Small Craft Advisory 324, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
354 PM AKDT TUE MAY 3 2011

.SHORT TERM...EARLY AFTERNOON SATELLITE IMAGERY SHOWS A
WEAKENING RIDGE OF HIGH PRESSURE...MOVES SLOWLY EASTWARD ACROSS
THE PANHANDLE WITH LIGHT RAIN SPREADING OVER THE FORECAST DOMAIN
FROM YAKUTAT SOUTHEAST TO HYDER EXCEPT NORTHERN MOST AREAS OF
SKAGWAY AND HAINES. ENHANCED SOUTHERLY PRESSURE GRADIENT ACROSS
THE NORTHERN INNER CHANNELS MAINTAINS SMALL CRAFT WIND FOR
NORTHERN LYNN CANAL WITH BREEZY CONDITIONS OVER SKAGWAY AND
HAINES. SOUTHEAST TO SOUTH WINDS ARE ALSO SLIGHTLY INCREASING
ACROSS THE CENTRAL AND SOUTHERN OUTER WATERS AHEAD OF THE
APPROACHING FRONTAL BOUNDARY. A DEVELOPING LOW IN THE FAR
SOUTHERN GULF PUSHES AN OCCLUDED FRONT NORTHEASTWARD ACROSS THE
CENTRAL AND EASTERN GULF WITH ITS TRIPLE POINT ORGANIZING NEAR
55N/140W.

MODELS ARE IN GENERAL AGREEMENT WITH THE WEAKENING RIDGE OF HIGH
PRESSURE ACROSS SOUTHEAST ALASKA CONTINUES TO MOVE EAST INTO
CANADA BY WEDNESDAY MORNING. THE DEVELOPING GALE FORCE LOW IN THE
SOUTHERN GULF WILL ENTER THE EASTERN GULF THROUGH WEDNESDAY
AFTERNOON. THE OCCLUSION WILL MOVE NORTH ACROSS THE EASTERN GULF
AND PANHANDLE COAST TONIGHT THEN STALL OVER THE PANHANDLE ON
WEDNESDAY. THE LOW WILL WEAKEN AS IT DRIFTS NORTH ACROSS THE
EASTERN GULF THROUGH LATE TONIGHT INTO THURSDAY MORNING. THE GFS
AND ECMWF SHOWS BETTER AGREEMENT THAN THE NAM FOR THE LOW TRACK
AND THE GRIDS FOR TONIGHT AND WEDNESDAY WERE BLEND 50/50 OF THE
GFS AND ECMWF.

CONTINUED ONSHORE LOW LEVEL FLOW WITH INCOMING FRONT...THE
FORECAST DOMAIN WILL REMAIN WET WITH CATEGORICAL POPS FOR TONIGHT
AND WEDNESDAY...EXCEPT THE NORTHERN MOST ZONES FROM YAKUTAT EAST
TO HAINES AND SKAGWAY WHERE THE ONSET OF RAIN BAND DELAYED UNTIL
LATE TONIGHT OR EARLY WEDNESDAY MORNING. MODERATE RAINFALL IS
EXPECTED ACROSS THE CENTRAL AND SOUTHERN PANHANDLE AS CONCENTRATED
MID LEVEL DYNAMICS FROM THE FRONTAL BOUNDARY NOSING TOWARDS THE
SOUTHERN PANHANDLE. AS THE LOW ENTERS THE EASTERN GULF AND THE
RIDGE MOVES EAST AWAY FROM THE AREA...SOUTHERLY PRESSURE GRADIENT
WILL CEASE OUT ACROSS THE NORTHERN INNER CHANNELS AND MORE EAST-
WEST ORIENTED GRADIENT WILL DEVELOP OVER THE FORECAST AREAS. THE
INCOMING LOW WILL GENERATE GALE FORCE WINDS ACROSS THE SOUTHERN
OUTER WATERS AND SOLID SMALL CRAFT WINDS OVER REST OF THE OUTSIDE
WATERS AND THE SOUTHERN INNER CHANNELS INCLUDING CROSS SOUND.
BREEZY CONDITIONS ARE ALSO EXPECTED CENTRAL AND SOUTHERN PANHANDLE
COASTAL SECTIONS.

.LONG TERM...THE GALE FORCE WINDS DISCUSSED IN THE SHORT RANGE
SECTION ABOVE WILL EXTEND INTO WEDNESDAY NIGHT FOR MARINE ZONES
41 AND 42. NO FURTHER GALE FORCE SYSTEMS ARE EXPECTED THROUGH
SUNDAY (DAY 5). CONFIDENCE IS AVERAGE.  CHANGES ARE SMALL AND
PRIMARILY OCCUR AS RAISED POPS. RUN TO RUN CONSISTENCY OF THE
GFS MODEL HAS RESULTED IN IT BEING THE PRINCIPAL GUIDANCE.

FOR 12Z FRI THROUGH 00Z MON THE FIVE-WAVE 500H GFS DEPICTS A
CHANGE TO A MORE ZONAL FLOW. AT 00Z MON THE ACCOCD LONG WAVE FIELD
INCLUDES A LOW AMPLITUDE TROUGH EXTENDING FM A 500H OVER WRANGELL
ISLAND TO OVER A CYDA TO PANT LINE.

LONG-RANGE MODEL CONSENSUS IS GOOD UNTIL THIS WEEKEND, AND THE
AK- HPC DISCUSSION MAKES THE CASE THAT THE GFS HAS A MORE CONSISTENT
SOLUTION WITH THE EC TENDING TO ADJUST TO IT. THEREFORE THE 0312
GFS SOLUTION WAS USED AS PRIMARY GUIDANCE FOR NEARLY ALL FIELDS
ALL THE WAY THROUGH DAY 7. THE EXCEPTIONS ARE MAINLY DUE TO USE OF
ADDITIONAL MODEL FIELDS IN A BLEND FOR TIMES BEFORE THIS WEEKEND.
TEMPERATURES FOR LATE WEEKEND AND EARLY NEXT WEEK DID FACTOR IN
SOME CLIMATOLOGY.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041-042.
         SMALL CRAFT ADVISORY FOR PKZ012-022-033>036-043-051.

&&

AHN/JBT