THE INTERIOR OF AK AND NWRN
CANADA WILL BUILD SSEWD THROUGH THU AFTERNOON AS A SERIES OF UPPER
DISTURBANCES ROTATE ESE ACROSS THAT REGION. WINDS AT SKAGWAY AND
NRN LYNN CANAL ARE ALREADY RESPONDING TO THE INITIAL SURGE OF HIGH
PRESSURE...AND WILL CONTINUE TO STRENGTHEN THROUGH THE NIGHT TO
HIGH WIND CRITERIA FOR SKAGWAY...AND STORM FORCE SPEEDS FOR NRN
LYNN CANAL...BY 12Z THU. IN ADDITION...TEMPERATURES IN THE TEENS
COMBINED WITH WATER TEMPERATURES AROUND 4C AND THE STRONG NLY
WINDS WILL FAVOR HEAVY FREEZING SPRAY FOR NRN LYNN CANAL.

ELSEWHERE...CROSS BARRIER FLOW IS FORECAST TO STRENGTHEN TO 50-70
KT BY 18Z OVER DOWNTOWN JUNEAU AND PERSIST THROUGH THE REMAINDER
OF THE SHORT TERM PERIOD. THIS FLOW COMBINED WITH A STRONG
BOUNDARY LAYER INVERSION AND CRITICAL LEVEL NEAR 600 MB WILL FAVOR
HIGH WINDS FOR DOWNTOWN JUNEAU AND S DOUGLAS...WITH GUSTS ABOVE 60
KT LIKELY...AND POSSIBLY REACHING 90 KT BY 03Z FRI.

STRONG OUTFLOW WINDS ARE ALSO FORECAST TO DEVELOP IN THE INTERIOR
PASSES SURROUNDING YAKUTAT...INVOF GUSTAVUS...ALONG LYNN CANAL
NEAR HAINES...AND PORTLAND CANAL S OF HYDER. GALES WILL BE
WIDESPREAD FOR MOST OF THE INNER CHANNELS...AND GALE FORCE WINDS
WILL ALSO EMANATE FROM INTERIOR BAYS...PASSES...AND CHANNELS AND
SPREAD ACROSS THE OUTSIDE WATERS. FINALLY...TEMPERATURES WILL
HOVER NEAR ZERO AT WHITE PASS...AND WHEN COMBINED WITH NELY WINDS
GUSTING FROM 40-60 MPH...WILL FAVOR WIND CHILL VALUES NEAR
-30F...AS WELL AS BLIZZARD CONDITIONS DUE TO BLOWING SNOW...LATE
TONIGHT THROUGH THU AFTERNOON.

OTHERWISE...AN UPPER-LEVEL SHORTWAVE TROUGH IS FORECAST TO DIG
INTO THE NERN GULF AND WILL BEGIN TO PHASE WITH ANOTHER TROUGH
LOCATED OVER THE SERN GULF/FAR NERN PAC THU AFTERNOON. MOISTURE
WILL SPREAD NWD INTO THE SRN PANHANDLE AS THIS OCCURS AND AID IN
INCREASING PRECIPITATION POTENTIAL. TEMPERATURES ARE FORECAST TO
RESIDE A DEGREE OR TWO BELOW ZERO IMMEDIATELY ABOVE THE
SURFACE...WHICH WILL FAVOR THE DEVELOPMENT OF SNOW LATE THU
AFTERNOON FROM KLAWOCK TO KETCHIKAN AND HYDER. COLDEST SURFACE
TEMPERATURES WILL BE LOCATED AT HYDER...THUS CURRENTLY EXPECT THEM
TO HAVE THE GREATEST PROBABILITY FOR SEVERAL INCHES OF
ACCUMULATION.

.LONG TERM...MODELS TRENDING FURTHER N WITH SIGNIFICANT PRECIP FOR
THU NIGHT-FRI NIGHT. PREFERRED 12Z GFS/EC BLEND FOR THEIR HANDLING
OF THE MAIN FEATURES. UPPER TROF WILL SHARPEN OVER THE NE GULF
WHILE SRN STREAM SHORTWAVES MOVE NNE INTO THE SRN AREA DURING THIS
TIME. THE ARCTIC FRONT WILL BE OVER THE SRN PANHANDLE...PROBABLY
JUST N OF A PAKT-PAKW LINE. AS SFC LOW MOVES NWD THU NIGHT...THE
ARCTIC FRONT WILL LIKELY DRIFT A BIT TO THE N AS WARMER AIR MOVES
IN. STRONG OVERRUNNING OF THE ARCTIC AIRMASS WILL OCCUR...AND IT
IS LOOKING MORE LIKELY THAT HEAVY SNOW WILL DEVELOP S OF FREDERICK
SOUND AND N OF A PAKT-PAKW LINE THU NIGHT...THEN MAY GET AS FAR N
AS PAGN FRI. LOOKS LIKE FRONTOGENESIS WILL BE STRONG OVER THE
CENTRAL PANHANDLE AS WELL...ENHANCING SNOWFALL. STILL A TRICKY CALL
FOR THE JUNEAU AREA FOR FRI AS THEY WILL BE ON THE MORE NW SIDE OF
THE PRECIP SHIELD...BUT IF MODELS TREND IT A LITTLE FURTHER
N...PAJN WILL NEED SNOW HEADLINE. ISSUED WINTER STORM WATCH FOR
ZONES 23...24...26...AND 29...ALL THRU 09Z SAT. 29 WILL START AT
03Z FRI...26 AT 09Z FRI...AND 23/24 AT 15Z FRI. THINK THE HEAVY
SNOW FOR 23 WILL BE MAINLY OVER SRN BARANOF ISLAND. SNOWFALL MAY
EXCEED 18 INCHES IN THE PAPG/PAWG/HYDER AREAS...WITH A FOOT OR
MORE POSSIBLE IN PAAP/PAGN AREAS. THINK MOST OF THIS PRECIP WILL
DIMINISH LATER FRI NIGHT AS SRN STREAM SHORTWAVE LIFTS NE OF THE
AREA.

WINDS WILL REMAIN A CONCERN FOR MOST OF THE NRN AND CENTRAL AREA
THRU FRI. THERE WILL BE A VERY TIGHT PRESSURE GRADIENT BETWEEN
ARCTIC HIGH TO N AND FAIRLY DEEP LOW TO S THU NIGHT INTO FRI. THE
GRADIENT ALONE WILL GENERATE STORM FORCE NLY WINDS OVER MUCH OF
THE NRN INNER CHANNELS. ALSO LOOKS FAVORABLE FOR TAKU WINDS IN THE
JUNEAU AREA...AND HAVE THE HIGH WIND WARNING LASTING UNTIL 4 PM
FRI THERE. PAGY/WHITE PASS WILL ALSO SEE VERY STRONG WINDS...AND
WHITE PASS WILL ALSO HAVE A LOT OF BLOWING SNOW AND VERY LOW WIND
CHILLS. HAVE ISSUED A BLIZZARD WARNING FOR WHITE PASS AND HIGH
WIND WARNING FOR LOWER ELEVATIONS OF ZONE 18. WILL KEEP STRONG
WINDS GOING FOR PAHN/PAYA THRU AT LEAST FRI AFTERNOON.

UPPER TROF WILL REDEVELOP FURTHER W OVER THE WEEKEND AS A STRONG
SHORTWAVE TROF DIGS SWD INTO THE WRN GULF. SFC LOW WILL LIKELY
FORM OVER THE CNTRL GULF AND DRIFT NWD...AND WILL SEE INCREASINGLY
MOIST SWLY FLOW ALOFT DEVELOP ESPECIALLY OVER THE NW HALF OF THE
AREA. THIS MAY LEAD TO ANOTHER ROUND OF PRECIP FOR THE AREA...WITH
POTENTIAL FOR SIGNIFICANT SNOW OVER THE NW HALF OF THE AREA.
WARMER AIR LOOKS LIKE IT WILL MAKE ITS WAY NWD SUN INTO EARLY NEXT
WEEK...WHICH WILL DIMINISH THE SNOW THREAT FROM THE S.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
     EVENING FOR AKZ026.
         WINTER STORM WATCH FROM FRIDAY MORNING THROUGH FRIDAY EVENING
     FOR AKZ023-024.
         HIGH WIND WARNING FROM 6 AM THURSDAY TO 4 PM AKST FRIDAY FOR
     AKZ025.
         STRONG WIND FROM THURSDAY MORNING THROUGH FRIDAY AFTERNOON FOR
     AKZ020-022-029.
         WINTER STORM WATCH FROM THURSDAY EVENING THROUGH FRIDAY EVENING
     FOR AKZ029.
         STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH FRIDAY AFTERNOON
     FOR AKZ019.
         HIGH WIND WARNING FROM 3 AM THURSDAY TO 4 PM AKST FRIDAY FOR
     AKZ018 AT LOWER ELEVATIONS.
         BLIZZARD WARNING FROM 3 AM THURSDAY TO 4 PM AKST FRIDAY FOR
     AKZ018 NEAR WHITE PASS.
         STRONG WIND THROUGH FRIDAY AFTERNOON FOR AKZ017.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         STORM WARNING FOR PKZ012-013-043-051.
         GALE WARNING FOR PKZ011-021-022-031>035-041-042-053.
         SMALL CRAFT ADVISORY FOR PKZ036-052.

&&

GARNER/RWT

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