Winter Storm in Alaska, January 5 to 7, 2015

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
350 PM AKST MON JAN 5 2015

.SHORT TERM...AN OCCLUDED FRONT EXTENDS FROM SOUTHWEST TO NORTHEAST
ACROSS THE GULF OF ALASKA. THE TRIPLE POINT LIES OVER HAIDA GWAII,
WITH THE WARM FRONT EXTENDING EAST ACROSS THE SOUTHERN PANHANDLE
AND THE COLD FRONT SOUTH OVER THE NORTHEAST PACIFIC. WARMER LOW
LEVEL AIR BEHIND THE WARM FRONT WILL CONTINUE TO MOVE NORTH WITH
THE FRONT THROUGH THE NIGHT. AT THE SURFACE, TEMPERATURES RANGE
FROM THE MIDDLE TEENS TO THE LOW 30S. SOME LOCATIONS ARE ALREADY
SEEING SNOW FRO THIS SYSTEM AND GENERALLY, THE MORE SOUTHERLY
LOCATIONS WILL TRANSITION FROM SNOW TO RAIN SOONEST. AS THIS
OVERRUNNING EVENT PROGRESSES AND THE WARMER AIR MOVES ALOFT OVER
THE COLDER SURFACE AIR, FREEZING RAIN BECOMES MORE LIKELY. THE
MORE SOUTHERLY LOCATIONS SHOULD SEE A CHANGE OVER FROM SNOW TO
RAIN MORE QUICKLY WITH ONLY A BRIEF PERIOD OF FREEZING RAIN.
FARTHER NORTH, THE DURATION OF THE FREEZING RAIN WILL LIKELY BE
LONGER WITH THE COLDER SURFACE AIRMASS REMAINING IN PLACE AND
FORCING THE WARMER AIR ALOFT. THIS FRONT BEGINS TO FALL APART
OVER THE CENTRAL PANHANDLE AND CATEGORICAL POPS EXTEND ONLY AS FAR
NORTH AS ZONE 26 THROUGH LATE TONIGHT. CHANCE POPS FARTHER NORTH
COMPLICATES THE ISSUE OF WHETHER OR NOT ANY PRECIPITATION OCCURS
AT ALL, FREEZING RAIN INCLUDED.

A STRONG NORTHEASTERLY PRESSURE GRADIENT CONTINUES TO CREATE VERY
WINDY CONDITIONS FOR THE ZONES CLOSEST TO THE COAST MOUNTAINS.
HAVE EXTENDED THE HIGH WIND WARNING FOR SKAGWAY TO MIDNIGHT.
STRONG WINDS IN DOWNTOWN JUNEAU FOR AT LEAST THE EVENING HOURS
TONIGHT. THE APPROACHING FRONT WILL ACTUALLY AMPLIFY THE PRESSURE
GRADIENT SOMEWHAT BEFORE WEAKENING, SO WINDY OR VERY WINDY
CONDITIONS THROUGH THE NIGHT FOR MANY LOCATIONS SEEMS HIGHLY
LIKELY. STRONG WIND HEADLINE IN HAINES PRIMARILY DUE TO THE VERY
STRONG WINDS IN LYNN CANAL AND THEIR PROXIMITY TO THE CHILKAT
PENINSULA.

STRONG WINDS AND VERY COLD TEMPERATURES WILL KEEP THE WIND CHILL
ADVISORY FOR THE KLONDIKE HIGHWAY GOING ALL NIGHT LONG AND THROUGH
MID MORNING. BLOWING SNOW IN ADDITION TO THE WIND CHILL IS ALSO A
CONCERN ALONG THE KLONDIKE TONIGHT.

FINALLY, HAVE ISSUED A WINTER STORM WARNING FOR MISTY FJORDS AND
HYDER WITH THE AFTERNOON FORECAST. SNOW TOTALS OVER THE NEXT 24
HOURS IN HYDER EXPECTED TO BE AROUND 12 INCHES WITH MORE SNOW
FALLING IN THE EARLY PORTION OF THE EXTENDED RANGE FORECAST.

NO CHANGES TO PRESSURE OR WIND TODAY. ADJUSTMENTS TO TEMPS AND
SNOW LEVELS PER ECMWF. POP AND QPF UPDATED USING ECMWF AS A
FOUNDATION WITH SOME HELP FROM BOTH GEM AND GFS. OVERALL FORECAST
CONFIDENCE IS AVERAGE.

.LONG TERM...MODEL PERFORMANCE HAS NOT BEEN IMPROVED MUCH...BUT
PREFERRED TO REFRESH THE INHERITED FORECAST WITH THE ECMWF AND GEM
GLOBAL FOR THEIR MOST ACCEPTABLE CONSISTENCY THROUGH THURSDAY
EVENING. POP FIELDS WERE REFRESHED WITH THE SREF POP GUIDANCE AS
WELL. USED THE LATEST WPC ENSEMBLE SOLUTIONS FOR THE REST OF LONG
TERM PERIODS. PERSISTING UPPER LEVEL RIDGE OVER SOUTHEAST ALASKA
WILL KEEP OPENING MOISTURE CHANNEL FROM THE SOUTH AND MOSTLY
FOCUSING TO THE SOUTHERN PANHANDLE AREAS THROUGH LATE WEDNESDAY.
WARMING TREND WILL CONTINUE...BUT THE COLD AIR ANCHORED OVER
BRITISH COLUMBIA WILL PRODUCE SIGNIFICANT SNOWFALL NEAR HYDER
THROUGH WEDNESDAY AFTERNOON. POSTED WINTER STORM WARNING FOR HYDER
INITIALLY THROUGH 6 PM WEDNESDAY WITH POSSIBLE TOTAL SNOW
ACCUMULATION 16 TO 27 INCHES.

CONTINUED MOISTURE FEEDING FROM THE SOUTH WILL REACH TO THE
NORTHERN HALF OF THE PANHANDLE. EXPECT SNOW INITIALLY DUE TO
REMAINING COLD AIR OVER THE AREAS...BUT CONTINUED WARMING TREND
WILL EVENTUALLY TURN THE SNOW TO RAIN. MAINTAINED LIGHT FREEZING
DRIZZLE IN THE FORECAST DUE TO WARMER AIR RIDING OVER COLD AIR
THROUGH SOMETIME THURSDAY...IN WHICH TIME SURFACE TEMPERATURES
BECOME WARM ENOUGH FOR RAIN. TIGHTENED PRESSURE GRADIENT FOR
GUSTY OFFSHORE FLOW WILL CONTINUE THROUGH THURSDAY...THEN RELAX A
BIT BEFORE TIGHTENING AGAIN TOWARD THE WEEKEND. GALE TO POSSIBLE
STORM FORCE WINDS WILL PERSIST ACROSS THE NORTHERN INNER CHANNELS
SOUTH TO STEPHENS PASSAGE WITH FREEZING SPRAY. EXPECT TAKU WIND
FOR DOWNTOWN JUNEAU AND SOUTH DOUGLAS AS WELL.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ025.
         STRONG WIND THROUGH TUESDAY AFTERNOON FOR AKZ019.
         HIGH WIND WARNING UNTIL MIDNIGHT AKST TONIGHT FOR AKZ018.
         STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH TUESDAY AFTERNOON
     FOR AKZ018.
         WIND CHILL ADVISORY UNTIL 9 AM AKST TUESDAY FOR AKZ018.
         WINTER STORM WARNING UNTIL 6 PM AKST WEDNESDAY FOR AKZ029.
MARINE...STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031-034>036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ032-033-043-051>053.

&&

FRITSCH/AHN

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