071 FXUS66 KMFR 080241 AFDMFRArea Forecast Discussion National Weather Service Medford OR 741 PM PDT Sun Sep 7 2025
...Updated the Aviation and Marine Sections...
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.AVIATION...08/00Z TAFs...Conditions are mostly VFR early this evening, with patchy MVFR fog along the coast and isolated light showers over the Cascades and northern portions of Klamath and Lake counties. Patches of IFR marine stratus will likely increase late tonight into early Monday morning, ahead of a low pressure system.
Showers will develop around 15Z, increasing in coverage and strength for Monday afternoon and evening. Isolated thunderstorms may be embedded with the showers, especially over the Cascades. Lightning strikes, locally heavy rainfall, and gusty and erratic winds are possible around thunderstorms. Shower and thunderstorm activity decreases later Monday night, though the arrival of another disturbance will shift the focus of showers to the coast and Coast Range mountains. -DW
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MARINE...Updated 740 PM PDT Sunday, September 8, 2025...Sub-advisory conditions will likely persist through the week. Low pressure will maintain light south winds, low seas and marine fog. Additionally, drizzle may start late tonight before more widespread rainfall starts Monday morning. Widespread showers are expected Monday into Monday night with isolated thunder as an area of low pressure moves inland. Far less shower activity is expected on Tuesday as this activity moves inland. Winds turn northerly Tuesday through Thursday.
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.PREV DISCUSSION... /Issued 154 PM PDT Sun Sep 7 2025/
DISCUSSION...
Overview:
Still expecting thunderstorms today, but less coverage than yesterday with focus around Crater Lake, Eastern Douglas, and northern portions of both Klamath and Lake counties. Then a much cooler air mass will settle in starting tomorrow which will feel much more like October. Monday has the potential for wetting rains across mainly westside areas with widespread showers anticipated. Isolated thunder cannot be ruled out next week, but we are not expecting widespread severe weather. Rain chances continue through Friday, with each subsequent day after Monday posing less chances for both rain and rainfall amounts. An Air Quality Alert remains in effect for eastern portions of Douglas County until this evening due to smoke/haze from nearby wildfires.
Further Details:
A broad area of cyclonic rotation is noted over the Pacific. This H5 low is progged to kick out small areas of PVA over the forecast area today through peak heating. This will result in convection this afternoon and early evening. Today will be far more isolated than yesterday and mainly across areas near Crater Lake like eastern Douglas County, and northern parts of both Klamath and Lake counties. A storm or two could be strong with lightning and gusty winds as the main threats. Not expecting much--if any--activity past 8pm.
For Monday, the aforementioned low pressure system will start to move inland, bringing widespread rainfall chances to the forecast area. This cool weather pattern will likely resemble stratiform rain with isolated embedded thunder versus more convective type of storm mode. Forecast soundings show very tropical like profiles with very weak lapse rates which is resulting in very "skinny" CAPE through the profile. This means skies will be mostly cloudy and more like stratus versus cumulonimbus. To further illustrate this, LCL heights are going to be atypical/very low given the tropical soundings. Updrafts will struggle in this environment, but given the dynamics we cannot rule out some thunder. Perhaps an isolated updraft could poke out through the cloud layers but this will not be common tomorrow as the wind field is nearly uniform and lacking overall shear. In fact, satellite already shows this cloud shield over the Pacific, and this area will move onshore tomorrow bring our widespread rainfall. Every single member from both the GFS and European ensemble suite is showing rainfall for Medford/Rogue Valley. In fact, this is the case for many westside areas where 24hr rainfall amounts (Monday morning through Tuesday morning) could be around 0.25-0.75 for most areas, but some areas could be closer to 1.00". This type of rainfall is more typical for October, but should be a welcoming experience, especially those areas dealing with wildfire suppression. Areas like the Emigrant Fire could see these higher rainfall amounts.
After Monday, rainfall chances continue but generally decrease each subsequent day as the low pressure system meanders over the forecast area. Temperatures will remain very mild for this time of year, and its not until Thursday until we start seeing more widespread highs back in the 80s. Through this stretch, isolated areas of thunder are expected with showers that develop. Not seeing any days that could experience widespread severe weather, but a couple storms could be strong with lightning and gusty outflows as the main threats.
-Guerrero
FIRE WEATHER...Updated 200 PM PDT Sunday, September 7, 2025... Thunderstorm chances return again today. The highest chances are over eastern Douglas and northern Klamath counties, with chances decreasing into northern Lake County. Rain showers are expected as parts of any activity. While periods of scattered coverage may be possible over those northernmost areas, limited timing and areal coverage do not support any warning products. Activity decreases into the evening hours.
On Monday, a pattern change will bring cool temperatures and widespread rain showers. Embedded thunderstorms are possible through the day Monday. Cool temperatures and shower chances continue into midweek, with shower chances decreasing day by day. Seasonal conditions are forecast to end the week, with another round of showers possible for next weekend.
-TAD
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.MFR WATCHES/WARNINGS/ADVISORIES... OR...None.
CA...None.
PACIFIC COASTAL WATERS...None.
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NWS MFR Office Area Forecast Discussion