641 FXUS66 KMFR 102322 AFDMFRArea Forecast Discussion National Weather Service Medford OR 422 PM PDT Wed Sep 10 2025
.UPDATE...Aviation Discussion Updated.
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.AVIATION...11/00Z TAFs...Showers and isolated to scattered thunderstorms will continue through this evening, with best chances from the Southern Oregon Cascades east and across Northern California with isolated activity west of the Cascades. Showers will persist overnight into Thursday, with a chance for thunderstorms again Thursday afternoon. The main risks with thunderstorms will be heavy downpours and lightning, but gusty winds also cannot be ruled out.
Along the coast, conditions are VFR but expect areas of MVFR to develop around 03z, then a mix of IFR/LIFR overnight into Thursday morning. These conditions will affect areas from Cape Blanco north and Brooking south. Low clouds will lift and clear to VFR late Thursday morning into early Thursday afternoon along the coast.
Inland, expect mainly VFR across this evening, except for the potential of local MVFR with thunderstorms. Then areas of MVFR conditions will develop late this evening and tonight, especially in the Umpqua valley as well as areas near and east of the Cascades. These conditions will continue into Thursday morning, then lift to VFR with local MVFR in the late morning or early afternoon. Areas of mountain obscurations are expected through Thursday morning.
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.PREV DISCUSSION... /Issued 140 PM PDT Wed Sep 10 2025/
DISCUSSION (Today through Tuesday)...
Overview:
System overhead will maintain shower chances today with isolated thunder risk. Showers will generally spread east to west over the Cascades by this afternoon. That said, most of the activity will be across eastside areas, along with the greater chance for lightning. There will be areas of slow moving showers that continue to redevelop over the same area that could lead to isolated areas of heavier rainfall. Shower chances continue tomorrow but will be more focused over eastside areas as the system slowly moves east, and then even farther east by Friday as the system exits. Isolated areas of thunder will exist through this stretch, but today has the highest potential for thunderstorms. Temperatures generally trend higher with a peak by Saturday, but a system on Sunday will briefly bring temperatures back down before another trend upward through next week. In fact, long term data suggest we will be back above normal through mid/late September with dry conditions returning. In other words, fall-like conditions will transition back to more typical summer-like conditions.
Further Details:
A stacked low pressure system remains over the forecast area today, and will continue isolated to scattered shower chances with isolated thunder through this evening. Main threats will be isolated areas of heavy rainfall, and isolated areas of lightning. The low pressure system is very stagnant, and the mean flow is generally very weak, so we are not expecting much in terms of widespread convective processes. This is also due to limited amounts of instability. These conditions will limit the overall threat for lightning, but isolated areas will experience a small threat for thunderstorms today/early tonight with small pockets of potential cloud-to-ground strikes. The slow nature of this system will result in slow moving storms in addition to "training" of storms/showers. The combination of these two factors will lead to some isolated areas picking up heavy rainfall. Fortunately, given the limiting chances for convective process, rainfall rates shouldn`t be too concerning overall and will be more of a long duration rainfall event. Some areas in and around the Crater Lake area and other parts of the southern Cascades could see an inch of rainfall between now and Thursday morning given terrain influences. There may be a brief lull in activity tomorrow morning, but chances essentially continue into tomorrow. 24 hour totals from tomorrow morning through Friday afternoon will be less than the current 24 hour window into Thursday morning. That said, there could be isolated areas on the eastside that see 24 hour amounts around an inch from Thursday morning through Friday morning. These chances are higher in Klamath and Lake counties, especially where local terrain may help influence lift. For example, Yamsay Mountain and other topography influences in the Fremont National Forecast may help with the training and redevelopment of showers/storms given the flow around the low.
By Friday our chances will only cover a small area of far eastside locations as the system begins to exit the region. Saturday will be the overall warmest day in the current forecast. However, other system on Sunday will bring us back below normal with rainfall chances increasing west to east early Sunday morning. Thunderstorm chances on Sunday are very low, but showers chances will spread across the entire area through Monday morning.
Thereafter, we will see temperatures trending back towards normal with above normal conditions anticipated middle of next week. In fact, middle to later parts of September are trending above normal for temperatures with the return of dry/below normal precipitation chances. This will feel much more like late summer than the recent stretch of fall-like conditions.
MARINE...Updated 100 PM PDT Wednesday, September 10, 2025... Breezy northerly winds be favored south of Port Orford and between 5 and 30 nm from shore through this evening and again Thursday afternoon/evening. 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 Thursday and persisting into the weekend.
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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