000  
FXUS66 KMFR 051157  
AFDMFR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEDFORD OR  
457 AM PDT FRI SEP 5 2025  
   
DISCUSSION
 
RADAR/SATELLITE HAS BEEN FAIRLY ACTIVE THIS MORNING  
WITH AN AREA OF SHOWERS/THUNDERSTORMS OVER THE UMPQUA BASIN  
WESTWARD TO THE COAST AND OVER THE MARINE WATERS NORTH OF CAPE  
BLANCO. MODELS SHOWED SOME ELEVATED INSTABILITY IN THIS REGION,  
AND OUTFLOWS MOVING WESTWARD FROM THURSDAY EVENING'S CONVECTION  
COMBINED WITH A SHORTWAVE MOVING THROUGH THE REGION, REALIZED THIS  
ELEVATED ENERGY. RADAR SHOWS CELLS MOVING GENERALLY  
NORTHWESTWARD, NOW NORTHWEST OF ROSEBURG/NORTH BEND AND WILL  
CONTINUE THIS TREND THROUGH SUNRISE. THERE IS MEASURABLE RAINFALL  
WITH THESE CELLS, WITH SOME SITES IN THE UMPQUA BASIN REPORTING A  
FEW HUNDRETHS AND THE ROSEBURG AIRPORT PICKING UP 0.28" AS THE  
CORE OF ONE OF THE CELLS MOVED DIRECTLY OVER THE AIRPORT. OVER THE  
REMAINDER OF THE AREA, QUIET CONDITIONS CONTINUE. THE MARINE  
LAYER IS WELL ENTRENCHED ALONG THE COAST AND INTO THE COASTAL  
VALLEYS, AND AREAS OF DRIZZLE ARE POSSIBLE THIS MORNING WITH A  
DEEP MARINE LAYER IN PLACE.  
 
A COOLING TREND IS EXPECTED TO START TODAY AND CONTINUE INTO NEXT  
WEEK, WITH HIGH TEMPERATURES EVENTUALLY REACHING 10-15 DEGREES BELOW  
NORMAL BY EARLY NEXT WEEK. HIGHS TODAY WILL BE AROUND 5 DEGREES  
COOLER THAN YESTERDAY FOR WEST SIDE VALLEYS WITH SIMILAR  
TEMPERATURES FOR THE REST OF THE AREA. OUR DAILY THUNDERSTORM  
CHANCES WILL CONTINUE TODAY AND INTO THE WEEKEND, WITH THE FOCUS OF  
ACTIVITY THIS AFTERNOON EXPECTED TO BE IN THE NORTHERN CASCADES, AND  
SOUTHEASTWARD INTO PORTIONS OF KLAMATH/LAKE/EASTERN MODOC COUNTIES.  
LATER THIS EVENING AND OVERNIGHT INTO SATURDAY MORNING, GUIDANCE  
SHOWS THE POTENTIAL FOR SOME OVERNIGHT THUNDERSTORMS AGAIN WEST OF  
THE CASCADES. WHILE NONE OF THE CAMS ARE SHOWING ACTIVITY TONIGHT,  
THEY ALSO DIDN'T SHOW THE CURRENT ACTIVITY. CONSIDERING THIS  
MORNING'S ACTIVITY LINES UP WITH MODEL INDICATED ELEVATED  
INSTABILITY, AND MODELS AGAIN SHOW THIS FOR TONIGHT COMBINED WITH A  
NEGATIVELY TILTED SHORTWAVE APPROACHING AND MOVING THROUGH THE  
REGION, IT'S REASONABLE TO BELIEVE THAT THERE WILL BE THUNDERSTORMS  
DURING THE OVERNIGHT PERIOD TONIGHT. ISOLATED SHOWERS/THUNDERSTORMS  
WILL BE POSSIBLE JUST ABOUT ANYWHERE WEST OF THE CASCADES, INCLUDING  
THE COAST AND OVER THE MARINE WATERS. THUNDERSTORM CHANCES CONTINUE  
INTO THE DAYTIME SATURDAY, FOCUSED ALONG AND EAST OF THE I-5  
CORRIDOR. EXPECT ANOTHER 5 DEGREES OR SO OF COOLING FOR AFTERNOON  
TEMPERATURES, INCLUDING AREAS EAST OF THE CASCADES AND IN NORTHERN  
CALIFORNIA.  
 
BEYOND SATURDAY, THE PARENT TROUGH THAT HAS DRIFTED AROUND OVER THE  
EASTERN PACIFIC FIRING SHORTWAVES AT US THIS WEEK WILL FINALLY MOVE  
ONSHORE AND STICK AROUND THROUGH MOST OF NEXT WEEK. THIS PATTERN  
CHANGE WILL RESULT IN BELOW NORMAL TEMPERATURES AND SEVERAL DAYS  
(ROUGHLY SUNDAY NIGHT THROUGH WEDNESDAY) OF LIGHT, BUT BENEFICIAL,  
PRECIPITATION CHANCES THAT WOULD MAKE THE AREA FEEL MORE LIKE  
OCTOBER THAN EARLY SEPTEMBER. IT IS STILL YET TOO EARLY IN THE  
SEASON, AND PRECIPITATION MAY BE TOO SPOTTY, TO CALL THIS A SEASON  
ENDING EVENT FOR AREA WILDFIRES. THAT BEING SAID, WE ARE MORE  
CONFIDENT THAT HEALTHY MEASURABLE RAINFALL WILL OCCUR ACROSS THE  
AREA OVER THE FIRST HALF OF NEXT WEEK, WHICH WOULD DEFINITELY BE  
HELPFUL WITH LOCAL FIREFIGHTING EFFORTS, AND WOULD PUT A LARGE DENT  
IN FIRE WEATHER CONCERNS. /BR-Y/BPN  
 

 
   
AVIATION...05/12Z TAFS
 
VFR CONDITIONS PREVAIL FOR MOST OF THE  
AREA AND WILL DO SO THROUGH THE TAF PERIOD. ALONG THE COAST AND  
OFFSHORE, LIFR CONDITIONS WILL PERSIST THROUGH THE MORNING.  
MEANWHILE, ISOLATED THUNDERSTORMS CONTINUE TO IMPACT THE MARINE  
WATERS AND COASTAL LOCATIONS, INCLUDING NORTH BEND, NORTH OF CAPE  
BLANCO. STORM ACTIVITY SHOULD WANE AROUND SUNRISE. OVERALL  
CONDITIONS SHOULD AT LEAST IMPROVE ALONG THE COAST TO MVFR, BUT MAY  
NOT FULLY CLEAR TO VFR THIS AFTERNOON. ANY CLEARING WILL LIKELY BE  
SHORT LIVED WITH MVFR/IFR CONDITIONS RETURNING BY LATE  
AFTERNOON/EARLY EVENING.  
 
FOR INLAND LOCATIONS, ANOTHER ROUND OF SCATTERED THUNDERSTORMS IS  
EXPECTED THIS AFTERNOON AND EVENING, WITH THE GREATEST ACTIVITY  
EXPECTED ALONG THE NORTHERN CASCADES AND SOUTHEASTWARD INTO  
KLAMATH/LAKE AND EASTERN MODOC COUNTIES. ISOLATED STORMS ARE  
POSSIBLE WEST OF THE CASCADES LATE TONIGHT INTO EARLY SATURDAY  
MORNING.  
 

 
   
MARINE...UPDATED 200 AM PDT FRIDAY, SEPTEMBER 5, 2025
 
ISOLATED  
SHOWERS AND THUNDERSTORMS WILL PERSIST OVER THE WATERS NORTH OF CAPE  
BLANCO THROUGH THIS MORNING. WHILE STORMS AREN'T EXPECTED TO BE  
STRONG, GUSTS OF 25-30 MPH ARE POSSIBLE WITH ANY THUNDERSTORM  
OUTFLOWS. NORTH WINDS WILL CONTINUE TO WEAKEN TODAY, WITH MARINE FOG  
AND LOW CLOUDS PERSISTING FOR THE NEXT SEVERAL DAYS. AN UPPER LEVEL  
LOW WILL PASS OVER THE AREA LATE TODAY INTO SATURDAY, WITH SHOWERS  
AND DRIZZLE LIKELY, AND A STRAY THUNDERSTORM OR TWO POSSIBLE.  
OUTSIDE OF POTENTIAL SHOWERS/THUNDERSTORMS, EXPECT GENERALLY CALM  
CONDITIONS WITH NO SIGNIFICANT SWELL AND LIGHT WINDS BECOMING SOUTH  
AHEAD OF AN AREA OF LOW PRESSURE MOVING ONSHORE EARLY NEXT WEEK.  
 

 
   
FIRE WEATHER...UPDATED 300 AM PDT FRIDAY, SEPTEMBER 5, 2025
 
THE  
PRIMARY FIRE WEATHER CONCERN FOR THROUGH SATURDAY, POSSIBLY SUNDAY,  
WILL BE ISOLATED TO SCATTERED THUNDERSTORMS IN THE  
AFTERNOONS/EVENINGS AS WELL AS POTENTIALLY OVERNIGHT. PERSISTENT LOW  
PRESSURE OVER THE EASTERN PACIFIC WILL CONTINUE TO SEND SHORTWAVES  
INTO THE AREA. ONE SHORTWAVE IS MOVING THROUGH THE REGION THIS  
MORNING, AND MANAGED TO KICK OFF SEVERAL ISOLATED STORMS IN THE  
UMPQUA BASIN AND WESTWARD TO ALONG THE COAST FROM NORTH BEND  
NORTHWARD. THERE HAS BEEN SOME MEASURABLE RAINFALL WITH THESE CELLS  
AS THE ROSEBURG AIRPORT RECORDED 0.28" WITH A CELL MOVING DIRECTLY  
OVERHEAD. THIS ACTIVITY WILL WANE DOWN AROUND SUNRISE WITH THE NEXT  
SHORTWAVE EXPECTED LATER TODAY AND OVERNIGHT INTO SATURDAY. WE  
EXPECT ANOTHER ROUND OF SCATTERED THUNDERSTORMS IN THE NORTHERN  
CASCADES AND SOUTHEASTWARD INTO KLAMATH/LAKE/EASTERN MODOC COUNTIES.  
THERE SHOULD BE RAINFALL WITH THESE STORMS, BUT STORM MOTION 20-25  
KT FROM THE SOUTHWEST, SO STORMS AREN'T EXPECTED TO LINGER AND  
STRIKES OUTSIDE OF STORM CORES WILL BE A CONCERN. A RED FLAG WARNING  
IS IN EFFECT FOR ABUNDANT LIGHTNING ON DRY FUELS FOR FIRE WEATHER  
ZONES (FWZS) 617/623/624/625 AND EASTERN 285 FROM 1PM THROUGH 9PM  
THIS EVENING.  
 
STORMS COULD DEVELOP OVER THE WEST SIDE AGAIN TONIGHT AS THE  
SHORTWAVE BECOMES NEGATIVELY TILTED AND MOVES OVERHEAD DURING THE  
OVERNIGHT HOURS. MODELS FREQUENTLY STRUGGLE WITH OVERNIGHT  
CONVECTION, BUT THERE ARE INDICATIONS OF ELEVATED INSTABILITY  
FOCUSED ALONG AND EAST OF THE I-5 CORRIDOR TONIGHT, THOUGH A SLIGHT  
CHANCE EXISTS FOR ANYWHERE WEST OF THE CASCADES INCLUDING ALL THE  
WAY TO THE COAST. ADDITIONAL SHORTWAVES PASS THROUGH THE AREA DURING  
THE DAY SATURDAY, BRINGING ELEVATED WINDS OVER TERRAIN EAST OF THE  
CASCADES. THUNDERSTORM CHANCES REMAIN IN THE FORECAST FOR SATURDAY  
AFTERNOON/EVENING, AGAIN FOCUSED ALONG AND EAST OF THE I-5 CORRIDOR.  
AS WE GET TO SUNDAY, THE ATMOSPHERE STABILIZES SOME, BUT ISOLATED  
THUNDERSTORMS ARE NOT OUT OF THE QUESTION FOR NORTHERN AREAS.  
 
MEANWHILE, TEMPERATURES WILL TREND COOLER FROM TODAY ONWARD, HELPING  
TO MODERATE DAYTIME RHS. PERSISTENT LOW PRESSURE OFFSHORE WILL  
FINALLY MOVE INTO THE REGION NEXT WEEK, AND THE COOLING TREND  
CONTINUES WITH AFTERNOON HIGHS EXPECTED TO BE 10-15 DEGREES BELOW  
NORMAL FOR EARLY TO MID-WEEK. WIDESPREAD CHANCES OF BENEFICIAL  
RAINFALL ARE INCREASING FOR EARLY TO MID WEEK, AND WHILE IT SEEMS  
TOO EARLY TO SAY IT'S A SEASON ENDING EVENT, IF THE CURRENT FORECAST  
COMES TO FRUITION, IT COULD BE CONSIDERED A SEASON SLOWING EVENT.  
 

 
   
MFR WATCHES/WARNINGS/ADVISORIES
 
 
OR...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 9 PM PDT THIS  
EVENING FOR ORZ617-623>625.  
 
CA...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 9 PM PDT THIS  
EVENING FOR CAZ285.  
 
PACIFIC COASTAL WATERS...NONE.  
 

 
 

 
 
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