496
FXUS66 KMFR 111026
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
326 AM PDT THU SEP 11 2025
DISCUSSION
A BROAD UPPER LEVEL LOW EXTENDS FROM NEAR LAKE TAHOE
NE UP INTO SE OREGON EARLY THIS MORNING. THIS LOW, RESPONSIBLE FOR
THE COOL, SHOWERY WEATHER OVER THE PAST COUPLE OF DAYS (AND SOME
THUNDERY DOWNPOURS AT TIMES), WILL CONTINUE TO SWIRL DISTURBANCES
ACROSS THE AREA TODAY. THIS WILL MAINTAIN BELOW NORMAL TEMPS. THE
FLOW AROUND THE LOW HAS SHIFTED AND IS NOW PRIMARILY OUT OF THE
NNE WITH SHOWERS AND STORMS MOVING LARGELY TOWARD THE SSW. WITH
LIMITED INSTABILITY/FORCING, MOST AREAS HAVE BEEN DRY DURING THE
OVERNIGHT, THOUGH THERE HAVE BEEN A FEW ISOLATED SHOWERS. CURRENT
WATER VAPOR SATELLITE IMAGERY IS SHOWING AN UPPER LEVEL
DISTURBANCE GENERATING SHOWERS/LIGHTNING FROM AROUND BURNS TO JUST
NE OF BEND/MADRAS, MOVING OFF TOWARD THE SSW. THIS DISTURBANCE
WILL DRIFT ACROSS EASTERN PORTIONS OF THE FORECAST AREA THIS
MORNING RESULTING IN ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS,
SOME OF WHICH WILL PRODUCE HEAVY RAINFALL. PRIMARY FOCUS FOR
PRECIPITATION WILL BE IN KLAMATH AND LAKE COUNTIES WHERE ACTIVITY
WILL PERSIST THIS AFTERNOON/EVENING. MOST ACTIVITY WILL BE
NEAR/EAST OF THE CASCADES TODAY, BUT ISOLATED SHOWERS COULD REACH
BACK AS FAR WEST AS SOME WEST SIDE VALLEYS. THUNDER PROBABILITIES
ARE ALSO HIGHEST OVER THE EAST SIDE THIS AFTERNOON/EVENING
(30-40%), THOUGH ONE CAN'T BE COMPLETELY RULED OUT (~10-15%
CHANCE) NEAR THE CASCADE FOOTHILLS (WEST SIDE).
THE DISTURBANCE WILL SETTLE INTO NW NEVADA THIS EVENING AS
INSTABILITY WANES, SO SHOWER CHANCES WILL GRADUALLY LOWER AND THE
THUNDER RISK WILL END. MOST SHOWERS WILL BE DONE BY AROUND 11 PM
OR SO. AN UPPER RIDGE WILL BUILD OFF THE WEST COAST ON FRIDAY AND
THIS WILL ALLOW FOR A PERIOD OF WARM, MAINLY DRY WEATHER THAT WILL
LAST THROUGH SATURDAY. THERE IS STILL A VERY SLIGHT CHANCE OF
SHOWERS OVER FAR EASTERN SECTIONS ON FRIDAY AFTERNOON. WE'LL SEE
ABOUT 5-10F OF WARMING (HIGH TEMPS) COMPARED TO TODAY AND ANOTHER
2-6F ON SATURDAY. SATURDAY WILL BE ABOUT AS SEASONABLE AS IT CAN
GET WITH HIGH TEMPS WITHIN A DEGREE OR TWO EITHER SIDE OF NORMAL.
OTHER THAN SOME MARINE LAYER CLOUDS/FOG TO START, IT WILL BE
SUNNY.
MODELS HAVE COME INTO AGREEMENT ON A FAIRLY SHARP, PROGRESSIVE
TROUGH AND SURFACE COLD FRONT THAT WILL ARRIVE AT THE COAST
SATURDAY EVENING, THEN MOVE ONSHORE OVERNIGHT AND THROUGH THE AREA
ON SUNDAY. THERE IS A HIGH LIKELIHOOD (60-80% CHANCE) OF A PERIOD
OF RAIN ALONG THE COAST, INTO THE UMPQUA BASIN AND TO ABOUT THE
ILLINOIS VALLEY WHERE MOST LIKELY AMOUNTS OF 0.25-0.50" ARE
FORECAST. HERE IN THE ROGUE VALLEY, POPS ARE IN THE 40-60% RANGE
AND AMOUNTS ARE LOWER, GENERALLY 0.05-0.15". POPS DROP OFF
(20-40%) EAST OF THE CASCADES AS DOWNSLOPE FLOW LIMITS PRECIP TO
ZERO OR PERHAPS A FEW HUNDREDTHS. POPS STRUGGLE TO REACH 10% IN
MODOC. BEST CHANCE FOR UP TO A TENTH OF AN INCH OF RAIN OVER THE
EAST SIDE WILL BE ALONG THE HIGHWAY 97 CORRIDOR NORTH OF
CHILOQUIN. GUSTY SW WINDS PRECEDE SUNDAY'S FRONT EAST OF THE
CASCADES WITH A WIND SHIFT TO NW IN THE AFTERNOON. IN-HOUSE
GUIDANCE IS SHOWING POTENTIAL WIND GUSTS IN THE 25-35 MPH RANGE.
IT'LL ALSO BE COOLER WITH A DROP OF ABOUT 5F TO AS MUCH AS 15F
COMPARED TO SATURDAY.
SINCE THE TROUGH IS PROGRESSIVE, THE NEXT UPPER RIDGE WILL BUILD
IN QUICKLY EARLY NEXT WEEK. THIS WILL LIKELY RESULT IN A PERIOD OF
OFFSHORE FLOW AND DRIER RHS ALONG WITH ANOTHER WARM-UP FOR THE
MIDWEEK TIME PERIOD. HIGH TEMPS WILL BE IN THE UPPER 70S/LOW 80S
OVER THE EAST SIDE WITH TEMPS IN THE 80S AND LOW 90S FOR WEST SIDE
VALLEYS. AFTER SUNDAY, THERE ISN'T MUCH CHANCE OF PRECIPITATION
ACROSS THE AREA UNTIL PERHAPS THE END OF NEXT WEEK. -SPILDE
AVIATION...11/12Z TAFS
ISOLATED SHOWERS THIS MORNING WILL
BECOME MORE NUMEROUS OVER THE AREA TODAY, ESPECIALLY EAST OF THE
CASCADES WHERE THERE IS A 70-90% CHANCE. THERE IS ALSO A CHANCE
OF THUNDERSTORMS WITH THE HIGHEST PROBABILITY (25-40%) ACROSS
KLAMATH/LAKE COUNTIES. ANY STORMS TODAY WILL HAVE THE ABILITY TO
BRING HEAVY RAINFALL AND CLOUD TO GROUND LIGHTNING. SHOWER
COVERAGE DIMINISHES FARTHER TO THE WEST WITH CHANCES OF 10% OR
LESS FROM AROUND ROSEBURG TO THE COAST.
ALONG THE COAST, EXPECT A MIX OF IFR/LIFR THIS MORNING. LOW
CLOUDS ARE EXPECTED TO LIFT AND CLEAR TO VFR (EXCEPT FOR SOME
LINGERING LOCAL MVFR) LATE THIS MORNING/EARLY THIS AFTERNOON.
THEN, AREAS OF MVFR/IFR WILL RETURN ALONG THE COAST THIS EVENING.
INLAND, EXPECT VFR WITH AREAS OF MVFR THIS MORNING. MVFR IS
LIKELY IN THE UMPQUA VALLEY, INCLUDING AT ROSEBURG, BUT ALSO
EXPECT CHANCES FOR MVFR CEILINGS TO DEVELOP AT MEDFORD AND KLAMATH
FALLS. THESE CONDITIONS ARE EXPECTED TO LIFT TO MAINLY VFR IN THE
LATE MORNING OR EARLY AFTERNOON. SOME TERRAIN OBSCURATION IS ALSO
LIKELY THIS MORNING. LOCAL OBSCURATIONS ARE EXPECTED IN HEAVIER
SHOWERS THIS AFTERNOON/EVENING, ESPECIALLY FROM THE CASCADES
EAST. -SPILDE
MARINE...UPDATED 300 AM PDT THURSDAY, SEPTEMBER 11, 2025
BREEZY NORTHERLY WINDS BE FAVORED SOUTH OF PORT ORFORD AND BETWEEN
5 AND 30 NM FROM SHORE BOTH AFTERNOONS/EVENINGS TODAY AND FRIDAY.
WHILE SUB-ADVISORY CONDITIONS ARE LIKELY TO PERSIST THROUGH THE
END OF THE WEEK AND INTO THE WEEKEND, SEAS DO INCREASE 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
TODAY AND PERSISTING INTO THE WEEKEND. WEST-NORTHWEST SEAS BUILD
FURTHER SUNDAY AND SUNDAY NIGHT. -SPILDE
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
MAS/MAS/MAS
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