Small Craft Advisory 64, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
249 PM AKST THU JAN 20 2011

.SHORT TERM...EARLY AFTERNOON SATELLITE LOOP SHOWS A WEAKENING
TROUGH ACROSS THE NORTHERN PANHANDLE DRIFTING EAST WITH SCATTERED
RAIN SHOWERS ACROSS THE CENTRAL INNER CHANNELS AND SNOW/RAIN MIX
OVER THE NORTHERN AREAS. BEHIND THE WEAKENING TROUGH...WINDS ARE
DIMINISHING. A DEVELOPING LOW IN THE FAR WESTERN GULF MOVES
NORTHEASTWARD AND PUSHES A FRONTAL BOUNDARY INTO THE CENTRAL
GULF. AHEAD OF THE INCOMING FRONT...SOUTHWESTERLY LOW LEVEL FLOW
SLOWLY INCREASES OVER THE OFFSHORE WATERS WITH ROUGH SEAS. WITH
DISSIPATING PRECIPITATION BEHIND THE TRAILING EDGE OF THE
TROUGH...AREAS OF SHALLOW FOG FORMING SOME LOCATIONS ACROSS THE
INNER CHANNELS AND REMAIN THROUGH THE EARLY EVENING HOURS.

MODELS ARE IN FAIR AGREEMENT WITH THE DEVELOPING LOW IN THE
WESTERN GULF THIS EVENING MOVING NORTHEASTWARD TO THE NORTHERN
GULF THROUGH LATE FRIDAY. THE WEATHER FRONT ASSOCIATED WITH THE
LOW WILL DRIFT NORTHEAST AND MOVE INTO THE EASTERN GULF TONIGHT
THEN ONSHORE THE PANHANDLE ON FRIDAY. REFRESHED THE INHERITED
GRIDS WITH THE GFS DUE TO ITS BEST CONSISTENCY. THE WARMING TREND
WILL CONTINUE ACROSS THE FORECAST DOMAIN BUT NOT REACHING AS FAR
NORTH TO THE SKAGWAY...HAINES AND YAKUTAT AREAS. WILL LOWER THE
TEMPERATURES A BIT FOR THE NORTHERN ZONES AND KEEP SNOW FORECAST
FOR LATE TONIGHT AND FRIDAY. EXPECT YAKUTAT AREA WILL WARM UP A
BIT THIS EVENING BUT COOLING DOWN OVERNIGHT BUT SKAGWAY AND HAINES
WILL REMAIN BELOW FREEZING.

SHOWERS WILL DIMINISH EARLY THIS EVENING ACROSS THE FORECAST
DOMAIN BEFORE THE PRE-FRONTAL BOUNDARY ARRIVES THE OUTSIDE COASTAL
WATERS. STRATIFORM PRECIPITATION WILL BEGIN LATE THIS EVENING
ALONG THE PANHANDLE COAST AND SPREADING ONSHORE THE PANHANDLE LATE
TONIGHT AND EARLY FRIDAY MORNING. AGAIN...WARM AIR MASS WILL BRING
ALL RAIN ACROSS THE CENTRAL AND SOUTHERN PANHANDLE BUT NORTHERN
MOST ZONES WILL SEE SNOW ACCUMULATION LATE TONIGHT AND FRIDAY. NO
SIGNIFICANT SNOWFALL IS EXPECTED BUT UP TO 3 INCHES OF
ACCUMULATION WILL BE POSSIBLE. THE FRONT WILL ALSO BRING SMALL
CRAFT WINDS/SEAS ACROSS THE COASTAL WATERS AND BREEZY CONDITIONS
ALONG THE SOUTHERN PANHANDLE COAST ON FRIDAY.

&&

.LONG TERM...IN GENERAL EXPECT A MILD AND WET PATTERN THROUGH THIS
LONG TERM. UPPER LEVEL RIDGE EXTENDING FROM CENTRAL PACIFIC TO THE
PACIFIC NORTHWEST WILL KEEP JET STREAM ACROSS THE NORTH PACIFIC
AND OVER SOUTHEAST ALASKA. A SERIES OF FAST MOVING SHORT WAVES
MOVING THROUGH THE AREA. THESE SYSTEMS GAIN MAXIMUM STRENGTH OVER
THE NORTH PACIFIC SOUTH OF KODIAK THEN WEAKEN AS THEY MOVE NE INTO
THE EASTERN GULF AND DIE AROUND YAKUTAT AREA. THERE IS A LOT OF
UNCERTAINTY WITH THE TIMING AND DETAILS OF THE INDIVIDUAL SHORTWAVES.

THE 984 MB LOW MOVING INTO THE EASTERN GULF JUST SOUTH OF YAKUTAT
SATURDAY HAS A LONG FETCH OF MOISTURE THAT ORIGINATES NEAR HAWAII
AND WILL LIKELY BRING PERIODS OF HEAVY RAIN TO THE AREA SATURDAY.
SW GALES SPREAD INTO THE EASTERN GULF SATURDAY AND WILL BE
ACCOMPANIED BY A LARGE SW SWELL AND HAVE SEAS AS HIGH AS 20 FT.
PRESSURE GRADIENT ORIENTATION THROUGH THE INNER CHANNELS IS
FAVORABLE FOR SE WINDS WITH MOST ZONES A SOLID SMCR ALTHO CANNOT
RULE OUT A PRE FRONTAL SE GALE IN CLARENCE AND A POST FRONTAL SW
GALES FOR CROSS SOUND. COULD STILL HAVE ENOUGH COLD AIR IN PLACE
IN HAINES FOR SOME SNOW BUT THINK RAIN WILL BE MAIN PRECIP TYPE.

A SIMILAR SYSTEM MOVES INTO THE EASTERN GULF EITHER SUNDAY WITH
ANOTHER ROUND OF GALES FOR THE EASTERN GULF AND SMCR WITH HEAVY
RAIN FOR INNER CHANNELS.

WITH UNCERTAINTY IN TIMING AND DETAILS OF INDIVIDUAL SHORT WAVES I
DID NOT WANT TO MAKE ANY WHOLESALE CHANGES AND OPTED TO KEEP
EXISTING GRIDS AND ONLY MAKE A FEW SMALL CHANGES. NO MODEL HAD A
PREFERENCE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ021-022-033>036-041>043-051-052.

&&

AHN/MM