textproduct: Medford

KEY MESSAGES

* Daytime highs today will be 5 to 10 degrees above normal today.

* A passing cutoff low will bring cooler temperatures across the area on Friday and over the weekend.

* Slight thunderstorm chances along the Cascades and into northern Klamath County are in the forecast for Friday afternoon and evening. Fire weather concerns are present in the Shasta Valley and east of the Cascades in the afternoons and evenings as well.

* Seasonal weather is expected next week.

DISCUSSION

With an upper level ridge over the southern United States nudging over the area, another day of above average temperatures is expected for inland areas of northern California and southern Oregon. The Umpqua Valley looks to be in the mid 90s, while other west side valleys are forecast to be in the high 90s to the low 100s. Farther east, area valleys and basins will be in the high 80s to low 90s. With a cutoff low approaching, southerly flow funneling into the Shasta Valley will bring elevated winds this afternoon and evening. A Red Flag Warning has been issued for the Shasta Valley for the combination of these winds and ongoing dry condition creating an environment where fires can quickly spread.

That cutoff low will pass to the west over the Pacific Ocean, but will push ridging to the east and bring lower temperatures across the area on Friday and through the weekend. Widespread precipitation is not expected, but some coastal areas may see light mist under marine stratus. Friday afternoon and evening will also have a slight chance (5-15%) 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. Also on Friday after noon and evening, gusty winds develop into the Shasta Valley and across areas east of the Cascades. A Red Flag Warning is in place for these areas on Saturday afternoon and evening for the combination of gusty winds and low humidities. Winds ease in the Shasta Valley on Saturday, reducing fire weather concerns. East of the Cascades, a Fire Weather Watch is in place to address continuing concerns from elevated winds. Winds ease further on Sunday.

By early next week, the cutoff low will be off to the northeast. With southwest flow between an upper trough to the northwest and ridging persisting to the southeast of the area, next week is looking fairly uneventful. Current imagery shows the trough keeping the ridge at bay, which will bring average 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. -TAD

AVIATION...21/00Z TAFs

Marine stratus will persist through much of the TAF period along the coast and over the marine waters with LIFR/IFR conditions this evening through Friday morning, lifting to MVFR by Friday afternoon.

Inland, VFR conditions will prevail with high clouds overhead. However, there is a low chance (20%) for MVFR to spread into the Umpqua early Friday morning, including at Roseburg. Otherwise, expect some enhanced breezes this evening, with gusty winds expected in the Shasta and Scott Valleys. Winds will ease after sunset, but mid and high level clouds will persist overnight into Friday as an upper level trough approaches the region. Gusty winds will develop Friday afternoon, strongest east of the Cascades and in the Shasta Valley.

MARINE...Updated 230 PM PDT Thursday, August 20, 2026

Below advisory seas continue through Saturday for area waters. A thermal trough pattern will bring gusty northerly winds to all waters on Sunday afternoon. Steep seas are expected south of Cape Blanco by the evening, with localized areas of very steep seas showing up south of Brookings in current guidance. Steep seas may reach as far north as Reedsport. The trough will not last long, with winds and seas easing by Monday afternoon. Below advisory seas are forecast through midweek, with a thermal trough possibly returning towards the end of next week. -TAD

FIRE WEATHER...Updated 200 PM PDT Thursday, August 20, 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.

Hot temperatures will peak today and RHs will trend lower a bit. We'll see an increase in afternoon winds today, but for most areas, winds won't quite be strong enough (widespread gusts of 15-20 mph) to reach critical fire weather thresholds. The exception will be in the Shasta Valley where southerly flow will enhance winds the most in that area. This combined with RHs in the low to mid teens should bring a long enough period of critical conditions today, so we've gone ahead with a Red Flag Warning for Fire Weather Zone (FWZ 281) for this afternoon/evening. Isolated critical conditions are possible for areas east of the Cascades today, but the more widespread critical conditions are expected Friday and Saturday.

Afternoon winds increase Friday (gusts 25-35 mph), but daytime humidities will also trend somewhat higher compared to today. 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. 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 Friday and Saturday, mid-level moisture increases today and Friday, 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. So it's not impossible for isolated activity, 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. With the approach of the trough tonight into Friday, we've been monitoring the potential for any nocturnal convection, but current guidance is lacking the necessary parameters for this. Even still, can't completely rule it out, but would only give it about a 5% chance of occurring and primarily for western Siskiyou County. Drier air in the mid-levels is well established for our region by Saturday, which shifts any thunderstorm threat northward into northern Oregon for 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 to 9 PM PDT Friday for ORZ624.

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

CA...Red Flag Warning until 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.