Small Craft Advisory 773, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
450 PM AKST FRI DEC 14 2012

.SHORT TERM...BUSY SHIFT. A 970 MB LOW IN THE NORTHEAST GULF
WILL DRIFT NORTHWEST AND SLOWLY WEAKEN. ITS WEATHER FRONT WILL
MOVE ASHORE INTO THE PANHANDLE THIS EVENING AND STEADILY MOVE
NORTHWARD AND DISSIPATE OVERNIGHT. THIS HAS PLACED THE NORTHEAST
GULF SHORELINE INCLUDING YAKUTAT...UNDER THE THREAT OF HEAVY SNOW
THROUGH TONIGHT. LYNN CANAL AREA WILL ALSO KEEP JUST ENOUGH COLD
AIR IN PLACE FOR SOME REALLY GOOD SNOWFALL. THE LOW SEEMS TO BE
MOVING IN THE SWEET SPOT JUST SOUTHWEST OFFSHORE OF YAKUTAT. THIS
SHOULD KEEP WINDS IN YAKUTAT AT LEAST EAST...IF NOT SLIGHTLY
NORTHEAST ALL NIGHT LONG. HENCE TEMPERATURES WILL REMAIN NEAR
FREEZING AND ACCUMULATIONS WILL BE HEAVY...WITH TOTAL
ACCUMULATIONS UP TO 10 INCHES. IN THE LYNN CANAL
ZONES...ACCUMULATIONS WILL BE HEAVIEST IN HIGHER ELEVATIONS SUCH
AS THE BORDER AND THE PASS...UP TO 11 INCHES.

 THIS FRONTAL PASSAGE WILL ALSO ACCELERATE WINDS ALONG THE
PANHANDLE COAST AS PLANNED WITH GUSTS TO 50 MPH ON THE SHORES OF
PRINCE OF WALES SOUND. THE PRESSURE GRADIENT EVEN ALONG GASTINEAU
CHANNEL HAS RISEN...AND WILL LIKELY REMAIN HIGH THROUGH FRONTAL
PASSAGE ROUGHLY AROUND MIDNIGHT...SO ADDED STRONG WIND HEADLINES
FOR ALL OF THESE AREAS INCLUDING JUNEAU. MARINE AREAS...A
PLETHORA OF GALES ASSOCIATED WITH PRE-FRONTAL WINDS IN THE
OUTSIDE WATERS. GALES WILL ALSO BE THE RULE THIS EVENING FOR
OCEAN ENTRANCES OF THE INSIDE. WE ALSO BEGAN STEPHENS PASSAGE
WITH GALE MOVING DOWN TO SMALL CRAFT LATE.

 SATURDAY...THE IDEA IS THAT COLD AIR WILL ADVECT INTO THE
PANHANDLE WITH BEGINNING TOMORROW MORNING AND SNOW LEVELS WILL
DESCEND TO THE SURFACE OVER THE INTERIOR ZONES THAT HAD RAIN ALL
NIGHT. ALSO...WITH FRONTAL PASSAGE USED SHOWER WORDING AFTER
MIDNIGHT IN THE SOUTHERN PANHANDLE AND WENT ALL SHOWER WORDING
FOR SOUTHEAST IN THE ENTIRE PANHANDLE SATURDAY. SNOW
ACCUMULATIONS ON SATURDAY WERE NOT THE ISSUE TODAY...SPENT LITTLE
TIME ON THEM. BUT THE IDEA SHOULD BE UP TO 3 INCHES ACROSS THE
BOARD.

 FELT NAM WAS DOING BETTER JOB WITH WINDS IN INSIDE PASSAGE. BUT
PREVIOUS SHIFTS HAD RELIED ON GFS SO BLENDED THE INHERENT GFS
PREVIOUS PRODUCT WITH NEW 12Z NAM FOR WINDS. RECENT SATELLITE
IMAGERY REVEALS A MORE INTENSE CIRCULATION BUILDING IN THE
OFFSHORE WATERS...WHICH MAY SUPPORT THE NAM AS IT WAS BUILDING AN
ALTERNATIVE LOW TO THE SOUTHEAST OF THE MAIN LOW OVERNIGHT.
CONFIDENCE IN FORECAST NOT HUGE...BUT FEEL THE HEALTHY SNOWFALL
TOTALS IN 17...18...AND 19 WERE IN ORDER.

.LONG TERM...THE LONG TERM PERIOD BEGINS WITH AN AREA OF HIGH
PRESSURE FROM YUKON BUILDING INTO THE NORTHERN PANHANDLE.
MEANWHILE...A REMNANT LOW AND ASSOCIATED FRONT WILL CONTINUE TO
DISSIPATE AND MOVE SOUTHEASTWARD OFF THE COAST. SNOW SHOWERS ARE
EXPECTED FOR SATURDAY NIGHT INTO SUNDAY...WITH 1 TO 2 INCHES OF
NEW SNOW ACCUMULATION. SNOW SHOULD BE ON THE DIMINISHING TREND AS
THE HIGH BUILDS IN ON SUNDAY AND SUNDAY EVENING. MONDAY SHOULD BE
A FAIRLY DRY DAY ACROSS THE PANHANDLE.

THE COLD AIR WILL ALSO START TO BUILD INTO THE NORTHERN PANHANDLE
STARTING SUNDAY. HIGH TEMPERATURES ON SUNDAY IN SKAGWAY AND
HAINES WILL OCCUR EARLY IN THE MORNING...AND THEN BECOME STEADY
AND FALL THROUGH THE AFTERNOON AS STRONG NORTHERLY WINDS (GUSTING
TO 45 MPH) BRINGS IN COLDER AND DRIER AIR.

THE STRONG WIND WILL ALSO MOVE INTO THE NORTHERN INNER CHANNEL
SUNDAY. FREEZING SPRAY WILL BE A CONCERN STARTING SUNDAY WITH HIGH
WIND GUSTS AND LOWERING TEMPERATURES. ALONG THE NORTH SOUTH
ORIENTED CHANNEL...WIND SPEED CAN BE GUSTING TO GALE FORCE WINDS
OR HIGHER. ALONG THE OUTER COAST...GALE FORCE NORTHEASTERLY WINDS
CAN ALSO BE EXPECTED ALONG THE TRADITIONAL OUTFLOW AREAS.

WHILE COLDER AND DRIER AIR REMAINS IN CONTROL OVER SOUTHEAST
ALASKA...A LOW PRESSURE WILL DEVELOP AND MOVE INTO THE GULF OF
ALASKA BY TUESDAY. MODELS ARE STILL TRYING TO RESOLVE THE DETAILS
ON THIS STORM SYSTEM. MODEL CONSENSUS SUGGEST THAT THE LOW
PRESSURE SYSTEM WILL NOT BE ABLE TO ERODE THE COLD AND DRY AIRMASS
IN PLACE OVER SOUTHEAST ALASKA. THERE MAY BE INCREASED CHANCE FOR
PRECIPITATION AND HIGHER WINDS FOR WEDNESDAY...ESPECIALLY ALONG
THE OUTER COAST AREA. OTHERWISE...COLDER AND DRIER CONDITIONS WILL
PERSIST THROUGH THE END OF THE LONG RANGE PERIOD ON FRIDAY.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ022-023-027.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ025.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ028.
         WINTER STORM WARNING UNTIL 5 AM AKST SATURDAY FOR AKZ017>019.
MARINE...GALE WARNING FOR PKZ021-022-033-035-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-031-032-034-053.

&&

JWA/RCL