964
FXUS66 KMFR 012108
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
208 PM PDT FRI MAY 1 2026
DISCUSSION
A CUTOFF LOW IS EXPECTED TO DROP THROUGH A BROADER
RIDGE AND RUN PARALLEL TO THE PACIFIC COAST THROUGH TODAY AND
SATURDAY. THE OVERALL EFFECT OF THIS PATTERN WILL BE CONTINUING WARM
TEMPERATURES, WITH CHANCES OF AFTERNOON AND EVENING THUNDERSTORMS.
FOR TODAY, THE HIGHEST CHANCES (15-20%) ARE PRESENT FROM WESTERN
SISKIYOU COUNTY ACROSS JACKSON COUNTY TO THE CASCADES. SOMEWHAT
MODEST CAPE VALUES, MODELED IN THE 200-400 J/KG RANGE, INDICATE
GENERALLY ISOLATED TO SCATTERED ACTIVITY. MODEL SOUNDINGS FOR
ROSEBURG AND MEDFORD ARE SHOWING INVERSIONS IN THE ATMOSPHERE, A
LAYER OF STABLE AIR THAT CAN "CAP" UPLIFT AND IN TURN PREVENT
THUNDERSTORM DEVELOPMENT. IF THIS CAP IS IN PLACE THROUGH THE
AFTERNOON, DEVELOPMENT IN THESE AREAS MAY BE LIMITED. INVERSIONS
ARE LESS PRESENT IN MODEL SOUNDING FOR WESTERN SISKIYOU COUNTY,
WHICH WOULD MAKE DEVELOPMENT EASIER IN THAT AREA. INVERSIONS CAN
WEAKEN INTO THE EVENING, MEANING CHANCES FOR THUNDERSTORM ACTIVITY
INCREASES INTO THE EVENING FOR JACKSON COUNTY AND EASTERN DOUGLAS
COUNTY. THUNDERSTORM CHANCES ACROSS THE CWA DISSIPATE INTO THE LATE
EVENING AND NIGHTTIME HOURS, ALTHOUGH SOME SHOWERS MAY PERSIST.
FOR SATURDAY AFTERNOON AND EVENING, THUNDERSTORM CHANCES EXPAND TO
JOSEPHINE AND MODOC COUNTIES. SPC PAINTBALL GUIDANCE SHOWS THE
HIGHEST CONCENTRATION OF STORMS WITH REFLECTIVITY OVER 40 DBZ (AN
INDICATOR OF MORE SUBSTANTIAL ACTIVITY) IS EXPECTED OVER MODOC,
JOSEPHINE, AND EASTERN MODOC COUNTIES ON SATURDAY. OTHER MODELS
STILL INCLUDE WESTERN SISKIYOU AND JACKSON COUNTIES IN CHANCES FOR
THUNDERSTORMS, SO A BROAD AREA OF 20-25% THUNDERSTORM CHANCES ACROSS
THESE AREAS IS IN PLACE TO ADDRESS THESE POSSIBILITIES. MODEL
SOUNDINGS AND GUIDANCE SHOW WEAKER OR NO INVERSIONS AND HIGHER CAPE
VALUES (200-400 J/KG OVER MODOC COUNTY AND 400-700 J/KG FOR WEST
SIDE AREAS), INDICATING MORE SUBSTANTIAL ACTIVITY IS POSSIBLE.
FOR SUNDAY AND MONDAY, THE CUTOFF LOW STARTS TO HEAD INLAND OVER
CALIFORNIA. THIS WILL BRING WRAPAROUND FLOW ALOFT AND CHANCES FOR
RAIN SHOWERS WITH EMBEDDED THUNDERSTORMS RATHER THAN THE CELLULAR
THUNDERSTORMS THAT ARE MORE LIKELY ON FRIDAY AND SATURDAY. CHANCES
FOR RAIN AND THUNDERSTORMS ARE BOTH DEPENDENT ON HOW FAR SOUTH THE
CUTOFF GOES BEFORE HEADING INLAND, SO FORECASTS MAY CONTINUE TO VARY
SLIGHTLY AS MODELS COME INTO BETTER AGREEMENT ON THAT PATH. BROADLY,
MOST AREAS WILL SEE SOME AMOUNT OF UNIMPACTFUL RAINFALL THROUGH
SUNDAY AND MONDAY WITH COOS, NORTHWEST DOUGLAS, AND NORTHEAST LAKE
COUNTIES POSSIBLY STAYING DRY. THUNDERSTORM POSSIBILITIES HAVE ALSO
SHIFTED SOME AS THE EXPECTED PATH OF THE CUTOFF CHANGES. FOR BOTH
SUNDAY AND MONDAY, 20-25% THUNDERSTORM CHANCES ARE PRESENT OVER
SISKIYOU AND MODOC COUNTIES. ON SUNDAY, 15-20% THUNDERSTORM CHANCES
ARE PRESENT OVER JOSEPHINE, JACKSON, AND EASTERN DOUGLAS COUNTIES.
ON MONDAY, THOSE 15-20% CHANCES MOVE TO KLAMATH AND SOUTHERN LAKE
COUNTIES.
THUNDERSTORMS ANYWHERE CAN INCLUDE GUSTY AND ERRATIC WINDS, LOCALLY
HEAVY RAINFALL, SMALL HAIL, AND LIGHTNING. GIVEN THE ISOLATED TO
SCATTERED NATURE OF POSSIBLE ACTIVITY AND HOW RAPIDLY THUNDERSTORMS
CAN DEVELOP , PLEASE BE AWARE OF YOUR LOCAL CONDITIONS WHILE
SPENDING TIME OUTSIDE OR TRAVELING.
SOME LIGHT RAIN SHOWERS MAY LINGER OVER MODOC AND EASTERN LAKE
COUNTIES INTO EARLY TUESDAY MORNING, BUT IN GENERAL TUESDAY LOOKS TO
START OF A WARM AND DRY PERIOD THAT COULD LAST THROUGH THE REST OF
NEXT WEEK UNDER AN UPPER RIDGE. CURRENTLY, TEMPERATURES WOULD PEAK
ON THURSDAY WITH HIGHS IN THE HIGH 70S TO MID 80S FOR LOWER
ELEVATION AREAS ACROSS THE CWA. LOW PRESSURE SYSTEMS OVER THE
PACIFIC COULD START FLATTENING THE RIDGE ON FRIDAY, BRINGING SOME
SLIGHTLY COOLER TEMPERATURES TO THE AREA. -TAD
AVIATION...01/18Z TAFS
IFR/MVFR CEILINGS PERSIST ALONG THE OREGON
COAST AND UMPQUA VALLEY THIS MORNING WITH VFR ELSEWHERE. THE LOWER
CEILINGS SHOULD TEND TO LIFT/BREAK UP LATER THIS MORNING/THIS
AFTERNOON, BUT MAY BE MORE PERSISTENT ALONG THE COAST. EXPECT MARINE
STRATUS TO RETURN AGAIN LATE TONIGHT, BRINGING ANOTHER ROUND OF
IFR/MVFR CEILINGS.
MEANWHILE, WE EXPECT CONVECTIVE ACTIVITY TO BEGIN THIS AFTERNOON
WITH SOME CUMULUS BUILDUPS DURING THE MID-LATE AFTERNOON. ISOLATED
SHOWERS AND THUNDERSTORMS SHOULD DEVELOP LATE AFTERNOON/EVENING NEAR
AND JUST WEST OF THE CASCADES, INCLUDING AROUND THE ROGUE VALLEY.
THE CHANCE OF THUNDERSTORMS IS ABOUT 20-30% AROUND THE MFR TERMINAL
THIS AFTERNOON, SO GUSTY OUTFLOWS ARE POSSIBLE WITH CLOUD TO GROUND
LIGHTNING. CONFIDENCE IS LOWER FOR THUNDERSTORM ACTIVITY NORTH OF
THE ROGUE-UMPQUA DIVIDE FOR THIS AFTERNOON/EVENING. HOWEVER, MODEL
GUIDANCE SHOWS SOME ELEVATED INSTABILITY UP THAT WAY OVERNIGHT
TONIGHT, AND THERE'S ABOUT A 10-20% CHANCE FOR SOME LIGHTNING
ACTIVITY NEAR THE ROSEBURG TERMINAL BETWEEN 10Z-15Z SATURDAY.
MARINE...UPDATED 1230 PM PDT FRIDAY, MAY 1, 2026.
A THERMAL
TROUGH PATTERN WILL BRING GUSTY NORTH WINDS WITH STEEP TO VERY STEEP
AND HAZARDOUS SEAS THROUGH SATURDAY EVENING. THE STRONGEST WINDS AND
VERY STEEP SEAS ARE EXPECTED SOUTH OF GOLD BEACH TODAY, WITH STEEP
SEAS ELSEWHERE. CONDITIONS IMPROVE SOME SATURDAY AFTERNOON AS WINDS
BEGIN TO WEAKEN, WITH ONLY STEEP SEAS EXPECTED FOR ALL AREAS FROM
COOS BAY SOUTHWARD. WINDS DIMINISH MORESO LATE SATURDAY NIGHT WHILE
A LONGER PERIOD NORTHWEST SWELL BUILDS, THEN BECOMES DOMINANT LATER
SUNDAY INTO MONDAY ALONG WITH A FRESH NORTH SWELL.
BEACH HAZARDS...UPDATED 115 PM PDT FRIDAY MAY 1, 2026
A SHORT
PERIOD NORTHWEST SWELL AND A BUILDING LONG PERIOD NORTHWEST SWELL
MAY COMBINE THEIR ENERGY TO PRODUCE UNPREDICTABLE WAVES WASHING UP
ON AREA BEACHES THIS WEEKEND. THE RISK WILL BE HIGHEST AROUND
SUNRISE ON SUNDAY MORNING.
SNEAKER WAVES CAN RUN UP SIGNIFICANTLY FARTHER ON BEACHES THAN
NORMAL, INCLUDING OVER ROCKS AND JETTIES. THESE WAVES CAN SUDDENLY
KNOCK PEOPLE OFF OF THEIR FEET AND SWEEP THEM INTO THE OCEAN. THE
WAVES CAN ALSO MOVE LOGS OR OTHER OBJECTS WHICH COULD CRUSH OR TRAP
ANYONE CAUGHT UNDERNEATH. NEVER TURN AWAY FROM THE OCEAN!
MFR WATCHES/WARNINGS/ADVISORIES
OR...BEACH HAZARDS STATEMENT FROM SATURDAY EVENING THROUGH SUNDAY
MORNING FOR ORZ021-022.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 PM PDT
SATURDAY FOR PZZ350-356-370-376.
HAZARDOUS SEAS WARNING UNTIL 11 AM PDT SATURDAY FOR PZZ376.
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