Gale Warning 285, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
114 PM AKDT WED OCT 14 2009

.SHORT TERM...SATELLITE IMAGERY THIS MORNING SHOWS A 978 MB LOW
WEST OF THE QUEEN CHARLOTTS SLOWLY TRACKING WEST-NORTHWEST. HIGH
PRESSURE OVER THE YUKON HAS KEEN A SIGNIFICANT PRESSURE GRADIENT
OVER THE PANHANDLE RESULTING IN ADV LVL OUTFLOW WINDS FOR AREAS
ALONG THE INSIDE PANHANDLE. UPPER LVL SMCR AND GALE FORCE WINDS
WERE CONSISTENT OVER THE CENTRAL AND NORTH CENTRAL INSIDE WATERS.
CLEAR SKIES OVER THE PANHANDLE WITH SOME MID TO HIGH CLOUDS FROM
THE LOW JUST BEGINNING TO MOVE OVER THE SOUTHERN PANHANDLE.
DOWNSLOPE WINDS KEPT WARMER MINIMUM TEMPERATURES OVER THE
PANHANDLE WITH WIND SHELTERED AREAS SIGNIFICANTLY LOWER.

 AS THE 978 LOW WEAKENS AND TRACKS NW INTO THE SOUTH CENTRAL GULF
CLOUD AND PRECIP BANDS WILL MOVE OVER THE SOUTHER PANHANDLE AND
SLOWLY TRACK NORTH. EAST WEST PRESSURE GRADIENT OVER TO COASTAL
MOUNTAINS WILL BEGIN TO WEAKEN AS HIGH OVER THE YUKON DRIFTS
EAST. STRONG OUTFLOW WINDS WILL REMAINS OVER THE AREA THROUGH
TONIGHT WHICH WILL HELP TO KEEP PRECIP LIMITED TO THE SOUTHERN
ZONES. EXTENDED WIND ADVISORIES FOR ZONE 18, 19, AND 29 OUT TO
MIDNIGHT. WIND AND WAVES ALONG THE SOUTHERN OUTSIDE WATERS WILL
PICK UP INTO TOMORROW WITH DEVELOPING GALES.

 USED A BLEND OF 12Z NAM12 WITH INHERITED GRIDS. WINDS SHOWED THE
MOST CHANGE FOR THE TONIGHT PERIOD.

&&

.LONG TERM...MEDIUM RANGE MODELS REMAIN IN FAIR AGREEMENT ON
LONGWAVE PATTERN TRANSITION THROUGH THE WEEKEND AND THEN EXHIBIT
CONSIDERABLE SPREAD ON TIMING TRACK AND INTENSITY OF LOW MOVING
OUT OF THE NORTHERN PACIFIC AND INTO THE EASTERN GULF TUESDAY AND
WEDNESDAY OF NEXT WEEK.

 12Z NAM12 CONTINUES TO HANDLE THE PRESSURE GRADIENT ALONG THE
COASTAL MOUNTAINS BETTER THAN BOTH THE GFS AND ECMWF AND WAS
BLENDED WITH 12Z GFS INTO INHERITED GRIDS THROUGH DAY 4. GFS HAS
A GOOD HOLD ON THE TRACK AND INTENSITY OF NEXT LOW MOVING NORTH
INTO THE GULF LATE THURSDAY AND FRIDAY. GFS WAS A NICE COMPROMISE
ON POSITION WITH BOTH THE NAM AND UKMET. THE ECMWF WAS SOMEWHAT OF
AN OUTLIER WITH LOW TRACK WELL TO THE NORTH AND WEST OF THE GFS
UKMET AND NAM. OCCLUDED FRONT EXTENDING EAST AND SOUTHEAST FROM
THE LOW IN THE GULF WILL APPROACH THE PANHANDLE THURSDAY EVENING
BRINGING AN INCREASE IN WIND AND POPS FOR THE PANHANDLE. LIKELY
POPS FOR THE SOUTHERN ZONES WITH SOUTH TO SOUTHEAST FLOW WHILE
CHANCE POPS FOR CENTRAL AND NORTHERN ZONES WITH A MORE OFF SHORE
EASTERLY FLOW. 6HR QPF AMOUNTS TO AROUND ONE THIRD OF AN INCH IN
THE SOUTHERN ZONES WITH LESSER AMOUNTS IN THE NORTHERN ZONES.
LOCALLY BREEZY TO WINDY CONDITIONS ESPECIALLY FOR THE SOUTHERN
PANHANDLE AS THE FRONT MOVES INLAND. A SECOND LOW PINWHEELS AROUND
THE PARENT LOW IN THE NORTHERN GULF FRIDAY AND MOVES OVER QUEEN
CHARLOTTE ISLAND AND INLAND NEAR PAKT LATE FRIDAY INCREASING BOTH
WINDS AND POPS FOR SOUTHERN PANHANDLE FRIDAY AND REST OF THE
PANHANDLE SATURDAY. ONSHORE FLOW AFTER THE LOW MOVES INTO BC WILL
ENHANCE POPS AND CLOUDS THROUGH SUNDAY.

 FOCUS THEN SHIFTS TO A POWERFUL LOW PROGGED TO MOVE NORTHEAST OUT
OF THE NORTHERN PACIFIC TOWARD QUEEN CHARLOTTE ISLAND TUESDAY OF
NEXT WEEK. 964MB LOW WEAKENS TO 970MB BEFORE LAND FALL NEAR QUEEN
CHARLOTTE ISLAND WEDNESDAY MORNING. ECMWF STRENGTHENS THE LOW TO
ONLY 974MB AND HAS A MORE SOUTHERLY TRACK. CONSIDERABLE SPREAD
EXISTS BETWEEN OPERATIONAL AND ENSEMBLE SOLUTIONS AS WELL AS
DIFFERENCES BETWEEN MODEL FAMILIES. OPTED TO BLEND INHERITED
GRIDS PAST DAY 5 WITH LATEST HPC GUIDANCE AND PRESENT A MIDDLE OF
THE ROAD SOLUTION WITH MINIMAL CONTINUITY CHANGES UNTIL THE MODELS
CONVERGE ON A SOLUTION. FORECAST CONFIDENCE IS ABOVE AVERAGE
THROUGH DAY 4 AND THEN BELOW AVERAGE PAST THAT POINT.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL MIDNIGHT AKDT TONIGHT FOR AKZ018-019-025-029.
MARINE...GALE WARNING FOR PKZ012-013-041>043.
         SMALL CRAFT ADVISORY FOR PKZ011-021-022-031>036-051-052.

&&

PRB/CCC