Area Forecast Discussion

KEY MESSAGES

* Today and Wednesday will be the hottest of the next several days with highs generally 5 to 10 degrees above normal (mid 80s to mid 90s on the east side and lower 90s to 103 for west side valleys). Near or slightly below normal temperatures at the coast will reach the 60s.

* Isolated light showers and thunderstorms are expected this afternoon/evening. Highest risk is in the Cascades north of Crater Lake, but can occur anywhere from the mountains of western Siskiyou County up the Cascades, over to Winter Rim and the Warner mountains. Rainfall amounts will be light.

* The highest risk of thunderstorms for the area will be on Wednesday (scattered coverage Cascades/Foothills eastward), including lesser chances for areas west of the Cascades. Some storms will be strong with gusty winds and possible hail. Best chance for this is up the Cascades into the Douglas County foothills and over to NW Klamath County.

* A drier pattern takes hold late week into the weekend, but probably with an increase in afternoon/evening breezes, especially east of the Cascades.

DISCUSSION

The forecast area remains wedged in between a strong ridge over the nation's mid section/Rockies and low pressure off the California coast (including tropical remnants). Monsoonal moisture continues to stream northward into the area and is generating a few light showers from Modoc into Lake County this morning. This flow pattern hasn't allowed things to cool off as readily at night, as evidenced by the daily record highest minimum set here at Medford yesterday morning (71F). The record was 68F set in 2023. As a result of the moist south flow, we are seeing plenty of mid to high level clouds, along with some scattered light high-based showers across the area, and especially over Modoc and Lake counties, where some light accumulations have been recorded (generally a few hundredths to a tenth of an inch). With somewhat thinner high cloud cover than yesterday, some instability could generate isolated thunderstorms, mainly near or just north of Crater Lake in the Cascades and southeastward down to around the Warners during the afternoon/evening.

As the tropical remnants move northward over the coastal waters, some models are indicating a low possibility of showers or even thunderstorms tonight into Wednesday morning, focusing on areas along the coast and into the Umpqua Basin where some upper level support will increase ahead of the approaching remnants. Confidence is low, given the difficulty models have with this type of event, but it is worth mentioning as a possibility.

Wednesday, stronger southerly flow aloft is expected between the trough offshore tracking northward (including the remnants of Tropical Storm Elida) and the persistent ridge over the Great Basin/Rockies. There is still a modest amount of uncertainty in the convective forecast (especially with areal extent), but there is a decent chance of scattered thunderstorm coverage over a broad portion of our area, to include areas from the Cascades eastward and also portions of the west side (most likely Douglas County east of Roseburg, but also along the western foothills of the Cascades east of the Rogue Valley). Farther south and west, where dry air is expected to intrude the lower levels, coverage should be more isolated or non-existent (coast and northern CA). Storms do look to trend wetter over time with highest precipitable water values at around 200% of normal (perhaps near or above 1.50 inches). While a widespread severe weather outbreak is not likely, a stronger cell or two could produce strong, gusty winds and hail. This appears most likely over the Cascades near/north of Crater Lake, the eastern Douglas Foothills and also NW Klamath County. Generally, any storms that develop Wednesday will move to the north to northeast, contain frequent lightning, small hail, and gusty winds, and could produce periods of heavy rainfall.

The region of greatest instability looks to shift northeastward out of the area Thursday with a shift to an onshore flow pattern Friday into this weekend. The result will be a more stable, dry air mass, but along with enhanced afternoon and evening winds. This will be the case here in the Rogue Valley, but also especially for areas east of the Cascade. -Spilde/BPN

AVIATION...22/00Z TAFs

VFR levels are present across northern California and southern Oregon under mid- and high-level clouds. Some areas of higher reflectivity over northern CA and east side areas indicate possible showers, but amounts should be unimpactful. Slight chances for evening thunderstorms remain in these areas, and any thunderstorm activity would likely be embedded in these rain showers. Thunderstorm chances dissipate into the evening.

Marine stratus looks to build the Oregon coast this evening, bringing IFR/LIFR levels overnight and into late Wednesday morning. These levels could lift to MVFR on Wednesday afternoon.

Thunderstorms are expected for Wednesday afternoon, especially over eastern Douglas County as well as northern Lake and Klamath counties. aActivity may also develop in Jackson, southern Lake and Klamath, and western Siskiyou counties. These storms may be strong enough to develop small hail, lightning, locally heavy rain, and gusty, erraic winds. While he most aggressive activity is currently expected to mostly stay away from area terminals, notes of vicinity activity have been included to communicate the possible initial development of thunderstorm activity. -TAD

MARINE...Updated 200 PM PDT Tuesday, July 21, 2026

Winds and seas are expected to remain below advisory levels through at least this week. North winds today switch to southerly Wednesday as the remnants of Elida move northward offshore. Isolated showers and even a couple of thunderstorms are possible. Mixed seas with fresh short period northwest swell and low longer period south swell are expected through Friday. South winds switch back to northerly this weekend, and a slight increase in southerly swell may bring some borderline steep seas in outer waters. Wind wave dominated seas probably hold off until early next week. -Spilde/TAD

FIRE WEATHER...Updated 200 PM PDT Tuesday, July 21, 2026

A large upper ridge remains centered over the Great Basin/Rockies and into the southern Plains, while low pressure is off the California coast. Southerly flow aloft continues to bring a broad moist plume northward across much of the West and this is resulting a swaths of mid-high level clouds across NW Nevada, northern California and into south-central/SW Oregon. As a result, we are seeing extensive areas of mid to high level clouds, along with some scattered light high- based showers across the area, and especially over Modoc and Lake counties, where some light accumulations have been recorded (generally a few hundredths to a tenth of an inch). The cloud cover isn't quite as thick (or persistent) as it was yesterday and this should allow temps today to be near or several degrees higher than yesterday. As such, the atmosphere should destabilize a bit better today. This afternoon and evening, cumulus buildups are expected with a slight chance of thunderstorms in western and central Siskiyou County, also north and northeastward along the Cascades and across much of south central Oregon and also Modoc County in NE Cal. Coverage of lightning doesn't appear to be very high (mainly isolated), so despite the lightning risk, we aren't planning any red flag warnings for today.

Some models are indicating a low possibility of nocturnal convection tonight into Wednesday morning, focusing on areas along the coast and into the Umpqua Basin. Models typically have a hard time nailing down overnight showers and storms in this type of environment, so confidence is low, but worth mentioning.

On Wednesday, there is a greater concern for increased afternoon and evening thunderstorm coverage. This is due to better instability expected in advance of moisture arriving in southerly flow aloft at peak heating along with the potential for better forcing as the remnants of Elida push northward just offshore. We think the greatest activity in terms of coverage will occur along the western slopes of the Cascades (eastern FWZs 622/617) east across the Cascades (FWZ623), and then also east of the Cascades in the typical arc from Crater Lake, across Winter Rim, and down to the Warners (FWZs 624/625). Isolated storms are also possible elsewhere across the area, including in northern California and across the valleys west of the Cascades, though a surge of drier air aloft does appear to be pushing into NorCal later in the afternoon/evening (this should keep best activity confined to areas north of the OR/CA border). Storms that do develop should be moving at a pretty good clip - in the 20-30 mph range, so while they are likely to be wetter storms with higher PWs, the faster storm motions should still raise the risk of lightning-induced fire ignitions. We have upgraded these areas of higher concern to a Red Flag Warning. Again, isolated thunderstorms remain possible for just about all areas outside of the Warning.

Of note, with PW approaching or exceeding 1.50 inches, or roughly 200 percent of normal, these storms should not only be wet, but could produce heavy rain as well. Should a storm pass directly over a recent burn, such as the East Evans Creek fire, mud and debris flows are possible down any adjacent drainages.

Later this week (Thursday/Friday), eastward movement in the upper level pattern is likely, which is likely to shift the region of instability east of our area with drier SW flow aloft winning out. As such, lightning risk will diminish to almost nil, but at the expense of enhanced westerly winds during the afternoons and evenings east of the Cascades, which could overlap with low humidity. Any new fire starts would then have the ability to spread/grow quickly. We'll continue to monitor this potential and consider potential wind/low RH headlines, especially and notably for Friday and Saturday afternoons/evenings in FWZs 624, 625, 284, and 285.

The dry, diurnally breezy pattern looks to last this weekend and into early next week. But, temperatures should also lower some compared to earlier this week. -Spilde/BPN

MFR WATCHES / WARNINGS / ADVISORIES

OR...Red Flag Warning from 11 AM to 11 PM PDT Wednesday for ORZ617- 622>625.

CA...None.

PACIFIC COASTAL WATERS...None.