Small Craft Advisory 678, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
547 AM AKST WED NOV 14 2012

.SHORT TERM...EARLY MORNING SATELLITE LOOP REVEALS AN OCCLUDED
FRONT MOVING ONSHORE OVER THE PANHANDLE. THE FRONT IS ASSOCIATED
WITH A GALE FORCE LOW OVER THE BERING SEA. THE LOW IS SLOWLY
MOVING SOUTHEAST. A TRIPLE POINT PASSING NORTH OF KODIAK
PROPAGATES NORTHEAST. WELL DEFINED PRECIPITATION BAND MOVES
ACROSS THE NORTHEASTERN GULF COAST AND SOUTHEAST ALASKA. A COLD
FRONT FORMS BEHIND THE RAIN BAND. RELATIVELY WARM AIR MASS
TRAPPED BETWEEN THE OCCLUSION AND THE COLD FRONT CONTINUES
ADVECTING TOWARD THE PANHANDLE. WARMER AIR MASS AND INCREASING
SOUTHEAST LOW LEVEL WINDS KEEPS PRECIPITATION MOSTLY
RAIN...EXCEPT YAKUTAT AREA WHERE RAIN MIXED WITH SNOW AND SNOW
OVER NORTHERN MOST PANHANDLE AND INLAND AREAS OF CENTRAL
PANHANDLE.

SATELLITE IMAGERY ALSO DEPICTS A BRIEF BREAK OF PRECIPITATION
OVER THE CENTRAL PANHANDLE BUT THE NEXT PRECIPITATION BAND WILL
MOVE INTO THE AREA BY 6 OR 7 AM WITH PRECIPITATION TYPE MOSTLY
RAIN...EXCEPT FURTHER INLAND AND HIGHER ELEVATION IN MENDENHALL
VALLEY. KEPT THE WINTER WEATHER ADVISORY FOR SNOW THROUGH NOON
WITH 1 TO 3 INCHES OF ADDITIONAL ACCUMULATION...BUT THE SNOW IS
EXPECTED TO MIX WITH RAIN BY MID MORNING AND CHANGE OVER ALL RAIN
BY THE LATE MORNING HOURS.

MODELS ARE IN FAIR AGREEMENT WITH THE STRONG LOW IN THE BERING
SEA MOVING INTO THE WESTERN GULF LATE THIS EVENING AND CONTINUE TO
SLIDE SOUTHEASTWARD ACROSS THE GULF. THE ASSOCIATED FRONTAL
PASSAGE WILL MOVE ACROSS SOUTHEAST ALASKA THROUGH LATE TONIGHT. A
WARMING TREND WILL CONTINUE THROUGH TONIGHT AND PRECIPITATION WILL
BE ALL RAIN EXCEPT ALONG THE KLONDIKE AND HAINES HIGHWAYS WHERE UP
TO 2 INCHES OF SNOW POSSIBLE OVERNIGHT. ALONG THE FRONTAL
PASSAGE...SMALL CRAFT WINDS WILL PREVAIL ACROSS THE OUTSIDE WATERS
AND MOST INNER CHANNELS TODAY. BEHIND THE TRAILING EDGE OF THE
FRONT...THE WINDS WILL EASE DOWN BELOW SMALL CRAFT LEVELS DURING
THIS AFTERNOON...BUT THE ROUGH SMALL CRAFT SEAS WILL REMAIN OVER
THE OUTER WATERS THROUGH TONIGHT.

.LONG TERM...FORECAST ADJUSTMENTS WERE MADE FOR THE REDEVELOPMENT
OF THE LOW THAT IS TO TRACK INTO THE GULF FROM THE WEST TONIGHT.
AN INCREASE IN N TO NE OUTFLOW WINDS FOR THU AFTERNOON THROUGH FRI
FOR MOST OF THE INNER CHANNELS, AND WIND INCREASES ALSO EXTEND TO
MOST OF THE OUTSIDE WATERS. LITTLE HAS BEEN CHANGED FOR THE
FORECASTS FOR BEYOND FRIDAY NIGHT, INCLUDING THE LOWERING
TEMPERATURES ASSOCIATED WITH AN ARCTIC OUTFLOW FROM THE NORTH.
CONFIDENCE IS AVERAGE.

A LARGE ARCTIC AIRMASS IN THE INTERIOR CONTINUES TO BE SUPPORTED
BY A LARGE-SCALE RIDGE ALOFT THAT EXTENDS N ALONG MERIDIAN
180 DEGREES. THIS ARCTIC OUTFLOW IS THE PRIMARY REASON FOR THE
LOWERING TEMPERATURES OF THE FORECAST PACKAGE FOR LATE THIS
WEEK.

A 973 MB LOW IN BERING WILL TRACK ESE THROUGH BRISTOL BAY AND
SLOWLY WEAKEN BEFORE REACHING KODIAK ISLAND ABOUT 06Z THU. WE WILL
GIVE THIS LOW THE NAME OF LOW NUMBER ONE.  AN ASSOCIATED TRIPLE
POINT LOW WILL DEVELOP IN THE GULF AHEAD OF LOW ONE. THIS TRIPLE
POINT LOW IS GIVEN THE NAME OF LOW NUMBER TWO. LOW TWO WILL DEEPEN
TO AT LEAST 991 MB IN THE VICINITY OF SEWARD AT 12Z THU, AND
WILL DEEPEN TO ABOUT 984 MB AS IT REACHES A POINT 300 NM SSW OF
YAKUTAT AT 12Z FRI.

THE CYCLONIC INTERACTION OF LOWS ONE AND TWO WILL INCLUDE LOW
ONE MOVING TO THE SOUTH OF LOW TWO. THE QUITE COLD CORE OF LOW TWO
WILL BE SENT SE TO A COMPARATIVELY WARM REGION IN THE SOUTHWEST
GULF, WITH THE ASSOCIATED INCREASE IN BAROCLINITY BEING SPENT AS
A REDEVELOPED CYCLOGENESIS OF LOW ONE. THIS REDEVELOPMENT IS THE
REASON FOR THE RAISED WIND SPEEDS IN THE FORECASTS, ESPECIALLY
FOR THU AND THU NIGHT.

LOW TWO WILL RE INTENSIFY TO ABOUT 984 MB AS IT REACHES A POINT
300 NM SSW OF YAKUTAT AT 12Z FRI.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL NOON AKST TODAY FOR AKZ025.
MARINE...SMALL CRAFT ADVISORY FOR PKZ021-022-031>036-041>043-051-052.

&&

AHN/JBT