Winter Storm Warning 28, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
433 PM AKST THU DEC 24 2015

.SHORT TERM...RIDGE AT THE SURFACE AND ALOFT CONTINUES TO TRACK
OVER THE GULF OF ALASKA TONIGHT AND TO BE EAST OF THE PANHANDLE BY
FRIDAY AFTERNOON. A PAIR OF LOWS WILL MERGE INTO A SINGLE FEATURE
NEAR COLD BAY WITH A DEPTH AROUND 960 MB THIS EVENING WHILE THE
FRONTAL BAND WILL MOVE TO THE EASTERN GULF BY FRIDAY AFTERNOON.
FORECAST FOR SOUTHEAST ALASKA SHOULD STAY DRY TONIGHT AND EARLY
FRIDAY...ALTHOUGH THERE COULD BE A FEW FLURRIES OVER THE SOUTHERN
PANHANDLE LATE THIS AFTERNOON.

GALE FORCE WINDS SPREADING EAST ACROSS THE GULF AND INTO THE
NORTHERN COASTAL WATERS TONIGHT AND FRIDAY. ALSO SOME GUSTY WINDS
THROUGH LYNN CANAL AREA TODAY AND INTO TONIGHT...ALTHOUGH THEY
SHOULD BE SUBSIDING FRIDAY SOME AS THE FRONT APPROACHES AND CHANGES
THE PRESSURE PATTERN. SHOULD SEE OUTFLOW WINDS FROM INTERIOR
PASSAGES AND THROUGH CROSS SOUND IN THE AFTERNOON.

SNOW SHOULD START FALLING ACROSS THE NORTHEAST GULF COAST REGION
FRIDAY AFTERNOON THROUGH NO LARGE ACCUMULATIONS EXPECTED THROUGH THE
AFTERNOON. THE COASTAL AREAS ALONG BARANOF AND CHICHAGOF ISLAND MAY
SEE A FEW LATE AFTERNOON FLURRIES BUT DO NOT EXPECT ANY MEASURABLE
SNOW BY LATE AFTERNOON.

.LONG TERM...SIGNIFICANT SNOW EVENT STILL LOOKS LIKELY ACROSS MOST
OF THE NORTHERN AND EASTERN AREAS FRI NIGHT AND SAT AS OCCLUDED
FRONT PUSHES IN. MODELS IN FAIRLY GOOD AGREEMENT ON STRENGTH OF
FRONT. THERE WERE SOME MINOR TIMING DIFFERENCES WITH 12Z NAM THE
FASTEST AND CANADIAN THE SLOWEST. 18Z NAM CAME INTO LINE WITH THE
GFS AND ECMWF MIDDLE GROUND TIMING. ENDED UP USING A GFS/NAM/PREVIOUS
FORECAST BLEND FOR FRI NIGHT THRU SUN...THEN WENT WITH WPC FROM
SUN NIGHT ONWARD.

FOR FRI NIGHT AND SAT...A STRONG OVERRUNNING EVENT WILL BE
UNDERWAY BY LATE FRI EVENING. STRONG S-SW FLOW ALOFT WILL RIDE
OVER THE COLD AIRMASS OVER THE AREA. SOME FACTORS THAT INCREASE
THE LIKELIHOOD OF SIGNIFICANT SNOWFALL (6+ INCHES) ARE A FAIRLY
DEEP DENDRITIC GROWTH ZONE ALOFT FRI NIGHT AND EARLY SAT MORNING...AND
INSTABILITY DEVELOPING OVER THE TROWAL AS COLD ADVECTION OCCURS
AT HIGHER LEVELS (600 MB ON UP) LATE FRI NIGHT AND SAT MORNING.
THE ORIENTATION OF THE FRONT WILL TRY TO MAINTAIN SOME N-NE WINDS
OVER THE NRN AREA AS WELL...WHICH SHOULD KEEP PTYPE ALL SNOW
THERE. IT WILL BE MOSTLY SNOW AS WELL OVER THE FAR ERN AREAS OF
THE CENTRAL AND SRN PANHANDLE UNTIL AT LEAST SAT AFTERNOON. HAVE
EXPANDED THE WINTER STORM WATCHES TO INCLUDE THE
HOONAH...GUSTAVUS...AND ELFIN COVE AREAS DUE TO COLD AIRMASS
HOLDING IN PLACE LONGER THAN PREVIOUSLY EXPECTED. BELIEVE THAT
ZONE 28 WILL PROBABLY CONVERT TO A WINTER WEATHER ADVY ONCE
DECISION TO UPGRADE IS MADE...BUT HAVE KEPT THE WATCH GOING THERE
FOR NOW. COULD NEED SOME WIND HEADLINES ESPECIALLY FOR THE SRN
COASTAL AREA.

FOR SAT NIGHT AND SUN...STILL SOME MODEL DIFFERENCES ON HANDLING
HOW MUCH WARMING WILL OCCUR DURING THIS TIME. OTHER CONCERN IS
POTENTIAL FOR LOW PRESSURE WAVE TO KEEP PRECIP GOING OVER THE FAR
SERN AREA DURING THIS TIME. THIS COULD LEAD TO A LONGER DURATION
SIGNIFICANT SNOW EVENT FOR THE HYDER AREA THAN CURRENT WATCH HAS
IT. THINK MUCH OF THE AREA TO THE N WILL SEE MIXED PRECIP AS TEMPS
MODERATE SOME ESPECIALLY SUN...BUT IT LOOKS LIKE BEST CHANCE FOR
PRECIP OVER THE CENTRAL/N WILL BE AROUND THE NE GULF COAST.

AFTER SUN...LARGE SCALE EVOLUTION FAVORS A WARMER PATTERN AS
TROF SETS UP OVER THE GULF AND ERN PAC AND RIDGE BUILDS E OF THE
AREA. THERE WILL BE SEVERAL SYSTEMS COMING IN DURING THIS TIME
WITH MODELS DIFFERING ON TIMING ESPECIALLY AFTER MON NIGHT. LOOKS
LIKE AN OCCLUDED FRONT WILL MOVE IN FOR SUN NIGHT AND MON. LOOKING
MORE LIKELY THAT MOST PRECIP WITH THIS SYSTEM WILL FALL AS RAIN.
THIS WILL LIKELY REMAIN THE CASE WITH FOLLOWING SYSTEMS FOR THE
REST OF THE WEEK. ENDED UP RAISING TEMPS SOMEWHAT FOR SUN NIGHT
INTO LATE WEEK WITH MOST PLACES REMAINING ABOVE FREEZING FOR THE
MOST PART.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     MORNING FOR AKZ026-028.
         WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY MORNING
     FOR AKZ019>022-025.
         WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY MORNING
     FOR AKZ017.
         WINTER STORM WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     AFTERNOON FOR AKZ029.
MARINE...GALE WARNING FOR PKZ012-013-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ022-031-036-041-042.

&&

BEZENEK/RWT

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