130  
FXUS66 KPDT 140251  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
751 PM PDT MON AUG 13 2018  
   
UPDATE
 
DENSE SMOKE CONTINUES TO SLOWLY ADVANCE SOUTHWARD ACROSS  
THE PACIFIC NORTHWEST AND THE FORECAST AREA FROM WILDFIRES TO THE  
NORTH. MANY STATIONS HAVE REPORTED LOWERED VISIBILITIES DOWN TO 1 TO  
3 MILES. THE SMOKE WILL CONTINUE OVERNIGHT AND INTO TUESDAY. THE  
FLOW ALOFT WILL GRADUALLY TRANSITION TO THE WEST AND THEN SOUTHWEST  
BY MID WEEK SO MAY SEE SOME IMPROVEMENT BY MID WEEK. TEMPERATURES  
DID NOT REACH THE FORECAST MAXIMUM ACROSS MOST STATIONS IN THE CWA  
ON MONDAY (TODAY) SO MAY NEED TO ADJUST TEMPERATURES DOWNWARD FOR  
TUESDAY WITH THIS EVENING'S FORECAST UPDATE. AN UPPER TROUGH WILL  
GRADUALLY DIG OFF THE COAST WITH AN UPPER RIDGE OVER THE ROCKY  
MOUNTAINS. THIS WILL CAUSE THE FLOW TO TURN TO THE WEST AND THEN  
SOUTHWEST BY MID WEEK WHICH MAY BRING THE IMPROVEMENT FROM THE  
SMOKE. WEDNESDAY WILL BE THE WARMEST DAY THIS WEEK. THEN THERE WILL  
BE A SLIGHT CHANCE OF AFTERNOON AND EVENING SHOWERS AND  
THUNDERSTORMS FROM WEDNESDAY AFTERNOON ONWARD. THIS WILL ALSO HELP  
TO CLEAR OUT THE SMOKE, BUT LIGHTNING FROM THUNDERSTORMS MAY IGNITE  
ADDITIONAL FIRES ACROSS THE AREA, ESPECIALLY OVER SOUTHERN AREAS OF  
THE CWA WHERE MID LEVEL MOISTURE AND INSTABILITY WILL BE THE  
GREATEST. 88  
 

 
   
AVIATION...06Z TAFS
 
SMOKE AND HAZE WILL CONTINUE TO KEEP  
VISIBILITIES LOWERED AT KDLS, KPDT, KALW, KYKM, AND KALW, CREATING  
MVFR CONDITIONS AT TIMES. KRDM AND KBDN WILL HAVE THE GREATEST  
VISIBILITIES WITH MAINLY VFR CONDITIONS TONIGHT. THE SMOKE HAS  
REACHED THE SURFACE SO ALL ELEVATIONS WILL HAVE LIMITED VISIBILITY  
AT THE STATIONS MENTIONED ABOVE WHERE SMOKE HAS INVADED THE AREA.  
OTHERWISE SKIES WILL BE MOSTLY CLEAR. WINDS WILL REMAIN GENERALLY  
LIGHT THROUGH THE NEXT 24 HOURS. 88  
 

 
   
PREV DISCUSSION
 
/ISSUED 250 PM PDT MON AUG 13 2018/  
 
SHORT TERM...TONIGHT THROUGH THURSDAY AFTERNOON...A WARMING TREND  
IS EXPECTED THROUGH THURSDAY WITH HIGH TEMPS IN THE MID TO UPPER 90S  
BY MID WEEK DUE TO HIGH PRESSURE YIELDING DRY CONDITIONS THROUGH  
WEDNESDAY MORNING IN THE OREGON FORECAST ZONES. DRY CONDITIONS WILL  
PERSIST THROUGH THURSDAY IN THE WASHINGTON FORECAST ZONES.  
 
FOR SEVERAL DAYS MODELS HAVE BEEN CONSISTENTLY SHOWING A MID/UPPER  
LEVEL TROUGH DEVELOPING JUST OFFSHORE OF THE OREGON COAST TONIGHT  
AND TUESDAY. THE TROUGH WILL TRANSPORT MID LEVEL MONSOON MOISTURE  
FROM CALIFORNIA AND THE GREAT BASIN, AS WELL AS MOISTURE FROM THE  
REMNANTS OF HURRICANE JOHN, NORTHWARD INTO CENTRAL OREGON, GRANT  
COUNTY AND THE SOUTHERN BLUE MOUNTAINS WEDNESDAY AFTERNOON. THE  
MOISTURE AND DAYTIME SURFACE HEATING WILL CREATE A MARGINALLY  
UNSTABLE ATMOSPHERE, WHICH WILL ALLOW FOR A SLIGHT CHANCE OF  
THUNDERSTORMS IN CENTRAL AND EAST CENTRAL OREGON WEDNESDAY  
AFTERNOON. AN UNSTABLE MID LEVEL LAYER ASSOCIATED WITH THE MONSOON  
MOISTURE WILL MOVE INTO CENTRAL AND EAST CENTRAL OREGON AND THE BLUE  
MOUNTAINS WEDNESDAY NIGHT, WHICH WILL ALLOW ISOLATED NOCTURNAL  
THUNDERSTORMS TO OCCUR IN CENTRAL OREGON, GRANT COUNTY AND THE BLUE  
MOUNTAINS FROM SUNDOWN WEDNESDAY TO SUNRISE THURSDAY. THURSDAY WILL  
SEE ANOTHER ROUND OF ISOLATED THUNDERSTORMS MAINLY IN THE MOUNTAINS  
IN CENTRAL AND NORTHEAST OREGON INCLUDING GRANT COUNTY. MODELS ARE  
SHOWING 30-40 KNOTS OF VERTICAL WIND SHEAR THURSDAY AFTERNOON AND  
EVENING EAST OF THE OREGON CASCADES WHICH MAY SUPPORT THUNDERSTORMS  
BECOMING STRONG THUS PRODUCING STRONG GUSTY WINDS AND HAIL. A FEW  
STORMS MAY BECOME SEVERE IN CENTRAL AND EAST CENTRAL OREGON THURSDAY  
AFTERNOON/EVENING. POLAN  
 
LONG TERM...THURSDAY NIGHT THROUGH MONDAY...A SLOW MOVING SHORTWAVE  
OFF THE COAST IS EXPECTED TO MOVE INLAND LATE THURSDAY THEN EXIT  
LATE FRIDAY. THIS WILL SERVE AS A TRIGGER TO GENERATE SHOWERS AND  
THUNDERSTORMS STARTING IN CENTRAL OREGON LATE THURSDAY AND SHIFTING  
INTO NORTHEAST OREGON OVERNIGHT AND FRIDAY. BEYOND THAT THERE IS  
SOME MODEL DIFFERENCES WHICH MAKES THE FORECAST LOW CONFIDENCE. A  
RIDGE OF HIGH PRESSURE WILL BEGIN TO BUILD OFF THE COAST OVER THE  
WEEKEND. MODELS DIFFER BY EITHER DEVELOPING A NORTHERLY FLOW INTO  
THE REGION ON THE BACK SIDE OF THE RIDGE OR HAVING THE RIDGE MOVE  
INLAND OVER THE REGION. BOTH SOLUTIONS SHOULD BE DRY OVER THE  
WEEKEND BUT COULD BE SOME TEMPERATURE DIFFERENCES DEPENDING ON WHICH  
SOLUTION PLAYS OUT.  
 
FIRE WEATHER...MODERATE TO POOR RH RECOVERIES ON RIDGES ARE EXPECTED  
TONIGHT AND AGAIN ON TUESDAY. MID-LEVEL MOISTURE FROM REMNANTS OF  
HURRICANE JOHN AND THE NORTH AMERICAN MONSOON WILL ADVECT INTO  
OREGON ON WEDNESDAY WITH A SLIGHT CHANCE OF THUNDERSTORMS DURING THE  
AFTERNOON, PRIMARILY CONFINED TO THE HIGHER TERRAIN FROM THE CENTRAL  
OREGON CASCADES EAST ACROSS THE CENTRAL AND SOUTHERN BLUES AND INTO  
THE WALLOWAS. BASED ON CURRENT GUIDANCE SUSPECT CONVECTIVE DEBRIS  
FROM TUESDAY NIGHT CONVECTION FURTHER SOUTH MAY LIMIT  
DESTABILIZATION OVER THESE AREAS WEDNESDAY AFTERNOON, ESPECIALLY  
WITH EASTWARD EXTENT. DO NOT CURRENTLY ANTICIPATE FIRE WEATHER  
HIGHLIGHTS FOR WEDNESDAY WITH COVERAGE FALLING SHORT OF RED FLAG  
CRITERIA (LAL 3). SHOULD SEE BETTER COVERAGE OF SIMILAR AREAS  
THURSDAY WITH APPROACHING WAVE AND ANY CONVECTION THAT DEVELOPS  
THURSDAY AFTERNOON WILL LIKELY PERSIST AHEAD OF THE TROUGH THROUGH  
THE EVENING AND INTO FRIDAY MORNING BEFORE FINALLY EXITING OUR AREA  
TO THE EAST FRIDAY AFTERNOON. THIS ACTIVITY MAY APPROACH LAL 3  
ESPECIALLY LATE THURSDAY AFTERNOON AND INTO THE EVENING AND MAY  
REQUIRE HIGHLIGHTS WITH TOMORROW'S PACKAGE. WINDS WILL INCREASE  
BEHIND THE TROUGH ON THURSDAY AND FRIDAY ESPECIALLY THROUGH THE  
CASCADE GAPS AS ONSHORE FLOW STRENGTHENS WITH SOME POTENTIAL WINDRH  
CONCERNS. PECK  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 59 93 62 97 / 0 0 0 0  
ALW 59 94 62 98 / 0 0 0 0  
PSC 56 95 58 99 / 0 0 0 0  
YKM 56 94 61 98 / 0 0 0 0  
HRI 56 96 59 99 / 0 0 0 0  
ELN 56 96 58 99 / 0 0 0 0  
RDM 49 94 54 95 / 0 0 0 20  
LGD 50 92 53 96 / 0 0 0 10  
GCD 55 95 59 95 / 0 0 10 20  
DLS 62 100 65 100 / 0 0 0 0  
 

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

 
 

 
 
88/91/88  
 
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