textproduct: Medford

KEY MESSAGES

* Daytime highs today will be about 10 degrees cooler than yesterday, then stay around normal for this time of year through the weekend.

* Slight thunderstorm chances along the Cascades and into northern Klamath County this afternoon and evening.

* Heightened fire weather concerns today and Saturday due to low humidity and gusty afternoon/evening winds in the Shasta Valley and east of the Cascades.

* Seasonal weather is expected next week.

DISCUSSION

A deep, closed low sits just offshore of southern Oregon and northern California this morning. With the Four- Corners ridge extending north over the Intermountain West, swift southerly upper-level flow has developed over the forecast area. This has produced some downsloping flow in the Rogue Valley early this morning, keeping temperatures warmer and humidity lower well into the overnight period (temperatures didn't drop to below 80 degrees until after midnight, and humidity has remained below 20% through the time of this writing).

The low will push northeast beginning today, passing onshore north of the mouth of the Columbia River by late Saturday. This will result in cooler temperatures today through the rest of the weekend, with daytime highs lowering to around normal for this time of year, or around 10 degrees lower than yesterday. In what basically amounts to the passage of a cold front, albeit a dry one, winds are expected to increase today and Saturday while humidity remains low for inland areas. This will result in heightened fire weather concerns this afternoon and evening in the Shasta Valley and for areas east of the Cascades. Saturday, as the upper level flow shifts more southwest, the alignment with the Shasta Valley ceases, so conditions will improve there. The Eats Side, however, will remain windy and dry Saturday. A Red Flag Warning is in place for these areas, with details available in the fire discussion below, and at PDXRFWMFR.

The frontal passage will be a dry one, for the most part, but some drizzle or very light rain is possible along the coast and in the coastal ranges as the front interacts with the marine layer. There is also a very slight chance (5-10%) for thunderstorms along and east of the Cascades. Increased moisture aloft is supporting these chances. However, weak instability and expected cloud cover reducing surface heating are keeping those chances low., and the most likely scenario will be some very isolated light showers or virga.

By early next week, the cutoff low will be off to the northeast. With southwest flow between another developing upper trough to the northwest and ridging persisting to the southeast of the area, next week is looking fairly uneventful, with continuing seasonal temperatures. Minor disturbances in the upper flow may bring breezy afternoons, but the timing remains unclear. Long term meteograms show little hope for precipitation through the rest of August.

AVIATION...21/12Z TAFs

Marine stratus will persist through much of the TAF period along the coast and over the marine waters with LIFR/IFR conditions this morning, lifting to MVFR by afternoon, then lowering again to LIFR/IFR this evening and tonight. Drizzle is possible along and west of the coastal ranges.

Inland, VFR conditions will prevail with high clouds overhead. There is a low chance (20%) for MVFR to spread into the Umpqua early this morning, including at Roseburg. Otherwise, high level clouds will persist overnight and Friday as an upper level trough approaches the region. Gusty winds will develop Friday afternoon and evening, strongest east of the Cascades and in the Shasta Valley.

MARINE...Updated 100 AM PDT Friday, August 21, 2026

Light winds and low seas will persist through the weekend. Some southerly winds will increase today, then shift to westerly Saturday as a weak front moves through the waters and passes onshore. A thermal trough will develop by Sunday evening with stronger northerly winds developing offshore. These winds will likely be hazardous to smaller crafts Sunday night into Monday morning

-Smith

FIRE WEATHER...Updated 100 AM PDT Friday, August 21, 2026

The upper level pattern is transitioning today as a trough offshore moves closer to the PacNW. This will start a period of increased winds that will persist through Saturday as this low pressure gradually moves inland into the PacNW through the weekend.

Afternoon winds increase today as the trough and associated dry cold front approach the region (gusts 25-35 mph), but daytime humidities will also trend somewhat higher compared to yesterday. Despite the uptick in humidities, it's close enough with the higher confidence on more widespread higher winds on Friday to warrant upgrading the Fire Weather Watch to a Red Flag Warning for FWZs 281, 284, 285 and 624. Decided to keep FWZ 625 out for Friday as confidence is not high enough for sustained winds to reach criteria on Friday. By Saturday, however, 700 mb winds peak in strength east of the Cascades and more widespread sustained winds of 15 to 20 mph are expected as the front passes. Additionally, daytime RHs will trend lower again, so another day of critical fire weather conditions is possible on Saturday. A Fire Weather Watch is also in effect for FWZs 284/285/624/625 for gusty winds and low RH.

In addition to wind/RH concerns for today and Saturday, mid-level moisture increases today, raising the concern for thunderstorm potential. Overall, the thunderstorm threat looks minimal for our area. Widespread cloud cover on Friday will likely inhibit daytime instability, and by the time any decent forcing arrives to tap into what little elevated instability there is, the mid-levels are beginning to dry out, likely resulting in nothing more than isolated very light showers, or more likely, just some virga. It's not impossible for isolated lightning, but it's only a low chance (10-15%) at this time, primarily along the Cascades from Crater Lake northward and across northern Klamath/Lake Counties. The convective threat pushes northeast of the area Saturday.

More typical summer conditions return Sunday and persist into early next week. There are some signals for thunderstorm chances across eastern 285/625 on Monday, but much will depend on how far west the Four Corners High retrogrades behind this trough passage. Otherwise, another trough drops southward from the Gulf of Alaska and lingers off the BC coast through early next week. There will likely be additional shortwaves/troughs to swing through the region early next week, bringing periods of enhanced winds. Stay tuned for updates. /BR-y

MFR WATCHES/WARNINGS/ADVISORIES

OR...Red Flag Warning from 2 PM this afternoon to 9 PM PDT this evening for ORZ624.

Fire Weather Watch from Saturday afternoon through Saturday evening for ORZ624-625.

CA...Red Flag Warning from 2 PM this afternoon to 9 PM PDT this evening for CAZ281-284-285.

Fire Weather Watch from Saturday afternoon through Saturday evening for CAZ284-285.

PACIFIC COASTAL WATERS...None.