AREA FORECAST DISCUSSION

 
 FXUS66 KPDT 251121 AAA
 AFDPDT
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE PENDLETON OR
 321 AM PST WED NOV 25 2009
 
 UPDATED AVIATION DISCUSSION
 
 .SHORT TERM...TODAY THROUGH THURSDAY...HIGH PRESSURE ALOFT WILL 
 CONTINUE TO BUILD AND AMPLIFY OVER THE REGION TODAY AND TONIGHT. 
 THIS WILL KEEP ANY MOISTURE TO THE NORTH OF THE FORECAST AREA... 
 ESPECIALLY THIS MORNING. THE FLOW WILL BACK TO THE SOUTHWEST TONIGHT 
 AND ON THURSDAY AS THE NEXT WEATHER SYSTEM APPROACHES FROM THE WEST. 
 THIS WILL SLOWLY BRING INCREASING MOISTURE OVER THE CASCADE CREST OF 
 CENTRAL WA OVER ONTO THE EAST SLOPES. WILL HOLD ON TO ISOLATED 
 RAIN/SNOW THERE BEGINNING TONIGHT...BUT SLOWLY INCREASING IN AREAL 
 COVERAGE OVER TIME. THERE ARE AREAS OF LOW CLOUDS/FOG FORMING 
 ALREADY AS SEEN ON THE FOG LOOP SATELLITE IMAGERY...AND IT HAS ALSO 
 BEEN REPORTED BY SPOTTERS AS WELL...WITH LOWERING CEILINGS AND 
 VISIBILITY IN SURFACE OBSERVATIONS. CURRENTLY THE GREATEST FOG 
 POTENTIAL FOR THIS MORNING AND AGAIN TONIGHT WILL BE IN THE YAKIMA 
 AND KITTITAS VALLEY AS WELL AS THE LOWER COLUMBIA BASIN...ESPECIALLY 
 NEAR THE LARGER RIVERS SUCH AS THE COLUMBIA AND YAKIMA RIVERS. ONE 
 LAST CONCERN IS A TIGHT PRESSURE/TEMPERATURE GRADIENT BETWEEN THE 
 BAKER AND GRANDE RONDE VALLEY WHICH IS RESULTING IN WINDY 
 CONDITIONS...MAINLY NEAR LADD AND PYLES CANONS AND THE SOUTH END OF 
 THE GRANDE RONDE VALLEY. THE WINDS ARE LIKELY TO INCREASE THIS 
 MORNING TO ADVISORY LEVELS AND WILL LEAVE THE CURRENT WIND ADVISORY 
 GOING THROUGH THIS MORNING INTO EARLY AFTERNOON. TEMPERATURES WILL 
 BE MILD FOR THE TIME OF YEAR...ESPECIALLY IN FOG FREE AREAS AS WELL 
 AS IN THE HIGHER TERRAIN THAT IS ABOVE ANY STRONG TEMPERATURE 
 INVERSIONS.
 
 .LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...WITH A SLIGHTLY SLOWER 
 MOVEMENT TO THE FRONTAL SYSTEM THURSDAY I DELAYED THE ONSET OF 
 PRECIPITATION MOVING ACROSS THE FORECAST AREA THURSDAY NIGHT AND 
 EARLY FRIDAY. EXPECT THIS TO MAINLY BE A RAIN EVENT WITH SNOW LEVELS 
 DROPPING BEHIND THE FRONT LATE THURSDAY NIGHT AND ON FRIDAY. THE 
 TROUGH WILL BE OVER THE REGION FRIDAY PRODUCING SOME INSTABILITY 
 SHOWERS. THERE IS A FAST MOVING SYSTEM THAT DROPS INTO THE TROUGH 
 FRIDAY NIGHT AND EARLY SATURDAY THAT WILL RE-ENERGIZE THE SHOWER 
 ACTIVITY OVERNIGHT. THIS SYSTEM HAS THE POTENTIAL TO BRING SNOW DOWN 
 TO AROUND 1000 FEET WITH A MIX OF RAIN AND SNOW IN THE BASIN. THIS 
 SYSTEM EXITS ON SATURDAY AS A RIDGE OF HIGH PRESSURE BEGINS TO 
 REBUILD OVER THE REGION WITH THE RIDGE PERSISTING INTO LATE MONDAY 
 BEFORE A FAST MOVING SYSTEM PASSING TO THE NORTH CLIPS THE REGION 
 WITH A CHANCE OF SHOWERS. HIGH PRESSURE QUICKLY REBUILDS TUESDAY AND 
 WEDNESDAY.  
 
 &&
 
 .AVIATION...12Z...VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS 
 WITH MAINLY HIGH CLOUDS ABOVE 15000 FT AGL. AN EXCEPTION WILL BE 
 SOME PATCHY MORNING FOG CREATING POSSIBLE MVFR VISIBILITIES ALONG 
 RIVERS IN THE COLUMBIA BASIN AFFECTING MAINLY KYKM...KDLS AND KPSC. 
 SURFACE WINDS WILL REMAIN UNDER 15 KTS AT ALL TAF LOCATIONS FOR THE 
 NEXT 24 HOURS.
 
 &&
 
 .PRELIMINARY POINT TEMPS/POPS...
 PDT  53  35  50  41 /   0   0   0  20 
 ALW  51  37  48  42 /   0   0   0  20 
 PSC  50  33  47  39 /   0   0   0  30 
 YKM  47  31  44  38 /   0   0  20  50 
 HRI  52  32  49  40 /   0   0   0  30 
 ELN  47  34  44  36 /   0   0  20  60 
 RDM  54  29  51  36 /   0   0   0  50 
 LGD  47  30  44  35 /   0   0   0  20 
 GCD  52  32  49  36 /   0   0   0  20 
 DLS  54  35  51  41 /   0   0   0  60 
 
 &&
 
 .PDT WATCHES/WARNINGS/ADVISORIES...
 OR...WIND ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR ORZ049.
 
 WA...NONE.
 &&
 
 THREAT INDEX
 TODAY : GREEN
 THURSDAY : GREEN
 FRIDAY : 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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