Gale Warning 406, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE JUNEAU AK
739 AM AKST SUN DEC 14 2014

.SHORT TERM.../ SUNDAY AND SUNDAY NIGHT / FORECAST PROGRESSING ON
TRACK WITH THE GULF LOW NOW SOUTHEAST OF KODIAK ISLAND AND THE
UPPER LEVEL TROUGH ASSOCIATED WITH THE SURFACE FEATURE NEGATIVELY
TILTED. THE SURFACE FRONT LIES ALONG THE TROUGH AXIS AND IS
ROUGHLY STALLED OVER THE EASTERN HALF OF THE GULF ALONG THE
OUTER COAST. CLOUDS AND RAIN ARE STREAMING NORTHWEST ALONG THE
COAST OCCASIONALLY SPREADING SOME RAIN TO THE COASTAL LAND AREAS
FROM DIXON ENTRANCE TO CROSS SOUND. THE FLOW PATTERN IS MORE
ONSHORE FROM YAKUTAT TO PRINCE WILLIAM SOUND WITH HEAVIEST
PRECIPITATION WEST OF YAKUTAT.

THE MARINE WINDS ARE 40 TO 50 KT AND BUOYS ARE REPORTING SEAS OF
18 TO 21 FEET SUNDAY MORNING. THE FRONT WILL MAKE VERY SLOW
EASTWARD MOVEMENT BUT THE WINDS AND SEAS WILL HANG ON FOR MOST OF
THE DAYLIGHT PERIOD OVER THE COASTAL WATERS THEN TRY SO SUBSIDE A
LITTLE TO 30 TO 45 KT DEPENDING ON LOCATIONS. SMALL SHORT WAVES
IN THE UPPER FLOW WILL SUPPORT SMALL INCREASES IN THE WINDS ALONG
THE FRONT AS THEY RUN NORTHWEST.

THE OUTER COASTAL EXPOSED AREAS WILL BE BLOWING FROM 30 TO 40 MPH
TODAY. HAVE SOME STRONG WIND HEADLINES THIS MORNING BUT THINK THEY
WILL LET UP A LITTLE DURING THE DAY THEN STRENGTHEN AGAIN OVER
NIGHT.

MAJORITY OF THE RAINFALL WILL BE OVER THE FAR NORTHERN PANHANDLE
AND NORTHEAST GULF COAST WHILE THE INNER CHANNELS FROM JUNEAU TO
WRANGELL MAY END UP IN THE DRIER AIR. THERE IS A SLIGHTLY HIGHER
CHANCE FOR PRECIPITATION OVER THE SOUTHERN PORTION OF THE PANHANDLE
AS IT WILL BE THE FIRST OF THE HIGHER TERRAIN TO PROVIDE OROGRAPHIC
LIFTING AS THE AIRMASS STREAMS TO THE NORTHWEST. FLOW PATTERNS LIKE
THIS ARE MORE LIKELY DRY UNTIL THE FRONT IS NEARLY ONSHORE THE
PANHANDLE.

LONG TERM...UPPER TROUGH CURRENTLY AMPLIFYING OVER THE ALEUTIANS
WILL DIG ACROSS THE SRN GULF MON MORNING...AND THEN EJECT INTO THE
NRN GULF THROUGH MON NIGHT. INDIVIDUAL DETERMINISTIC MODEL
SOLUTIONS HANDLE THE SPEED AND MAGNITUDE OF THIS TROUGH
DIFFERENTLY. THE GFS IS FASTER IN LIFTING THE TROUGH N ON
MON...WHILE THE ECMWF AND GEM ARE SLOWER AND DEEPER...AND THE NAM
RESIDES IN BETWEEN. THIS INTRODUCES LARGE FORECAST UNCERTAINTY
FROM THE OUTSET OF THE LONG TERM. ATTM...USED A BLEND OF THE ECMWF
AND NAM IN ORDER TO INCORPORATE GREATER AGREEMENT BETWEEN
ECMWF/GEM...BUT ALSO INCLUDE THE POSSIBILITY FOR A SLIGHTLY
FASTER/MORE OPEN SURFACE WAVE AS DEPICTED BY THE NAM. AS A
RESULT...CURRENT PRESSURE GRIDS HAVE TRENDED TOWARD A CLOSED
SURFACE LOW THAT MOVES N ACROSS THE CNTRL/ERN GULF MON AND
TUE...AND THEN DISSIPATES OVER THE NRN GULF TUE NIGHT...AT WHICH
POINT PRESSURE GRIDS TRANSITION BACK TOWARD WPC GUIDANCE. THIS
YIELDS A CONTINUATION OF GALES OVER THE OUTSIDE WATERS...CLARENCE
STRAIT...AND CROSS SOUND THROUGH TUE...WITH WINDS GRADUALLY
WEAKENING THEREAFTER. SEAS OVER THE GULF WILL RESIDE IN THE 19-27
FOOT RANGE DUE TO A COMBINATION OF BOTH WIND WAVE GENERATION AND
LONG PERIOD SWELLS.

MODEL GUIDANCE ADVERTISES ANOTHER DEEP UPPER TROUGH AND ASSOCIATED
SURFACE CYCLONE MOVING OVER THE GULF ON THU.
HOWEVER...PREDICTABILITY REMAINS LOW WITH THIS FEATURE DUE TO
PERSISTENTLY LARGE SPREAD OBSERVED IN MODEL OUTPUT. IN THE MEAN
TIME...RAIN OCCURRING ALONG A STALLED FRONT INVOF THE GULF COAST
MON MORNING WILL BEGIN TO SPREAD INLAND THROUGH TUE AS THE FIRST
TROUGH EJECTS NE TOWARD THE NERN GULF COAST. AFTERWARDS...EMBEDDED
UPPER WAVES WITHIN SWLY FLOW ALOFT WILL YIELD MODERATE
PRECIPITATION CHANCES THROUGH MID WEEK...WITH A MORE ORGANIZED
PRECIPITATION EVENT POSSIBLE THU AND FRI AS THE SECOND TROUGH MOVES
ACROSS THE GULF. COOLER TEMPERATURES AT THE SURFACE AND ALOFT WILL
SUPPORT THE POTENTIAL FOR LIGHT SNOW OVER HAINES/SKAGWAY TUE NIGHT
THROUGH THU NIGHT...AS WELL AS JUNEAU THU...AND HYDER THROUGHOUT
THE LONG TERM PERIOD.

IN GENERAL...FORECAST CONFIDENCE IS LOW DUE TO PREVIOUSLY
MENTIONED MODEL SPREAD. UPDATES TO PRESSURE/WIND GRIDS WERE
DESCRIBED IN THE FIRST PARAGRAPH. POP AND QPF GRIDS WERE UPDATED
VIA ECMWF/GEM BLENDED IN WITH INHERITED GRIDS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 AM AKST THIS MORNING FOR AKZ022-027.
MARINE...GALE WARNING FOR PKZ022-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ013-021-031>035-053.

&&

BEZENEK/GARNER

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