102  
FXUS66 KMFR 302123  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
223 PM PDT WED JUL 30 2025  
   
DISCUSSION
 
WITH TSUNAMI WAVES DECREASED BELOW WARNING THRESHOLDS  
IN THE LATE MORNING HOURS, ATTENTION TURNS TO ELEVATED THUNDERSTORM  
CHANCES THIS AFTERNOON INTO TONIGHT. A NEGATIVELY-TILTED SHORTWAVE  
TROUGH ASSOCIATED WITH A LOW PRESSURE SYSTEM OVER THE GULF OF ALASKA  
IS MOVING OVER NORTHERN CALIFORNIA AND SOUTHERN OREGON. THIS  
SHORTWAVE TROUGH WILL PROVIDE INSTABILITY THAT LOOKS TO HELP FUEL  
SCATTERED TO WIDESPREAD THUNDERSTORMS TODAY. THE HIGHEST CHANCES FOR  
THUNDERSTORMS (30-35%) ARE OVER SISKIYOU COUNTY AND THE CASCADES.  
CHANCES ARE SLIGHTLY LOWER IN MODOC, LAKE, AND EASTERN KLAMATH  
COUNTIES (25-30%), THEN LOWER AGAIN OVER JACKSON AND EASTERN DOUGLAS  
COUNTIES (20-25%) AND JOSEPHINE COUNTY (15-20%). PRECIPITABLE WATER  
VALUES LOOK TO BE HIGHER WEST OF THE CASCADES AT 0.85 IN, WITH 0.65  
IN TO THE EAST. THESE VALUES AREN'T PARTICULARLY EXCEPTIONAL, BUT DO  
INDICATE THAT AREAS EAST OF THE CASCADES HAVE A BETTER CHANCE OF  
SEEING DRIER THUNDERSTORMS. MODELS HAVE MOVED AWAY FROM OVERNIGHT  
ACTIVITY, ALTHOUGH ISOLATED THUNDERSTORMS OVER NORTHERN LAKE AND  
KLAMATH COUNTIES ARE POSSIBLE IN THE EARLY THURSDAY MORNING HOURS.  
 
WITH THE SHORTWAVE TROUGH STILL MOVING OVER THE AREA ON THURSDAY,  
INCREASED THUNDERSTORM CHANCES ARE IN THE FORECAST FOR THE AFTERNOON  
AND EVENING AS WELL. THAT TROUGH WILL HAVE TRAVELED TO THE  
NORTHEAST, WHICH PUTS THE HIGHEST CHANCES FOR ACTIVITY (35-40%) IN  
NORTHERN LAKE COUNTY. LOWER CHANCES (25-35%) ARE IN THE FORECAST FOR  
KLAMATH, MODOC, SISKIYOU, JACKSON, AND EASTERN DOUGLAS COUNTIES.  
WITH THE SHORTWAVE TROUGH ON THE WAY OUT OF THE AREA, THURSDAY'S  
THUNDERSTORMS DO NOT LOOK TO GO INTO THE NIGHTTIME HOURS. PW VALUES  
DROP ABOUT 0.1 INCHES ACROSS THE AREA ON THURSDAY AFTERNOON. ANY  
LINGERING CLOUD COVER FROM TODAY'S ACTIVITY COULD FURTHER IMPACT  
THURSDAY'S THUNDERSTORM CHANCES.  
 
STORM PREDICTION CENTER GUIDANCE DOES NOT INDICATE SIGNIFICANT  
SEVERE THUNDERSTORM CHANCES FOR TODAY AND THURSDAY, BUT SEVERE  
ACTIVITY IS STILL POSSIBLE. EVEN NORMAL THUNDERSTORMS POSE A NUMBER  
OF THREATENING CONDITIONS. CLOUD-TO-GROUND LIGHTNING, GUSTY AND  
ERRATIC WINDS, SMALL HAIL, AND LOCALLY HEAVY RAINFALL MAY BE PRESENT  
UNDER ANY ACTIVE STORM.  
 
WHILE THE MAIN SHORTWAVE TROUGH WILL BE ABSENT AFTER THURSDAY,  
WEAKER SHORTWAVES WILL CONTINUE TO MOVE OVER THE AREA. THUNDERSTORM  
CHANCES REMAIN IN THE FORECAST FOR FRIDAY THROUGH SUNDAY, BUT ARE  
CURRENTLY LOWER (10-20%) AND LIMITED TO NORTHERN CALIFORNIA AND EAST  
OF THE CASCADES. WARM SUMMER TEMPERATURES AND NORMAL DIURNAL WINDS  
WILL CONTINUE ACROSS THE AREA THROUGH SATURDAY. A FAST-MOVING UPPER  
TROUGH LOOKS TO BRING SLIGHTLY COOLER TEMPERATURES ON SUNDAY AND  
MONDAY BEFORE SEASONALLY WARM TEMPERATURES RETURN IN THE MIDDLE OF  
NEXT WEEK. -TAD  
 

 
   
AVIATION...30/18Z TAFS
 
WHILE IFR LEVELS CONTINUE AT NORTH BEND,  
SATELLITE IMAGERY SHOWS MARINE STRATUS TRYING TO CLEAR ALONG THE  
OREGON COAST. GUIDANCE SUGGESTED MARINE CLOUDS PERSISTING THROUGH  
MOST OF THE TAF PERIOD, BUT PERIODS OF VFR MAY OCCUR ALONG THE COAST  
BEFORE MARINE STRATUS RETURNS IN THE AFTERNOON OR EVENING.  
 
INLAND, VFR LEVELS GENERALLY LOOK TO CONTINUE THROUGH THE DAY.  
SCATTERED TO WIDESPREAD THUNDERSTORMS WILL DEVELOP THIS AFTERNOON  
AND EVENING ACROSS MUCH OF THE AREA. THIS MAY BRING TEMPORARILY  
LOWER CEILINGS AND/OR VISIBILITY UNDER ACTIVE STORM CELLS. THE MAIN  
RISKS WITH THUNDERSTORMS WILL BE GUSTY AND ERRATIC OUTFLOW WINDS,  
CLOUD TO GROUND LIGHTNING AND SMALL HAIL. SUBSTANTIAL NOCTURNAL  
THUNDERSTORMS LOOK UNLIKELY, BUT SOME LINGERING ISOLATED CELLS OVER  
LAKE COUNTY ARE NOT IMPOSSIBLE TONIGHT. -TAD  
 

 
   
MARINE...UPDATED 200 PM PDT WEDNESDAY, JULY 30, 2025
 
A WEAK  
THERMAL TROUGH ALONG THE COAST WILL MAINTAIN GUSTY NORTH WINDS SOUTH  
OF PORT ORFORD TODAY. THIS IS RESULTING IN LOW END ADVISORY LEVEL  
WINDS AND STEEP SEAS THAT WILL PERSIST THROUGH THIS EVENING.  
CONDITIONS BRIEFLY IMPROVE WITH LOW PRESSURE IN THE AREA LATER  
TONIGHT INTO THURSDAY. SLIGHT STRENGTHENING OF THE THERMAL TROUGH IS  
LIKELY TO BRING A RETURN OF STEEP SEAS TO THE SOUTHERN WATERS DURING  
THE AFTERNOON AND EVENING HOURS FROM THURSDAY AFTERNOON INTO  
SATURDAY EVENING. /BR-Y  
 

 
   
FIRE WEATHER...UPDATED 200 PM PDT WEDNESDAY, JULY 30, 2025
 
THE  
MAIN CONCERN WILL BE SCATTERED TO NUMEROUS THUNDERSTORMS LATE THIS  
AFTERNOON INTO THIS EVENING. GUSTY ERRATIC OUTFLOW WINDS ARE ALSO A  
CONCERN NEAR THUNDERSTORMS DURING THE SAME TIME PERIOD.  
 
SATELLITE IMAGE SHOWS A NEGATIVELY TILTED UPPER TROUGH OVER THE  
NORTHERN SIERRAS AND IS EXPECTED TO MIGRATE NORTH THIS AFTERNOON  
THROUGH TONIGHT. SATELLITE IMAGE ALSO SHOWS BUILDING CUMULUS ALONG  
THE CASCADES, PORTIONS OF THE EASTSIDE AND NORTHERN CALIFORNIA, WITH  
ISOLATED THUNDERSTORMS ALREADY DEVELOPING IN PORTIONS FIRE WEATHER  
ZONES 280, 281 AND 284.  
 
AS THE NEGATIVELY TILTED UPPER TROUGH MOVES NORTH, THIS WILL LEAD  
LEAD TO SCATTERED TO WIDESPREAD THUNDERSTORMS ACROSS THE REGION. WE  
EXPECT STORMS AS FAR WEST AS THE ILLINOIS VALLEY LATER THIS  
AFTERNOON AND EVENING, WITH THE GREATEST COVERAGE EXPECTED FROM THE  
CASCADES EASTWARD AND ACROSS NORTHERN CALIFORNIA, AND A RED FLAG  
WARNING REMAINS IN EFFECT FOR ALL FIRE ZONES AWAY FROM THE COAST AND  
FIRE ZONE 616 UNTIL 11 PM PDT.  
 
THE GENERAL CONSENSUS IS FOR STORMS TO BECOME LESS FREQUENT THIS  
EVENING AND DIMINISHING IN THE OVERNIGHT HOURS. ISOLATED STORMS WILL  
STILL BE A CONCERN, BUT THE LATEST GUIDANCE SUGGEST THE BEST CHANCE  
SHOULD BE MAINLY CONFINED TO PORTIONS OF FIRE ZONES 624 AND 625.  
 
ANOTHER ROUND OF SCATTERED STORMS ARE POSSIBLE THURSDAY, BUT UNLIKE  
TODAY, THE FOCUS FOR STORMS WILL BE IN NORTHERN CAL, AND ALONG AND  
EAST OF THE CASCADES. WE'LL BE IN A LESS FAVORABLE DYNAMIC REGION AS  
THE TROUGH WILL HAVE SHIFTED NORTH OF THE AREA. THE GREATEST  
COVERAGE IS MORE LIKELY TO BE WHERE THERE ISN'T CLOUD COVER IN THE  
MORNING, WHICH AT THIS TIME LOOKS TO BE EAST OF THE CASCADES AND  
ACROSS NORTHERN CALIFORNIA. ISOLATED STORMS COULD SNEAK THROUGH THE  
CRACKS IN PORTIONS OF FIRE ZONES 621 AND 622 LATE THURSDAY AFTERNOON,  
AND EARLY THIS EVENING, BUT NOT ENOUGH TO WARRANT A CONCERN. DUE TO  
THE EXPECTED SCATTERED STORMS, THE FIRE WEATHER WATCH HAS BEEN  
UPGRADED TO A RED FLAG WARNING. PLEASE SEE RFWMFR FOR MORE DETAILS.  
 
FRIDAY, THERE'S GOOD AGREEMENT ANOTHER SHORTWAVE, WITH A SLIGHT  
NEGATIVE TILT IS EXPECTED TO MOVE INTO THE AREA DURING THE TIME OF  
MAX HEATING AND INSTABILITY. THE COMBINATION OF THE BOTH PLUS A  
TRIGGER COULD BE CAUSE FOR CONCERN TO WARRENT ANOTHER FIRE WEATHER  
WATCH FOR PORTIONS OF NORTHERN CAL AND EAST OF THE CASCADES FRIDAY  
AFTERNOON INTO FRIDAY EVENING. HOWEVER, DUE TO THE TWO HEADLINES  
CURRENTLY OUT, AND THAT WERE STILL A FEW DAYS OUT, WE'LL WAIT UNTIL  
THE FIRST RED FLAG WARNING TO END, THEN REEVALUATE THE SITUATION  
EITHER TONIGHT OR TOMORROW MORNING TO SEE IF ANOTHER HEADLINE IS  
NEEDED. STAY TUNED.  
 
FOR THE WEEKEND, SATURDAY PRETTY MUCH LOOKS HO-HUM IN THAT ANY  
STORMS SHOULD BE ISOLATED AND CONFINED TO PORTIONS OF FIRE ZONES  
280, 281, 624 AND 625 LATE IN THE AFTERNOON AND EARLY EVENING.  
 
SUNDAY, THERE'S GOOD AGREEMENT A STRONGER UPPER TROUGH WILL MOVE  
INTO THE AREA SUNDAY AFTERNOON WHICH COULD TRIGGER THUNDERSTORMS  
ALONG AND EAST OF THE CASCADES AND NORTHERN CALIFORNIA. ANOTHER  
CONCERN FOR SUNDAY COULD ALSO BE MODERATE TO OCCASIONALLY STRONG  
WINDS AHEAD OF THE UPPER TROUGH SUNDAY AFTERNOON. -PETRUCELLI  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ620>622.  
 
RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ617.  
 
RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ623>625.  
 
RED FLAG WARNING FROM 2 PM TO 8 PM PDT THURSDAY FOR ORZ623>625.  
 
CA...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ280-281-284-  
285.  
 
RED FLAG WARNING FROM 2 PM TO 8 PM PDT THURSDAY FOR CAZ280-281-  
284-285.  
 
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 8 PM PDT THIS  
EVENING FOR PZZ356-376.  
 

 
 

 
 
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