Gale Warning 409, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
534 AM AKST MON DEC 15 2014

.SHORT TERM...HIGH DEGREE OF UNCERTAINTY EXISTS IN THE SHORT
TERM...RANGING FROM WIND HAZARDS...WINTER WEATHER...ONSET OF
PRECIPITATION FOR INLAND LOCATIONS...AND TEMPERATURES. THE GENERAL
SYNOPTIC PATTERN APPEARS TO BE STRAIGHT FORWARD. NEGATIVE TILT
TROUGH WILL CONTINUE TO DIG SEWD THROUGH THIS AFTERNOON AS COLD
MIDLEVEL AIR IS INJECTED INTO IT...AND 160+ KT 300 MB JET SPREADS
ESEWD INTO THE NERN PAC. UPPER RIDGE EXISTS DOWNSTREAM FROM THE
TROUGH OVER WRN CANADA...WHILE A SHORTWAVE IMPULSE IS LIFTING N
ACROSS THE NERN GULF THIS MORNING...LIKELY AIDING IN ENHANCED
ASCENT AND ADVISORY LEVEL SNOWFALL W OF HAINES /NEAR THE BORDER/.
BY TONIGHT...THE TROUGH DIGGING E ACROSS THE GULF WILL BECOME
BIFURCATED AS A SHORTWAVE BREAKS OFF AND EJECTS NWD INTO THE NRN
GULF. DETERMINISTIC MODEL GUIDANCE VARIES IN THE EVOLUTION OF THIS
SHORTWAVE. THE 00Z GFS KEEPS THE WAVE OPEN AND MORE
PROGRESSIVE...WHILE THE 00Z NAM AND ECMWF DEVELOP A SMALL CLOSED
LOW RESULTING IN SLOWER NWD MOVEMENT.

AS WOULD BE EXPECTED...THE DIFFERING MIDLEVEL SOLUTIONS YIELD
MAJOR DIFFERENCES AT THE SURFACE. THE GFS AND GEM SHOW A
WEAKER...MORE TROUGH LIKE SURFACE LOW THAT SPINS UP INTO A CLOSED
LOW LATE TONIGHT INTO TUE MORNING AS IT APPROACHES THE NRN GULF
COAST. MEANWHILE...THE NAM AND ECMWF PRODUCE A DEEP CLOSED LOW
FROM THE ONSET OF CYCLOGENESIS THIS MORNING/AFTERNOON OVER THE SRN
GULF...AND MOVE THIS FEATURE TO THE NRN GULF COAST BY MIDDAY TUE.
GIVEN THE CONSISTENCY OF THE ECMWF...AND SUPPORT FROM HIGHER RES
WRF MEMBERS /INCLUDING 12KM NAM/...BLENDED THE NAM/ECMWF WITH
INHERITED PRESSURE GRIDS...BUT ALSO ADDED THE GEM IN ORDER TO
NUDGE SLIGHTLY TOWARD THE POSSIBILITY OF A FASTER MORE OPEN WAVE.

GOING WITH THIS SCENARIO...EXPECT WINDS OVER THE OUTSIDE WATERS TO
STRENGTHEN/PERSIST TO GALE FORCE AS THE LOW PROGRESSES NWD...WITH
WINDS THEN WEAKENING IN ITS WAKE. ONLY EXCEPTION WILL BE MARINE
ZONE 310...WHERE A SECONDARY MAX IN BOUNDARY LAYER WINDS WILL
OCCUR S OF THE LOW CENTER. GAP WINDS ARE ALSO FORECAST TO
STRENGTHEN TO HIGH END SMALL CRAFT OVER CROSS SOUND...WITH STRONG
GUSTS TO 50 KT SPREADING OUT ACROSS MARINE ZONE 43. OVER THE
INSIDE WATERS...A 45-55 KT 925 MB SLY JET WILL BE POSITIONED FROM
CLARENCE STRAIT NWD INTO STEPHENS PASSAGE AND LYNN CANAL. THIS
WILL SUPPORT GALE FORCE WINDS FOR CLARENCE...AND SMALL CRAFT WINDS
IN STEPHENS PASSAGE. THE SURFACE PRESSURE GRADIENT OVER LYNN CANAL
SUGGESTS WINDS SHOULD BE OUT OF THE N THROUGH TONIGHT.
HOWEVER...EXPECT THE LLJ TO OVERCOME THE WEAK SURFACE PRESSURE
GRADIENT...RESULTING IN LIGHT NLY WINDS IN NRN LYNN CANAL...AND
SSELY SMALL CRAFT WINDS IN SRN LYNN. UNCERTAINTY IS HIGH FOR LYNN
CANAL REGARDING WIND DIRECTION AND SPEED...AND WILL NEED TO BE
MONITORED CLOSELY DURING THE DAY SHIFT. ELSEWHERE...MARGINAL
STRONG WINDS WILL BE POSSIBLE IN SITKA THIS MORNING. THEN...A WEAK
FRONTAL BOUNDARY LIKE FEATURE MOVES ONSHORE OVER ZONE 27 LATE THIS
AFTERNOON INTO THE EVENING...WHICH WILL AID IN ACCELERATING WINDS
TO STRONG WIND CRITERIA FOR LOCATIONS SUCH AS HYDABURG.

THE SNOW ADVISORY FOR AREAS W OF KLUKWAN APPEARS TO BE ON TRACK
FOR A NOON EXPIRATION...AS ELY WINDS WILL CONTINUE TO AID IN
GRADUAL WARMING IN THE BOUNDARY LAYER...AND PRECIPITATION RATES
DECREASE AS AN IMPULSE OVER THE NERN GULF EXITS THE REGION. CALM
TO OCCASIONALLY WEAK NLY WINDS HAVE OCCURRED AT SKAGWAY ALL
NIGHT...RESULTING IN THE MAINTENANCE OF SURFACE TEMPERATURES
AROUND 33F. AS A RESULT...SNOW HAS BEEN THE PREDOMINANT
PRECIPITATION TYPE...BUT A CHECK OF SKAGWAY WEBCAMS SHOWS
ACCUMULATIONS HAVE BEEN FAIRLY LIGHT DESPITE RELATIVELY IMPRESSIVE
HOURLY LIQUID AMOUNTS. A SNOW/RAIN IS EXPECTED TO PREVAIL AT
SKAGWAY THROUGH THE MORNING...AND THEN COME TO AN END AFTER
MIDDAY. FARTHER S...DOWNSLOPE WINDS OFF OF THE COAST RANGE
COMBINED WITH WARM SYNOPTIC SLY FLOW HAS PRODUCED VERY LARGE
DEWPOINT DEPRESSIONS /UPWARDS OF 30 DEGREES F/ AT THE
SURFACE...AND TEMPERATURES HAVE REMAINED IN THE 40S TO LOW 50S ALL
NIGHT /AND ARE EXPECTED TO HOLD FAIRLY STEADY THROUGH THE
AFTERNOON DUE TO THE STRONG LOW-LEVEL SLYS/. PREVIOUSLY MENTIONED
WEAK FRONT WILL PROGRESS INLAND OVER THE CNTRL/SRN PANHANDLE
TONIGHT...BUT THE ONSET OF PRECIPITATION MAY BE DELAYED DUE TO THE
PRESENCE OF THE DRY AIR. CURRENT FORECAST INDICATES THE BOUNDARY
LAYER WILL SATURATE BY 09Z TONIGHT...AT WHICH POINT POP/S WILL
BECOME MAXIMIZED DURING THE SHORT TERM PERIOD.

.LONG TERM...GIVEN CONTINUED MODEL SPREAD THROUGH THE REST OF THE
WEEK, THE FORECAST FOR THE PANHANDLE REMAINS GENERAL IN NATURE.
GENERALLY WARM AND WET THROUGH THE NEXT WEEKEND WITH NO SNOW TO
BUILD FROSTY FOR MOST AREAS OF SOUTHEAST.

A SURFACE LOW WILL PULL NORTHWEST INTO THE NORTH CENTRAL GULF
TUESDAY MORNING AND CAUSE A 40 KT BARRIER JET OVER 51 AND 52 FOR
TUESDAY. THIS SYSTEM AND ITS ASSOCIATED FRONT WILL ENHANCE
PRECIPITATION ACROSS THE PANHANDLE TUESDAY. LAPSE RATES WILL BEGIN
TO STEEPEN BEHIND THE FRONT THUS PRECIPITATION WILL FALL FROM
SHOWERS. DESPITE THE COOL AIR FILTERING THROUGH, THICKNESSES DO
NOT SUGGEST SNOW AND NOR WILL TEMPERATURES FOR THE MOST PART. EVEN
HAINES AND SKAGWAY WILL EXPERIENCE RAIN SHOWERS, DUE TO THE FRONT
INDUCING A SOUTHERLY GRADIENT THROUGH THE CANAL. WITH CLOUDY AND
SOME BREEZY CONDITIONS, ANY COOLING WILL BE SLOW.

SOME DRYING STILL SCHEDULED TO TAKE PLACE WEDNESDAY AS SHORT-TERM
RIDGING DEVELOPS BEFORE A POSSIBLE NEXT SYSTEM. THIS SYSTEM SHOULD
IT ARRIVE IN THE CENTRAL GULF BY WEDNESDAY MORNING IS SUBJECT TO
DEBATE REGARDING STRENGTH AND POSITION, AND IN THE CASE OF THE
GFS...EXISTENCE. THE ECMWF HAS BEEN THE MOST STALWART OF THIS
FEATURE AND HAS STRENGTHENED IT OVER THE LAST COUPLE OF RUNS. THE
NAM HAS ALSO BEEN INDICATING IT, BUT ADVERTISING MORE OF A WAVE
THAN A CLOSED LOW. MEANWHILE THE GEM'S LATEST RUN SEEMED TO LATCH
ONTO IT WHEREAS THE PREVIOUS RUN CAST DOUBT. AT THIS POINT, EVEN
AMONG MODELS SUGGESTING A LOW, THERE IS LITTLE CONSENSUS ON
LOCATION. AS THIS IS A NEW FEATURE, WE PREFERRED TO NOT JUMP ON A
RUSHED INTRODUCTION, AS THIS WOULD PRESENT A SIGNIFICANT AND BUMPY
CHANGE TO MAKE REGARDING WINDS. HOWEVER, WE DID ENSURE ALL AREAS
OF THE PANHANDLE HAVE AT LEAST A CHANCE OF RAIN WEDNESDAY NIGHT TO
COVER A CONTINGENCY FOR A LOW IN THE GULF.

BEYOND MID-WEEK, MODELS RELATIVELY UNITE WITH A LARGESCALE NORTH
PACIFIC LOW SETTLING IN THE GULF SPREADING GALE FORCE WINDS ACROSS MUCH
OF THE EASTERN GULF AND SENDING PRECIPITATION FROM ROTATING SHORT-
WAVES AND FRONTS ACROSS THE PANHANDLE. WITH THE EXCEPTION OF HAINES/
SKAGWAY...THE EXTENDED FORECAST COULD BE SUMMED UP PANHANDLE
WIDE...RAIN LIKELY TEMPERATURES AROUND 40 DEGREES. BREEZY FROM
TIME TO TIME. FROSTY THE SNOWMAN WILL HAVE SEEN BETTER DAYS.

FORECAST CONFIDENCE LOWER THAN AVERAGE ON WINDS...ESPECIALLY FROM
WEDNESDAY ONWARD. BETTER FOR PRECIPITATION AND P-TYPE. USED
ENSEMBLE ECMWF, NAM, AND GEM FOR CHANGES TUESDAY.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM NOON AKST TODAY THROUGH THIS AFTERNOON FOR
     AKZ027.
         STRONG WIND UNTIL 9 AM AKST THIS MORNING FOR AKZ023.
         WINTER WEATHER ADVISORY UNTIL NOON AKST TODAY FOR AKZ019.
MARINE...GALE WARNING FOR PKZ033-035-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ013-021-022-031-034-053.

&&

GARNER/ADKINS

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
745 AM AKST MON DEC 15 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0741 AM     HEAVY SNOW       40 NW HAINES            59.65N 136.25W
12/15/2014  M7.0 INCH        XXX                XX   CO-OP OBSERVER

            HAINES CUSTOMS REPORTS THAT THIS SNOW FELL MAINLY
            OVERNIGHT.

&&

GLS