143
FXUS66 KMFR 091148
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
448 AM PDT TUE SEP 9 2025
DISCUSSION
THE WEATHER HAS CHANGED ACROSS MOST OF SW OREGON AND
NORCAL OVER THE PAST 24 HOURS, WITH AREAS FROM THE CASCADES
WESTWARD RECEIVING WIDESPREAD WETTING RAINFALL. A FEW HEFTY
THUNDERSTORMS ALSO DEVELOPED YESTERDAY AFTERNOON RESULTING IN
DOWNPOURS IN PORTIONS OF JACKSON, JOSEPHINE AND DOUGLAS COUNTIES,
WHERE CG (CLOUD TO GROUND) LIGHTNING TALLIES WERE AROUND 500-600
STRIKES. THERE WAS QUITE A DIFFERENCE IN RAIN AMOUNTS ACROSS
JACKSON COUNTY WITH EASTERN LOCATIONS RECEIVING 0.10 OF AN INCH
OR LESS, WHILE AREAS FROM JACKSONVILLE TO GOLD HILL AND ROGUE
RIVER HAD MORE THAN A THIRD OF AN INCH (AND COUNTING). FAR
SOUTHERN AND EASTERN SECTIONS OF THE CWA ARE STILL PROBABLY
WONDERING WHAT ALL THE HUBBUB IS ABOUT. BUT, THEY'LL GET THEIRS
TOO OVER THE NEXT COUPLE OF DAYS; THEY'LL JUST HAVE TO BE PATIENT.
LOW PRESSURE IS JUST OFF THE COAST EARLY THIS MORNING AND WILL
SLOWLY MOVE ONSHORE TODAY. CURRENT RADAR IS SHOWING AN AREA OF
LIGHT TO MODERATE RAINFALL WORKING FROM SOUTH TO NORTH ACROSS THE
WEST SIDE EARLY THIS MORNING WITH ISOLATED TO SCATTERED SHOWERS
FARTHER EAST ACROSS NORCAL AND EAST OF THE CASCADES. WATER VAPOR
IMAGERY IS ACTUALLY SHOWING A BROAD MID-LEVEL CIRCULATION WITH
SOME ELEMENTS THAT APPEAR TO HAVE ALREADY MOVED ONSHORE, BUT THE
SURFACE LOW IS STILL ABOUT 100 MILES OFF THE COAST. THIS SHOULDN'T
BE TOO MUCH OF A FACTOR IN THE EXPECTED WEATHER ACROSS THE AREA
TODAY SINCE THE UPPER LOW IS EXPECTED TO PIVOT NEAR THE COAST,
CONSOLIDATE, AND THEN HEAD ACROSS NORCAL TONIGHT INTO WEDNESDAY.
THE AIR MASS IS QUITE JUICY FOR THIS TIME OF YEAR. KMFR SOUNDINGS
FROM MONDAY EVENING INDICATE PWATS AT AROUND 1.20", WHICH IS UP
AROUND THE 90TH PERCENTILE FOR THE DATE. WITH THE UPPER LOW
EXPECTED TO MOVE OVERHEAD TODAY, WE'LL SEE A CONTINUATION OF
SHOWERS WITH EMBEDDED THUNDERSTORMS. MODEL SOUNDINGS SHOW SOME
TALL, SKINNY CAPE AND THIS MAY LEAD TO SOME LIGHTNING AGAIN,
ESPECIALLY THIS AFTERNOON AND EVENING. PROFILES WEST OF THE
CASCADES ARE EXHIBITING ALMOST-TROPICAL CHARACTERISTICS, SO STORMS
SHOULD HAVE FAIRLY WEAK UPDRAFTS, BUT DUE TO THE HIGH MOISTURE
CONTENT IN THE ATMOSPHERE, THE MAIN RISK WITH STORMS TODAY WILL
BE HEAVY DOWNPOURS. EXPECT HIGH TEMPS ABOUT 10-15F BELOW NORMAL
FOR MOST INLAND AREAS, UP TO 20F IN SOME CASES. HOWEVER, COASTAL
AREAS WILL HAVE HIGH TEMPS RIGHT AROUND NORMAL.
THE MAIN AXIS OF ACTIVITY (SHOWERS AND THUNDERSTORMS) WILL SHIFT
FROM WEST OF THE CASCADES TODAY TO NORCAL AND FROM THE CASCADES
EASTWARD (80% POPS) ON WEDNESDAY AS THE CORE OF THE UPPER LOW
MOVES INTO NE CALIFORNIA. THERE WILL STILL BE SOME SHOWERS FROM
THE CASCADE FOOTHILLS WESTWARD ON WEDNESDAY, BUT SHOWER CHANCES
DIMINISH TO 30% OR LESS NEAR THE COAST. WE'RE EXPECTING ANOTHER
COOL AFTERNOON WITH HIGH TEMPS LARGELY 10-15F (UP TO 20F IN SOME
AREAS AGAIN) BELOW NORMAL, EXCEPT NEAR NORMAL AT THE COAST.
WETTING RAINFALL SHOULD BE REALIZED IN MOST AREAS EAST OF THE
CASCADES.
ON THURSDAY, WE EXPECT A BROAD CIRCULATION TO BE OVER THE GREAT
BASIN, SO THIS SHOULD PUSH THE MAIN FOCUS AREAS FOR SHOWERS AND
THUNDERSTORMS TO NEAR AND EAST OF THE CASCADES.
BY FRIDAY, A SHORT WAVE UPPER RIDGE WILL BUILD INTO THE WEST
COAST, SO MOST AREAS WILL DRY OUT AND WARM UP. HIGH TEMPS WILL BE
CLOSER TO NORMAL WEST OF THE CASCADES, BUT ISOLATED TO SCATTERED
SHOWERS COULD LINGER OVER PORTIONS OF THE EAST SIDE WHERE HIGHS
TEMPS WILL STILL BE ABOUT 10F BELOW NORMAL. THE UPPER RIDGE WILL
REMAIN IN PLACE THROUGH SATURDAY AND SHOWER CHANCES SHOULD REMAIN
LOW INLAND (BUT UP TO 30% AT THE COAST DURING THE AFTERNOON).
THEN, MODELS ARE SHOWING ANOTHER TROUGH MOVING IN SATURDAY NIGHT
INTO SUNDAY. THERE ARE STILL SOME UNCERTAINTIES WITH TIMING AND
STRENGTH OF THIS SYSTEM, BUT SHOWERS CHANCES INCREASE TO LIKELY
(~60%) NEAR THE COAST SATURDAY NIGHT AND EVENTUALLY INLAND DURING
SUNDAY. THIS BRINGS A BRIEF COOL DOWN, BUT ANOTHER UPPER RIDGE
COULD RETURN BY EARLY NEXT WEEK. -SPILDE
AVIATION...09/12Z TAFS
A MOIST SHOWERY AIR MASS WILL REMAIN IN
PLACE BRINGING WIDESPREAD SHOWERS AND SOME EMBEDDED THUNDERSTORMS
TODAY. ALONG THE COAST, MVFR AND IFR WITH AREAS OF LIFR ARE
EXPECTED. CONDITIONS ARE FORECAST TO IMPROVE THIS AFTERNOON TO
MVFR AND AREAS OF VFR. INLAND, CONDITIONS WILL BE MAINLY VFR WITH
AREAS OF MOUNTAIN OBSCURATIONS. ADDITIONALLY, MVFR CEILINGS IN THE
UMPQUA THIS MORNING LIFT TO VFR BY LATE MORNING. THUNDERSTORM
CHANCES WILL BE LOW/ISOLATED AT 5-15% THIS MORNING, THEN INCREASE
TO 20-35% THIS AFTERNOON, WITH BEST CHANCES FROM THE CASCADES
WEST. MAIN RISKS WILL BE HEAVY DOWNPOURS AND LIGHTNING, BUT GUSTY
WINDS ALSO CANNOT BE RULED OUT.
MARINE...UPDATED 230 AM PDT TUESDAY, SEPTEMBER 9, 2025
UPPER
LEVEL LOW PRESSURE WILL MOVE INLAND TODAY WITH SHOWERS MOST
NUMEROUS THIS MORNING, THEN FAR LESS ACTIVITY THIS AFTERNOON.
BELOW ADVISORY CONDITIONS LIKELY PERSIST THROUGH MIDWEEK,
THOUGH WINDS BECOME MORE NORTHERLY TODAY COULD BE BRIEFLY GUSTY,
ESPECIALLY SOUTH OF CAPE BLANCO, TONIGHT INTO WEDNESDAY.
NORTHERLY WINDS COULD BE A BIT STRONGER IN THE FAVORED
LOCATION SOUTH OF PORT ORFORD AND BETWEEN 5 AND 30 NM FROM SHORE
DURING THE AFTERNOONS TUESDAY AND WEDNESDAY. WHILE SUB-ADVISORY
CONDITIONS ARE LIKELY TO PERSIST THROUGH THE END OF THE WEEK AND
INTO THE WEEKEND, SEAS DO INCREASE SOME DURING THE LATTER HALF OF
THE WEEK (FROM 3-5 FT TO 5-7 FT)AS A LOW NORTHWEST SWELL (5-6 FT @
12-14 SECONDS) BUILDS INTO THE WATERS STARTING THURSDAY AND
PERSISTING INTO THE WEEKEND.
FIRE WEATHER
FIRE WEATHER CONCERNS ARE LOW. THERE WILL BE SOME
LIGHTNING THROUGH MIDWEEK, BUT THE AIR MASS IS MOIST AND STORMS
WILL LIKELY CONTAIN WETTING RAINFALL. WITH THE RAINFALL YESTERDAY
AND THE EXPECTED RAINFALL TODAY AND WEDNESDAY, FIRE DANGER
INDICES SHOULD LOWER SIGNIFICANTLY AREA WIDE. THERE IS SOME RISK
FOR HEAVY RAINFALL IN SLOW-MOVING STORMS TODAY, WHICH, IF THEY
OCCUR OVER RECENT BURN SCARS, COULD RESULT IN A DEBRIS FLOW.
HOWEVER, THE RISK IS TOO LOW (5-15%) FOR ANY PRODUCTS AT THIS
TIME. -SPILDE
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
MAS/MAS/MAS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page