Storm Warning 6, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
314 PM AKST SUN JAN 17 2016

.SHORT TERM...SATELLITE IMAGERY AND SURFACE WEATHER OBSERVATIONS
INDICATE THE STORM FORCE 969 MB LOW CENTER IS ABOUT 200 NM WSW OF
CRAIG AT 3 PM/00Z. IT HAS BEEN MOVING NW ABOUT 30 KT PARALLEL TO
THE PANHANDLE COAST. HIGH WIND WARNING FOR WINDS AT OR ABOVE 60
MPH REMAINS IN EFFECT FOR ZONE 27 THROUGH 9 PM SUNDAY.

OBSERVATIONS ALONG COASTAL BRITISH COLUMBIA SUN AFTERNOON INCLUDE
WIDE SPREAD WIND GUSTS OF 50-55 KT. STRONGEST WINDS SEEM TO BE
ASSOCIATED WITH INNER CURLS OF OCCLUDED FRONT WRAPPED AROUND THE
LOW CENTER. HI RESOLUTION NAM MODEL MAINTAINS 70 KTS WIND BETWEEN
1000 AND 2000 FT MSL ALG THE ERN PERIPHERY OF THE LOW. MIXING
THESE LOW LEVEL WINDS DOWN TO THE SURFACE IS LIKELY AND HENCE
WIND WARNING JUSTIFIED. WIND SHEAR WILL IMPACT SE AK AIRPORTS
TONIGHT. SRN PANHANDLE WIND GUSTS REACHING 40-50 MPH SO FAR. MAIN
IMPACTS OF WIND SHOULD BE BETWEEN 4 PM AND 9 PM.

EXTRAPOLATING STORM MOVEMENT COINCIDES WITH MODEL CONSENSUS AND
KEEPS THE TRACK OF THIS LOW CENTER HEADED THROUGH THE OFFSHORE
WATERS ZONE OVERNIGHT AND GRADUALLY WEAKENING. THERE IS PRECIP
WITH THE ASSOCIATED SURFACE FRONT BEGINNING TO SPREAD INTO THE
SOUTHERN PANHANDLE. PRECIP SHOULD STEADILY LIFT NORTH INTO MONDAY
BUT AMOUNTS MAY BE MINIMIZED BY DOWNSLOPING EASTERLY WINDS OVER
COASTAL MTNS. RAIN UP TO ONE INCH POSSIBLE ALONG EXTREME OUTER
COAST AND GENERALLY HALF INCH OR LESS MOST OF INNER CHANNELS
THROUGH MON AFTERNOON. PRECIP EXPECTED TO BE RAIN MOST ALL AREAS
DUE TO WARMER SLY ORIGINS OF THIS SYSTEM. HOWEVER, LOCALLY TRAPPED
COLD AIR INNER CHANNELS AND ESPECIALLY LYNN CANAL WILL LIKELY
CAUSE PRECIP AS SNOW. 1-4 INCHES OF SNOW MENTIONED THERE MAINLY
INLAND AWAY FROM WATERWAYS.

A NEW BUT WEAKER GALE WILL FOLLOW NNW ALONG THE COAST MON NIGHT AT
THE START OF THE LONG TERM PERIOD. MODELS SHOW IT TAKING A VERY
SIMILAR PATH AS TONIGHTS STORM. SEE DISCUSSION BELOW. MADE ONLY
MINOR ADJUSTMENTS TO EXISTING GRIDDED FORECASTS USING THE HI
RESOLUTION NAM. CONFIDENCE ON EVOLUTION OF WIND AND RAIN TONIGHT
AND MON IS AT OR ABOVE AVERAGE. CONFIDENCE ON SNOW AMOUNTS NRN
INNER CHANNELS NOT AS HIGH.

.LONG TERM...ANOTHER GALE FORCE LOW MOVES UP INTO THE AK GULF FROM
THE SOUTH MONDAY NIGHT INTO TUESDAY AS THE REMNANTS OF THE
CURRENT GALE FORCE LOW TRACK WESTWARD TOWARD KODIAK. THIS NEW
SYSTEM WILL FOLLOW A SIMILAR TRACK, JUST CENTERED MORE TO THE
WEST AND A BIT WEAKER, THUS EXPECTING LOWER WINDS OVER THE
PANHANDLE. WINDS WILL DROP OFF AFTER THIS SYSTEM TRACKS WEST
THROUGH TUESDAY JUST A ANOTHER GALE FORCE LOW MOVES UP FROM THE
SOUTH TRACKING NORTH NORTHWEST THROUGH THE AK GULF. LATEST MODEL
RUNS HAVE THIS LOW DEEPER THAN PREVIOUS RUNS AND THUS HAVE STARTED
TO INCREASE WINDS OVER THE GULF. DID NOT GO AS HIGH AS LATEST
MODEL RUNS, WOULD LIKE TO SEE MODELS STABILIZED A BIT MORE. THIS
SYSTEM WILL LINGER OVER THE AK GULF WHILE WEAKENING THROUGH
SUNDAY. INNER CHANNEL WINDS WILL BE MAINLY NORTHERLY WITH EASTERLY
OUTFLOW BETWEEN THE GULF LOWS AND HIGH PRESSURE OVER WESTERN
CANADA.

EACH SYSTEM THROUGH THE WEEK BRINGS IN ANOTHER BAND OF
PRECIPITATION MOVING NORTHWARD. OVERALL THINK THE SOUTHERN PORTIONS
WILL GET THE BRUNT OF THESE BANDS AS THEY WILL BEGIN TO SHEAR AS
THEY MOVE NORTH. CONTINUED THE TREND TO TONE DOWN MODEL QPF
AMOUNTS WITH THE NEXT SYSTEMS DUE TO THE EASTERLY FLOW.
TEMPERATURES HAVE BEEN TRICKY THE PAST FEW DAYS. NOT GETTING A
GOOD CONSENSUS ON SURFACE TEMPS BUT OVERALL MODEL 1000-850 MB
THICKNESS KEEP A RAIN-SNOW LINE JUST NORTH OF JUNEAU. MOS
GUIDANCE STARTED TO SHOW SOME COOLER TEMPS BUT NO ONE MODEL HAS
BEEN HANDLING IT WELL. EITHER THEY KEEP THE NORTH TOO WARM OR DROP
THE RAIN SNOW LINE TOO FAR SOUTH. WITH THE SOUTHERLY TRACK OF THE
SYSTEM AND EASTERLY OUTFLOW AND DOWN SLOPE WINDS THINK THE CENTRAL
PANHANDLE WILL BE MAINLY RAIN WITH SOME SNOW MIXED IN OVERNIGHT,
THE NORTHERN PANHANDLE WILL HAVE MORE SNOW, BUT FOR NOW NO MAJOR
ACCUMULATIONS WHILE THE SOUTH WILL KEEP PRECIP AS RAIN. THE
EXCEPTION BEING WIND SHELTERED LOCATIONS WHERE TEMPS WILL BE AT OR
BELOW FREEZING AND MAY BE COLD ENOUGH MORE MORE SNOW IN THE RAIN
SNOW MIX.

WHILE MODELS HAVE NOT HAVE BEEN HANDLING TEMP WELL GETTING FAIR
AGREEMENT BETWEEN THE 12Z GFS/ECMWF AND NAM FOR THE NEXT FEW DAYS
FOR TRACK OF THE GULF LOWS. GEM BECAME AN OUTLIER VERY EARLY SO
WAS IGNORED. USED A BLEND OF 12Z GFS/ECMWF TO UPDATE INHERITED
GRIDS THROUGH DAY 4. THIS BUMPED UP SOME WINDS OVER THE INNER
CHANNELS BUT OVERALL FORECAST REMAINED THE SAME. DAY 5 ONWARD USED
NEW WPC FOR AN ENSEMBLE BLEND, WHICH HAD THE BIGGEST CHANGE
INCREASING WINDS OVER THE AK GULF. FORECAST CONFIDENCE IS AVERAGE
FOR THE SYNOPTIC PATTERN THROUGH THE WEEK BUT LOWER CONFIDENCE
WITH MESOSCALE DETAILS SUCH AS TEMP AND QPF.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING UNTIL 9 PM AKST THIS EVENING FOR AKZ027.
         STRONG WIND FROM 9 PM THIS EVENING TO 3 AM AKST MONDAY FOR
     AKZ027.
         STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ025.
         STRONG WIND UNTIL 3 AM AKST MONDAY FOR AKZ023.
         STRONG WIND UNTIL 3 AM AKST MONDAY FOR AKZ028.
MARINE...STORM WARNING FOR PKZ041>043.
         GALE WARNING FOR PKZ012-022-033-034-036-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-031-032-035-053.

&&

TA/PRB

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