Small Craft Advisory 295, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
408 PM AKDT FRI MAY 4 2012

.SHORT TERM...A WEAK LOW OVER THE CENTRAL GULF WILL DRIFT N AND
WEAKEN TO A TROF TONIGHT. THE TROF WILL MOVE ONSHORE SE AK LATE
TONIGHT AND LIKELY DISSIPATE BY SAT AFTERNOON OVER THE INNER
CHANNELS. LOW PRESSURE WILL BEGIN TO DEVELOP WELL S OF THE GULF
TONIGHT AND MOVE NNE TO NEAR 51/148 BY LATE SAT AFTERNOON.
CURRENT GRIDS LOOKED GOOD HANDLING THESE FEATURES SO MADE NO
CHANGE TO THE PRESSURE FIELDS.

MAIN FORECAST ISSUES WILL BE PRECIP POTENTIAL AND WINDS. RIGHT
NOW...SHOWERS ARE ON THE INCREASE OVER THE AREA WITH MID-LEVEL
TROF APPROACHING THE AREA FROM THE SW. EXPECT THE INCREASE TO
CONTINUE THRU THIS EVENING WITH A FAIRLY ORGANIZED BAND OF SHOWERS
EXPECTED AS TROF MOVES ONSHORE TONIGHT. THE UPPER PART OF THE
TROF...ABOVE 700 MB...WILL BE FORWARD TILTED...WITH LOWER PART OF
TROF...700 MB AND BELOW...FAIRLY VERTICAL. ONCE THE UPPER PART OF
THE TROF MOVES PAST LATE TONIGHT AND TEMPS ALOFT BEGIN TO WARM
SOME...THE SHOWERS WILL LIKELY DECREASE SOME IN COVERAGE AND
INTENSITY BUT STILL BE ENOUGH TO MAINTAIN HIGH POPS OVER THE AREA.
THIS WILL CONTINUE SAT WITH ONSHORE FLOW CONTINUING AND SOME
ENHANCED LIFT DEVELOPING WELL OUT AHEAD OF THE LOW MOVING NNE.

AS FOR WINDS...RIGHT NOW A NARROW BAND OF SCA LEVEL WINDS IS
EXPECTED OVER THE NE GULF TONIGHT..AND ALONG THE N GULF COAST NEAR
CAPE SUCKLING SAT MORNING...JUST AHEAD OF SFC TROF. WINDS WILL
DROP SOME BEHIND THE TROF BUT INCREASE AGAIN TO SCA LEVELS LATE
SAT OVER THE SE GULF AHEAD OF APPROACHING LOW. ALSO WILL HAVE SOME
SCA LEVEL S WINDS OVER NRN LYNN CANAL LATE THIS AFTERNOON THAT
DROP TO 15-20 KT THIS EVENING. MAY HAVE SOME SCA LEVEL WINDS IN
CLARENCE STRAIT THIS EVENING AS WELL.

&&

.LONG TERM...MAIN FOCUS FOR THE EXTENDED FORECAST WAS WITH THE
STRONG FRONT EXPECTED TO IMPACT THE REGION THIS WEEKEND. A LOW
PRESSURE SYSTEM WILL MOVE NORTH INTO THE GULF SATURDAY EVENING.
ITS ASSOC FRONTAL BAND WILL BRING WITH IT SELY GALE FORCE WINDS
OVER THE GULF SATURDAY NIGHT INTO SUNDAY. THE FRONT WILL MOVE OVER
THE PANHANDLE THROUGH SUNDAY WITH SOME GUSTY WINDS AND HEAVY RAIN. HAVE
INCREASED WINDS SLIGHTLY ALONG THE FRONT AS MODEL 850MB WINDS ARE
PEAKING AT 50-60KT...WHICH IS AN INDICATION THAT SOME OF THOSE
COULD MIX DOWN AS GUSTS. FORECAST WILL NEED TO BE ADJUSTED UP
FURTHER IF THIS TREND CONTINUES. STRONGEST WINDS LOOK TO BE ALONG
THE OUTER COASTAL AREAS AND UP CLARENCE STRAIT WITH FROPA. TROPICAL
CONNECTION WITH THE FRONT WILL ENHANCE RAINFALL AMOUNTS. HEAVIEST
RAIN WILL BE OVER THE SOUTHERN AREAS ALL DAY SUNDAY INTO
MONDAY...ALTHOUGH GUSTY WINDS WILL MAKE THE RAIN SEEM HEAVIER
ACROSS OTHER AREAS AS WELL. STORM TOTAL QPF FROM SATURDAY EVENING
THROUGH EARLY MONDAY SHOWS RAINFALL AMOUNTS OF 5-6IN OVER THE
KETCHIKAN ZONE. THIS ALONG WITH STRONG WINDS COULD MAKE FOR SOME
SLIDE ISSUE DEPENDING ON HOW SATURATED THE GROUND/SNOW ALREADY IS.

FOR NEXT WEEK THE WET PATTERN CONTINUES WITH SERIES OF FRONTAL
BANDS AND WAVES MOVING ACROSS THE REGION AS WE REMAIN UNDER
ONSHORE FLOW. MODELS DIFFER ON TIMING OF THESE QUITE A BIT BUT
OVERALL IDEA IS SIMILAR. DID NOT MAKE SIGNIFICANT TWEAKS TO THE
SHORT TERM OTHER THAN TO INCREASE WINDS ALONG THE FRONT AND UPDATE
QPF AMOUNTS. FOR NEXT WEEK USED MAINLY HPC GUIDANCE DUE TO MODEL
UNCERTAINTY. FORECASTER CONFIDENCE IS AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-036-041>043-051-052.

&&

RWT/HANNON