textproduct: Medford

DISCUSSION

The main players in our weather pattern this week will be low pressure over the eastern Pacific (including tropical remnants), ridging centered near the Rockies, and a plume of monsoonal moisture wedged in between. This plume of moisture aloft will continue to bring mid and high level clouds into the area today, generating a few showers, but instability is weak and convection allowing models are suggesting little or no lightning activity. Most precip will evaporate before reaching the ground, but could bring a few hundredths here or there (especially higher terrain). Showers tend to diminish this afternoon and since the mid and high level clouds linger through at least early this afternoon, we don't think we'll get enough instability for much thunderstorm activity (if any). Models keep probabilities today at generally 10% or less.

On Tuesday, a general lack of instability and forcing will keep the convective forecast at a minimum. Even so, we should see at least a thinning of the high cloud cover, so some instability could generate isolated activity, mainly near or just north of Crater Lake in the Cascades and southeastward down to around the Warners during the afternoon/evening. Storm coverage will be isolated at best.

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). Farther south and west, coverage should be more isolated or non-existent (coast). Storms do look to trend wetter over time with highest precipitable water values at around 200% of normal. Some could cause significant rainfall. And while a widespread severe weather outbreak is not likely, a stronger cell or two could produce strong, gusty winds.

The region of greatest instability looks to shift northeastward on Thursday, possibly lingering into northern and/or eastern portions of the east side. For Friday into next weekend, a shift to an onshore flow pattern is likely with a more stable, dry air mass. -Spilde

AVIATION...20/12Z TAFs

VFR conditions will prevail for most areas with mid-high level clouds streaming over the region. Wildfire smoke will maintain general hazy conditions and could bring periods of MVFR visibilities and/or ceilings to the valleys south of the Rogue-Umpqua Divide, the Shasta Valley and the Klamath Basin as well as the northern portions of Lake County. The marine layer will maintain LIFR conditions along the coast this morning, with improvement to VFR expected again by late this morning/afternoon.

Increasing moisture streaming into the region will bring some elevated shower activity primarily east of the Cascades and across northern California this morning. Isolated showers are possible west of the Cascades as well, but overall there should be minimal impact for aviation concerns. Instability is minimal, but there is a 5-10% chance of a thunderstorm. -Spilde

MARINE...Updated 200 AM PDT Monday, July 20, 2026

While seas will remain steep through early this evening, north winds will gradually subside today and conditions will improve for all areas later tonight. Mixed seas then persist Tuesday through mid week with fresh short period northwest swell and also a low longer period south swell due to the remnants of Tropical Storm Elida. Northwest swell dominated seas may increase slightly late in the week. -Spilde

FIRE WEATHER...Updated 245 AM PDT Monday, July 20, 2026

A broad moist plume is moving through the area from south to north this morning. With relatively warm air aloft and the high elevation of the moisture, this is limiting the extent of instability. It is resulting in a relatively thick layer of mid and high level cloudiness and there are plenty of radar returns this morning, but as of this writing, there has been no lightning. Some of the radar returns are reaching the ground as light rain showers/sprinkles (especially at higher elevations), but measurable rainfall has been hard to come by. We did see Summit RAWS east of Lakeview measure 0.02" earlier, but mostly just trace amounts indicated at Mount Shasta, Alturas, Klamath Falls and Lakeview. This will remain the case this morning with most precip falling as virga, though some higher terrain areas seeing the best chance of light measurable rain amounts (generally less than 0.05"). The probability of lightning is not zero, but odds stand at around 5-10%.

By this afternoon and evening, instability remains weak and don't think much will be able to get going just due to the canopy of mid level clouds that will persist at least into early afternoon. Isolated showers could still occur near the Cascades/Siskiyous.

On Tuesday, there is still an overall lack of instability and forcing, so the chances for showers and thunderstorms remain low. The best chance will be late in the day/evening near the Cascades north of Crater Lake and southeastward along Winter Rim over to the Warner Mtns. This activity looks isolated at best and don't think any headlines are necessary.

By 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 Tropical Storm Elida push northward offshore. We think the greatest activity in terms of coverage will occur from the Umpqua NF east of Roseburg (eastern FWZ617) and the Cascades (northern FWZ623), and then also east of the Cascades in the typical arc (FWZs 624/625) extending southeastward to the Warners (FWZ285) again. Lightning potential appears to be more abundant then, so there's some potential for a fire weather watch. Confidence isn't high enough just yet, but we'll be monitoring. There is also less of a model consensus on whether activity will also extend farther southwest to the remainder of our Cascades/Siskiyous and possibly the Interstate-5 corridor. Activity there, if it were to occur, would be more isolated. We should mention that since we're expecting this air mass to be modified tropical, these storms should become wetter over time.

Late in the 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. But, a plausible, slower solution would keep instability and some slight thunderstorm risk over the east side on Thursday. The bigger impact late in the week into next weekend would be the risk of enhanced westerly winds occurring during the afternoons and evenings east of the Cascades. -Spilde

MFR WATCHES/WARNINGS/ADVISORIES

OR...CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT this evening for PZZ356-376.

Small Craft Advisory until 5 PM PDT this afternoon for PZZ350- 370.