Small Craft Advisory 722, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
438 PM AKST MON NOV 26 2012

.SHORT TERM...CHANGES ARE GENERALLY SMALL, AND THE DIMINISHING
WINDS APPEAR TO BE ON SCHEDULE FOR THIS AFTERNOON AND EVENING.
NOTE THE TREND FOR TOMORROW IS FOR INCREASING WIND ESPECIALLY IN
LYNN CANAL. NOTE THE FREEZING SPRAY IN NORTHERN LYNN CANAL.
CONFIDENCE IN THE SHORT RANGE PACKAGE IS AVERAGE.

 AREAS OF FOG: THE GUSTAVUS AND PETERSBURG OBS HAVE CARRIED FOG
THROUGH THE DAILY MAX HEATING, AND THIS FOG CAN  PERSIST THROUGH
TOMORROW MORNING. A SMALL INCREASE IN THE OUTFLOW OF LOW-LEVEL
CONTINENTAL AIRMASS WILL FLOW AT A  FASTER RATE TUESDAY AND WILL
RESULT IN DISSIPATION.

 GOES IR SHOWS THE EXTENSIVE CIRRIFORM SHIELD THAT EXTENDS FROM
AN OCCLUSION ABOUT 900 NM S OF YAKUTAT. THIS SHIELD IS EXTENDING
NNE THROUGH A BROAD RIDGE ALOFT THAT EXTENDS FROM ABOUT 100 NM SW
OF HAIDA GWAII TOWARD A COL OVER MIDDLETON ISLAND. THE RESULT IS
A CIRRIFORM CLOUD MASS THAT WILL CONTINUE TO DISSIPATE FROM BEING
A CEILING JUST AS IT REACHES OUR AREA OF RESPONSIBILITY. THE
OCCLUSION WILL MATURE WHILE TRACKING N TOWARD THE EASTERN GULF.

 NAM DID THE BEST INITIALIZATION OVERALL, INC 500-300 RH FIELD
COMPARED TO GOES WV FOR THE SYSTEM CURRENTLY 900 NM S OF YAKUTAT.
NAM ALSO HAD THE BEST FIT WITH AN MDCARS AIRLINER WIND
OBSERVATION AT 34 KFT AS COMPARED TO 250 MB MODEL WINDS. MODELS
DO DECREASE THE CLOUD COVER TOO QUICKLY FOR THIS EVENING, BUT NOT
BY MUCH.

&&

.LONG TERM...FOCUS TODAY HAS BEEN LIMITED TO GRIDS THROUGH
THURSDAY NIGHT WITH PARTICULAR EMPHASIS ON A POTENTIAL TAKU WIND
EVENT FOR JUNEAU AND DOUGLAS FROM TUESDAY EVENING THROUGH
WEDNESDAY AFTERNOON. CROSS BARRIER FLOW, LOW LEVEL INVERSION AND
CRITICAL LEVEL INDICATORS ARE ALL 4S AND 5S ON A SCALE OF 1 TO 7
AND ARE STRONGER THAN THOSE PREDICTED FOR THE THANKSGIVING HIGH
WIND EVENT. THE SKAGWAY-JUNEAU PRESSURE GRADIENT MAXES OUT AT
11.9 MB FOR THIS EVENT BUT STRENGTHENS EVEN MORE - UP TO 13.7 MB
BY THURSDAY MORNING. AMONG OTHER THINGS, THIS WILL LIKELY RESULT
IN A SUSTAINED PERIOD OF HIGH WINDS BEGINNING WEDNESDAY AFTERNOON.
HAVE NOT LABELED THIS SECOND ROUND OF HIGH WINDS A TAKU EVENT
PRIMARILY BECAUSE THE CRITICAL LEVEL DESCENDS TOO LOW IN THE
ATMOSPHERE. CROSS BARRIER FLOW DOES, HOWEVER, REMAIN STRONG ENOUGH
TO EASILY SUPPORT HIGH WINDS IN THE JUNEAU AREA UNTIL THURSDAY
MORNING.

EXTREMELY STRONG OFFSHORE PRESSURE GRADIENT RESULTING FROM STRONG
SURFACE HIGH PRESSURE DESCENDING SOUTHEAST IN THE YUKON AND A VERY
POTENT STORM APPROACHING THE PANHANDLE FROM THE SOUTHWEST WILL
RESULT IN STRONGEST WINDS OVER THE FAR NORTHERN INNER CHANNELS.
HAVE GONE WITH NORTHERLY STORM FORCE WARNING TO 60 KTS IN NORTHERN
LYNN AND 50 KT STORM WARNING FOR SOUTHERN LYNN CANAL. INCLUDED
HEAVY FREEZING SPRAY FOR BOTH NORTHERN LYNN AND GLACIER BAY.
DURING THIS TIME AS WELL. STRONG WIND HEADLINES ALMOST A CERTAINTY
FOR BOTH HAINES AND SKAGWAY DURING THIS TIME AS WELL.

PRECIP NOT TOO MUCH OF A CONCERN WITH THE ONLY SIGNIFICANT
SNOWFALL MENTIONED BEING AROUND 1 INCH FOR THE HYDER AREA DOWN IN
MISTY FJORDS FOR TUESDAY NIGHT AND QPF VALUES ARE NOT THAT
NOTEWORTHY. FOR PRESSURE AND WIND...USED NAM TUESDAY NIGHT
THROUGH WEDNESDAY, THEN ECMWF THROUGH THURSDAY NIGHT. BLENDED
ECMWF AND HPC FRIDAY THROUGH SUNDAY EVENING. CHANGES TO POP AND
QPF THROUGH THURSDAY NIGHT AND ARE A BLEND OF ECMWF AND GEM. MODEL
GUIDANCE FOR TEMPS WAS SIGNIFICANTLY COLDER THAN CURRENT FORECAST.
STARTED TEMPS THAT DIRECTION, BUT DID NOT MAKE CHANGES ANYWHERE
CLOSE TO THE DELTAS BEING CALCULATED WITH CURRENT MODEL DATA.
OVERALL FORECAST CONFIDENCE IS ABOVE AVERAGE FOR WINDS THROUGH
THURSDAY NIGHT, BUT BELOW AVERAGE FOR TEMPS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY AFTERNOON
     FOR AKZ025.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-041-042.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043-051-052.

&&

JBT/FRITSCH