Gale Warning 402, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
355 PM AKST FRI NOV 20 2015

.SHORT TERM...A STRONG OCCLUDED FRONT WILL MOVE ACROSS THE EASTERN
GULF TONIGHT AND SE ALASKA SAT. A STRONG LOW WILL MOVE NE TO THE
FAR NW GULF BY LATE TONIGHT...THEN WEAKEN SLOWLY NEAR PRINCE
WILLIAM SOUND SAT. MODELS WERE IN GOOD AGREEMENT ON THE MAIN
FEATURES.

MAIN FORECAST CONCERNS WILL BE WINDS...PRECIP AMOUNTS/PTYPE...AND
TEMPS. WINDS WILL PICK UP OVER MUCH OF THE AREA TONIGHT AS
OCCLUDED FRONT MOVES CLOSER TO THE AREA. LOOKS LIKE THE STRONGEST
WINDS WILL BE OVER THE NW HALF OF THE AREA...NEAREST TO THE UPPER
JET CORE AND LOW LEVEL JET AXIS. MUCH OF THAT AREA WILL HAVE GALE
FORCE WINDS TONIGHT AND SAT...WITH STORM FORCE WINDS EXPECTED FOR
CROSS SOUND LATE TONIGHT AND NRN LYNN CANAL SAT MORNING AFTER
FRONT MOVES THRU. THERE WILL ALSO BE A BAND OF GALE FORCE WINDS ON
S SIDE OF LOW MOVING INTO THE NRN GULF LATE TONIGHT AND SAT. THERE
WILL BE GALE FORCE WINDS OVER THE CENTRAL TO E-CENTRAL GULF
TONIGHT WITH THE OCCLUDED FRONT MOVING THRU. DECIDED TO GO WITH A
HIGH WIND WARNING FOR THE PAGY AREA LATE TONIGHT AND SAT AS
STRENGTH OF CROSS BARRIER FLOW AND SLY PRESSURE GRADIENT BOTH
SUPPORT WIND GUSTS TO 65 MPH ESPECIALLY SAT MORNING. ALSO...MUCH
OF THE NRN AND CENTRAL AREAS AND SRN COAST WILL SEE STRONG WINDS
AHEAD OF THE FRONT...WITH THE PAYA AREA GETTING INTO THE STRONG
WINDS SAT AS WSW FLOW INCREASES THERE ON SE SIDE OF LOW.

PRECIP WILL BE LOCALLY HEAVY ESPECIALLY ON THE SW FACING TERRAIN
AHEAD OF THE FRONT. RAINFALL UP TO 4 INCHES IS LIKELY BY LATE SAT
MORNING ALONG THE FAVORED SLOPES. THERE MAY BE CONSIDERABLE RAIN
SHADOWING WITH THIS SYSTEM ON ERN SLOPES AS LOWER LEVELS OF
ATMOSPHERE ARE ONLY WEAKLY STABLE...SO RAINFALL AMOUNTS WILL VARY
GREATLY OVER SHORT DISTANCES. THE SNOW LEVEL WILL RISE TO AROUND
3500 FEET OVER THE FAR N AND 7000 FEET OVER THE S TONIGHT...THEN
FALL ON SAT AS COLDER AIR MOVES IN BEHIND THE OCCLUDED FRONT.
RIGHT NOW WE ARE NOT EXPECTING ANY RIVER OR STREAM FLOODING BUT
PONDING OF WATER ON ROADS COULD BE AN ISSUE WHERE DEEPER SNOW
REMAINS. PRECIP WILL TRANSITION TO SHOWERS SAT BUT WITH DEPTH OF
UNSTABLE LAYER ONLY INCREASING GRADUALLY...THERE MAY BE MORE
BREAKS IN BETWEEN THE INDIVIDUAL SHOWERS AND BETWEEN THE
STRATIFORM TO CONVECTIVE TRANSITION AFTER FROPA. THE DEEPEST
INSTABILITY WILL BE OVER THE NRN GULF AND ADJACENT COASTAL AREA
SAT...SO EXPECT THE HEAVIEST SHOWERS THERE.

TEMPS WILL GENERALLY REMAIN STEADY OR RISE SLOWLY TONIGHT...WITH
MOST AREAS NEAR SEA LEVEL WELL INTO THE 40S BY LATE TONIGHT. MOST
OF THE ZONE FORECASTS WILL HAVE THAT TEMPERATURE TREND FOR
TONIGHT. HAVE DECIDED TO KEEP THE BLIZZARD WARNING GOING UNTIL
6 PM FOR WHITE PASS...WITH MAINLY THE VERY TOP OF THE PASS HAVING
ANY REMAINING BLIZZARD CONDITIONS AS TEMPS ARE CLOSE TO FREEZING
NOW. WARMING TEMPS TO ABOVE FREEZING WILL END THE BLIZZARD THREAT
EARLY IN THE EVENING IN WHITE PASS. THEN...MOST OF THE NRN AND
CENTRAL AREAS WILL SEE TEMPS PEAK SAT MORNING THEN FALL SLOWLY
DURING THE AFTERNOON AFTER FROPA ...WHILE THE SRN AREA WILL SEE
TEMPS TEND TO REMAIN STEADY OR RISE ONLY ANOTHER DEGREE OR TWO
BEFORE STEADYING DURING THE DAY SAT.

.LONG TERM...FORECAST LARGELY REMAINS ON TRACK. WESTERLIES AND
SOUTHERLIES WILL BE DIMINISHING SATURDAY NIGHT AS THE FRONT FROM
ABOVE TRACKS TO THE EAST ALLOWING COLDER AIR TO FILTER THROUGH THE
REGION. HOWEVER, WINDS SHOULD REMAIN STRONG WITH 40MPH INTO THE
EVENING FOR AREAS SUCH AS HAINES, GUSTAVUS, ELFIN COVE, AND
POSSIBLY JUNEAU SATURDAY EVENING. SKAGWAY AND WHITE PASS WILL SEE
WINDS REMAIN STRONG THROUGH THE NIGHT. ATMOSPHERIC COLUMN
TEMPERATURES WILL BE COLD ENOUGH TO SUPPORT SNOW BEGINNING TO MIX
IN WITH THE RAIN SHOWERS EVEN AT SEA LEVEL BEGINNING SATURDAY
EVENING ONCE AGAIN. THICKNESSES FALL BELOW 1290 LINE FAIRLY
QUICKLY IN THE EVENING. BUT GIVEN TEMPERATURES AND TRAJECTORY OF
COLD AIR ACROSS THE WATER, WE RELIED ON A MORE CONSERVATIVE RAIN-
SNOW LINE OF 1288 M THICKNESS WITHIN THE 1000-850 MB LAYER. SURFACE
TEMPERATURES THOUGH SHOULD REMAIN ABOVE FREEZING FOR MOST OF THE
NORTHERN PANHANDLE DURING THE NIGHT. BUT HEAVIER SHOWERS MAY
ACCUMULATE SNOW AT SUCH A RATE TO YIELD AN INCH OR
TWO...ESPECIALLY WHERE OROGRAPHICS AID IN THE INSTABILITY SUCH AS
JUNEAU. LOW TEMPERATURES FOR SATURDAY NIGHT WILL ACTUALLY BE
DELAYED UNTIL MID-MORNING SUNDAY, AFTER WHICH THERE WILL BE VERY
LITTLE WARMING INTO THE AFTERNOON...AS COLD AIR ADVECTION
CONTINUES TO OVERWHELM MORE THE MORE TYPICAL DIURNAL TEMPERATURE
CHANGES. AFTER THIS SIGNIFICANT WARM UP ACROSS THE
PANHANDLE...SUNDAY SHOULD FEEL COLD AGAIN.

AS THE SYSTEM SINKS TO THE SOUTHEAST AND OFFSHORE COMPONENTS TAKE
OVER IN THE MID-LEVELS ACROSS THE PANHANDLE...SHOWERS WILL BEGIN
DIMINISHING RAPIDLY SUNDAY NIGHT. THIS WILL ALSO ALLOW SKIES TO
BEGIN CLEARING LATE SUNDAY NIGHT INTO MONDAY. HIGH PRESSURE SETS
UP IN CANADA, AND COUPLED WITH A THERMAL THROUGH HANGING ACROSS
THE CENTRAL AND SOUTHERN PANHANDLE, A WEAK OUTFLOW EVENT MAY SET
UP. AT THIS TIME...NOTHING TOO STRONG. SOME NORTHERLY BREEZES
THROUGH SKAGWAY AND NORTHEASTERLIES INTO DOWNTOWN JUNEAU. PERHAPS
MORE IMPORTANTLY...CLEARING SKIES WILL MAXIMIZE RADIATIONAL
COOLING EVEN WITHIN AN ALREADY CHILLY AIR MASS. THUS WE ARE
LOOKING AT TEMPERATURES IN THE TEENS OVER MUCH OF THE NORTH FOR
LOWS MONDAY NIGHT AND TUESDAY NIGHT WITH SINGLE DIGITS POSSIBLE TO
THE FAR NORTH IN HAINES AND SKAGWAY. TWENTIES WILL EXPAND EVEN TO
THE COAST AND TO THE FAR SOUTHERN ZONES. THERE LOOKS TO BE A
WARMUP INTO THE THANKSGIVING HOLIDAY AS THE STORM TRACK ONCE AGAIN
BECOMES MORE ACTIVE IN THE WESTERN GULF ALLOWING SOUTHERLIES TO
RAISE TEMPERATURES...ESPECIALLY THURSDAY INTO FRIDAY.

ONE ISSUE THAT WE HAVE TOUCHED CONCERNS IMPACTS ON TRAVEL SHOULD
FOG DEVELOP ACROSS THE PANHANDLE. CONFIDENCE IS NOT HIGH, AND OUR
SKILL LEVEL IS NOT GOOD ENOUGH TO GO WITH FOG THIS EARLY, BUT AIR
TRAVELERS OUT OF JUNEAU, PETERSBURG, WRANGELL, KETCHIKAN MAY NEED
TO KEEP ABREAST WITH THE WEATHER TUESDAY INTO WEDNESDAY. IT STILL
REMAINS A POSSIBILITY THAT COULD IMPACT FLIGHTS. FERRY SERVICE
SHOULD BE LESS IMPACTED AS WINDS SHOULD NOT BE AN ISSUE.

WE ADDED SOME RAIN/SNOW CHANCES TOWARD FRIDAY AFTER
THANKSGIVING...BUT THIS QUICKLY LOOKS TO TURN MORE LIQUID AS NEXT
WEEKEND DRAWS CLOSER.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH LATE TONIGHT FOR
     AKZ026.
         STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH LATE TONIGHT FOR
     AKZ027.
         STRONG WIND UNTIL 6 PM AKST THIS EVENING FOR AKZ025.
         STRONG WIND FROM MIDNIGHT AKST TONIGHT THROUGH SATURDAY
     AFTERNOON FOR AKZ025.
         STRONG WIND THROUGH SATURDAY EVENING FOR AKZ019-022.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ023.
         STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH SATURDAY EVENING
     FOR AKZ020.
         STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH SATURDAY
     AFTERNOON FOR AKZ021.
         HIGH WIND WARNING FROM 3 AM TO 6 PM AKST SATURDAY FOR AKZ018.
         BLIZZARD WARNING UNTIL 6 PM AKST THIS EVENING FOR AKZ018.
         STRONG WIND FROM 3 AM AKST SATURDAY THROUGH SATURDAY AFTERNOON
     FOR AKZ017.
MARINE...STORM WARNING FOR PKZ012-022.
         GALE WARNING FOR PKZ011-013-021-031>034-041>043-051>053.
         SMALL CRAFT ADVISORY FOR PKZ035-036.

&&

RWT/JWA

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