Small Craft Advisory 609, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
335 PM AKDT FRI OCT 19 2012

.SHORT TERM...AFTERNOON SATELLITE IMAGERIES SHOW A 1002 MB LOW
JUST OFFSHORE FROM PRINCE OF WALES ISLAND. THIS LOW IS EXPECTED
TO CONTINUE TO WEAKEN AND TRACK SOUTHEASTWARD TOWARDS HAIDA GWAII
ISLAND THROUGH TONIGHT AND SATURDAY. A HIGH PRESSURE SYSTEM OVER
YUKON WILL BUILD INTO THE NORTHERN AREAS THROUGH THE SHORT TERM
PERIOD. THE COMBINATION OF THESE WEATHER SYSTEMS ARE GOING TO
BRING STRONGER WINDS TO THE AREA FOR SATURDAY ALONG WITH COOLER
AND DRIER AIR.

 AS COOLER AND DRIER CONTINENTAL AIR CONTINUES TO FILTER INTO THE
AREA OVERNIGHT...DECIDED TO KEEP MOST OF THE NORTHERN AREAS FREE
OF PRECIP THROUGH SATURDAY AFTERNOON. SCATTERED SHOWERS WILL
STILL LINGER IN THE SOUTHERN AREAS FROM DEPARTING SURFACE/UPPER
LOW...BUT THEY SHOULD DIMINISH AND MOVE OUT BY THE AREA BY MIDDAY
SATURDAY WITH INCREASING OFFSHORE FLOW.

 HIGH CLOUDS FROM EASTERLY FLOW IS SPILLING OVER THE AREA FROM
WESTERN BRITISH COLUMBIA ACROSS THE COAST MOUNTAIN. ON THE OTHER
HAND...SOUTHERN AREAS ARE UNDER CLOUDS FROM THE LOW PRESSURE
SYSTEM IN SOUTHEAST GULF OF ALASKA. THESE CLOUDS WILL BE ON THE
DECREASE SATURDAY AFTERNOON AS OFFSHORE FLOW STRENGTHENS.

 WINDS WILL CONTINUE TO INCREASE OVERNIGHT OVER THE GULF OF
ALASKA...ESPECIALLY IN OUTFLOW AREAS OVER THE NORTHEAST GULF.
WINDS AS HIGH AS 40 KT ARE EXPECTED IN THOSE AREAS BY TOMORROW
AFTERNOON. EASTERLY WINDS OUT OF CROSS SOUNDS WILL BE AS HIGH AS
50 KT FOR SATURDAY. WINDS IN NORTHERN LYNN CANAL WILL CONTINUE TO
INCREASE THROUGH SATURDAY TO BE NEAR 40 KT BY THE AFTERNOON. THE
REST OF THE N/S CHANNELS OVER THE NORTHERN HALF WILL SEE SMALL
CRAFT WINDS WITH HIGH GUSTS FROM INTERIOR PASSES.

 OVERLAND AREAS...STRONG WIND HEADLINES ARE ISSUED FOR SKAGWAY
AND JUNEAU (MAINLY FOR DOWNTOWN AND DOUGLAS) DURING THE DAY FOR
TOMORROW. DUE TO STRONG CROSS BARRIER FLOW FROM THE EAST AND
ALONG WITH A TIGHT PRESSURE GRADIENT BETWEEN THE INTERIOR AND THE
PANHANDLE. NORTHEASTERLY WIND WILL GUSTS AS HIGH AS 40 MPH IN
SKAGWAY, DOWNTOWN JUNEAU AND DOUGLAS BY LATE SATURDAY MORNING.
OTHER PLACES WILL SEE LOCALLY GUSTY WINDS IN EXPOSED AREAS.

 YAKUTAT WILL SEE LOW TEMPERATURES DROPPING TO AROUND 20 DEGREES
OVERNIGHT DUE TO EFFECTIVE RADIATIVE COOLING FROM MOSTLY CLEAR
SKIES, NEW SNOW COVER, AND CALM WINDS. MOST OF THE WIND-SHELTERED
AREAS ACROSS THE NORTHERN PANHANDLE WILL SEE TEMPERATURES DROP
INTO THE MID 20S WHILE OTHER AREAS WILL SEE TEMPS IN THE UPPER
30S WITH CLOUD COVER OR MORE WIND. DAYTIME HIGH TEMPERATURES WILL
RANGE FROM MID TO UPPER 30S IN THE NORTHERN PANHANDLE...TO AROUND
LOW TO MID 40S IN THE SOUTHERN PANHANDLE. DAYTIME MAXIMUM
TEMPERATURES WILL BE MUCH LOWER IF CALM CONDITIONS PERSIST
THROUGHOUT THE DAY.

 FORECAST CONFIDENCE IS ABOVE AVERAGE. USES ECMWF/NAM AS THE
MODEL OF CHOICE...AS THEY SIMULATES THE TIGHTENING PRESSURE
GRADIENT ACROSS THE NORTHERN PANHANDLE FAIRLY WELL. MINOR CHANGES
TO THE FORECAST ARE TO INCREASE THE WIND SLIGHTLY FOR THE
NORTHERN CHANNELS AND WINDS IN SKAGWAY AND JUNEAU AREAS.

&&

.LONG TERM...MODELS REMAIN IN FAIR AGREEMENT THROUGH EARLY NEXT
WEEK WITH A WEAKENING UPPER LEVEL LOW SLOWLY DRIFTS SOUTHEASTWARD
ACROSS THE EASTERN GULF AND ALASKAN PANHANDLE OVER THE WEEKEND
THEN STALLS OVER THE FAR SOUTHEASTERN GULF THROUGH LATE MONDAY.
STRONG UPPER HIGH BUILDING OVER THE WESTERN ALASKA WILL DRIFT
EAST. A WEAKENING LOW NEAR HAIDA GWAII LATE SATURDAY WILL SLOWLY
DRIFT SOUTHEASTWARD THROUGH EARLY NEXT WEEK AND STRONG ARCTIC HIGH
BUILDS ACROSS THE ALASKAN INTERIOR AND NORTHWESTERN CANADA. THIS
SYNOPTIC PATTERN WILL MAINTAIN A WEAK INVERTED TROUGH OF LOW
PRESSURE ACROSS THE EASTERN GULF AND ALONG THE PANHANDLE COASTS.
REFRESHED THE INHERITED FORECAST PACKAGE WITH THE NAM FOR ITS GOOD
INITIALIZATION AND HANDLING THE TIGHTENING NORTHERLY PRESSURE
GRADIENTS THROUGH MONDAY.

 ISOLATED SHOWERS ASSOCIATED WITH THE WEAKENING LOW DRIFTING
SOUTHEASTWARD WILL CONTINUE TO MOVE SOUTHEAST AWAY FROM THE
SOUTHERN PANHANDLE LATE SATURDAY...FOLLOWED BY INCREASING OFFSHORE
LOW TO MID LEVEL FLOW WITH PARTLY CLOUDY TO MOSTLY CLEAR SKIES
THROUGH EARLY NEXT WEEK. THE TIGHTENING NORTHERLY PRESSURE
GRADIENT WILL MAINTAIN GALE FORCE WINDS OVER THE NORTHERNMOST
INNER CHANNELS AND OUT OF INTERIOR PASSES WITH SOME TAKU WINDS
INGREDIENTS. WITH LESS CLOUD COVER...OVERNIGHT RADIATION COOLING
WILL BE ENHANCED AND COLD AIR ADVECTION WILL CONTINUE FROM THE
COLD ARCTIC AIR ENTRAINMENT FROM THE NORTH. OVERNIGHT LOWS WILL
COMMONLY DROP INTO THE LOWER TO MID 20S ACROSS THE NORTHERN HALF
OF THE PANHANDLE WITH MID TO UPPER TEENS OVER YAKUTAT AREA.

 MODEL DIFFERENCES BECOME LARGER BEGINNING ON LATE MONDAY ONWARD
AND LEANED OVER THE HPC ENSEMBLE APPROACH FOR THE REMAINING LONG
TERM PERIODS. IN GENERAL...DRY WEATHER WILL CONTINUE THROUGH MUCH
OF THE NEXT WEEK WITH A LITTLE TEMPERATURE MODIFICATIONS. MODEL
CONSENSUS HINTS A DEVELOPING LOW IN THE NORTH PACIFIC ON FRIDAY
WILL MOVE NORTHEASTWARD INTO THE SOUTH CENTRAL GULF BY LATE
SATURDAY. THIS INCOMING SYSTEM WILL INCREASE CLOUDS OVER THE
SOUTHERN PANHANDLE FROM THE SOUTHWEST ON FRIDAY AND SATURDAY WITH
SLIGHT CHANCE POPS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM SATURDAY MORNING THROUGH SATURDAY EVENING FOR
     AKZ025.
         STRONG WIND FROM SATURDAY MORNING THROUGH LATE SATURDAY NIGHT
     FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-022-043-051.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-031-032-042.

&&

RCL/ABJ/AHN