Gale Warning 276, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
240 PM AKDT FRI OCT 23 2009

.SHORT TERM...WATER VAPOR SATELLITE LOOP SHOWS A WEAK UPPER
LEVEL SHORTWAVE TROUGH MOVING NORTHEASTWARD ACROSS THE NORTHERN
GULF WITH A CLOSED LOW NEAR KODIAK ISLAND. A SOUTHERN JET STREAM
PUSHES A DRY SLOT TOWARDS THE BRITISH COLUMBIA COAST AND SHEARS
APART DEFORMATION ZONES OVER THE SOUTHEAST ALASKA. INFRA RED
SATELLITE LOOP REVEALS A DISSIPATING OCCLUSION ARCING OUT FROM A
LOW NEAR KODIAK ISLAND. THE DISSIPATING OCCLUDED FRONT MOVING
NORTHEAST ACROSS THE COAST MOUNTAIN AND A WEAK RIDGE IS BUILDING
ACROSS THE PANHANDLE. A COLD AIR ALOFT BEHIND THE FRONTAL
BOUNDARY GENERATES UNSTABLE ATMOSPHERIC CONDITIONS ACROSS THE
EASTERN GULF. CONVECTIVE CLOUDS ARE CONSOLIDATING ACROSS THE
OUTSIDE WATERS FROM CAPE SPENCER TO DIXON ENTRANCE...DRIFTING
NORTHEASTWARD TOWARDS THE NORTHERN AND CENTRAL PANHANDLE COASTS.
AHEAD OF THE DEVELOPING CONVECTIVE CLOUDS...BREAK IN OVERCAST
SKIES ARE SHOWN ACROSS THE CENTRAL AND SOUTHERN PANHANDLE. ALONG
WITH THE FRONTAL BOUNDARY...SMALL CRAFT WINDS ARE REPORTED ON
ELDRED ROCK AND SMALL CRAFT WIND GUSTS AT CAPE SPENCER. VERY
ROUGH SEAS UP TO 20 FEET ARE PERSISTING ACROSS THE OFFSHORE AND
OUTSIDE WATERS.

 MODELS ARE IN FAIR AGREEMENT WITH A WEAK RIDGE OF HIGH PRESSURE
CONTINUING TO BUILD ACROSS THE EASTERN GULF AND SOUTHEAST ALASKA
THROUGH SATURDAY MORNING THEN DRIFT EAST AS A DEVELOPING LOW IN
THE SOUTH CENTRAL GULF MOVING NORTHWARD TO NEAR MIDDLETON ISLAND
THROUGH SATURDAY NIGHT. THE 12Z RUN NAM SHOWS A BIT MORE
PROGRESSIVE AND AMPLIFIED PATTERN THAN OTHER MODELS WITH THE
UPPER LEVEL TROUGH MOVING ACROSS THE AREA ON SATURDAY...BUT THE
NAM KEEPS A BETTER CONTINUITY OVERALL. WILL BLEND THE INHERITED
GRIDS WITH THE NAM FOR TONIGHT AND SATURDAY TO MAINTAIN A MAXIMUM
CONSISTENCY.

 UNSTABLE ATMOSPHERE WILL PERSIST AND MODEL SOUNDING DEPICTS COLD
DRY AIR ALOFT WITH PRETTY HIGH CAPE VALUES ACROSS THE COASTAL
SECTIONS THIS AFTERNOON AND EVENING. WILL KEEP ISOLATED
THUNDERSTORMS WITH POSSIBLE SMALL HAIL IN THE AFTERNOON FORECAST
PACKAGE FROM YAKUTAT SOUTHEAST TO SITKA AREAS. THE DEVELOPING LOW
IN THE SOUTH CENTRAL GULF WILL PUSH ANOTHER FRONTAL BOUNDARY
ACROSS THE EASTERN GULF SATURDAY AS THE LOW DRIFTING NORTHWARD TO
THE NORTHERN GULF THROUGH SATURDAY NIGHT. LIKELY TO CATEGORICAL
POPS WILL CONTINUE ACROSS THE FORECAST DOMAIN EXCEPT NORTHERN
INNER CHANNELS WHERE A LOWER POPS ARE EXPECTED. AS THE FRONT
SWEEPS ACROSS THE EASTERN GULF SATURDAY...ADVISORY LEVEL WIND
GUSTS ARE EXPECTED FROM YAKUTAT TO SITKA DURING THE AFTERNOON
INTO THE EARLY EVENING HOURS. WILL ISSUE A WIND ADVISORY FOR ZONE
17 FROM 12 NOON TO 9 PM AND ZONES 22 AND 23 FROM 12 NOON TO 6 PM
SATURDAY. SMALL CRAFT WINDS WILL DEVELOP ACROSS THE MOST INNER
CHANNELS SATURDAY AFTERNOON WITH GALE FORCE WINDS ACROSS THE
OFFSHORE AND OUTSIDE WATERS.

&&

.LONG TERM...LONG RANGE BEGINS WITH GALE FORCE LOW MOVING NORTH
THROUGH THE CENTRAL GULF WITH WIND ADVISORY FOR ZONE 17 AND WIND
ADVISORIES HAVING JUST ENDED IN ZONES 22 AND 23. GALE FORCE WINDS
WILL STILL BATTERING THE OUTSIDE WATERS EARLY SATURDAY NIGHT. THE
LOW CONTINUES TO FILL AS IT MOVES SLOWLY TOWARD THE PAYA. LIKELY TO
CATEGORICAL POPS FOR ENTIRE PANHANDLE AS OCCLUDED FRONT STALLS OUT
OVER THE PANHANDLE SATURDAY NIGHT AND SUNDAY.  AS LOW STALLS IN
NORTHERN GULF.

 12Z NAM12 ALONG WITH THE 12 GFS AND UKMET ALL INDICATE THAT THE
WAVE CURRENTLY NEAR 48N AND AND 155W WILL MOVE RAPIDLY NORTHEAST
THROUGH THE DAY SATURDAY AND DEVELOP INTO ANOTHER GALE FORCE LOW
CENTERED IN THE SOUTHEASTERN GULF BY SUNDAY EVENING AND MONDAY
MORNING. UKMET IS SLOWER AND IS PLAYING CATCH UP WITH THIS
DEVELOPMENT WHILE THE GFS AND NAM ARE IN BETTER AGREEMENT ON
INTENSITY AND POSITION OF THE LOW. THE 12 ECMWF DEVELOPS THE LOW
FURTHER WEST AND MOVES IT INTO THE NORTHERN GULF. NONE OF THE
MODELS HAVE BEEN DOING WELL WITH TRACK AND INTENSITY OF THIS LOW.
OPTED TO USED A NAM GFS BLEND STARTING WITH HAND OFF SATURDAY
NIGHT THROUGH 84 HOUR POINT WHERE A STRONGER BLEND WITH 12 GFS
BLENDED NICELY WITH HPC GUIDANCE. BOTH THE GFS AND NAM INITIALIZED
WELL AND THE NAM WAS USED IN THE SHORT TERM MAKING A NICE
TRANSITION. A NAM GFS AND CANADIAN BLEND WAS USED BY AFC AND
BLENDED WELL ALONG OUR BORDER. THE NAM AND GFS BLEND FOR SUNDAY
INTO TUESDAY INTRODUCED CONSIDERABLY MORE WIND INTO THE SOUTHERN
MARINE AND PUBLIC ZONES FOR LATE SUNDAY...MONDAY AND TUESDAY.
GALES AND WIND ADVISORIES ARE LIKELY TO BE NEEDED IF THE NAM AND
GFS SOLUTION PANS OUT.

 THE GLOBAL MODELS CONTINUE TO DISPLAY VERY POOR RUN TO RUN
CONSISTENCY AND EXHIBIT LARGE TRACK STRENGTH AND TIMING ISSUES
FROM SATURDAY NIGHT THROUGH MONDAY. REMARKABLY THE 12Z ECMWF AND
12Z GFS ARE IN FAIRLY GOOD AGREEMENT TUESDAY AND WEDNESDAY AND
THEN DIVERGE AGAIN THROUGH THE REST OF THE LONG TERM. OPTED TO
UPDATE INHERITED GRIDS BEGINNING WITH DAY 4 AND GOING THROUGH THE
REST OF THE LONG RANGE WITH THE LATEST HPC GUIDANCE WHICH ALSO
BLENDED WELL WITH GFS AND ECMWF GUIDANCE ON DAY 4 AND DAY 5.
BEYOND DAY 6 12Z ECMWF AND 12Z GFS DIVERGE ON SOLUTIONS WITH THE
GFS BRINGING ANOTHER DEEP LOW INTO THE SOUTHERN GULF. GIVEN THE
POOR PERFORMANCE OF LONG RANGE MODELS PREFERRED HPC GUIDANCE TO
TAKE ADVANTAGE OF MULTIPLE ENSEMBLES AND TO MINIMIZE LARGE SCALE
CHANGES IN THE GRIDS. FORECAST CONFIDENCE REMAINS WELL BELOW
AVERAGE FOR THE LONG RANGE PERIOD.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM NOON TO 6 PM AKDT SATURDAY FOR AKZ022-023.
         WIND ADVISORY FROM NOON TO 9 PM AKDT SATURDAY FOR AKZ017.
MARINE...GALE WARNING FOR PKZ022-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-032>036.

&&

AHN/CCC