Gale Warning 327, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
242 PM AKST SUN NOV 2 2014

.SHORT TERM...AFTERNOON SATELLITE IMAGE REVEALS A WEAKENING LOW
NEAR KENAI PENINSULA WITH A TROUGH STRETCHING EAST ALONG THE
NORTHERN GULF COAST TO SOUTHEAST ACROSS THE PANHANDLE. RAIN
SHOWERS CONTINUE OVER SOUTHEAST ALASKA WITH SOUTHERLY WINDS 20 TO
25 MPH AND OCCASIONAL HIGHER GUSTS AT SKAGWAY...HAINES AND JUNEAU
AREAS. SOUTHWESTERLY WINDS 15 TO 25 KNOTS PREVAIL OVER THE OUTER
WATERS WITH ROUGH SEAS 12 TO 16 FEET. SMALL CRAFT LEVEL SOUTHERLY
WINDS CONTINUE OVER THE NORTHERN INNER CHANNELS. NO LIGHTNINGS
HAVE BEEN DETECTED SO FAR...BUT CONDITIONALLY UNSTABLE ATMOSPHERE
WILL CONTINUE TO SUPPORT THE NORTHEASTERN GULF COAST FOR A SLIGHT
CHANCE OF THUNDERSTORMS. AFTERNOON TEMPERATURES REMAIN IN THE
LOWER TO MID 40S...EXCEPT IN THE UPPER 40S ACROSS THE SOUTHERN
COASTAL SECTIONS. NEAR HYDER...TEMPERATURES STEADY IN THE UPPER
30S.

MODELS REMAIN IN GENERAL AGREEMENT FOR THE WEAKENING LOW OVER THE
NORTHWESTERN GULF MOVES SOUTH OF KODIAK ISLAND THROUGH MONDAY
BEFORE DISSIPATING BY MONDAY NIGHT. A DEVELOPING STORM FORCE LOW
WILL ENTER THE SOUTHEASTERN GULF EARLY ON MONDAY AND TRACK NORTHWARD
ALONG THE OUTER COAST. REFRESHED THE INHERITED FORECAST PACKAGE
WITH THE MOST CONSISTENT ECMWF SOLUTIONS FOR TONIGHT AND MONDAY.
MAIN FORECAST CONCERN STAYS ON THE DEVELOPING STORM FORCE LOW OVER
THE NORTHEASTERN PACIFIC...MOVING INTO THE SOUTHEASTERN GULF EARLY
MONDAY MORNING.

BEHIND THE TRAILING EDGE OF THE WEAKENING TROUGH OVER THE
PANHANDLE...PRESSURE GRADIENT ACROSS THE NORTHERN INNER CHANNELS
WILL RELAX AND EXPECT DECREASING SOUTHERLY WINDS LATE IN THE
EVENING BEFORE SHIFTING TO THE NORTHERLY FLOW EARLY ON MONDAY.
AHEAD OF THE INCOMING LOW FROM THE SOUTHWEST...SOUTHEASTERLY WINDS
WILL PICKUP SMALL CRAFT LEVEL OVER THE SOUTHERN COASTAL WATERS ON
MONDAY MORNING...BECOMING GALE FORCE BY THE AFTERNOON. AS THE LOW
TRACKS NORTHWARD ALONG THE OUTER COAST...NORTHERLY PRESSURE
GRADIENT WILL ONCE AGAIN BECOME TIGHT ACROSS THE NORTHERN INNER
CHANNELS MONDAY MORNING INTO THE AFTERNOON HOURS. POSTED STRONG
WIND HEADLINES FOR SOUTHWESTERN PANHANDLE COASTS AND THE
NORTHERNMOST PANHANDLE AREAS. AS MID LEVEL DYNAMICS WEAKEN...EXPECT
RAIN SHOWERS WILL CONTINUE DIMINISHING ACROSS THE YAKUTAT AND
NORTHERN PANHANDLE THROUGH LATE MONDAY. FOR THE REMAINING
SOUTHEAST ALASKA...HOWEVER...DISSIPATING MID LEVEL DYNAMICS WILL
DIMINISH SHOWERS MOMENTARILY LATE TONIGHT INTO EARLY MONDAY
MORNING BEFORE THE INCOMING LOW FROM THE SOUTH SPREADING ANOTHER
ROUND OF WET WEATHER.

.LONG TERM...ON MONDAY PM (06Z TUES) THE WELL-ADVERTISED 980 MB LOW
SHOULD BE POSITIONED JUST SOUTH OF SITKA, MOVING NORTHWARD.
MODELS GENERALLY AGREE ON THIS SYSTEM, FINALLY, AND PREVIOUS
FORECAST PACKAGE HAS SET IT UP WELL...VARIOUS OFFSHORE GALES,
STRONG WIND HEADLINES IN 3 ZONES (23, 27 AND THE FAR NORTH), AND
GALES FOR CLARENCE, FREDERICK, NORTHERN LYNN, AND AND SUMNER
BUMPING UP TO THIS TIME PERIOD (03Z TUES). HAVE CONTINUED STRONG
WINDS THROUGH TUES MORNING FOR 23 AND 27, AS WELL AS SLIGHT
THUNDERSTORM CHANCES FOR 27 28 AND SOUTH OFFSHORE THROUGH 21Z
TUES. WE HAVE ELECTED TO NOT INCLUDE STRONG WINDS ON TUES IN ZONES
INLAND ELSEWHERE AS LOW IS FAIRLY COMPACT AND IT IS DEBATABLE HOW
MUCH IMPACTED AREAS WILL HAVE 40MPH GUSTS IN 22-26. DECIDED IT
WOULD ONLY BE ISOLATED SMALL AREAS BUT IT IS CERTAINLY POSSIBLE.
OTHERWISE ONLY SOME MINOR QPF AND POP TWEAKS PER LATEST GUIDANCE
WERE NECESSARY.

THEN TO THE SECOND BIG PROBLEM WITH THIS LONGWAVE TROUGH...THE SECOND
GALE+ LOW THAT MOST MODELS AGREE WILL TRACK UP THE COAST LATER ON
WED WITH PRESSURES AS LOW AS 975-980ISH MB, JUST AS PREVIOUS
FORECASTER FEARED. MODELS HAVE NARROWED THE POSSIBILITIES
SIGNIFICANTLY AND WE UPDATED DYNAMIC MODEL FIELDS BEGINNING AT 15Z
WED OR SO AS THE 12Z EC/GFS/GEM MODELS ALL FORM A STRONGER LOW
THAN PREVIOUS RUNS. USED AN ENSEMBLE APPROACH WITH THESE MODELS
FOR THE UPDATES. FROM 12Z THURS WE MIGRATED ON TO PRIMARLY HPC
GUIDANCE. LOOKS LIKE ANOTHER SHOT OF SIGNIFICANT RAIN AND VERY
STRONG WINDS, AT LEAST GALE- FORCE IN MANY AREAS, WITH THE WED SYSTEM.
THE NAM WAS REALLY THE ONLY MODEL NOT ON BOARD WITH THIS AND HENCE
THE MAJOR CHANGES TO GRIDS. THINGS SHOULD GET SERIOUS BY THE
21-00Z PERIOD ON WED. BEGINNING IN THE SOUTH WITH STRONG GRADIENTS
SUPPORTING RAPIDLY INCREASING ESE WINDS. LOOKS AT THIS POINT LIKE
GALES OVER THE SOUTHERNMOST CHANNELS WHICH WILL MIGRATE STEADILY
NORTHWARDS AND INCLUDE LYNN BY 06-09Z THURS. STRONGEST WINDS AS USUAL
WILL BE PRIMARILY CHANNEL- DRIVEN. LOW CIRCULATION STAYS OFFSHORE,
PARALLELS COAST BUT CLOSE, JUST OFF SITKA AND CROSS SOUND AT 985
MB ON THIS ENSEMBLE FOR 09-12Z THURS. RAINFALL TOTALS WILL LIKELY
BE IN THE 1-2" RANGE BUT MUCH HIGHER AMOUNTS WILL BE HARD TO GET
WITH THE PROGRESSIVENESS OF THE SYSTEM...HOWEVER MUDSLIDE
POSSIBLITIES WILL CONTINUE. WINDS AND RAINIEST AREAS WILL
OBVIOUSLY DEPEND ON THE EXACT TRACK OF THE SYSTEM AND SINCE IT IS
3 DAYS AWAY MODELS THERE IS UNCERTAINTY ON THIS. THE SYSTEM THEN ON
THURSDAY WEAKENS FAIRLY RAPIDLY AND MOVES OFF TO THE NW...WHETHER
THIS ACTUALLY HAPPENS IS DIFFICULT TO ASCERTAIN UNTIL UPDATED
MODEL GUIDANCE BECOMES AVAILABLE. ANOTHER LOW MOVES RAPIDLY INTO
THE GULF ON THURS NIGHT/FRI AND AT THIS POINT ON MODELS MOST OF
THE DYNAMICS STAY OVER THE WESTERN GULF...ITS IMPACT WILL LIKELY
NOT BE AS LARGE AS THE TWO SYSTEMS EARLIER THIS WEEK, AND SOME
MODELS ADVERTISE A BIT OF A WEEKEND BREAK AFTER THIS SYSTEM.

THOUGH SYSTEMS STEADILY ARE GETTING COLDER, IT APPEARS THAT WITH
THE GIVEN STORM TRACK SNOW CHANCES AT SEA LEVEL THROUGH THE WEEK ARE
STILL MARGINAL. WE HAVE CHANCES IN THE NORTHERN/CENTRAL AND HYDER ZONES
FROM MID- WEEK ONWARD AND IT WILL HAPPEN AT SOME POINT BUT LIKELY
NOT UNTIL AT LEAST THURS...TOO EARLY TO TELL EXACTLY WHEN. OVERALL
MODEL CONFIDENCE IS AVERAGE FOR THE PERIOD AND MOST MODELS ARE
CONVERGING ON WHAT APPEARS TO BE A COHERENT SOLUTION FOR THE WED
LOW. AFTER THAT POINT MODEL DIVERGENCE INCREASES SIGNIFICANTLY.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR
     AKZ027.
         STRONG WIND FROM MONDAY AFTERNOON THROUGH LATE MONDAY NIGHT FOR
     AKZ023.
         STRONG WIND MONDAY AFTERNOON FOR AKZ018-019.
MARINE...GALE WARNING FOR PKZ012-034>036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031>033-051-052.

&&

AHN/WESLEY

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