943  
FXUS66 KSEW 071620  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
920 AM PDT TUE JUL 7 2020  
   
SYNOPSIS
 
AN UPPER DISTURBANCE WILL CROSS THE REGION TODAY WITH  
A FEW SHOWERS AND COOLER TEMPERATURES. AFTER A SHORT BREAK ON  
WEDNESDAY, ADDITIONAL WEATHER SYSTEMS WILL ROTATE THROUGH THE  
REGION ON THURSDAY AND OVER THE WEEKEND FOR CONTINUED COOLER THAN  
NORMAL TEMPERATURES AND A CHANCE OF SHOWERS AT TIMES.  
 

 
   
SHORT TERM /TODAY THROUGH THURSDAY/
 
ANOTHER UPPER LEVEL TROUGH  
IS SHIFTING ONSHORE TODAY, PROVIDING FOR INCREASING SHOWERS AND  
ABUNDANT CLOUD COVER, ALONG WITH COOLER AIR SETTLING INTO THE  
REGION. THE TROUGH WILL SHIFT EAST OF THE CASCADES THIS AFTERNOON  
WITH WEAK UPPER RIDGING BUILDING INTO THE AREA LATE TONIGHT AND  
WEDNESDAY. ALTHOUGH WEDNESDAY LOOKS DRIER FOR MOST OF THE AREA,  
PERSISTENT LOW LEVEL ONSHORE FLOW WILL LIKELY ENSURE SIGNIFICANT  
CLOUD COVER WITH ONLY SOME PARTIAL SUNSHINE OVER INTERIOR LOWLAND  
AREAS IN THE AFTERNOON. THIS WILL HELP BOOST AFTERNOON HIGH  
TEMPERATURES BY A FEW DEGREES, BUT THEY WILL REMAIN BELOW NORMAL  
FOR THIS TIME OF YEAR. THE NEXT IN THE SERIES OF WEAK UPPER  
TROUGHS MOVES ONSHORE ON THURSDAY FOR AN ADDITIONAL ROUND OF  
SHOWERS AND TEMPERATURES REMAINING ON THE COOL SIDE. 27/12  
   
LONG TERM /FRIDAY THROUGH MONDAY/
 
WEAK UPPER RIDGING RETURNS  
ON FRIDAY. BY LATER FRIDAY AND PART OF SATURDAY, WESTERN  
WASHINGTON WILL BE ON NORTHERN PERIPHERY OF A VERY STRONG UPPER  
RIDGE EXPECTED TO DEVELOP OVER THE FOUR CORNERS REGION. THIS  
BRIEFLY PUSHES 500 MB HEIGHTS INTO THE 576-580 DAM RANGE. LOW  
LEVEL FLOW WILL REMAIN ONSHORE, THOUGH, SO THAT WILL TEMPER ANY  
KIND OF BRIEF WARM UP WE SEE AT THE END OF THE WEEK. IF ANYTHING,  
WE'LL SEE TEMPERATURES CLOSER TO NORMAL LEVELS FRIDAY AFTERNOON  
AND PERHAPS SATURDAY. BUT ALL GOOD THINGS MUST COME TO AN END AS  
YET ANOTHER UPPER TROUGH IS EXPECTED TO SWING ACROSS THE AREA IN  
THE SUNDAY/MONDAY TIME FRAME FOR ANOTHER POSSIBILITY OF SHOWERS  
AND COOLER TEMPERATURES. 27  

 
   
AVIATION
 
CEILINGS THIS MORNING ARE LARGELY MVFR AT THE TAF SITES  
AND THESE CONDITIONS WILL LIKELY PERSIST INTO THE AFTERNOON HOURS.  
LOCAL RADARS ARE PICKING UP ON SOME LIGHT SHOWERS ACROSS THE AREA,  
SOME OF WHICH MAY TEMPORARILY DROP CEILINGS DOWN TO IFR. ALTHOUGH  
SIGNIFICANT RECOVERY IS NOT EXPECTED TODAY, CEILINGS MAY BE ABLE TO  
LIFT TO LOW END VFR BY MID-LATE AFTERNOON. THEY WILL LIKELY THEN  
DROP BACK TO MVFR AGAIN OVERNIGHT. WINDS WILL REMAIN OUT OF THE  
SOUTH AT 8-12KTS, THO WILL LIKELY TAKE ON MORE OF A NW COMPONENT AT  
CLM AND PAE AS WESTERLY WINDS PUSH DOWN THE STRAIT.  
 
KSEA...MVFR CEILINGS WILL LINGER INTO THE AFTERNOON BEFORE  
ATTEMPTING TO RECOVER BACK TO LOWER-END VFR LATER IN THE DAY. WINDS  
WILL REMAIN OUT OF THE SOUTH AT 8-12KTS.  
 
KOVACIK  
 

 
   
MARINE
 
NO CHANGES WERE MADE TO THE ONGOING MARINE FORECAST THIS  
MORNING AND NO HEADLINES ARE CURRENTLY IN PLACE. PREVIOUS DISCUSSION  
HAS BEEN INCLUDED BELOW:  
 
WEAK ONSHORE FLOW WILL CONTINUE INTO SATURDAY AS  
HIGH PRESSURE REMAINS CENTERED OFFSHORE. THERE IS THE POSSIBILITY  
OF LOW END SMALL CRAFT ADVISORY WINDS IN THE CENTRAL AND EASTERN  
STRAIT OF JUAN DE FUCA EACH EVENING. THE DAYS WITH THE BEST  
CHANCES WILL BE THIS WEEKEND.  
 
KOVACIK/FELTON  
 

 
   
HYDROLOGY
 
THE DAILY HYDROLOGY DISCUSSION HAS ENDED UNTIL THE  
START OF THE NEXT RAINY SEASON; IT WILL ONLY BE UPDATED AS NEEDED  
UNTIL THEN.  
 

 
   
SEW WATCHES/WARNINGS/ADVISORIES
 
 
WA...NONE.  
PZ...NONE.  

 
 

 
 
WWW.WEATHER.GOV/SEATTLE  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab WA Page Main Text Page