308
FXUS66 KMFR 082158
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
258 PM PDT MON SEP 8 2025
SYNOPSIS
SHOWERS AND THUNDERSTORMS WILL BRING WETTING RAIN TO THE REGION
FROM MONDAY AFTERNOON THROUGH WEDNESDAY. TEMPERATURES WILL BE
ABOUT 10 DEGREES COOLER THAN NORMAL DURING THIS TIME. CONDITIONS
BEGIN TO DRY OUT TOWARDS THE END OF THE WEEK BEFORE ANOTHER SYSTEM
POTENTIAL HITS THE REGION ON SUNDAY.
DISCUSSION
SHOWERS HAVE STARTED TO POP UP ON RADAR THIS AFTERNOON AHEAD OF A
VERY DYNAMIC LOW. WE'VE ALREADY OBSERVED LIGHTNING FROM THE
GEOSTATIONARY LIGHTNING MAPPER ON GOES 18 EARLIER THIS MORNING IN
THE OUTER WATERS, SO MID LEVEL MOISTURE AND LAPSE RATES ALOFT ARE
ALREADY ENOUGH FOR FOR LIGHTNING. THUNDERSTORM PROBABILITIES WILL
CONTINUE TO INCREASE INTO THE AFTERNOON HOURS ARE ARE CURRENTLY
SITTING AT ABOUT 20 TO 30%. THOSE 4 HOUR LIGHTNING PROBABILITIES
PEAK UP TO 80 OR 90 PERCENT LATER THIS AFTERNOON AND EARLY EVENING
OVER THE CENTRAL CASCADES. THE GOOD NEWS IS THESE STORMS SHOULD
BE ON THE WET SIDE. PRECIPITABLE WATER(PWAT) IS AROUND 1 TO 1.25
INCHES BASED ON POLAR ORBITING SATELLITE DATA, SO STORMS SHOULD
LEAN WETTER. RIGHT NOW, WE'RE FORECASTING A WIDE SWATH OF 0.25 TO
0.5 INCHES OF RAIN WEST OF THE CASCADES THROUGH TODAY.
BY TONIGHT, THE LOW WILL BE SITTING JUST OFF THE OREGON COASTLINE
WITH THE BEST DIVERGENCE ALOFT FARTHER TO THE NORTH AND EAST IN
WASHINGTON. THERE IS SOME CHANCE FOR NOCTURNAL THUNDERSTORMS
ACROSS THE AREA AS LOW HAS SOME NEGATIVE TILT AT 500MB. WE DON'T
HAVE IT IN THE FORECAST AT THIS TIME, ALTHOUGH THE CHANCES ARE
DEFINITELY NOT ZERO. SHOWERS WILL PERSIST OVERNIGHT AS THE LOW
REMAINS OVER HEAD.
BY TUESDAY, WE SHOULD SEE MORE POP UP SLOW MOVING SHOWERS AND
THUNDERSTORMS THROUGH THE DAY. IT WILL FEEL A LOT LIKE EARLY FALL
AS THE SUN BREAKS THROUGH THE CLOUDS AND WARMS US UP INTO THE MID
TO UPPER 70'S WEST OF THE CASCADES AND EVEN UPPER 60'S ALONG THE
COAST. OVERALL, NO MAJOR WEATHER IMPACTS ANTICIPATED AS THE RAIN
SHOULD DAMPEN FIRE ACTIVITY AND SMOKE PRODUCTION.
MORE OF THE SAME ON WEDNESDAY BEFORE THE UPPER LEVEL LOW BEGINS TO
SHIFT EASTWARDS ON THURSDAY. WE'LL SEE PRECIPITATION CHANCES ON
THE DOWNTREND AROUND THAT TIME AS TEMPERATURES GRADUALLY BEGIN TO
WARM UP ON FRIDAY AND SATURDAY.
THE LAST NOTEWORTHY TOPIC IS THE START OF NEXT WEEK ON SUNDAY.
ENSEMBLES SEEM PRETTY EVENLY SPLIT ON IF AN UPPER LEVEL LOW PUSHES
INTO THE FORECAST AREA. ABOUT 50% ARE SHOWING THIS HAPPENING WHILE
THE OTHER 50% ARE KEEPING US DRY. BECAUSE OF THIS, WE HAVE ABOUT A
50 TO 60% CHANCE OF RAIN SUNDAY AFTERNOON AND EVENING.
-SMITH
AVIATION...08/18Z TAFS
VFR CONDITIONS PREVAIL LATE THIS
MORNING ACROSS ALL AREAS, INCLUDING ALONG THE COAST AND OVER THE
MARINE WATERS. HOWEVER, CONDITIONS AT THE COAST LOWER TO MAINLY MVFR
IN THE AFTERNOON AS LOW PRESSURE APPROACHES AND SHOWERS DEVELOP.
MVFR IS EXPECTED TO PERSIST AT THE COAST THROUGH 18Z TUESDAY
MORNING.
MEANTIME, VFR CONDITIONS WILL PREVAIL FOR MOST INLAND AREAS, EVEN AS
SHOWERS INCREASE IN COVERAGE THROUGH THE AFTERNOON. THE EXCEPTION
WILL BE AREAS OF MOUNTAIN OBSCURATIONS FROM THE COAST RANGE TO THE
CASCADES AND INTO NORTHERN KLAMATH COUNTY. MODERATE TO HEAVY RAIN
RATES MAY ACCOMPANY SHOWERS WITH PERIODS OF VISIBILITIES LOWERED TO
MVFR. EMBEDDED THUNDERSTORMS (15-30% CHANCE) ARE EXPECTED FOR INLAND
AREAS, INCLUDING AT ROSEBURG AND MEDFORD, FROM 23Z THROUGH 04Z.
HEAVY RAINFALL AND GUSTY AND ERRATIC WINDS ARE POSSIBLE AROUND
THUNDERSTORMS.
CEILINGS WILL REMAIN MAINLY VFR WHILE THE PROBABILITY OF
THUNDERSTORMS, AND SHOWER COVERAGE DECREASES AFTER 04Z, BUT
SCATTERED SHOWERS AND AREAS OF MOUNTAIN OBSCURATION WILL CONTINUE
OVERNIGHT INTO TUESDAY MORNING. -DW
MARINE...UPDATED 200 PM PDT MONDAY, SEPTEMBER 8, 2025
UPPER
LEVEL LOW PRESSURE WILL MOVE INTO THE REGION TODAY, BRINGING
WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS THROUGH THIS
EVENING. FAR LESS SHOWER ACTIVITY IS EXPECTED ON TUESDAY AS THIS
ACTIVITY MOVES INLAND. SUB-ADVISORY CONDITIONS WILL PERSIST
THROUGH MID-WEEK UNDER LIGHT WINDS AND LOW SEAS. SOUTH TO
SOUTHEAST WINDS TODAY WILL TURN NORTHERLY LATE TONIGHT INTO
TUESDAY, THEN PERSIST THROUGH THE END OF THE WEEK.
NORTHERLY WINDS SHOULD GENERALLY REMAIN BELOW ADVISORY CRITERIA
THROUGH THE WEEK, THOUGH 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
JUST SOME LIMITED FIRE WEATHER CONCERNS TODAY DUE TO THE GUSTY
WINDS AND RHS IN THE UPPER TEENS IN SOUTH CENTRAL LAKE COUNTY
AHEAD OF THIS LOW. ALL THIS INCOMING RAIN HAS ALSO RAISED SOME
CONCERNS OF A DEBRIS FLOW ON A BURN SCAR LATER THIS AFTERNOON OR
EVENING, ESPECIALLY OVER THE EMIGRANT FIRE. SPC HREF WAS SHOWING
1HR RATES OF 0.5 TO 1" AND THE PROBABILITY OF 1" PER HOUR WAS
ABOUT 20 TO PERHAPS 30%. WE OPTED NOT TO GO WITH A FLASH FLOOD
WATCH AS STORMS SHOULD BE FASTER MOVING, ALTHOUGH THE RISK OF A
DEBRIS FLOW IS DEFINITELY NOT ZERO.
-SMITH
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
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