Gale Warning 413, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
209 PM AKST FRI DEC 11 2009

.SHORT TERM...CONFIDENCE IS HIGH FOR THE CONTINUED CHANGE FROM
THE OVERCAST WITH LITTLE OR NO PRECIP, TO THE INTENSIFYING COLD
AND DRY OUTBREAK. AT THIS TIME THE ST DECK COVERS MOST OF  THE
PNHDL S OF A CSP-PAJN LINE.  THIS CHANGE TO DRY AND COLDER
CONDITIONS WILL CONT IN A N TO S SEQUENCE WITH THE LAST CIGS  TO
BE OVER POW ISLAND SAT MORNING.

 &&

 .LONG TERM...THE MODELS HAVE BEEN SHIFTING THEIR SOLUTIONS
AROUND A BIT OVER THE PAST 24 HOURS. COLD AIR OUTBREAK FOR THE
PANHANDLE SATURDAY NIGHT INTO SUNDAY IS STILL IN THE CARDS YET
THE STRENGTH OF THE OUTFLOW WINDS FORECAST TO ACCOMPANY IT HAVE
DIMINISHED. THIS IS MAINLY A RESULT OF THE UPPER RIDGE OVER THE
GULF REFUSING TO RETROGRADE AS FAR WEST AS PREVIOUS RUNS HAVE
INDICATED BEFORE IT BREAKS DOWN. AT THE SURFACE THIS MEANS THAT
THE COLD HIGH IN CANADA DOES NOT GET AS FAR WEST AND SOUTH AS
PREVIOUSLY FORECAST. INSTEAD, MOST MODELS SEEM TO INDICATE THAT
THE 1035 MB HIGH WILL ONLY GET TO NE BC BEFORE IT IS SHOVED TO
THE SE. PRESSURE GRADIENT FORECASTS BETWEEN THE PANHANDLE AND
CANADIAN STATIONS ARE ABOUT 2/3RDS AS STRONG FOR THE SAT NIGHT
AND SUN PERIOD AS WAS SUGGESTED 24 HOURS AGO. AS SUCH HAVE
DROPPED DOWN THE OUTFLOW WINDS OUT OF CROSS SOUND AND THE PASSES
SOUTH OF YAKUTAT. STILL FEEL THAT THE PRESSURE GRADIENT WILL BE
ENOUGH FOR WIND ADVISORY WINDS IN JUNEAU, SKAGWAY, AND HAINES AND
A GALE WARNING FOR NORTHERN LYNN.

 A MINOR TAKU WIND EVENT IS ALSO A POSSIBILITY FOR SATURDAY
NIGHT. CROSS BARRIER FLOW OF ABOUT 30 KT IS FORECAST, YET THE
INVERSION IS RATHER WEAK AND WHILE THERE IS A WEAK CRITICAL LEVEL
AT AROUND 500 MB RELATIVE TO THE RIDGE, IT IS NOT A NO FLOW CL.
WINDS AT THAT LEVEL ARE BLOWING PARALLEL TO THE RIDGE AXIS AT
ABOUT 30 TO 40 KT FROM THE NW AND GRADUALLY TURN TO THE NE AS YOU
GO DOWN TO 850 MB. AT THIS TIME, THINKING IS THAT THERE MAY BE A
FEW HIGHER GUST IN DOWNTOWN AND SOUTHWARD FOR SATURDAY NIGHT BUT
MOST OF THAT WILL BE GAP FLOW AND NOT TAKU WINDS.

 ADDITIONALLY, TEMPERATURES WILL ALSO BE COLD SATURDAY NIGHT
THROUGH MONDAY. OVERNIGHT LOWS WILL BE IN THE SINGLE DIGITS IN
THE NORTH TEENS IN THE SOUTH SAT NIGHT AND HIGHS SUN WILL
STRUGGLE TO GET INTO THE MID 20S. THE COMBINATION OF LOW
TEMPERATURES AND HIGH WINDS WILL LEAD TO THE THREAT OF FREEZING
SPRAY IN A FEW OF THE NORTHERN INNER CHANNELS SAT NIGHT AND SUN.

 FARTHER OUT, MORE SHIFTING IN THE MODELS IS APPARENT AS THE
FIRST LOW TO AFFECT THE PANHANDLE IN A WHILE PAYS US A VISIT MID
WEEK. GFS HAS SHIFT ITS SOLUTION FROM TWO FAST MOVING LOWS TO ONE
WEAKER SLOWER LOW THAT TRACKS INTO THE SOUTHERN PANHANDLE EARLY
WED. THE EC ON THE OTHER HAND HAS SLOWED DOWN ITS LOW AND ALSO
HAS IT TRACKING FURTHER WEST THEN PREVIOUS RUNS HAVE SHOWN. IN
BOTH SCENARIOS THE SYSTEMS ARE RATHER WEAK AND LACK MOISTURE AS
MOST OF THE JET ENERGY IS WELL TO THE SOUTH IN THE NORTHER
PACIFIC. EITHER WAY WHEN THE PRECIP STARTS IT WILL BE IN THE FORM
OF SNOW FOR MOST AREAS AND SHOULD STAY AS SNOW FOR AREAS NORTH OF
FREDERICK SOUND. AT THIS TIME, ACCUMULATION SHOULD REMAIN LIGHT
YET IF A OVERRUNNING SITUATION WITH A ARCTIC BOUNDARY SETS UP
ACCUMULATIONS COULD BE HIGHER.

 MID RANGE FORECAST WAS UPDATED WITH THE NAM DUE TO GOOD
REPRESENTATION OF THE PRESSURE GRADIENT ALONG THE COAST
MOUNTAINS. LATER ON, THE EC AND LATER THE HPC GUIDANCE WERE
INCORPORATED DUE TO GOOD CONSISTENCY AND GOOD REPRESENTATION OF
SURFACE FEATURES. FORECAST CONFIDENCE IS ABOUT AVERAGE FOR THE
MID RANGE DUE TO SOME SHIFT IN MODEL SOLUTIONS FROM RUN TO RUN
AND BELOW AVERAGE FOR THE LONGER RANGE DUE TO MODEL DISAGREEMENT
PAST MONDAY.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 3 PM SATURDAY TO 3 PM AKST SUNDAY FOR AKZ019-
     025.
         WIND ADVISORY FROM NOON SATURDAY TO 3 PM AKST SUNDAY FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ011-013-022-031-051.

&&

JBT/EAL