368  
FXUS66 KSEW 170305  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
805 PM PDT SUN JUN 16 2024  
   
SYNOPSIS
 
AN UPPER LEVEL TROUGH OVER WESTERN WASHINGTON WILL  
SHIFT EAST OF THE AREA ON MONDAY. HIGH PRESSURE ALOFT WILL  
GRADUALLY BUILD THROUGH THE WEEK FOR A TREND TOWARD DRIER AND  
WARMER CONDITIONS. ANOTHER UPPER TROUGH IS EXPECTED TO APPROACH  
THE REGION LATE NEXT WEEKEND FOR A COOLING TREND AND A RETURNING  
CHANCE OF SHOWERS TO PORTIONS OF THE AREA.  
 

 
   
SHORT TERM /TONIGHT THROUGH THURSDAY/
 
THERE ARE JUST A FEW  
SHOWERS LEFT, WITH SOME PRODUCING CLOUD FLASHES OF LIGHTNING IN  
PIERCE AND LEWIS COUNTIES. ACTIVITY SHOULD WANE CONSIDERABLY AFTER  
SUNSET. OTHER THAN THAT, NO FORECAST CHANGES HAVE BEEN MADE THIS  
EVENING AND THE PREVIOUS DISCUSSION WILL FOLLOW, INCLUDING AN  
UPDATE TO THE AVIATION AND MARINE SECTIONS.  
 
THE TROUGH AXIS WILL BE EAST OF THE CASCADES ON MONDAY, BUT  
CONTINUED WEAK TROUGHING ALOFT WILL KEEP CLOUDS AND A CHANCE OF  
SHOWERS IN THE FORECAST. HEIGHTS CONTINUE TO RISE ON TUESDAY WITH  
ONSHORE FLOW WEAKENING. THIS WILL ALLOW MUCH OF THE AREA TO CLEAR  
OUT BY TUESDAY AFTERNOON WITH TEMPERATURES BOUNCING BACK TO NEAR  
SEASONAL LEVELS. UPPER RIDGING CENTERED WELL OFFSHORE CONTINUES TO  
STRENGTHEN ON WEDNESDAY AS 500 MILLIBAR HEIGHTS APPROACH 570 DAM  
WITH 850 MILLIBAR TEMPS APPROACHING 14 C. WITH THERMAL TROUGHING  
JUST TO OUR SOUTH AND ONLY WEAK ONSHORE FLOW, MUCH OF THE INTERIOR  
OF WESTERN WASHINGTON SHOULD WARM INTO THE MID TO UPPER 70S WITH  
60S ALONG THE COAST.  
 
   
LONG TERM /FRIDAY THROUGH MONDAY/
 
LOW AMPLITUDE RIDGING  
CONTINUES TO BUILD ACROSS THE AREA THURSDAY AND FRIDAY FOR  
CONTINUED DRY AND WARMER CONDITIONS WITH PORTIONS OF THE INTERIOR  
FROM SEATTLE SOUTHWARD REACHING NEAR OR ABOVE 80 DEGREES.  
ENSEMBLES ARE IN FAIRLY GOOD AGREEMENT THAT THE RIDGE AXIS WILL  
SHIFT EAST OF THE REGION EARLY IN THE COMING WEEKEND AS AN UPPER  
TROUGH DEEPENS ALONG THE BRITISH COLUMBIA COAST. THIS WILL RESULT  
IN A COOLING TREND ALONG WITH A RETURNING CHANCE FOR  
SHOWERS...ESPECIALLY OVER THE OLYMPIC PENINSULA AND ACROSS THE  
NORTH INTERIOR. 27  
 

 
   
AVIATION
 
BROAD UPPER LOW WILL PASS OVER THE PAC NW TONIGHT WITH A  
COOL AND SLIGHTLY UNSTABLE AIR MASS OVER WESTERN WASHINGTON (VIA  
NORTHWESTERLY FLOW ALOFT). SHOWERS CONTINUE THIS EVENING IN THE  
INTERIOR/RAINIER REGION (WITH A COUPLE OF SMALL THUNDERSTORMS STILL  
POSSIBLE UNTIL DUSK). THE SHOWERS WILL CONTINUE IN THE INTERIOR  
THROUGH MONDAY MORNING. DRIER CONDITIONS EXPECTED MONDAY AFTERNOON  
AS THE UPPER TROUGH DEPARTS EAST. CEILINGS ARE EXPECTED TO DROP TO  
MVFR OVERNIGHT, BUT WILL IMPROVE TO VFR BY MID TO LATE MONDAY  
AFTERNOON. SURFACE WINDS OUT OF THE NORTH THIS EVENING WILL TAPER  
OVERNIGHT, AND BECOME SOUTHWESTERLY BY MONDAY. FEW GUSTS TO 18 KT  
POSSIBLE IN THE INTERIOR MONDAY AFTERNOON.  
 
KSEA...SHOWERS STILL IN THE VICINITY THIS EVENING, BUT WILL TAPER  
GOING INTO TONIGHT. W/NW WIND TO 10 KT THROUGH 06Z, BECOMING S. LOW  
CLOUDS, LIGHT RAIN AND MVFR CONDITIONS EARLY MONDAY. LOWER  
CEILINGS POSSIBLY PERSISTING THROUGH MID TO LATE AFTERNOON.  
 
33/HPR  
 

 
   
MARINE
 
HIGH PRESSURE OVER THE NE PACIFIC WILL MAINTAIN ONSHORE  
FLOW OVER WESTERN WA THIS WEEK. HIGHEST WIND AND WAVES WILL BE  
THROUGH THE STRAIT OF JUAN DE FUCA, MAINLY DURING THE AFTERNOON AND  
EVENING HOURS. THE STRONGEST PUSHES WILL BE TONIGHT AND MONDAY  
AFTERNOON, WHICH MAY AFFECT SMALL CRAFT. SEAS REMAIN AT 4 TO 6 FEET  
THROUGHOUT THE WEEK.  
 
33/HPR  
 

 
   
SEW WATCHES/WARNINGS/ADVISORIES
 
 
WA...NONE.  
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT MONDAY FOR CENTRAL U.S.  
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS  
STRAIT OF JUAN DE FUCA.  
 

 
 

 
 
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