560  
FXUS66 KPDT 040009  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
509 PM PDT WED JUN 3 2020  
   
..UPDATED AVIATION DISCUSSION
 
 
   
AVIATION...00Z TAFS
 
LOW AVIATION CONCERNS THE NEXT 24 HOURS  
WITH GENERALLY VFR CONDITIONS ANTICIPATED. LATEST SATELLITE  
IMAGERY SHOWS CIRRUS MOVING EAST ACROSS NORTHEAST OR AND PARTS OF  
CENTRAL OR WITH SOME MID CLOUDS OVER PARTS OF THE KITTAS VALLEY.  
OBS SHOW LIGHT BREEZES IN PLACE THAT WILL BY AND LARGE LESSEN  
OVERNIGHT WITH THEN INCREASING WEST TO NORTHWEST BREEZES BY  
TOMORROW AFTERNOON. THIS WILL COINCIDE WITH PARTLY CLOUDY SKIES  
TOMORROW AS WELL. 80  
 

 
   
PREV DISCUSSION
 
/ISSUED 228 PM PDT WED JUN 3 2020/  
 
SHORT TERM...TONIGHT THROUGH THURSDAY...WATER VAPOR AND VISIBLE  
SATELLITE SHOW A WEAK SHORTWAVE TRAVERSING THE REGION, WITH  
ASSOCIATED HIGH DECK OF CIRRUS COVERING MUCH OF THE FORECAST AREA.  
REGION WILL CONTINUE TO BE FAIRLY QUIET THROUGH TOMORROW NIGHT AS  
A DRY WESTERLY FLOW PERSISTS ALOFT. BREEZY CONDITIONS WILL  
CONTINUE ACROSS THE COLUMBIA GORGE AND KITTITAS VALLEY THROUGH  
THIS EVENING UNDER A TIGHTENING OF SURFACE PRESSURE GRADIENTS AND  
HIGHER UPPER LEVEL WINDS MIXING DOWN TO SURFACE.  
 
THURSDAY NIGHT THROUGH FRIDAY NIGHT...BY THURSDAY NIGHT, FLOW  
ALOFT WILL BEGIN TO SHIFT TO THE SOUTHWEST AS AN UPPER LEVEL  
CLOSED LOW STARTS TO DIVE SOUTH OUT OF THE GULF OF ALASKA,  
RESULTING IN INCREASED MOISTURE AND CLOUD COVER EAST OF THE  
CASCADES. FRIDAY, CLOSED LOW WILL CONTINUE TO SLOWLY MOVE SOUTH  
DOWN THE BC COAST WHILE PUSHING A FEW EMBEDDED IMPULSES ACROSS THE  
REGION. THESE IMPULSES WILL BRING SHOWER CHANCES TO MOST OF THE  
FORECAST AREA. SOME INSTABILITY WILL BE AVAILABLE FOR ISOLATED  
THUNDERSTORM DEVELOPMENT OVER THE EASTERN MOUNTAINS WITH A 500MB  
JET OF 60-65KTS PROVIDING SHEAR THAT WILL SUPPORT FURTHER  
ORGANIZED CONVECTION IN THESE AREAS. THAT SAID, THE INCREASE IN  
CLOUD COVER OVERNIGHT AND INTO THE AFTERNOON MAY STIFLE SURFACE  
INSTABILITY FROM DAYTIME HEATING, POTENTIALLY LIMITING  
THUNDERSTORM ACTIVITY FOR FRIDAY. LAWHORN/82  
 
LONG TERM...SATURDAY THROUGH NEXT WEEK...ON SATURDAY, A CUTOFF  
LOW ORIGINALLY IN SOUTHERN CA WILL STILL BE IN THE PROCESS OF  
REJOINING THE MAIN TROUGH OFF THE PAC NW COAST, GIVING THE  
OVERALL TROUGH ORIENTATION A BIT OF A NEGATIVE TILT AS THE PATTERN  
MOVES EAST ACROSS OUR REGION. THIS WILL RESULT IN CONTINUED  
SHOWER/LIGHT RAIN CHANCES THROUGH MUCH OF THE EARLY WEEK AS LIFTED  
MOISTURE LINGERS. STORMS MAY RE-FIRE FOR MUCH OF THE OR CASCADES  
AND EASTERN MOUNTAINS SATURDAY AFTERNOON AND EVENING BUT CONTINUED  
CONVECTION AND CLOUD COVER MAY STILL INHIBIT THE FULL POTENTIAL  
OF THE NEGATIVE TILT TROUGH. SNOW LEVELS WILL ALSO LOWER TOWARD  
5-6KFT. WHILE THESE LOWER SNOW LEVELS ARENT UNCOMMON, IT IS  
UNUSUAL FOR MODELS TO INDICATE ENOUGH MOISTURE TO LINGER IN SUCH  
A COOL ENVIRONMENT. WITH THE SPRING RECREATION SEASON COMMENCING,  
SOME EARLY HIKERS ON THE SLOPES OF THE CASCADE VOLCANOS OR IN THE  
EAGLE CAPS/WALLOWAS MAY SEE SOME FLAKES FLY SUNDAY INTO MONDAY. A  
FINAL CONCERN IS EXPRESSED FOR THE SLIGHT POTENTIAL FOR EXCESSIVE  
RAINFALL. MOST DETERMINISTIC GLOBAL MODELS HAVE A RELATIVELY SLOW  
SWATH OF RAIN TRAVERSING FROM NEAR THE KLAMATH REGION TOWARD  
THE ID PANHANDLE SUNDAY. IT'S A BIT EARLY TO IDENTIFY WHAT BASINS  
MAY BE AFFECTED, IF ANY, BUT THE PATTERN OF A CUTOFF LOW  
REJOINING A PROGRESSIVE TROUGH IN A NEGATIVE TILT DOES SIGNAL THIS  
RAINFALL POTENTIAL. MONDAY INTO TUESDAY MAY FEATURE WEAK RIDGING,  
ENOUGH TO PREVENT AT LEAST THE BASIN/VALLEYS FROM SEEING  
CONTINUED RAIN. ANOTHER WEAK PLUME OF MOISTURE APPROACHES THE  
REGION TUE, BRINGING AN UPTICK IN SHOWERS/LIGHT RAIN BY  
AFTERNOON. ANOTHER QUICK RIDGE/POSSIBLE DRYING IS EXPECTED FOR  
MID TO LATE WEEK, BUT MODEL PREDICTABILITY BEGINS TO FALTER HERE  
THOUGH THE OVERALL PATTERN SEEMS QUITE COOL AND WET FOR MID-JUNE.  
WE SEEM TO END THE WEEK WITH STRENGTHENING DEEP SOUTHERLY FLOW  
ALOFT AND INCREASING MOISTURE. CLARK/76  
 
PREV DISCUSSION... /ISSUED 1053 AM PDT WED JUN 3 2020/  
   
UPDATED AVIATION DISCUSSION
 
 
AVIATION...18Z TAFS...VFR CONDITIONS TO PREVAIL. WINDS MAY BE  
BREEZY THIS AFTERNOON, PARTICULARLY IN THE KITTITAS VLLY AND  
COLUMBIA GORGE, GUSTING TO ABOUT 20KTS. OTHERWISE, GOOD CEILINGS  
AND SURFACE VISIBILITY EXPECTED. SOME PASSING CLOUDS EVIDENT WITH  
A BKN MID LEVEL DECK OVER NE OREGON AND A HIGH LEVEL CIRRUS  
SHIELD MOVING OVER THE OR CASCADES. WINDS WILL EASE OVERNIGHT. 76  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 50 76 52 76 / 0 0 0 10  
ALW 51 78 53 78 / 0 0 0 20  
PSC 54 80 55 80 / 0 0 0 10  
YKM 50 77 52 75 / 0 0 0 10  
HRI 53 79 54 78 / 0 0 0 10  
ELN 48 73 49 72 / 0 0 0 10  
RDM 44 77 47 74 / 0 0 0 10  
LGD 46 72 50 77 / 0 0 0 30  
GCD 47 76 52 81 / 0 0 0 30  
DLS 52 77 53 74 / 0 0 0 10  
 

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

 
 

 
 
76/82/80  
 
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