Gale Warning 442, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
405 PM AKST SUN DEC 30 2012

.SHORT TERM...EARLY AFTERNOON SATELLITE LOOP REVEALS AN OCCLUDED
FRONT STRETCHES EAST TO SOUTHEASTWARD ACROSS THE NORTHERN AND
EASTERN GULF FROM A PARENT LOW NEAR KODIAK ISLAND. WITH CONTINUED
WARMING TREND...WELL DEFINED FRONTAL BOUNDARY MOVES NORTH TO
NORTHEASTWARD ACROSS THE FORECAST DOMAIN WITH RAIN...MODERATE AT
TIMES...EXCEPT SNOW AT HIGHER ELEVATION...HAINES AND KLONDIKE
HIGHWAYS. THE FRONT EXTENDS SOUTHWARD AND A WEAK LOW NEWLY
DEVELOPS OVER THE FAR SOUTHEASTERN GULF. ALONG AND AHEAD OF THE
FRONTAL PASSAGE...SMALL CRAFT WINDS/SEAS ARE PREVAILING ACROSS
THE OUTER COASTAL WATERS AND OCEAN ENTRANCES OF INNER CHANNELS
WITH MINIMUM GALE FORCE OVER THE SOUTHERN COASTAL WATERS. NO
SIGNIFICANT WINDS ARE OBSERVED OVER THE INLAND AREAS.

 MODELS ARE IN GENERAL AGREEMENT WITH THE NEWLY DEVELOPED WEAK
LOW IN THE FAR SOUTHEASTERN GULF THIS AFTERNOON MOVES NORTHWARD
ALONG THE OUTER COAST THROUGH TONIGHT...THEN DISSIPATES OVER
SOUTHWESTERN YUKON BY MONDAY MORNING. A RIDGE OF HIGH PRESSURE
WILL BUILD ACROSS THE EASTERN GULF AND SOUTHEAST ALASKA THROUGH
LATE MONDAY. REFRESHED THE INHERITED FORECAST PACKAGE WITH THE
GFS AND ECMWF FOR THEIR GOOD CONSENSUS.

 AS THE LOW DRIFTS NORTHWARD...MINIMUM GALE FORCE ACROSS THE
SOUTHERN COASTAL WATERS WILL EASE TO SMALL CRAFT LEVEL LATER
TONIGHT. WITH CONTINUED SOUTHERLY LOW TO MID LEVEL FLOW...WARMING
TREND WILL BRING RAIN ACROSS THE FORECAST DOMAIN AND SNOW ALONG
THE HAINES AND KLONDIKE HIGHWAYS. WILL KEEP THE WINTER WEATHER
ADVISORY FOR HAINES HIGHWAY...MAINLY WEST OF KLUKWAN WITH
HEAVIEST SNOWFALL NEAR THE BORDER...THROUGH MIDNIGHT TONIGHT.
2 TO 4 INCHES OF ADDITIONAL ACCUMULATION IS POSSIBLE THIS
AFTERNOON WITH ANOTHER 1 TO 3 INCHES BEFORE TAPERING OFF LATE
TONIGHT.

.LONG TERM...UNLIKE THE SHORT-TERM, THERE IS NOT A LOT OF
CONSENSUS WITH THE WEATHER MAKERS IN THE EXTENDED TIME PERIOD,
ESPECIALLY WITH THE APPROACHING LOW MOVING NORTH THROUGH THE
EASTERN GULF LATE TUESDAY INTO WEDNESDAY MORNING. WHAT ARE FAIRLY
CONFIDENT ABOUT IS THE LOW APPROACHING KODIAK ISLAND MONDAY
EVENING AND CROSSING THE ALEUTIAN CHAIN BY TUESDAY MORNING TO
ENTER BRISTOL BAY. MEANWHILE ITS ASSOCIATED WEATHER FRONT WILL
MOVE MOVE INTO THE EASTERN GULF BY TUESDAY. THE UNCERTAINTY LIES
WITHIN A DEVELOPING LOW OVER THE TRIPLE POINT MOVING NORTH TUESDAY
NIGHT INTO WEDNESDAY. ALL MODELS HAVE BACKED OFF ON A STRENGTH OF
SUCH A FEATURE. MOST ARE NOW SUGGESTING A MERE OPEN WAVE TO FORM
AND MOVE NORTH ALONG THE FRONT LATE TUESDAY NIGHT INTO
WEDNESDAY...SUCH AS THE NAM AND THE GFS. IN THE NAME OF
CONTINUITY...DECIDED TO FOLLOW GUIDANCE FROM THE ECMWF AND THE
GEM. THE GEM REMAINS THE STRONGEST WITH THE FEATURE, BUT EVEN IT
HAS BACKED OFF FROM EARLIER RUNS. THE ECMWF RETAINS A CLOSED LOW
BUT HAS SLOWED THE FEATURE DOWN. IN THE END FAIRLY CONFIDENT OF
GALE FORCE WINDS OVER THE OUTSIDE WATERS TUESDAY INTO TUESDAY
NIGHT, BUT HAVE BACKED OFF ON THE STRENGTH ROUGHLY AROUND 5 KT
FROM THE EARLIER ISSUANCE. LOOKING AT THE INSIDE PASSAGES...BACKED
OFF WINDS IN THE NORTH SOUTH PASSAGES THROUGH THURSDAY AND KEPT
WIND DIRECTION FOLLOWING GEOSTROPHIC WITH PARALLEL FLOW. FOR THE
MOST PART THE FORECAST WILL READ 20 KT...BUT THINK AT TIMES THE
SPEEDS WILL BE LOWER GIVEN THE SETUP. VARIOUS SMALL CRAFT WILL BE
INTRODUCED IN THE EAST-WEST PASSAGES AS THE FRONT AND THE LOW
APPROACH THE COAST MONDAY NIGHT INTO TUESDAY NIGHT. CROSS SOUND
WILL POP TO GALE LATE MONDAY NIGHT AND TUESDAY NIGHT WHILE CLARENCE
WILL SPIKE TO GALE TUESDAY NIGHT.

POPS HAVE ALSO BEEN DELAYED WITH A GENERAL LEAN TOWARDS ECMWF.
AHEAD OF THE FRONT, CONTINUED WARM AIR ADVECTION WILL KEEP
TEMPERATURES WARM ENOUGH FOR LIQUID PRECIPITATION WITH THE
EXCEPTIONS OF THE FAR NORTHERN ZONES MIXING WITH SNOW AT TIMES. AS
THE FRONT PASSES WEDNESDAY MORNING...COOL AIR SHOULD BEGIN
ADVECTING INTO THE REGION AND THUS MORE SNOW WILL BE FOUND BY
MIDWEEK...AGAIN MAINLY NORTH OF FREDERICK SOUND AND ICY STRAIT.

BEYOND WEDNESDAY...UNSETTLED PATTERN CONTINUES WITH RELATIVELY
STRONG LOWS PASSING INTO THE WESTERN GULF AND BRISTOL BAY WHILE
SHORTWAVES PERIODICALLY DEVELOP ALONG WEATHER FRONTS OVER THE
EASTERN GULF AND THE PANHANDLE. PHASE CHANGES BETWEEN ECMWF AND
GFS WILL DO NOT LEND A LOT OF CONFIDENCE WITH EACH SYSTEM. HAVE
LEANED ON HPC WITH AN ECMWF BENT FOR THURSDAY INTO THE WEEKEND.

CONFIDENCE FOR FORECAST IS ABOVE AVERAGE FOR MONDAY NIGHT BUT
CONFIDENCE DROPS ON TUESDAY WITH TRIPLE POINT LOW MOVING NORTH
THROUGH THE EASTERN GULF...HOWEVER GALE FORCE WINDS OVER OUTSIDE
WATERS AND THE POSSIBILITY OF STRONG WINDS NEEDED OVER THE COASTAL
AREAS LOOK GOOD. MODEL OF CHOICE WAS ECMWF WITH SOME GEM MONDAY
NIGHT THROUGH TUESDAY. THIS TRANSITIONS WITH ECMWF WEDNESDAY NIGHT
INTO HPC THURSDAY.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 6 PM AKST THIS EVENING FOR AKZ023-027.
         WINTER WEATHER ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ019.
MARINE...GALE WARNING FOR PKZ036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ021-022-033>035-043-051-052.

&&

AHN/JWA