FXUS66 KPDT 232335 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
335 PM PST WED DEC 23 2009
UPDATED FOR AVIATION DISCUSSION
.SHORT TERM...HIGH PRESSURE WILL REMAIN
IN PLACE OVER THE AREA THROUGH THE SHORT TERM PERIOD. TONIGHT WILL
SEE MOSTLY CLEAR SKIES AND LIGHT WINDS WHICH WILL GIVE THE AREA A
COOL NIGHT...PERHAPS 3 TO 5 DEGREES COOLER THAN LAST NIGHT. A NORTH
TO NORTHWEST FLOW WILL CONTINUE TOMORROW AND THIS WILL BRING A
COOLER AIR MASS OVER THE AREA. A GRADUALLY STRENGTHENING INVERSION
WILL TAKE HOLD TOMORROW AND BY TOMORROW NIGHT PATCHY FOG AND
FREEZING FOG WILL DEVELOP. THE INVERSION WILL REMAIN INTO THE
WEEKEND AND ALONG WITH LIGHT WINDS WILL TRAP SMOKE AND POLLUTANTS
NEAR THE SURFACE. HAVE ISSUED AN AIR STAGNATION ADVISORY FROM
THURSDAY MORNING THROUGH SATURDAY AFTERNOON FOR MOST OF THE AREA
BELOW 3500 FEET. SEE PRODUCT PDXNPWPDT FOR FURTHER DETAILS.
TEMPERATURES ON THURSDAY WILL BE COLDER WITH MOST OF THE AREA
FAILING TO REACH 30 EXCEPT DOWN IN CENTRAL OREGON WHICH WILL BE IN
THE MID 30S. FORESEE CONTINUED COLD TEMPERATURES THROUGH SATURDAY
WITH NO PRECIPITATION ANTICIPATED. THE LOW CLOUDS AND FOG WILL
BECOME MORE ENTRENCHED BY FRIDAY NIGHT AND EXPECT THAT THE COLUMBIA
BASIN MAY WELL BE FOGGED IN ON SATURDAY. WINDS WILL BE LIGHT THROUGH
THE PERIOD. PERRY
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...AN UPPER LEVEL RIDGE
CONTINUES TO LINGER OVER THE PACIFIC NORTHWEST. AREAS OF FREEZING
FOG WILL CONTINUE IN THE LOWER ELEVATIONS THROUGH MONDAY. CONDITIONS
ELSEWHERE WILL REMAIN COOL AND DRY. FORECAST BEYOND MONDAY WILL BE A
BIT TRICKY AS ECMWF AND GFS BOTH INDICATE A BREAKDOWN OF THE RIDGE
WITH THE NEXT SYSTEM. HOWEVER...QPF AMOUNTS AND PLACEMENT OF THE THE
PRECIPITATION IS STILL QUESTIONABLE. THE SYSTEM WILL CUT OFF THE
UPPER LEVEL RIDGE AND PROVIDE A GOOD SWATH OF MOISTURE TO THE
SOUTHWESTERN CONUS. ECMWF HAS A DEFORMATION ZONE OVER EASTERN
OREGON...BUT PRECIPITATION AMOUNTS FROM MONDAY MORNING TILL TUESDAY
EVENING ARE STILL FAIRLY WEAK. GFS HAS A WEAK LOW PRESSURE SYSTEM
RETROGRADING OVER THE SPOKANE AREA BY TUESDAY MORNING PULLING
MOISTURE IN FROM THE NORTHWEST. THIS PARTICULAR PATTERN USUALLY ENDS
UP WITH A RAINSHADOW EFFECT OFF THE CASCADES...KEEPING AREAS ALONG
THE EAST SLOPES WITH SLIGHT CHANCE SHOWERS...AND THE LOWER
ELEVATIONS DRY. UPSLOPE FLOW WILL ALLOW FOR SHOWERS TO REDEVELOP
ALONG THE FOOTHILLS OF THE BLUE MOUNTAINS AND PROGRESS EASTWARD.
AGAIN QPF AMOUNTS ARE STILL FAIRLY WEAK...AND DO NOT APPEAR TO BE OF
ANY THREAT FOR THE TIME BEING. MODELS HAVE BEEN BACK AND FORTH
THE PAST SEVERAL DAYS AS TO WHAT WILL HAPPEN IN THE
EXTENDED...THEREFORE FORECAST CONFIDENCE IS LOW. WEBER
&&
.AVIATION...00Z TAFS...VFR CONDITIONS ARE EXPECTED OVER THE NEXT 24
HOURS AT ALL TAF SITES...EXCEPT FOR KALW WHICH MAY EXPERIENCE MVFR
CONDITIONS DUE TO LOWERED VISIBILITIES AND CIGS OVERNIGHT
TONIGHT...AND INTO TOMORROW MORNING. WINDS WILL BE LESS THAN 10KTS
AND VARIABLE AT MOST TIMES. CLOUD CIGS WILL GENERALLY BE 20K FEET
OR HIGHER. THERE MAY BE SOME LOW LEVEL CLOUDS DEVELOP IN THE
OVERNIGHT HOURS TO EARLY MORNING HOURS AT OTHER SITES...BUT LOW
CLOUDS ARE NOT EXPECTED TO INTERFERE WITH FLIGHT CONDITIONS. WEBER
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 18 27 17 27 / 0 0 0 0
ALW 20 27 19 26 / 0 0 0 0
PSC 18 28 18 29 / 0 0 0 0
YKM 16 29 15 28 / 0 0 0 0
HRI 17 29 17 29 / 0 0 0 0
ELN 16 29 15 27 / 0 0 0 0
RDM 12 37 13 37 / 0 0 0 0
LGD 10 27 11 31 / 0 0 0 0
GCD 15 33 17 36 / 0 0 0 0
DLS 23 34 20 32 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY FROM 4 AM THURSDAY TO 4 PM PST SATURDAY
FOR ORZ041>044-049-501-504-505.
WA...AIR STAGNATION ADVISORY FROM 4 AM THURSDAY TO 4 PM PST SATURDAY
FOR WAZ024-026>029-501-502.
&&
THREAT INDEX
THURSDAY : GREEN
FRIDAY : GREEN
SATURDAY : 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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