201  
FXUS66 KPDT 202123  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
223 PM PDT WED SEP 20 2017  
   
SHORT TERM...TONIGHT THROUGH SATURDAY
 
AN UPPER LEVEL LOW IS  
MOVING OVER SOUTHEASTERN WA THIS AFTERNOON. THE ASSOCIATED TROUGH  
IS DIGGING OFFSHORE BECAUSE A VORT MAX IS MOVING DOWN THE BACKSIDE  
OF THE TROUGH. ANOTHER VORT MAX IS MOVING OVER WA/OR THIS  
AFTERNOON. THE COLDER AIR ALOFT FROM THE LOW AND DYNAMIC LIFT FROM  
THE SECOND VORT MAX HAS TRIGGERED A FEW THUNDERSTORMS THIS  
AFTERNOON. THE FIRST VORT MAX WILL MOVE INTO CENTRAL CA TONIGHT  
AND ELONGATE THE TROUGH ALONG THE COAST. THIS WILL KEEP NORTHERLY  
FLOW AND SHOWERS OVER THE MOUNTAINS IN EASTERN WA AND OR TONIGHT.  
THE UPPER PART OF THE TROUGH WILL SHIFT SLOWLY EAST THURSDAY  
WHILE AN UPPER LEVEL LOW FORMS IN THE SOUTHERN PART. MOISTURE AND  
INSTABILITY ROTATING AROUND THIS LOW WILL KEEP SHOWERS IN THE  
MOUNTAINS THURSDAY NIGHT. SHOWERS WILL LINGER IN THE CENTRAL OR  
MOUNTAINS TO WALLOWA COUNTY FRIDAY AS THIS LOW MOVES SLOWLY EAST.  
SATURDAY A RIDGE WILL BUILD OFFSHORE WITH DRIER NORTHERLY FLOW  
DEVELOPING IN EASTERN WA AND OR. TEMPERATURES WILL INCREASE EACH  
DAY AS THE UPPER LEVEL LOW MOVES OUT AND WARMER AIR ALOFT MOVES  
INTO THE CWA. COONFIELD  
   
LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
 
SUNDAY NIGHT AN  
UPPER TROUGH WILL MOVE EAST INTO MONTANA AND UTAH AND AN OFFSHORE  
RIDGE WILL EXPAND OVER THE PACIFIC NORTHWEST. THE RIDGE WILL REMAIN  
THE DOMINANT FEATURE THROUGH THE LONG TERM PERIOD THIS WILL LEAD TO  
DRY WEATHER WITH A WARMING TREND. THE RIDGE AXIS WILL REMAIN  
OFFSHORE THROUGH MONDAY WITH A FEW DISTURBANCES RIDING OVER THE  
RIDGE INTO CANADA. THE MAIN IMPACT WILL BE PARTLY CLOUDY SKIES AT  
TIMES. WINDS WILL BE GENERALLY UNDER 10 MPH THROUGH THE PERIOD.  
TEMPERATURES ON SUNDAY WILL BE IN THE 60S AND LOWER 70S THEN WILL  
WARM TO THE MID 60S TO MID 70S ON MONDAY. ON TUESDAY, THE RIDGE AXIS  
WILL MOVE OVERHEAD AND TEMPERATURES WILL WARM TO THE UPPER 60S AND  
70S. BY WEDNESDAY THE RIDGE AXIS WILL MOVE INTO IDAHO BUT OUR AREA  
WILL REMAIN WARM WITH HIGHS IN THE 70S TO AROUND 80. PERRY  
 

 
   
AVIATION...00Z TAFS
 
AN UPPER LEVEL TROUGH WILL CONTINUE TO SEND  
PARTLY TO MOSTLY CLOUDY SKIES AND UNSETTLED WEATHER ACROSS THE AREA  
THIS EVENING. CONDITIONS WILL BE MAINLY VFR, THOUGH MVFR CIGS AND  
VISIBILITIES MAY OCCUR WITH SOME MODERATE RAIN SHOWERS AND OR  
THUNDERSTORMS AT TIMES THROUGH AROUND 03Z THIS EVENING. THUNDERSTORM  
ACTIVITY WILL BE TOO LIMITED TO MENTION AT ANY TAF SITE. AFTER 03Z,  
CLOUD COVER WILL BE MORE SCATTERED AND RAIN SHOWERS WILL BE MAINLY  
CONFINED TO THE MOUNTAINS THROUGH 00Z TOMORROW AFTERNOON. WINDS AT  
KRDM, KBDN, KPDT, KALW AND KDLS WILL CONTINUE AT 10-20 KTS WITH  
GUSTS TO 25 KTS THIS EVENING THEN DECREASE TO BELOW 12 KTS BY 05Z.  
OTHERWISE, WINDS WILL REMAIN BELOW 12 KTS THROUGH 00Z TOMORROW  
AFTERNOON. PERRY  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 41 58 41 62 / 40 10 20 10  
ALW 45 60 45 63 / 40 20 20 10  
PSC 44 65 44 68 / 20 10 10 10  
YKM 38 62 44 68 / 20 10 20 10  
HRI 43 63 43 67 / 20 10 10 10  
ELN 40 62 42 67 / 20 20 20 10  
RDM 30 54 33 59 / 30 20 20 10  
LGD 36 53 36 58 / 60 30 30 20  
GCD 37 52 36 56 / 60 20 20 20  
DLS 48 65 48 72 / 30 20 10 10  
 

 
   
PDT WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  

 
 

 
 
76/83/83  
 
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