Small Craft Advisory 307, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
415 PM AKDT TUE MAY 8 2012

.SHORT TERM...A SMALL LOW OVER THE NORTHERN PANHANDLE WILL
CONTINUE MOVING NORTH AND BE OUT OF THE AREA BY EARLY AFTERNOON.
A RIDGE BUILDING IN BEHIND THIS LOW HAS INCREASED THE PRESSURE
GRADIENT ACROSS SOUTHEAST ALASKA THIS MORNING. CURRENTLY HAVE
SMCR WINDS THOUGH SOUTHERN AND CENTRAL INNER CHANNELS WITH A
SOLID GALE OCCURRING THROUGH LYNN CANAL. WITH THE UNSTABLE ATMO
ALSO HAVE STRONGER GUSTS WORKING DOWN TO THE SURFACE IN SHOWERS
ACROSS MANY OF THE PUBLIC AREAS. THE RIDGE SHIFTS EAST TONIGHT
AND EXPECT OVERALL GRADIENT TO EASE THROUGH THE AFTERNOON AND AND
BECOME WEAK BY LATE TONIGHT. WINDS WILL DIMINISH ACROSS THE SOUTH
THIS EVENING AS UPPER LOW MOVES INLAND BUT WILL INCREASE AGAIN ON
WEDNESDAY AS FLAT RIDGE PUSHES NORTH. NORTHERN PANHANDLE WILL SEE
WINDS EASE SOME OVERNIGHT BUT REGAIN STRENGTH BY WEDNESDAY
AFTERNOON.

A COLD UPPER LEVEL LOW CENTERED ABOUT 150 NM WEST OF HAIDA GWAII
IS FORECAST TO MOVE NE OVER THE CENTRAL PANHANDLE TONIGHT AND
WEAKEN INTO A TROUGH AS IT EMERGES IN WESTERN CANADA WEDNESDAY
MORNING. THERE IS A FAIRLY DEEP COLUMN OF COLD AIR ASSOCIATED WITH
THE UPPER LOW THAT WILL KEEP ATMO UNUSUALLY UNSTABLE THROUGH
TONIGHT. WILL KEEP A CHANCE OF THUNDERSTORMS OVERNIGHT FOR
SOUTHERN HALF OF THE PANHANDLE. THESE SHOWERS ALSO HAVE POTENTIAL
TO PRODUCE SMALL HAIL. ALSO WITH THE CAA SNOW LEVELS ARE LOWERING
AND ALREADY DOWN TO ABOUT 1200 FEET ON PAJN PROFILERS AND EXPECTED
TO BE CLOSER TO 500 FEET BY MORNING AND COULD SEE SOME SNOW MIX IN
THE HEAVIER SHOWERS FOR CENTRAL INNER CHANNELS.

THE BROAD FLAT RIDGE BUILDING NORTH INTO THE GULF WILL KEEP
WESTERLY FLOW ACROSS THE GULF AFTER TO UPPER LOW MOVES INLAND.
THERE IS A WEAK SURFACE TROUGH THAT IS MOVING ATOP THE RIDGE AND
FORECAST TO KEEP MOISTURE MOVING ONSHORE. SHOWERS REMAIN LIKELY ON
WEDNESDAY...ESPECIALLY ALONG THE HIGHER TERRAIN OF COAST MOUNTAINS
HOWEVER AMOUNTS SHOULD BE CONSIDERABLY LESS TODAY. WESTERLY WIND
ACROSS THE GULF SHOULD STAY BELOW SMCR LEVELS ON WED BUT WITH A
BUILDING SW SWELL WILL HAVE SMCR DUE TO SEAS BY WED AFTN.

SYNOPTICALLY MODELS IN GOOD AGREEMENT BUT THEY DID NOT INITIALIZE
THE SMALL LOW OVER THE NORTHERN PANHANDLE VERY WELL. NAM12 WAS
CLOSEST WITH THIS FEATURE AND USED FOR WINDS AND PRES. GFS HAS
BEEN DOING WELL WITH QPF LAST FEW DAYS AND USED IN MASS FIELDS.

&&

.LONG TERM...WET PATTERN CONTINUES THROUGH MUCH OF THE EXTENDED
FORECAST. A GALE FORCE FRONT WILL MOVE INTO THE EASTERN GULF ON
THURSDAY. THIS WILL BRING HEAVY RAIN TO THE NORTHERN GULF COAST
THURSDAY AND FRIDAY. THE YAKUTAT AREA COULD SEE QPF AMOUNTS OF
AROUND 6 INCHES WITH THIS FRONT THURSDAY THROUGH SATURDAY. 850MB
TEMPS WILL BE WARM ENOUGH FOR THIS TO FALL AS RAIN...HOWEVER A FEW
FLAKES COULD MIX IN WITH THE HEAVY DOWNPOURS.

AS THE FRONT MOVES INLAND OVERNIGHT FRIDAY INTO EARLY SATURDAY
EXPECT THE GUSTY WINDS TO ARRIVE WITH IT. SIMILAR TO LAST WEEKENDS
FRONT MODELS ARE SHOWING 850MB WINDS OF AROUND 60KT WHEN ITS OUT
OVER THE GULF AND 40-50KT WHEN IT MOVES OVER THE PANHANDLE...THIS
ALONG WITH THE PROLONGED RAINFALL WILL CONTINUE THE TREAT OF
SLIDES. THE NEXT BREAK IN THE RAIN LOOKS TO BE ON SUNDAY OVER THE
SOUTHERN HALF OF THE AREA...WHERE PARTLY CLOUDY SKIES ARE
EXPECTED. CHANCES OF RAIN RETURN FOR MONDAY AND TUESDAY.

MODELS WERE IN VERY GOOD AGREEMENT IN THE EXTENDED FORECAST. MAIN
CHANGES WERE TO INCREASE WINDS SLIGHTLY ALONG THE FRONT. IF 850MB
WINDS CONTINUE THIS TREND THEY MAY NEED TO BE NUDGED UP TO STORM
FOR THE OUTSIDE WATERS. FORECASTER CONFIDENCE IS AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ031.
         SMALL CRAFT ADVISORY FOR PKZ012-013-033-036-041.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ042-043.

&&

MM/HANNON