Small Craft Advisory 612, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
348 PM AKDT SUN OCT 21 2012

.SHORT TERM...LATEST SATELLITE LOOP SHOWS AN INVERTED TROUGH
EXTENDS NORTHWESTWARD FROM A LOW SOUTH OF HAIDA GWAII ACROSS THE
NORTHERN AND EASTERN GULF. HIGH PRESSURE CONTINUES TO BUILD OVER
ALASKAN INTERIOR AND YUKON...MAINTAINING TIGHT NORTH TO NORTHEAST
PRESSURE GRADIENT ACROSS THE PANHANDLE. STRONG NORTHEAST WIND
GUSTS UP TO 60 MPH IN DOWNTOWN JUNEAU AND SOUTH DOUGLAS HAD
DECREASED DURING THE LATE MORNING HOURS...BUT STRONG GUSTY WINDS
UP TO 40 MPH STILL EXIST AND THUS KEEP STRONG WIND HEAD LINE FOR
THE JUNEAU ZONE THIS EVENING.

 SATELLITE SIGNATURE FOR OUTFLOW DIMINISHED LATE MORNING...BUT
REESTABLISHED EARLY IN THE AFTERNOON. SOLID GALE FORCE WINDS
PREVAIL OVER THE NORTHERN AND CENTRAL INNER CHANNELS.
SOUTHEASTERN PERIPHERY OF THE HIGH PRESSURE BRINGS SOME MID
CLOUDS TO THE NORTHERN MOST PANHANDLE...AND AROUND THE LOW NEAR
HAIDA GWAII PUSHES MID TO HIGH CLOUDS OVER THE SOUTHERN AREAS.

 MODELS ARE FAIRLY CONSISTENT WITH THE HIGH PRESSURE OVER ALASKAN
INTERIOR AND YUKON PERSISTS WITH THE INVERTED TROUGH OF LOW
PRESSURE ACROSS THE EASTERN GULF THROUGH MONDAY. THIS SYNOPTIC
PATTERN WILL CONTINUE TO PROVIDE SOUTHEAST ALASKA DRY AND COLD
WEATHER WITH STRONG OFFSHORE FLOW. REFRESHED THE INHERITED
FORECAST PACKAGE WITH THE NAM FOR ITS BEST INITIALIZATION AND
HANDLING THE TIGHTENED NORTHERLY PRESSURE GRADIENT. IN ADDITION
TO THE RADIATION COOLING...THE ENTRAINMENT OF COLD
CONTINENT-ARCTIC AIR WILL KEEP THE OVERNIGHT LOWS RANGING FROM
THE MID TEENS OVER YAKUTAT AREA TO THE 20S REST OF THE SOUTHEAST
ALASKA.

 &&

.LONG TERM...VERY LITTLE CHANGE FROM THE BEGINNING TO THE END OF
THE EXTENDED RANGE FORECAST PERIOD. HIGHLIGHTS ARE LITTLE TO NO
POP AND MOSTLY CLEAR SKIES UNTIL NEXT SATURDAY NIGHT AND STRONG
NORTHERLY/NORTHEASTERLY WINDS ACROSS ALL OF SOUTHEAST ALASKA.
SYNOPTIC FEATURES RESPONSIBLE FOR THIS STRONG HIGH PRESSURE
SITUATED OVER THE INTERIOR OF ALASKA AND ACROSS NORTHERN CANADA,
AND LOW PRESSURE OFF THE COAST SOUTHERN BRITISH COLUMBIA WITH AN
INVERTED TROUGH THAT EXTENDS NORTHWEST INTO THE EASTERN GULF OF
ALASKA. WITH BOTH OF THESE FEATURES REMAINING NEARLY STATIONARY
THROUGH MID WEEK, EXPECT NORTHERLY/EASTERLY SMALL CRAFT WINDS OVER
THE MANY OF THE INNER CHANNELS. ALSO, LOOK FOR VERY STRONG GUSTS
OUT OF INTERIOR PASSES ALONG THE EASTERN SHORES OF STEPHENS
PASSAGE. EXCEPTION TO THIS GENERALIZATION WILL BE CLARENCE STRAIT,
WHICH WILL AT TIMES FEATURE A NORTHWEST WINDS AND AT OTHER TIMES A
SOUTHEAST WIND DEPENDING ON THE LOCATION OF THE INVERTED TROUGH
AXIS. GREATEST CHANCE FOR SMALL CRAFT WINDS IN CLARENCE STRAIT
EXTEND FROM MONDAY NIGHT INTO TUESDAY.

USED 12Z NAM THROUGH WEDNESDAY MORNING FOLLOWED BY THE 00Z ECMWF
UNTIL THURSDAY MORNING FOR PRESSURE AND WINDS WITH HPC THEREAFTER.
NO CHANGES TO POP, QPF, OR SKY GRIDS. ADJUSTED TEMPS A FEW DEGREES
EITHER WAY WITH BIAS CORRECTED MOS. FORECAST CONFIDENCE IS ABOVE
AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ025.
MARINE...GALE WARNING FOR PKZ012-022-043.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-031-032-035-051-053.

&&

AHN/FRITSCH