845  
FXUS66 KPDT 131131  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
431 AM PDT TUE APR 13 2021  
   
SHORT TERM...TODAY THROUGH THURSDAY NIGHT
 
AN UPPER LOW IS  
DEEPENING OVER FAR EASTERN OREGON AND WILL DEVELOP INTO A CLOSED  
LOW TODAY. THE UPPER LOW WILL DIP SOUTHWARD OVER THE GREAT BASIN  
TONIGHT AND REMAIN OVER NV WEDNESDAY AND WEDNESDAY NIGHT. ON  
THURSDAY, A SERIES OF WAVES ROTATING AROUND THE CLOSED LOW WILL  
RESULT IN A BROAD CYCLONIC CIRCULATION OVER THE WESTERN HALF OF  
THE U.S. THE LOW WILL EVENTUALLY WEAKEN INTO AN OPEN TROUGH  
AND WILL NO LONGER BE AN INFLUENCE IN OUR FORECAST AREA THURSDAY  
NIGHT. BY THIS TIME, A STRENGTHENING HIGH PRESSURE RIDGE TO THE  
NORTH WILL MAKE ITS WAY ACROSS THE PACNW.  
 
DESPITE THE LARGE CYCLONIC CIRCULATION OVER THE FORECAST AREA THE  
FIRST 60 HOURS, POPS WILL BE LESS THAN 15 PERCENT. THERE MAY BE A  
FEW FLURRIES SOUTH OF JOHN DAY TODAY, BUT ANY SNOW SHOWERS WILL BE  
SOUTH OF THE FORECAST AREA.  
 
THE MAIN WEATHER CONCERN DURING THE SHORT TERM PERIOD WILL BE THE  
WINDS AND THE BLOWING DUST TODAY. WINDS ARE ALREADY GUSTING TO  
25-30 MPH FROM THE NE IN MANY AREAS THIS MORNING. WINDS AS STRONG  
AS 56 MPH HAVE BEEN OBSERVED ALONG THE WIND EXPOSED RATTLESNAKE  
HILLS. CURRENT WIND FORECAST LOOKS GOOD, AND ONE UPDATE WILL BE TO  
INCLUDE A FEW MORE ZONES IN THE BLOWING DUST ADVISORY. THAT IS,  
THE YAKIMA VALLEY AND THE OREGON PORTION OF THE LOWER COLUMBIA  
BASIN AND BLUE MTN FOOTHILLS. MAIN CONCERN FOR THE YAKIMA VALLEY  
IS THE AREA FROM SUNNYSIDE TO PROSSER. THE BLOWING DUST ADVISORY  
WILL BE IN EFFECT FROM 11 AM TO 8 PM. WINDS GUSTS 40-45 MPH ARE  
LIKELY FOR MANY LOWER ELEVATION AREAS WHICH FALL JUST UNDER WIND  
ADVISORY CRITERIA. ONE AREA TO WATCH IS CENTRAL OREGON WHERE  
MAV/LAV GUIDANCE HAS SUSTAINED WINDS AT 30-35 MPH FOR REDMOND AND  
BEND. THIS MAY BE OVERDONE, AS THE HRRR AND HREF ARE SHOWING LESS  
WIND, AND THESE MODELS TYPICALLY DO WELL WITH GRADIENT DRIVEN  
WINDS. NOT ONLY BLOWING DUST WILL BE A CONCERN, BUT WIND DRIVEN  
FIRES IN DRY GRASSY AREAS. DEWPOINTS ARE CURRENTLY IN THE TEENS,  
AND THE RH TODAY WILL RANGE FROM ABOUT 15-25 PCT.  
 
WINDS WILL DECREASE SOME TONIGHT AND WILL BE BREEZY FROM THE NNE  
ON WEDNESDAY. THERE MAY BE PATCHY BLOWING DUST ON WEDNESDAY BUT  
NOT AS WIDESPREAD AS TODAY. THE BREEZY WINDS TONIGHT MAY HELP  
PROVIDE JUST ENOUGH MIXING TO KEEP OVERNIGHT LOWS FROM PLUMMETING,  
BUT IT WILL BE COLD WITH LOWS IN THE MID 20S TO MID 30S AND  
DEWPOINTS IN THE TEENS. WISTER  
   
LONG TERM
 
THURSDAY NIGHT THROUGH MONDAY. MODELS IN GOOD  
AGREEMENT THROUGH THE EXTENDED PERIOD WITH A STRONG RIDGE OVER THE  
AREA. AIRMASS IS DRY AND EXPECT MAINLY CLEAR SKIES. TEMPERATURE  
PROFILES SHOW A GRADUAL WARMING TREND THROUGH THE WEEKEND WITH  
850MB TEMPS REACHING 12-16C. THIS WILL PUT HIGH TEMPERATURES INTO  
THE 70S WHICH IS 10-15 DEGREES ABOVE NORMAL LEVELS. OVERNIGHT LOWS  
WILL REMAIN ON THE COOL SIDE WITH 30S AND 40S. UPPER LOW WILL  
MOVE INTO THE REGION ON TUESDAY WITH A COOLING TREND AND POSSIBLE  
SHOWERS.  
 
AVIATION...12Z TAFS. MAIN IMPACTS FOR THE TAF SITES WILL BE  
INCREASING WINDS AND POTENTIAL FOR REDUCED VISIBILITY IN BLOWING  
DUST. NORTHERLY WINDS WILL INCREASE TO 15-30KT WITH GUSTS TO 35KT.  
THIS WILL LIKELY RESULT IN BLOWING DUST LATE MORNING THROUGH THE  
AFTERNOON AND INTO EARLY EVENING. VISIBILITY MAY BE REDUCED TO  
3-6SM. WINDS WILL DECREASE OVERNIGHT.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 58 28 61 33 / 0 0 0 0  
ALW 62 31 65 37 / 0 0 0 0  
PSC 64 37 68 41 / 0 0 0 0  
YKM 62 33 68 39 / 0 0 0 0  
HRI 63 32 66 36 / 0 0 0 0  
ELN 59 30 66 37 / 0 0 0 0  
RDM 54 22 56 28 / 0 0 0 0  
LGD 54 28 56 30 / 0 0 0 0  
GCD 56 28 56 31 / 10 0 0 0  
DLS 63 35 68 41 / 0 0 0 0  
 

 
   
PDT WATCHES/WARNINGS/ADVISORIES
 
 
OR...BLOWING DUST ADVISORY FROM 11 AM THIS MORNING TO 8 PM PDT THIS  
EVENING FOR ORZ044-507-508.  
 
WA...BLOWING DUST ADVISORY FROM 11 AM THIS MORNING TO 8 PM PDT THIS  
EVENING FOR WAZ027>029.  
 

 
 

 
 
SHORT TERM...85  
LONG TERM....94  
AVIATION...94  
 
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