Gale Warning 52, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
539 AM AKST TUE JAN 6 2015

.SHORT TERM...UPPER RIDGE IS IN THE PROCESS OF AMPLIFYING OVER THE
W COAST OF N AMERICA THIS MORNING DOWNSTREAM FROM A LARGE TROUGH
POSITIONED S OF THE ALEUTIANS. PLUME OF VERY MOIST AIR /PW VALUES
FROM 0.5 TO 1 INCH/ IS SPREADING N FROM THE NERN PAC...AND IS
FORECAST TO ENTER THE SRN/CNTRL PANHANDLE LATE THIS AFTERNOON
THROUGH TONIGHT. MODEL GUIDANCE ALSO SHOWS A MINOR UPPER
DISTURBANCE AND ASSOCIATED LOW AT THE SURFACE EMANATING OUT OF THE
ERN PORTION OF THE PAC TROUGH THIS AFTERNOON AND MOVING N TO THE
CNTRL COAST OF THE PANHANDLE BY 12Z WED. LARGE-SCALE ASCENT WILL
INCREASE OVER THE SRN PANHANDLE AS THIS OCCURS...AND ITS
INTERACTION WITH STRENGTHENING MOIST SLY FLOW AND ASSOCIATED WAA
REGIME...WILL FAVOR LOCALLY HEAVY RAINFALL. MEANWHILE...HIGH
PRESSURE OVER NWRN CANADA WILL LOCK IN COLDER CONTINENTAL AIR FOR
HYDER...YIELDING A TEMPERATURE PROFILE SUPPORTIVE OF SNOW...WITH
TOTALS THROUGH TONIGHT EXPECTED TO RANGE BETWEEN 1-2 FEET.

FARTHER N OVER THE CNTRL PANHANDLE...MOISTURE WILL SPREAD INTO THE
AREA TONIGHT ALONG WITH INCREASING LOW-LEVEL WAA AND ISENTROPIC
UPGLIDE. IN ADDITION...PRONOUNCED BAROCLINIC ZONE LOCATED OVER THE
LOWEST FEW KM WILL YIELD AN ADDITIONAL MESOSCALE ZONE OF ASCENT
THROUGH FRONTOGENESIS. TEMPERATURES IMMEDIATELY ABOVE THE SURFACE
WILL HOVER AROUND FREEZING...WHICH SHOULD FAVOR WET SNOW GIVEN THE
DEGREE OF ASCENT...POSSIBLY MIXED WITH BRIEF PERIODS OF FREEZING
DRIZZLE. FORECAST UNCERTAINTY HINGES ON THE AMOUNT OF DRY AIR
EMANATING FROM THE COAST RANGE...WHICH MAY DELAY COMPLETE COLUMN
SATURATION UNTIL LATE WED MORNING. CURRENT SHORT TERM FORECAST
CALLS FOR SNOW ACCUMULATION IN THE JUNEAU AREA BETWEEN 1-4 INCHES
TONIGHT.

NLY PRESSURE GRADIENT REMAINS TIGHT THROUGH TONIGHT OVER THE
CNTRL/NRN INNER CHANNELS...WHICH WILL FAVOR CONTINUED GALES FOR
NRN LYNN CANAL...AS WELL AS GALE FORCE GAP WINDS IN CROSS SOUND.
TEMPERATURES IN THE MID TO UPPER 20S COMBINED WITH THE STRONG
WINDS WILL ALSO LEAD TO A RISK FOR LIGHT FREEZING SPRAY IN LYNN
CANAL. BUMPED UP WAVE HEIGHTS TO 10-12 FT FOR LYNN CANAL DUE TO
A PROLONGED PERIOD OF 40+ KT WINDS FLOWING DOWN THE LENGTH OF THE
CHANNEL. STRONG WINDS WITH GUSTS UP TO 50 MPH ARE EXPECTED FOR
SKAGWAY TO WHITE PASS DUE TO THE TIGHT PRESSURE GRADIENT. IN
ADDITION...TEMPERATURES ARE EXPECTED TO WARM VERY LITTLE AT WHITE
PASS...WHICH WILL CONTINUE TO SUPPORT WIND CHILL VALUES TO -35F.

CROSS BARRIER FLOW WILL WEAKEN DURING THE DAY OVER JUNEAU...BUT
THEN RESTRENGTHEN TO 40 KT LATE TONIGHT /PER HI-RES MODEL
GUIDANCE/. HOWEVER...THE RIDGE TOP INVERSION WILL DISSIPATE
OVERNIGHT. GIVEN THESE FACTORS...THE HIGH WIND WARNING WILL BE
ALLOWED TO EXPIRE AT 15Z...BUT PERIODIC STRONG WIND GUSTS FROM
40-50 MPH WILL REMAIN A POSSIBILITY THROUGH THE AFTERNOON...AND
THEN SUBSIDE TONIGHT WITH THE LOSS OF THE INVERSION. OVER SRN
AREAS...40-50 KT LOW-LEVEL SLY JET WILL SPREAD ACROSS CLARENCE
STRAIT TONIGHT RESULTING IN THE DEVELOPMENT OF GALE FORCE WINDS.

NUDGED PRESSURE GRIDS TOWARD THE ECMWF IN ORDER TO REFLECT MORE OF
A CLOSED SURFACE LOW APPROACHING THE GULF COAST TONIGHT. USED A
COMBINATION OF HI-RES AND COARSE-RES GUIDANCE FOR POP AND QPF.
FORECAST CONFIDENCE IS AROUND AVERAGE.

.LONG TERM.../ WEDNESDAY TO MONDAY / HIGH PRESSURE OVER NORTHWEST
CANADA GENERALLY PERSISTENT THROUGH THE WEEKEND. WEDNESDAY
DEALING WITH SHORT WAVE DRIVING NORTHWARD OUT OF ITS MID TROPICS
STARTING POINT. GOOD MOISTURE VALUES WITH IT AS IT MOVE NORTH AND
OVER THE COLD AIR CAUGHT IN THE INNER CHANNELS. IT SEEMS TO BE
ABLE TO MOVE THE RAIN SNOW LINE ALONG WITH THE FIRST FEATURE
MONDAY TO THE TENAKEE INLET-TAKU INLET LINE. SO EXPECT RAIN SOUTH
HALF WITH SNOW NORTH. JUST CONFIDENT ENOUGH TO GO WITH WATCH FOR
NORTHERN INNER CHANNELS WEDNESDAY FOR THIS WAVE BEFORE IT MAKES
TURN OVER RIDGE ALONG ALONG COAST MOUNTAINS. LOOKS LIKE 5 TO 10
INCHES POSSIBLE FOR THE HOONAH GUSTAVUS JUNEAU HAINES AND SKAGWAY
AREAS...MORE ALONG WHITE PASS BEFORE THE WINDS BLOW THAT WAY.

PRECIPITATION TAPERS OFF WEDNESDAY NIGHT AS THE SHORTWAVE MOVES
AWAY AND HIGH PRESSURE CENTER MOVES FROM ARCTIC SLOPE TO SOUTHERN
YUKON AGAIN. THIS WILL TRY AND HOLD THE PRECIPITATION AND OUT OVER
THE GULF AS THE UPPER LEVEL TROUGH IS NEGATIVELY TILTED. FROM THIS
PATTERN LOOKS LIKE NO MAJOR WEATHER SYSTEMS UNTIL THE WEEKEND.

WINDS TEMPERATURES AND LOOSE SNOW IN NORTHERN LYNN CANAL AREA
LEADING TO WIND CHILL ADVISORIES BLOWING SNOW WORDING FOR
HIGHWAYS TO CANADA.

CONFIDENCE IS AVERAGE... WITH BIGGEST CONCERNS FOR SOME OF THE
ZONES WITH THE WINTER STORM WATCH.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THROUGH THIS AFTERNOON FOR AKZ025.
         WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON FOR AKZ018>021-025.
         WINTER STORM WARNING UNTIL 6 PM AKST WEDNESDAY FOR AKZ029.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ018.
         WIND CHILL ADVISORY UNTIL 6 PM AKST WEDNESDAY FOR AKZ018.
MARINE...STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ013-021-022-031-034>036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ011-032-033-051>053.

&&

GARNER/BEZENEK

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