FXUS66 KPDT 300455 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
855 PM PST SUN NOV 29 2009
UPDATED UPDATE TEXT AND AVIATION DISCUSSIONS
.UPDATE...A COUPLE OF CHANGES MADE THIS EVENING FOR TONIGHT AND
TOMORROW. FOR TONIGHT, HAVE DRAMATICALLY REDUCED SKY COVER. THE
UPPER RIDGE AXIS IS NEARING THE COASTLINE WITH VERY LITTLE IF ANY
CIRRUS EXPECTED TO REMAIN OVER THE AREA AFTER THE EVENING HOURS.
ALSO BROUGHT EVENING FREEZING FOG INTO THE YAKIMA AREA WITH THE
AIRPORT ALREADY DIPPING DOWN TO 4 MILES VISIBILITY. THINK OTHER
AREAS WILL DEVELOP AFTER MIDNIGHT. FOR LATE TONIGHT AND TOMORROW,
HAVE INCREASED WINDS THROUGH THE GRANDE RONDE VALLEY WITH THE LADD
AND PYLES CANYON AREAS APPROACHING LOW END ADVISORY CRITERIA BASED
ON THE FORECASTED KBKE-KMEH GRADIENTS CONSISTENTLY SHOWN BY THE
NAM12. WITH PEAK GRADIENTS JUST BELOW 5 MB AROUND MIDDAY, THINK
THERE WILL ONLY BE SHORT PERIODS WHERE THAT AREA HITS 30 TO 35 MPH
SUSTAINED. AM DECIDING AGAINST ISSUING A WIND ADVISORY AT THIS
TIME BUT WILL NEED TO CONTINUE MONITORING SHOULD FORECASTED OR
OBSERVED GRADIENTS TIGHTEN. HAVE ALSO REMOVED FOG MENTION THERE LATE
TONIGHT AND TOMORROW WITH THE EXPECTED WINDS DECREASING THE
LIKELIHOOD. FOR TOMORROW EVENING, POST-FRONTAL WESTERLY WINDS WILL
DOWNSLOPE ACROSS THE CENTRAL WASHINGTON CASCADES BRINGING BREEZY
CONDITIONS TO MOST VALLEYS WITH WINDY CONDITIONS TO PORTIONS OF THE
KITTITAS VALLEY ALONG WITH RIDGETOPS. PEAK WINDS SHOULD BE LATE
AFTERNOON AND EARLY EVENING THEN DECREASING OVERNIGHT. UPDATES HAVE
BEEN PUBLISHED AND ARE AVAILABLE. /JBONK
&&
.AVIATION...06Z TAF PACKAGE. EXPECT VFR CONDS TO PREVAIL FOR THE
NEXT 24 HOURS EXCEPT FOR KYKM WHERE VSBYS ARE EXPECTED TO DROP TO
IFR IN A FEW HOURS. WESTERLY DRAINAGE WINDS SHOULD INHIBIT A FURTHER
DROP BUT WILL LIKELY RESULT IN A SCATTERED DECK JUST OFF THE
SURFACE. HAVE CONCERNS ABOUT KPSC RADIATING TEMEPRATURES DOWN TO THE
DEWPOINT BUT DID NOT HAVE CONFIDENCE TO BRING VSBYS THERE BELOW 4SM
YET. IN BOTH CASES, CONDS SHOULD IMPROVE BACK TO VFR IN THE 17Z TO
20Z TIMEFRAME AS A WEAKENED FRONT CROSSES THE REGION. /JBONK
.PREV DISCUSSION... /ISSUED 350 PM PST SUN NOV 29 2009/
SHORT TERM...TONIGHT THROUGH WEDNESDAY...THE UPPER RIDGE ALONG 128W
THIS AFTERNOON WILL SHIFT EAST ACROSS THE PACIFIC NORTHWEST TONIGHT.
THIS RIDGE WILL KEEP CONDITIONS GENERALLY FAIR TONIGHT...THOUGH
THERE SHOULD BE SOME THIN HIGH CLOUDINESS AT TIMES. WITH THE RIDGE
OVERHEAD TONIGHT SHOULD SEE BETTER REDEVELOPMENT OF INVERSIONS OVER
THE COLUMBIA BASIN AND SOME MOUNTAIN VALLEYS. THE HIGH CLOUDINESS
SHOULD HELP TO LIMIT DEVELOPMENT THOUGH. THUS WILL KEEP SOME MENTION
OF PATCHY FOG AND FREEZING FOG WITH SCATTERED LOW CLOUDINESS IN THE
COLUMBIA BASIN BELOW 1000 FEET AND A FEW MOUNTAIN VALLEYS. THE FOG
AND LOW CLOUDINESS SHOULD MOSTLY DISSIPATE MONDAY BUT INCREASING
CLOUDINESS WILL SLOW THE DISSIPATION...WHICH MOST LIKELY WILL FINISH
AROUND NOON. DUE TO THE INVERSIONS AND POSSIBLE FOG...DO NOT EXPECT
TEMPS TO WARM QUITE AS WELL AS THEY DID TODAY AT LOCATIONS BELOW
ABOUT 2000 FEET. TEMPS SHOULD BE UP ANOTHER DEGREE OR TWO ABOVE 2000
FEET THOUGH. A WEAKENING DISTURBANCE WILL SWING THROUGH BRITISH
COLUMBIA TO NORTHEAST MONTANA MONDAY NIGHT. THIS SYSTEM WILL BE
MAINLY DRY AS IT MOVES ACROSS THE PACNW. SOME LIGHT PRECIP IS
EXPECTED ALONG THE WASHINGTON CASCADE EAST SLOPES AND ALSO INTO THE
BLUE MOUNTAINS. LIGHT SHOWERS MAY PERSIST OVER THE BLUE AND WALLOWA
MOUNTAINS TUESDAY DUE TO THE NORTHWEST FLOW BEHIND THE SYSTEM. ALSO
THIS SYSTEM WILL BRING A CHANGE OF AIR MASS THAT SHOULD MIX OUT THE
SHALLOW INVERSIONS OVER THE COLUMBIA BASIN. AS SUCH WILL NOT MENTION
FOG MONDAY NIGHT INTO TUESDAY MORNING. THE UPPER RIDGE LOOKS TO
REBUILD TUESDAY NIGHT AND WEDNESDAY. THUS EXPECT DRY CONDITIONS WITH
SEASONAL TEMPS. AT THIS TIME DO NOT EXPECT ANY FOG DEVELOPMENT EARLY
WEDNESDAY DUE A PERSISTENT...DRY NORTH SURFACE FLOW. 90
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS CONTINUE TO
SHOW SIGNIFICANT DIFFERENCES IN THE LONG TERM AND CONTINUE TO CHANGE
THEIR SOLUTIONS FROM RUN TO RUN. CONFIDENCE IS NOT HIGH AFTER FRIDAY
AND HAVE TRIED TO FIND A MIDDLE GROUND BETWEEN THE VARIOUS
SOLUTIONS. INITIALLY A STRONG RIDGE WILL BE CENTERED JUST OFF THE
PACIFIC NORTHWEST COAST AND FAIR AND DRY WEATHER IS EXPECTED ASIDE
FROM A FEW SHOWERS IN THE WASHINGTON CASCADE CREST AREA THURSDAY.
WITH HIGH PRESSURE AND LIGHT WINDS...HAVE KEPT PATCHY FOG IN THE
COLUMBIA BASIN ON THURSDAY. THURSDAY NIGHT AND FRIDAY (OR FRIDAY AND
FRIDAY NIGHT DEPENDING ON THE MODEL) A FRONT MOVES INTO THE AREA AND
FLATTENS THE RIDGE. HAVE KEPT MAINLY A CHANCE OF SNOW SHOWERS IN THE
MOUNTAINS WHILE IN THE LOWER ELEVATIONS HAVE RAIN SHOWERS DURING THE
DAY AND A RAIN/SNOW MIX AT NIGHT. CENTRAL OREGON AND MOST OF THE
COLUMBIA BASIN LOOKS DRY FROM THIS SYSTEM. THE SYSTEM SHOULD STIR UP
THE ATMOSPHERE SO FOG IS NOT EXPECTED. SATURDAY NIGHT AND SUNDAY THE
MODELS ARE HINTING AT COLD AIR MOVING SOUTH OUT OF CANADA...WHICH
THEY HAVE NOT DONE PREVIOUSLY. HAVE LOWERED TEMPERATURES TO UPPER
30S AND LOWER 40S IN THE LOWER ELEVATIONS AND KEPT A SLIGHT CHANCE
OF LIGHT SNOW SHOWERS MAINLY IN THE MOUNTAINS. PERRY
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 49 29 47 32 / 0 0 0 10
ALW 52 32 47 35 / 0 0 0 10
PSC 51 29 46 31 / 0 0 0 10
YKM 46 25 45 28 / 0 0 0 10
HRI 48 26 46 29 / 0 0 0 10
ELN 57 35 46 31 / 0 0 0 10
RDM 50 21 51 22 / 0 0 0 0
LGD 40 24 42 28 / 0 0 0 10
GCD 42 24 45 26 / 0 0 0 0
DLS 51 31 47 34 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&
THREAT INDEX
TODAY : GREEN
MONDAY : GREEN
TUESDAY : GREEN
GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
$$
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