FXUS66 KPDT 291022
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
220 AM PST SUN NOV 29 2009
.SHORT TERM...TODAY THROUGH MONDAY NIGHT...HIGH PRESSURE ALOFT
CONTINUES TO AMPLIFY AND STRENGTHEN OVER THE REGION THIS MORNING.
THIS IS KEEPING GENERALLY FAIR CONDITIONS OVER THE FORECAST AREA.
THE ONLY CONCERN AT THIS TIME IS THE POSSIBILITY OF FOG/STRATUS IN
THE LOWER COLUMBIA BASIN AND SURROUNDING VALLEYS AND DRAINAGES DUE
TO RADIATIONAL COOLING TO THE SATURATION POINT UNDER SURFACE BASED
TEMPERATURE INVERSIONS. THE MOST LIKELY AREAS TO EXPERIENCE ANY FOG
OR STRATUS ARE ALONG THE COLUMBIA AND YAKIMA RIVERS...BUT IT COULD
FORM ANYWHERE IN THE ABOVE MENTIONED AREAS. THE FOG LOOP SATELLITE
IMAGERY SHOWS SOME LOW CLOUDS CURRENTLY OVER THE JOHN DAY RIVER
BASIN NEAR FOSSIL AND MONUMENT BUT SURFACE OBSERVATIONS DO NOT
INDICATE FOG. AS SUCH THIS IS MOSTLY LIKELY LOW STRATUS BEING
TRAPPED WITHIN THE JOHN DAY BASIN. THERE IS ALSO A HINT OF FOG
BEGINNING TO FORM IN THE YAKIMA AND KITTITAS VALLEYS. ELSEWHERE SO
FAR IT IS FOG FREE. THE UPPER RIDGE IS EXPECTED TO PERSIST BY ALL
MODELS THROUGH MOST OF MONDAY WITH THE DRY CONDITIONS AND FOG
SCENARIO CONTINUING. THE FOG MAY BECOME MORE WIDESPREAD WITH TIME
DUE TO THE STAGNANT CONDITIONS. BY LATE MONDAY INTO MONDAY NIGHT A
WEAK WEATHER DISTURBANCE BEGINS TO MOVE INTO THE PACIFIC NORTHWEST.
THIS IS ESPECIALLY TRUE WITH THE ECMWF MODEL...WHICH IS ALSO LIKELY
OVER DONE...AS COMPARED TO THREE OTHER MODELS WHICH ARE IN CLOSER
AGREEMENT WITH EACH OTHER (SREF...NAM AND GFS). AS SUCH WILL NOT
JUMP TOO MUCH ON THE PRECIP CHANCES MONDAY NIGHT AND FOR NOW WILL
JUST INTRODUCE A SLIGHT CHANCE IN THE FAR NW PORTION OF THE CWA
ALONG THE CENTRAL WASHINGTON CASCADE CREST/EAST SLOPE AREA. 88
.LONG TERM...TUESDAY THROUGH SATURDAY...THE UPPER LEVEL RIDGE WILL
REBUILD OVER THE PACIFIC NORTHWEST BY LATER TUESDAY AND WEDNESDAY...
WITH DRY STABLE CONDITIONS OVER EASTERN WASHINGTON AND OREGON.
PATCHY FOG MAY DEVELOP AGAIN IN THE LOWER COLUMBIA BASIN WEDNESDAY
NIGHT AS WARM AIR AT 850 MB ADVECTS INTO THE AREA AND STRENGTHENS
SURFACE BASED INVERSIONS. THURSDAY THROUGH SATURDAY THERE IS WIDE
SPREAD SOLUTIONS IN THE GFS ENSEMBLE AND TOTALLY DIFFERENT SOLUTIONS
BETWEEN THE ECMWF (RIDGE THURSDAY-FRIDAY AND TROUGH SATURDAY) AND
GFS (TROUGH THURSDAY AND NORTHERLY FLOW FRIDAY-SATURDAY). INCREASED
POPS THURSDAY-FRIDAY TO COVER UNCERTAINTY. EXPECT A DISTURBANCE TO
MOVE INTO THE REGION EITHER THURSDAY OR FRIDAY. THE DEPTH...SPEED
AND FORM THIS DISTURBANCE WILL TAKE HAS BEEN CHANGING WITH EACH
OPERATIONAL RUN OF THE VARIOUS MID-RANGE MODELS. MADE NO CHANGE TO
TEMPERATURES THURSDAY THROUGH SATURDAY THAT HINTED A COOLER NORTH
FLOW MAY SET UP BEHIND THIS DISTURBANCE. COONFIELD
&&
.AVIATION...PREVIOUS DISCUSSION...06Z TAF PACKAGE...DECIDED TO
REMOVE IFR CONDS FOR MOST TAFS EXCEPT FOR KYKM WHERE CLOUD COVER MAY
MOVE AWAY PRIOR TO SUNRISE. OTHERWISE SOME MVFR CIGS EXPECTED
THROUGH EARLY MORNING BUT WITH ONLY MODERATE CONFIDENCE. EXPECT ALL
TAF SITES TO BE FULL VFR AFTER 18Z WITH WINDS AROUND 5 KTS OR LESS.
/JBONK
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 45 32 44 31 / 0 0 0 10
ALW 47 35 44 34 / 0 0 0 10
PSC 45 29 44 28 / 0 0 0 10
YKM 46 28 45 27 / 0 0 0 10
HRI 45 28 44 27 / 0 0 0 10
ELN 47 30 44 29 / 0 0 0 10
RDM 47 25 47 24 / 0 0 0 0
LGD 43 30 43 29 / 0 0 0 10
GCD 44 31 47 30 / 0 0 0 10
DLS 47 32 46 31 / 0 0 0 10
&&
.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
$$
88/76/76
