783  
FXUS66 KPDT 232338  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
438 PM PDT WED SEP 23 2020  
   
SHORT TERM...TODAY THROUGH FRIDAY NIGHT
 
 
A SERIES OF SHORTWAVES EMBEDDED IN AN ELONGATED UPPER TROUGH WILL  
AFFECT THE REGION THROUGH THE REMAINDER OF THE WEEK. THIS WILL  
BRING SEVERAL OPPORTUNITIES FOR RAINFALL, ESPECIALLY OVER THE  
MOUNTAINS, AS WELL AS A SPELL OF COOLER TEMPERATURES.  
 
WIDESPREAD LIGHT TO MODERATE RAIN CONTINUES TO SPILL IN ACROSS  
NORTHWEST OREGON AND WESTERN WASHINGTON AS PLENTIFUL PACIFIC  
MOISTURE IS BROUGHT ONSHORE. MUCH OF THIS IS VANISHING AS IT MOVES  
EAST OF THE CASCADE CREST, THOUGH THIS WILL CHANGE AS A FRONT  
MOVES ACROSS OREGON AND WASHINGTON THROUGH TONIGHT AND INTO EARLY  
THURSDAY, BRINGING MEASURABLE RAINFALL TO MANY AREAS. THE  
MOUNTAINS LOOK TO PICK UP THE MOST SUBSTANTIAL RAINS, ESPECIALLY  
THE CASCADES AND ADJACENT EAST SLOPES, WHERE 1 TO 2 INCHES WILL BE  
POSSIBLE BETWEEN NOW AND THE END OF THE WEEK. LOWER ELEVATIONS  
INCLUDING THE COLUMBIA BASIN AND GORGE WILL SEE LESS, GENERALLY  
ANYWHERE FROM A TENTH OF AN INCH TO A HALF INCH AT MOST.  
REGARDLESS, AFTER THE PREVALENCE OF DRY AND HOT CONDITIONS FOR  
MUCH OF SEPTEMBER, ANY RAINS WILL BE WELCOMED AND SHOULD ALSO HELP  
TO SCOUR OUT LINGERING SMOKE ACROSS THE REGION.  
 
IN ADDITION TO THE RAIN, GUSTY WINDS WILL PERSIST FOR THE  
REMAINDER OF TODAY INTO THIS EVENING. WINDS WILL SPREAD FROM  
CENTRAL OREGON, WHERE THEY ARE CURRENTLY LOCATED, NORTH AND EAST  
WITH THE PASSAGE OF A FRONT. WINDS MAY LOCALLY GUST TO 30 TO 40  
MPH, WITH THE STRONGEST WINDS CONFINED TO PORTIONS OF THE OREGON  
CASCADES AND THEIR EAST SLOPES, AND HIGHER ELEVATIONS OF CENTRAL  
OREGON. WINDS SHOULD SUBSIDE OVERNIGHT.  
 
ON THURSDAY WITH ABUNDANT CLOUD COVER, AND IN THE WAKE OF A COLD  
FRONT, EXPECT NOTICEABLY COOLER CONDITIONS WITH OVERCAST SKIES.  
HIGHS IN THE LOWER ELEVATIONS WILL STRUGGLE TO REACH THE LOW 70S  
WITH MOUNTAINS IN THE 50S AND 60S. WITH A MORE ZONAL FLOW PATTERN,  
MOST SHOWER ACTIVITY WILL BE CONFINED TO THE CASCADES AND  
MOUNTAINS OF EASTERN OREGON WITH MAINLY DRY CONDITIONS ELSEWHERE.  
 
ON FRIDAY, MODELS DEPICT A SECOND SHORTWAVE MOVING THROUGH THE  
REGION, BRINGING ANOTHER CHANCE AT WIDESPREAD RAINS, EVEN ACROSS  
THE COLUMBIA BASIN. MODELS VARY QUITE A BIT WITH RESPECT TO  
AMOUNTS, BUT ANOTHER WETTING RAIN APPEARS PROBABLE FOR MANY AREAS  
WITH THE MOUNTAINS GETTING THE BULK OF THE MOISTURE. A STOUT  
PRESSURE GRADIENT WILL ALSO FOSTER BREEZY WINDS ACROSS MUCH OF THE  
COLUMBIA BASIN AND GORGE. WITH EXPANSIVE CLOUDINESS, ANOTHER  
RELATIVELY COOL DAY IS ON TAP WITH HIGHS IN THE LOW 70S IN THE LOW  
ELEVATIONS AND 50S AND 60S IN THE MOUNTAINS.  
   
LONG TERM...SATURDAY THROUGH WEDNESDAY
 
 
RAIN CHANCES WILL LINGER THROUGH THE WEEKEND AS THE BROAD TROUGH  
PROGRESSES EASTWARD, ALTHOUGH RAIN CHANCES WILL GENERALLY BE  
LIMITED TO THE MOUNTAINS, AS ANY ROBUST UPPER-LEVEL FORCING  
DRIVING THE SHOWERS FROM EARLIER THIS WEEK WANES AS THE TROUGH  
ENTERS THE GREAT PLAINS. SATURDAY NIGHT THROUGH SUNDAY LOOKS TO BE  
MOSTLY DRY OTHERWISE, WITH HIGHS RAPIDLY CLIMBING FROM THE UPPER  
60'S/LOW 70'S SATURDAY TO UPPER 70'S ON SUNDAY.  
 
HEADING INTO NEXT WEEK, THE BROAD TROUGH IMPACTING OUR AREA THIS  
WEEK WILL DIG INTO THE EASTERN CONUS, ALLOWING A RIDGE AND STRONG  
HIGH PRESSURE TO BUILD OVER THE WEST COAST. MODELS IN PRETTY GOOD  
AGREEMENT THIS FAR OUT FOR CONDITIONS TO WARM DRAMATICALLY THROUGH  
AT LEAST WEDNESDAY, POSSIBLY LONGER, AS BOTH THE GFS AND ECMWF  
DEPICT A HIGH-AMPLITUDE, POSITIVELY TILED RIDGE SETTLING IN OVER  
OUR AREA STARTING MONDAY NIGHT. HIGHS LOOK TO CLIMB INTO THE MID  
80'S BY WEDNESDAY THROUGHOUT THE BASIN, WHICH WOULD BE AROUND  
10-15 DEGREES HIGHER THAN WHAT WE'D EXPECT FOR THE LAST WEEK OF  
SEPTEMBER IN SOME AREAS. QUESTION REMAINS HOW MUCH DOES NIGHTTIME  
RADIATIONAL COOLING OFFSET RAPID DAYTIME HEATING, AS WE APPROACH  
DAYS WITH LONGER NIGHTS HEADING INTO OCTOBER. WILL STICK WITH NBM  
GUIDANCE FOR NOW, BUT WOULD NOT BE SURPRISED IF TEMPS START TO  
TREND HIGHER, GIVEN THE CONSENSUS GLOBAL MODELS HAVE ON OVERALL  
PATTERN THIS FAR OUT IN ADVANCE.  
   
AVIATION
 
00Z TAFS. LIGHT RAIN WILL OVERSPREAD THE TAF SITES  
THIS EVENING AS A FRONT SLOWLY MOVES SOUTH ACROSS THE REGION. YKM  
DLS WILL BE THE FIRST SITES STARTING 00-03Z. THE REMAINING SITES  
WILL LIKELY HAVE RAIN BEGIN 04-08Z. BREEZY SOUTHWESTERLY WINDS  
10-20KT. CEILINGS LOWERING TO BKN-OVC 030-060.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 54 70 49 69 / 80 10 20 50  
ALW 57 72 51 70 / 80 20 20 60  
PSC 58 74 55 71 / 70 0 20 50  
YKM 49 72 49 69 / 90 20 50 70  
HRI 57 74 53 72 / 70 0 20 40  
ELN 48 68 46 64 / 90 20 60 70  
RDM 47 69 41 66 / 80 10 10 40  
LGD 54 69 44 66 / 70 50 20 50  
GCD 55 71 44 71 / 60 50 10 20  
DLS 57 73 56 70 / 90 30 50 70  
 

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

 
 

 
 
UPDATE...94  
 
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