000 FXUS66 KPDT 240434 AFDPDT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PENDLETON OR 834 PM PST MON NOV 23 2009 .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 && .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 AVIATION...0Z TAFS...VFR CONDITIONS WILL PREVAIL THROUGH TONIGHT WITH INCREASING MID AND HIGH CLOUDS. ANOTHER WEATHER DISTURBANCE WILL MOVE INTO THE AREA OVERNIGHT WITH ANOTHER CHANCE OF RAIN AND MOUNTAIN SNOW. KRDM IN CENTRAL OREGON WILL LIKELY NOT SEE ANY PRECIPITATION FROM THIS SYSTEM. THERE MAY BE BRIEF PERIODS OF MVFR OVERNIGHT IN RAIN/SNOW SHOWERS...ESPECIALLY AT KDLS AND KYKM...AND TO A LESSER DEGREE AT KPDT AND KALW. WINDS MAINLY LESS THAN 15 KTS...BUT PERHAPS 10 TO 20 KTS AT TIMES NEAR SHOWERS. 76 && .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 $$ 83/76/76