Small Craft Advisory 39, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
320 PM AKST FRI JAN 10 2014

.SHORT TERM...A COMPLEX LOW PRESSURE SYSTEM DEVELOPING OVER THE
NORTHEAST PACIFIC WILL TRACK ACROSS HAIDA GWAII TONIGHT AND
WEAKEN RAPIDLY AS IT MOVES INLAND OVER BRITISH COLUMBIA ON
SATURDAY. AT THE UPPER LEVELS THIS SYSTEM IS SUPPORTED BY BEING
IN THE LEFT EXIT REGION OF A 140 KT JET. THE BROAD WEAK AREA OF
LOW PRESSURE THAT HAS PERSISTED OVER THE NORTHERN GULF THE PAST
SEVERAL DAYS WILL DISSIPATE BY LATE THIS EVENING.

 SHOWER ACTIVITY HAS MAINLY BEEN CONFINED TO THE NORTHERN HALF OF
THE PANHANDLE TODAY. THERE HAVE BEEN REPORTS OF SOME SNOW MIXED
IN AT TIMES AND YAKUTAT HAS SEEN ICE PELLETS IN A HEAVIER SHOWER
EARLY THIS AFTERNOON. EXPECT A GRADUAL DIMINISHING TREND IN THE
SHOWERS THROUGH THE EVENING HOURS AND OVERNIGHT. LOW PRESSURE
SYSTEM CROSSING HAIDA GWAII WILL BRING STEADIER PRECIPITATION TO
THE FAR SOUTHERN PANHANDLE LATE TONIGHT AND THE FIRST HALF OF
SATURDAY BEFORE DIMINISHING. OVER MUCH OF THE REMAINDER OF THE
PANHANDLE SATURDAY WILL START DRY, BUT A TROUGH CROSSING INTO THE
AREA WILL INCREASE SHOWERS AGAIN ALONG THE COAST AND OVER THE
NORTHERN PANHANDLE LATE MORNING AND AFTERNOON. TRICKIEST PART OF
THE FORECAST WAS CLOUD COVER TONIGHT. STUCK WITH PREVIOUS
FORECAST THINKING OF DECENT BREAKS IN THE CLOUD COVER ACROSS THE
CENTRAL PANHANDLE GETTING AS FAR NORTH AS THE JUNEAU AREA. WITH
BREAKS IN THE CLOUD COVER AND RESIDUAL MOISTURE EXPECT FOG TO
DEVELOP ACROSS PORTIONS OF THE CENTRAL AND NORTHERN PANHANDLE.
SOME CLEARING WILL ALSO ALLOW TEMPERATURES TO FALL BELOW FREEZING
LEADING TO THE DEVELOPMENT OF BLACK ICE IN COLDER LOCATIONS.

 STRONG SOUTHERLY WINDS WILL WEAKEN THIS AFTERNOON AND EVENING AS
LOW PRESSURE SYSTEM TO THE SOUTH CONTINUES TO MOVE EAST. THIS
WILL TURN THE GRADIENT TO THE NORTH TONIGHT AND SATURDAY. THE
STRONGEST WINDS DURING THIS TIME FRAME WILL BE OVER THE SOUTHERN
PANHANDLE WITH SMALL CRAFT NORTHERLIES IN CLARENCE STRAIT AND A
PERIOD OF GALES OVER THE FAR SOUTHEAST GULF. NORTHERLY WINDS
ACROSS THE NORTHERN INNER CHANNELS ARE ONLY EXPECTED TO BE AROUND
10-20 KT AS THE LOW AND STRONGEST GRADIENT REMAIN TO THE SOUTH .

 BLENDED IN THE 12Z ECMWF WITH THE INHERITED GRIDS FOR THE SHORT
RANGE PORTION OF THE FORECAST. THIS RESULTED IN A SLIGHTLY
FARTHER NORTH TRACK OF THE SURFACE LOW MOVING ACROSS HAIDA GWAII.
FORECASTER CONFIDENCE IS AVERAGE THROUGH THE NEXT 24 HOURS.

&&

.LONG TERM...MODELS REMAIN IN GENERAL AGREEMENT THROUGH EARLY NEXT
WEEK WITH THE ECMWF HANDLES THE LOW IN THE NORTHEASTERN GULF OVER
THE WEEKEND A BIT FASTER THAN THE GFS AND NAM. REFRESHED THE
INHERITED FORECAST WITH THE ECMWF TO SLOW DOWN THE FORWARDING
SPEED A BIT. WITH THE FRONTAL PASSAGE ASSOCIATED WITH THE LOW
SHOWERY PRECIPITATION SATURDAY EVENING WILL BECOME MORE STRATI
FORM OVERNIGHT. MODEL SOLUTIONS BEGIN DIVERTING BY MID WEEK AND
USED THE WPC ENSEMBLE APPROACH FROM TUESDAY ONWARD.

 AHEAD OF THE THE INCOMING LOW IN THE NORTHEASTERN GULF...LOW
LEVEL WINDS WILL BECOME MORE SOUTHERLY AND SLIGHTLY INCREASE WITH
INCREASING POPS TO LIKELY TO CATEGORICAL THROUGH LATE SATURDAY
NIGHT. WITH THE ONSET OF THE FRONTAL PASSAGE...LIKELY TO
CATEGORICAL POPS WILL CONTINUE ACROSS THE PANHANDLE ON SUNDAY.
ONSHORE FLOW WILL CONTINUE BEHIND THE FRONTAL BOUNDARY AND
MAINTAIN HIGHER POPS THROUGH LATE MONDAY. TEMPERATURES WILL STAY
COLD ENOUGH TO BRING SNOW...MIXING WITH RAIN DURING THE DAY...FOR
1 TO 3 INCHES OF POSSIBLE ACCUMULATION MAINLY OVER THE NORTHERN
HALF.

 WITH GROWING UNCERTAINTIES...A LOW PRESSURE SYSTEM IS EXPECTED
TO MOVE ACROSS THE GULF LATE MONDAY NIGHT INTO TUESDAY FOLLOWED BY
A HIGH AMPLITUDE RIDGE BUILDING OVER THE EASTERN GULF AND
SOUTHEAST ALASKA BY LATE WEDNESDAY AND CONTINUE THROUGH THE
SECOND HALF OF THE WEEK WITH MODERATE WARMING TREND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041.
         SMALL CRAFT ADVISORY FOR PKZ012-013-036-042.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-043-051>053.

&&

TPS/AHN