000
FXAK67 PAJK 271450
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
550 AM AKST MON DEC 27 2010
.SHORT TERM...SATELLITE AND RADAR THIS MORNING REVEAL A FEW WEAK
WAVES MOVING UP THE PANHANDLE BRINGING PERIODS OF RAIN AND SNOW
TO THE AREA. MOST PLACES IN THE PANHANDLE HAVE REPORTED ON AND
OFF SNOW THROUGH THE NIGHT. THE EXCEPTION IS ALONG THE OUTER
COAST AND IN THE SOUTHERN PANHANDLE WHERE THE PRECIP IS ALL RAIN
OR HAS MIXED WITH RAIN. PRECIP AMOUNTS HAVE BEEN LIGHT BUT
HEAVIER SHOWERS MAY DROP A QUICK INCH OR TWO.
AS FOR WINDS MOST PLACES ARE SHOWING LESS THAN 20 KT THIS
MORNING, BUT THERE ARE A FEW EXCEPTIONS. SKAGWAY IS STILL GUSTING
TO 45 MPH AT TIMES DESPITE THE DECREASING NORTHERLY PRESSURE
GRADIENT. JUNEAU TO SKAGWAY PRESSURE GRADIENT IS DOWN TO 1.7 MB
WHICH IS REFLECTED BY THE 20 KT WINDS AT ELDRED ROCK. THE MOST
LIKELY CAUSE IS THAT MOST OF THE GRADIENT IS ON MOUNTAINS AND NOT
ON THE CANAL AND THAT THERE IS STILL A SIGNIFICANT COLD POOL IN
CANADA THAT IS DRAINING THROUGH WHITE PASS. THIS THEORY IS
SUPPORTED BY THE PRESSURE GRADIENT BETWEEN WHITEHORSE AND JUNEAU
STILL READING ABOUT 10 MB AND THERE IS STILL A COLD LAYER ABOUT
3000 FT DEEP IN CANADA AS SEEN IN THE WHITEHORSE SOUNDING. THOSE
WINDS SHOULD SLACK OFF LATER TODAY AS THE PRESSURE GRADIENT
CONTINUES TO DROP. THE OTHER EXCEPTION TO THE LIGHT WINDS IS
LINCOLN ROCK WHICH IS BLOWING SMALL CRAFT AS ANOTHER WEAK BAND
PULLS THROUGH THERE.
FOR TODAY, PERIODS OF SNOW AND RAIN WILL CONTINUE AS MORE BANDS
COME NORTHWESTWARD AND SHOWERS ALSO GET INTO THE MIX IN BETWEEN
THE BANDS. MOST AREAS IN THE PANHANDLE SHOULD SEE SNOW FROM THESE
FEATURES BUT AREAS FARTHER SOUTH WILL SEE SOME RAIN MIXED IN.
THAT MAY CHANGE BY THIS EVENING AND TONIGHT AS A STREAM OF GULF
MODIFIED COLD AIR ARRIVES IN THE SOUTHERN PANHANDLE. THIS AIR
MASS IS NOT VERY COLD, BUT IT HAS ENOUGH BITE THAT THE RAIN COULD
CHANGE OVER TO SNOW IN THE SOUTH PARTICULARLY LATE TONIGHT. WITH
THE WEAK UPPER FORCING AND LACK OF MOISTURE TO PULL FROM, SNOW
FALL AMOUNTS SHOULD BE ONLY A FEW INCHES, BUT HIGHER AMOUNTS ARE
POSSIBLE WHERE THE SNOW SHOWERS TRAIN ACROSS ONE AREA. THE BEST
CHANCE FOR A MORE THAN JUST ONE OR TWO INCHES IS ALONG A LINE
FROM JUNEAU TO PORT ALEXANDER LATE TONIGHT AS A MID LEVEL
DEFORMATION BAND MAY STALL THERE. AREAS UNDER THIS MAY SEE AROUND
2 TO 4 INCHES BY LATE TONIGHT. AMOUNTS MAY BE HIGHER BUT PROBLEMS
IN BAND PLACEMENT AS WELL IN QPF AMOUNTS MAKE THE FORECAST
PROBLEMATIC. ELECTED TO GO WITH A MIDDLE OF THE ROAD SHOT AT SNOW
AMOUNTS GIVEN THE MODEL DISAGREEMENT AND THE LACK OF HIGH PROBS
IN THE SREF FOR ADVISORY LEVEL SNOW FALL.
USED A BLEND TO THE NAM WITH A BIT OF THE GFS THROWN IN AS THE
NAM SEEMED TO MODEL THE VARIOUS WAVES COMING UP THE PANHANDLE
WELL. FORECAST CONFIDENCE IS GOOD THROUGH THE SHORT TERM PERIOD.
&&
.LONG TERM...POOR MODEL AGREEMENT IN THE EXTENDED RANGE IN TERMS
OF PRESSURE...WIND...AND POP. ONE THING THAT THERE IS GOOD
AGREEMENT ON IS A FAIRLY WIDE SPREAD AND SIGNIFICANT WARM UP IN
THE SECOND HALF OF THIS WEEK. OVERNIGHT MODELS ALL INDICATING
DAYTIME HIGHS ABOVE FREEZING ACROSS THE ENTIRE PANHANDLE BY
THURSDAY. EARLY MORNING MODEL UPDATE IS CONSISTENT WITH THIS AND
MAINTAINS THE WARMTH THROUGH INTO NEXT WEEK. NIGHT TIME LOW STILL
REGULARLY GETTING DOWN BELOW FREEZING BUT THERE WILL BE SOME
SIGNIFICANT MELTING GOING ON LATER THIS WEEK FOR THOSE LOCATIONS
CURRENTLY WITH A SNOW COVER.
BETWEEN NOW AND THEN...HOWEVER...THERE WILL BE SOME FRESH SNOW
WITH SOME LOCATIONS POSSIBLY SEEING UP TO 5 NEW INCHES BETWEEN
TUESDAY MORNING AND THURSDAY MORNING.
LONG RANGE FORECAST UPDATES TONIGHT LIMITED TO TUESDAY THROUGH
THURSDAY MID DAY. BLENDED NAM AND GFS FOR POP FIELDS AND BLENDED
WINDS HEAVILY TOWARDS NAM. TEMPERATURE UPDATES THROUGH THE WEEK
BASED ON GFS ENSEMBLE MEAN AND RESULTED IN TEMPERATURES CHANGES OF
ONLY A DEGREE OR TWO...MOSTLY TOWARDS WARMER TEMPS. FORECAST
CONFIDENCE AVERAGE TO BELOW AVERAGE.
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 9 AM AKST THIS MORNING FOR AKZ018.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-036-052.
SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041.
&&
$$
EAL/FRITSCH
