AREA FORECAST DISCUSSION

 
 FXUS66 KPDT 240543 AAA
 AFDPDT
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE PENDLETON OR
 943 PM PST MON NOV 23 2009
 
 UPDATED AVIATION DISCUSSION.
 
 .UPDATE...A FRONTAL SYSTEM CONTINUES TO MOVE INTO THE PACIFIC 
 NORTHWEST THIS EVENING ALTHOUGH MORE SLOWLY THAN ANTICIPATED. HAVE 
 ADJUSTED WEATHER GRIDS TO BRING PRECIPITATION INTO THE AREA 3 OR SO 
 HOURS LATER. THIS WOULD KEEP RAIN OUT OF THE COLUMBIA BASIN AND THE 
 BLUE MOUNTAINS UNTIL AFTER MIDNIGHT AND OUT OF WALLOWA COUNTY UNTIL 
 AFTER 3 AM...POSSIBLY UNTIL AFTER SUNRISE. HAVE ALSO ADJUSTED SKY 
 COVER TO SHOW A SLOWER PROGRESSION OF CLOUDINESS. THIS WILL IMPACT 
 TEMPERATURES AS PARTLY CLOUDY SKIES AND A SLOWER ARRIVAL OF THE WARM 
 FRONT WILL ALLOW TEMPERATURES TO DROP A FEW DEGREES COLDER THAN 
 FORECAST. HAVE DROPPED TEMPERATURES IN SEVERAL PLACES WITH 
 TEMPERATURES ALREADY WITHIN 3-5 DEGREES OF OVERNIGHT LOWS. MADE SOME 
 MINOR WIND ADJUSTMENTS AS WELL...MAINLY TO LIGHTER WINDS WHICH WILL 
 HELP LOWER TEMPERATURES AS WELL. UPDATE OUT SOON. PERRY
 
 &&
 
 .AVIATION...06Z TAFS...VFR CONDITIONS WILL BE PREVALENT FOR THE NEXT 
 24 HOURS. A WEATHER DISTURBANCE WILL MOVE THROUGH THE AREA TONIGHT 
 AND TOMORROW MORNING WITH BROKEN-OVERCAST SKIES SKIES GENERALLY 
 ABOVE 5000 FEET AGL. SCATTERED RAIN AND SNOW SHOWERS WILL ACCOMPANY 
 THE FRONTAL SYSTEM AND COULD LOWER CEILINGS AND VISIBILITIES TO MVFR 
 LEVELS NEAR THE HEAVIER SHOWERS...AFFECTING ALL TAF LOCATIONS EXCEPT 
 KRDM. SHOWERS WILL END AND SKIES WILL PARTIALLY CLEAR AFTER 24/20Z. 
 SURFACE WINDS WILL PRIMARILY STAY BELOW 15 KTS FOR THE NEXT 24 HOURS 
 BUT COULD REACH 10 TO 20 KTS BRIEFLY NEAR THE HEAVIER SHOWERS. PERRY
 
 &&
 
 .PREV DISCUSSION... /ISSUED 320 PM PST MON NOV 23 2009/ 
 
 SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT. LOW PRESSURE ENTERING 
 THE PACNW WILL CONTINUE TO SPREAD CLOUDS INTO THE AREA TONIGHT. 
 SHOWERS WILL ALSO DEVELOP ALONG THE EAST SLOPES OF THE WASHINGTON 
 CASCADES AND THEN SPREAD EAST INTO PORTIONS OF THE WASHINGTON 
 COLUMBIA BASIN AND NORTHERN BLUE MOUNTAINS OVERNIGHT. THE PCPN 
 SHOULD BE MOSTLY LIQUID BUT ACROSS THE HIGHER ELEVATIONS THIS COULD 
 BE SOME SNOW AS WELL. AS THE SYSTEM SAGS SOUTH AND EAST THE PCPN 
 WILL MIGRATE INTO THE OREGON PORTIONS OF THE BASIN AND BLUE MTNS AND 
 SURROUNDING AREA OVERNIGHT. MOISTURE LINGERS OVER THE BLUE/WALLOWA 
 MTNS AND ALONG THE EAST SLOPES OF THE WA CASCADES TOMORROW WITH 
 SHOWERS CONTINUING. WITH THE CLEARING SKIES SOME FOG MAY DEVELOP 
 OVER THE LOWER COLUMBIA BASIN TUESDAY NIGHT. A RIDGE OF HIGH 
 PRESSURE MOVES INTO THE REGION WEDNESDAY SHOVING ANOTHER STORM 
 SYSTEM NORTH AND AWAY FROM OUR AREA. HOWEVER ENOUGH MOISTURE WILL 
 SKIRT THE FAR NW AND SOME SHOWERS WILL DEVELOP OVER THE EAST SLOPES 
 OF THE WA CASCADES WEDNESDAY AND WEDNESDAY NIGHT. FURTHER EAST FOG 
 SHOULD DEVELOP AND EXPAND IN COVERAGE TO NOT ONLY INCLUDE THE LOWER 
 COLUMBIA BASIN BUT ALSO INTO PORTIONS OF THE BLUE MTN FOOTHILLS AND 
 PERHAPS THE GORGE AS WELL WEDNESDAY NIGHT. 
 
 LONG TERM...THURSDAY THROUGH MONDAY...AN UPPER LEVEL RIDGE WILL 
 MOVE EAST OF THE AREA THURSDAY. LINGERING EFFECTS OF THE RIDGE WILL 
 KEEP PATCHY FOG IN THE LOWER COLUMBIA BASIN. A SPLITTING UPPER LEVEL 
 LOW AND FRONT WILL APPROACH THE CASCADES THURSDAY AFTERNOON...AND 
 MOVE OVER EASTERN WASHINGTON AND OREGON THURSDAY NIGHT AND FRIDAY. 
 THIS SYSTEM WILL BRING SOME PRECIPITATION AND WINDS TO THE AREA. 
 SATURDAY THE ENSEMBLES START TO DIVERGE INDICATING MORE UNCERTAINTY 
 IN THE FORECAST. BOTH THE GFS AND ECMWF INDICATE A BUILDING RIDGE 
 SATURDAY NIGHT...BUT THIS PATTERN DOES NOT HAVE ANY RUN TO RUN 
 CONSISTENCY. TRENDED FORECAST TO DRIER RIDGE-LIKE PATTERN...BUT DID 
 KEEP SOME LOW POPS IN THE MOUNTAINS DUE TO LOW CONFIDENCE. ADDED 
 FOG/FREEZING FOG TO THE LOWER COLUMBIA BASIN SATURDAY NIGHT THROUGH 
 MONDAY NIGHT WITH SPREADING PATTERN THROUGH TIME.  COONFIELD
 
 &&
 
 .PRELIMINARY POINT TEMPS/POPS...
 PDT  35  48  33  44 /  30  20   0   0 
 ALW  37  47  35  41 /  30  20   0   0 
 PSC  33  50  32  46 /  20  10   0   0 
 YKM  31  48  30  45 /  40  20   0   0 
 HRI  27  48  31  45 /  30  10   0   0 
 ELN  31  47  31  44 /  40  20  10   0 
 RDM  28  52  25  50 /  10  10   0   0 
 LGD  28  44  27  43 /  20  30  10   0 
 GCD  27  47  27  52 /  10  10   0   0 
 DLS  35  51  37  52 /  40  20   0   0 
 
 &&
 
 .PDT WATCHES/WARNINGS/ADVISORIES...
 OR...NONE.
 WA...NONE.
 &&
 
 THREAT INDEX
 TUESDAY : GREEN
 WEDNESDAY : GREEN
 THURSDAY : 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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