633
FXUS66 KMFR 090523
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
1023 PM PDT MON SEP 8 2025
DISCUSSION
UPDATED AVIATION DISCUSSION.
AVIATION...09/06Z TAFS
A MOIST SHOWERY AIR MASS WILL REMAIN IN
PLACE THROUGH TUESDAY, BRINGING WIDESPREAD SHOWERS AND SOME EMBEDDED
THUNDERSTORMS. ALONG THE COAST, MVFR AND IFR WITH AREAS OF LIFR ARE
EXPECTED TO DEVELOP OVERNIGHT. THESE CONDITIONS ARE FORECAST TO
IMPROVE TUESDAY AFTERNOON TO MVFR AND AREAS OF VFR. INLAND,
CONDITIONS WILL BE MAINLY VFR WITH AREAS OF MOUNTAIN OBSCURATIONS.
ADDITIONALLY, AREAS OF MVFR ARE EXPECTED TO SPREAD INTO THE UMPQUA
BY EARLY TUESDAY MORNING, LIFTING TO VFR IN THE LATE MORNING.
ISOLATED THUNDERSTORMS ARE POSSIBLE WITH SHOWERS (5-15% CHANCE)
OVERNIGHT INTO TUESDAY MORNING, THEN THUNDERSTORM CHANCES
(20-35%) INCREASE TUESDAY AFTERNOON, WITH BEST CHANCES FROM THE
CASCADES WEST. HEAVY DOWNPOURS, LIGHTING AND GUSTY WINDS ARE
POSSIBLE WITH THESE STORMS.
PREV DISCUSSION
/ISSUED 931 PM PDT MON SEP 8 2025/
MARINE...UPDATED 800 PM PDT MONDAY, SEPTEMBER 8, 2025...UPPER LEVEL
LOW PRESSURE WILL REMAIN OVER THE WATERS TONIGHT, BRINGING
WIDESPREAD SHOWERS. FAR LESS SHOWER ACTIVITY IS EXPECTED ON TUESDAY
AS THE LOW MOVES INLAND. SUB-ADVISORY CONDITIONS WILL PERSIST
THROUGH MID-WEEK UNDER LIGHT WINDS AND LOW SEAS. SOUTH TO SOUTHEAST
WINDS 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 THEY WILL TREND STRONGER IN THE FAVORED
LOCATION SOUTH OF PORT ORFORD AND BETWEEN 5 AND 30 NM FROM SHORE
DURING THE AFTERNOONS ON 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.
PREV DISCUSSION... /ISSUED 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
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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