Gale Warning 123, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
117 PM AKST SAT FEB 12 2011

.SHORT TERM...ANOTHER COMPLICATED FORECAST IN THE WORKS FOR
TONIGHT AND SUN AS COLD AIR ATTEMPTS TO ENTER THE PANHANDLE FROM
TWO DIRECTIONS. THE FIRST DIRECTION IS FROM OFF THE GULF AS GULF
MODIFIED COOL AIR WRAPS AROUND THE LOW IN THE NORTHERN GULF.
BUOYS IN THE CENTRAL AND NORTHERN GULF HAVE OBSERVED AIR TEMPS AS
LOW AS 34 DEGREES AND PORT ALEXANDER, SITKA, AND ELFIN COVE HAVE
SWITCHED OVER TO SNOW TODAY AS THE COOL AIR GOT TO IT. THE SECOND
DIRECTION IS FROM THE NORTH AS ARCTIC AIR BUILDS IN THE INTERIOR.
THE ARCTIC FRONT HAS ALREADY INFILTRATED THE NORTHERN PANHANDLE
AS WINDS HAVE SWITCHED AROUND TO NE AND TEMPS HAVE STARTED TO
DROP AT SKAGWAY, AND HAINES HAS ALSO SEEN A WIND SHIFT TO NW AND
A TEMPERATURE DROP AS WELL TODAY.

 FOR TONIGHT AND TOMORROW, THE COLD AIR WILL CONTINUE ITS
INVASION. WITH THE MOST PROGRESS MADE BY THE AIR MASS ARRIVING
FROM THE GULF. THE NORTHERN FRONT WILL BE STALLED BY TERRAIN AND
PERSISTING SW FLOW. BY LATE TONIGHT MOST OF THE REMAINING RAIN
WILL HAVE SWITCHED OVER TO SNOW IN THE NORTHERN AND CENTRAL
PANHANDLE. ONLY THE VERY SOUTHERN PANHANDLE MAY STAY AS RAIN.
SPEAKING OF THE PRECIP, ONCE THE TROUGH THAT IS CURRENTLY OVER
THE OUTER COAST MOVES THROUGH THE PRECIP RATES WILL DIMINISH AS
THE ENVIRONMENT BECOMES SOMEWHAT CONVECTIVE. SO I AM EXPECTING
ONLY A FEW INCHES OF SNOW AT BEST TONIGHT. TOMORROW IS ANOTHER
STORY AS ANOTHER LOW/TROUGH ROUNDS THE SOUTH SIDE OF THE NORTHERN
GULF LOW AND BRINGS ANOTHER FRONTAL BAND TO THE AREA. WITH THE
COLD AIR ALREADY IN PLACE EXPECTING MOST INNER CHANNEL AREAS TO
SEE MOSTLY SNOW OUT OF THIS. PRECIP RATES ARE ENOUGH ALONG WITH
GOOD ISENTROPIC LIFT AND QVECTOR CONVERGENCE THAT I EXPECT
ADVISORY LEVEL SNOW FALL FOR HYDER, PETERSBURG, JUNEAU AND ANGOON
BY TOMORROW AFTERNOON AS THAT FRONT MOVES UP THE PANHANDLE.
SOUTHERN AREAS I THINK WILL BE JUST A BIT TOO WARM FOR HIGH SNOW
AMOUNTS, BUT SOME SNOW MIXED IN WITH THE RAIN IS NOT OUT OF THE
QUESTION.

 MODELS ARE HAVING SOME TROUBLES WITH THE MOVEMENT OF THE COLD
AIR TODAY. NONE OF THE MODELS ARE DEPICTING THE ARCTIC FRONT AS
FAR SOUTH AS THE OBSERVATIONS ARE INDICATING. PLUS THERE ARE SOME
DIFFERENCES ON HOW THE MODELS HANDLE THE INTERACTION BETWEEN THE
TWO LOWS IN THE GULF. GFS AND EC LOOKED A BIT ODD TO ME AS THEY
MERGED THE TWO LOWS. THE PINWHEEL TYPE SCENARIO SHOWN IN THE NAM
AND UK LOOKED MUCH MORE BELIEVABLE TO ME. FORECAST CONFIDENCE IS
FAIR.

.LONG TERM...MADE ONLY SMALLER CHANGES TO THE LONG TERM...MAINLY
TO THE SUN NIGHT AND MON PERIODS TO CONTINUE ADJUSTMENTS MADE
DURING SHORT RANGE. WILL STILL HAVE THE ARCTIC FRONT PRESSING SWD
THRU THE NRN AREA ALTHOUGH TIMING WILL BE TRICKY AS NOTED ABOVE.
MAY HAVE ANOTHER SHORTWAVE MOVING NWD AND THIS MIGHT BRING A ROUND
OF OVERRUNNING SNOW SUN NIGHT INTO MON MORNING...ALTHOUGH THE
SECOND HALF OF THAT PERIOD IS A TRICKIER CALL AS FAR AS AMOUNTS GO.
WILL KEEP WINTER WX ADVYS FOR THE PAJN AND HYDER AREAS GOING UNTIL
06Z MON. LATER SHIFTS MAY NEED TO EXTEND THE PAJN ADVY FURTHER OUT
DEPENDING ON HOW MUCH SLY FLOW ALOFT IS STILL GOING ON AFTER THEN.
AM A LITTLE CONCERNED ABOUT SNOWFALL IN THE PAHN/PAOH/PAGS/PAEL
AREAS LATER SUN NIGHT INTO MON MORNING AS COLDER AIR WILL ARRIVE
THERE ABOUT LATE SUN EVENING IT APPEARS...AND UPPER TROF WILL BE
SHARPENING UP TO THE W. WILL NOT ISSUE ANY OTHER PUBLIC HEADLINES
ATTM DUE TO POOR CONFIDENCE. USED A BLEND OF THE 12Z UKMET AND
NAM12 FOR THE SUN NIGHT AND MON PERIOD.

MADE ALMOST NO CHANGE TO THE TEMPS. DID ADJUST THE PAGY TEMPS
DOWNWARD SOME LATE SUN NIGHT INTO MON TO BETTER REFLECT TEMPS AT
SURROUNDING AREAS AND MODEL TRENDS THERE. FURTHER OUT THE MODELS
DIVERGE ESPECIALLY LATE IN THE WEEK AND WEEKEND...WHEN GFS SHOWS
ANOTHER TROF MOVING INTO THE GULF WHILE ECMWF HAS A STRONG RIDGE
HOLDING OVER THE ERN GULF AND SE AK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FROM 3 AM TO 3 PM AKST SUNDAY FOR AKZ024-
     026.
         WINTER WEATHER ADVISORY FROM 9 AM TO 9 PM AKST SUNDAY FOR AKZ025.
         WINTER WEATHER ADVISORY FROM 3 AM TO 9 PM AKST SUNDAY FOR AKZ029.
MARINE...SMALL CRAFT ADVISORY FOR PKZ021-022-033>036-041>043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-052.

&&

EAL/RWT