Small Craft Advisory 830, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
304 PM AKST SAT NOV 29 2014

.SHORT TERM...WEAK SURFACE LOW (~1015 MB ) WITH UPPER LEVEL
TROUGH SUPPORT MOVING ACROSS THE NORTHERN GULF FOR OVERRUNNING
SNOW EVENT FOR MUCH OF THE PANHANDLE. MODELS HAVE BEEN ON
GENERALLY ON TRACK WITH THIS SYSTEM AND THE HANDLING. SNOW HAS
STARTED IN THE YAKUTAT AREA SATURDAY AFTER AS EXPECTED AND WILL
SEE THIS PROGRESS INTO THE PANHANDLE OVER NIGHT.

MADE MINIMAL ADJUSTMENTS TO THE FORECAST WITH THE WARNING EVENT
IN PLACE AND NO SIGNIFICANT REASONING TO MAKE ALTERATIONS TO IT.
SNOW AMOUNTS ACROSS THE REGION AND TIMING DEPEND ON THE LOCATIONS
AND THE AMOUNT OF COLD AIR. SOME WARMER TEMPERATURES CREEPING INTO
THE BARANOF ISLAND AND WESTERN PRINCE OF WALES ISLAND SO LITTLE IN
WAY OF SNOW TONIGHT AND SUNDAY EXPECTED. BEST AMOUNTS FOR HEAVIER
SNOW ARE GOING TO BE THE INLAND VALLEYS OF THE COAST RANGE FROM
ABOUT JUNEAU TO HYDER. THE HAINES AREA MAY GET SOME SNOW
TOO...HOWEVER LOW TRACK IS TAKING ALL THE FUN AWAY FROM THEM.

IN THE MARINES WITH THE LOW APPROACHING THE COAST THE PRESSURE
GRADIENT WILL INCREASE OF THE NORTH ON SUNDAY WITH A HIGH BUILDING
OVER THE YUKON SO SMALL CRAFTS REBUILDING TO MIN GALES FOR THE
NORTHERN GALES.

.LONG TERM...UPPER DISTURBANCE ENTERING THE NRN GULF THIS
AFTERNOON IS FORECAST TO RESIDE OVER THE SRN PANHANDLE BY THE
START OF THE LONG TERM PERIOD /06Z MON/. STRONGEST ASCENT WILL BE
LOCATED CLOSE TO THIS FEATURE. THUS...GREATEST POTENTIAL FOR
MODERATE SNOWFALL SUN NIGHT WILL BE FOCUSED ALONG AND E OF A
PETERSBURG TO KETCHIKAN LINE...WITH HYDER MOST PROBABLE DUE TO
COLDER AIRMASS LOCATED INLAND. THE UPPER VORT MAX THEN SHIFTS INTO
B.C. BY MON AFTERNOON...WITH PRECIPITATION EFFECTIVELY SHUTTING
DOWN IN ITS WAKE OVER THE PANHANDLE.

NEXT UPPER TROUGH ENTERS THE WRN/CNTRL GULF ON TUE...WITH AN
ASSOCIATED SURFACE FRONTAL BOUNDARY ENTERING COASTAL AREAS OF THE
PANHANDLE TUE NIGHT. SUBFREEZING AIRMASS WILL STILL BE IN PLACE
AHEAD OF THE FRONT OVER NRN/CNTRL PORTIONS OF SERN AK...AS WELL AS
HYDER. THEREFORE...EXPECT ANOTHER 1-2 INCHES OF SNOW TUE MORNING
INTO TUE NIGHT AS MOIST ISENTROPIC ASCENT OCCURS IN COMBINATION
WITH THE COLD AIR. CHANGE OVER TO RAIN WILL EVENTUALLY TAKE
PLACE...FIRST FOR YAKUTAT TUE AFTERNOON...AND THEN INLAND TUE
NIGHT...AS LOW-LEVEL SLYS USHER IN ABOVE FREEZING TEMPERATURES
NEAR THE SURFACE.

FOR WED THROUGH THE REMAINDER OF THE LONG TERM...MODEL GUIDANCE
SHOWS THE REGION WILL REMAIN IN SSWLY FLOW ALOFT. SPREAD INCREASES
WITH REGARD TO INDIVIDUAL EMBEDDED SHORTWAVES...ONE WHICH PASSES
ACROSS THE PANHANDLE ON FRI...AND A SECOND THAT ENTERS THE GULF ON
SUN. IN GENERAL...THIS PATTERN WILL SUPPORT WET WEATHER...WITH
TEMPERATURES CURRENTLY EXPECTED TO BE WARM ENOUGH TO NEGATE THE
THREAT FOR SIGNIFICANT SNOWFALL. REGARDING MARINE HAZARDS...SMALL
CRAFT WINDS MAY OCCUR OVER THE OUTSIDE WATERS AS PREVIOUSLY
MENTIONED FRONT APPROACHES THE AREA ON TUE. IN ADDITION...SEAS ARE
FORECAST TO INCREASE TO AROUND 10 FEET BEHIND THE FRONT.

NO CHANGE TO PRESSURE GRIDS WAS MADE THROUGH 06Z WED...WITH ONLY
MINOR MODIFICATIONS NECESSARY FOR WINDS. WPC WAS THEN BLENDED IN
FOR PRESSURE AND DERIVED WINDS 12Z WED THROUGH THE REMAINDER OF
THE LONG TERM. AN ECMWF/GFS/OFFICIAL BLEND WAS USED FOR POP FIELDS
THROUGH 06Z WED...WITH HEAVIER RELIANCE ON WPC THEREAFTER. QPF
VALUES WERE LIMITED TO A TENTH OF AN INCH OR LESS FOR 12Z WED AND
BEYOND DUE TO INCREASING MODEL SPREAD. FORECAST CONFIDENCE IS
AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING FROM 5 AM SUNDAY TO MIDNIGHT AKST SUNDAY
     NIGHT FOR AKZ026.
         WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 4 PM AKST
     SUNDAY FOR AKZ020>022-024.
         WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 4 PM AKST SUNDAY
     FOR AKZ025.
         WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON AKST
     SUNDAY FOR AKZ019.
         WINTER WEATHER ADVISORY UNTIL 5 AM AKST SUNDAY FOR AKZ017.
         WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO MIDNIGHT AKST SUNDAY
     NIGHT FOR AKZ028.
         WINTER STORM WARNING FROM 5 AM SUNDAY TO 5 AM AKST MONDAY FOR
     AKZ029.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ013-034>036-041>043.

&&

BEZENEK/GARNER

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