Gale Warning 318, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
343 PM AKDT MON OCT 1 2012

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWING LOW
PRESSURE SYSTEM EXITING THE SOUTHERN PANHANDLE EASTWARD INTO
BRITISH COLUMBIA AND A HIGH PRESSURE RIDGE BUILDING OVER THE AK
GULF. STRONG NORTHWESTERLY WINDS OVER THE GULF AND COASTAL AREAS
FROM GRADIENT AND GEOSTROPHIC FLOW BETWEEN THE BUILDING HIGH AND
EXITING LOW TODAY. CLOUD PATTERN IN VISIBLE SATELLITE IMAGERY
SHOWING STRONG WAVE ACTION IN MID LEVELS WINDS WITH CONVECTIVE
SHOWER CELLS MOVING SOUTH. WHILE RADAR VELOCITY AND REFLECTIVITY
DID NOT INDICATE ANY ROTATION FORM THESE CELLS COASTAL STATIONS
REPORTED PERIODS OF VERY STRONG GUSTS. THESE GUSTY WINDS SHOULD
DROP OFF THROUGH THE REMAINDER OF THE AFTERNOON AND EARLY EVENING
AS THE POSSIBLE THERMAL TROUGH MOVES SOUTHWARD. OVER THE NORTHERN
PANHANDLE A WEAK SHORT WAVE IN THE YUKON DID STAY INTACT OVER THE
PASS AND DROPPED AS FAR SOUTH AS JUNEAU WITH CLOUDY SKIES AND
SOME ISOLATED SHOWERS. AS THE HIGH PRESSURE RIDGE IN THE GULF
CONTINUES TO BUILD AND THE RIDGE AXIS MOVES FURTHER EAST WILL SEE
INCREASED CLEARING OVERNIGHT. WITH THE CLEAR SKIES EXPECT ANOTHER
NIGHT OF RADIATION COOLING...BUT 850 MB TEMPS INCREASE OVER NIGHT
AS THE RIDGE TRACKS IN. THESE WARMER MID LEVELS TEMPS MAY OFFSET
THE RADIATIONAL COOLING IF THERE IS ENOUGH MIXING...BUT AT THIS
TIME SEEING WINDS BECOMING LIGHT WITH LIMITED MIXING OCCURRING.
SHOULD SEE SIMILAR MINIMUM TEMPERATURES IN THE UPPER 20S TO LOW
30S FOR THE CENTRAL AND NORTHERN PANHANDLE WITH FROST IN THE
MORNING. THE SOUTHERN PANHANDLE WILL SEE COOLER TEMPERATURES THAN
LAST NIGHT BUT WITH SOME LINGERING CLOUD COVER EXPECTING MINIMUM
TEMPERATURES ONLY IN THE UPPER 30S TO LOW 40S. TUESDAY LOOKS TO
BE A DRY DAY FOR THE PANHANDLE WITH SOME PATCHY FOG IN THE
MORNING FROM OVERNIGHT COOLING AND RESIDUAL MOISTURE. AS WINDS
DROP OVERNIGHT WILL SEE A SHIFT TO THE SOUTH WITH WINDS IN THE
GULF INCREASING IN THE AFTERNOON WITH THE NEXT APPROACHING FRONT.

 MODELS WERE IN FAIR AGREEMENT AND INITIALIZED THE SYNOPTIC
PATTERN WELL BUT MOST MODELS MISSED ANY MESOSCALE FEATURES FOR
MONDAY. USED A BLEND OF 12Z NAM WITH INHERITED GRIDS WITH SOME
HIGH RES ARW USED FOR EVENING POPS. OVERALL CHANGES WERE FAIRLY
MINOR. WHILE GENERAL PATTERN IS FAIRLY SIMPLE THE MESOSCALE
FEATURES WILL BE RATHER COMPLEX TONIGHT SO FORECAST CONFIDENCE IS
BELOW AVERAGE.

&&

.LONG TERM...A BLOCKING HIGH THAT EXTENDS FROM THE NORTHEAST
PACIFIC NORTH ACROSS THE EASTERN GULF AND INTO CANADA WILL BE IN
PLACE BY THE START OF THE EXTENDED RANGE FORECAST PERIOD TUESDAY
NIGHT. HOWEVER, A LOW AND ASSOCIATED FRONT WILL PRESSING UP
AGAINST THE HIGH FROM THE WEST. FAIR MID LEVEL VORTICITY AND JET
SUPPORT, BUT BELIEVE THIS WILL BE ENOUGH TO PUSH A FRONT AND
ASSOCIATED PRECIPITATION THROUGH THE HIGH AND INTO SOUTHEAST
ALASKA TUESDAY NIGHT THROUGH WEDNESDAY. HAVE CATEGORICAL POPS
WITH THIS THIS, BUT QPF AMOUNTS NOT OVERLY HIGH. BEYOND WEDNESDAY,
A CHANCE OF RAIN FOR THE NORTHERN HALF AT TIMES THROUGH SATURDAY.
MOSTLY DRY FOR THE SOUTHERN HALF FOR THE REMAINDER OF THE WEEK
AND THROUGH THE WEEKEND.

OVERNIGHT LOWS TUESDAY NIGHT GETTING DOWN TO THE MID 30S OVER THE
NORTHERN HALF AND MID 40S FOR LOCATIONS FURTHER SOUTH. WARM SECTOR
ASSOCIATED WITH THIS FRONT WILL CAUSE OVERNIGHT LOWS FOR WEDNESDAY
NIGHT AND THE REMAINDER OF THE WEEK TO BE SEVERAL DEGREES WARMER
AND SAFELY ABOVE FREEZING. DAYTIME HIGHS NOT VERY REMARKABLE DUE
TO PREVAILING MOSTLY CLOUDY SKIES.

WINDS ASSOCIATED WITH THE WEDNESDAY FRONT EXPECTED TO BE GALE
FORCE FOR MUCH OF OFFSHORE MARINE ZONE 310 AND COASTAL ZONE 52 FOR
TUESDAY NIGHT. BY WEDNESDAY, MAX WINDS WILL ABATE A BIT, BUT
SMALL CRAFT SOUTHEASTERLIES WILL EXTEND ALL THE WAY DOWN TO CAPE
DECISION. MARINE WINDS WILL DIMINISH THROUGH THE DAY EXCEPT FOR
CLOSE COASTAL BETWEEN ICY BAY AND CAPE SUCKLING, WHERE A BARRIER
JET WILL REMAIN IN PLACE THROUGH WEDNESDAY NIGHT. TYPICAL OUTFLOW
WINDS AND WIND SPEEDS FOR ICY STRAIT, CROSS SOUND, SOUTHERN
CHATHAM AND WESTERN SUMNER STRAITS. HAVE ONLY 20 KT
SOUTHEASTERLIES IN CLARENCE STRAIT FOR WEDNESDAY NIGHT AND THIS
MAY NEED TO BE INCREASED OVER THE COURSE OF THE NEXT COUPLE
SHIFTS.

USED A BLEND OF NAM AND ECMWF EARLY ON, THEN GFS AND ECMWF. MAINLY
HPC FROM FRIDAY ONWARD FOR WINDS. POP AND QPF HEAVILY WEIGHTED
TOWARDS ECMWF. FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022-033-035-036-041>043-051-052.

&&

PRB/FRITSCH