textproduct: Medford

KEY MESSAGES

* Temperatures peak about 5 to 10 degrees above normal on Monday before returning to seasonal levels near midweek.

* There will be a slight chance (20 percent) of thunderstorms across southeastern Lake County and Modoc County Monday afternoon. * A passing shortwave will bring elevated fire weather conditions (gusty winds and low humidities) to areas west of the Cascades on Monday. A red flag warning is in effect for the southern Oregon Cascades and westward into Jackson County, the Siskiyou Mountains and western/central Siskiyou County.

DISCUSSION

The upper trough that has been guiding conditions over the weekend has moved on to the northeast, leaving southwest flow aloft under the western side of a continental ridge. This pattern will bring some warming to most areas today, with easternmost Lake and Modoc County seeing similar temperatures as on Saturday.

Monday will be the warmest day of the forecast period for most areas. Temperatures west of the Cascades may reach up to 10 degrees above normal, while to the east highs look to be about 5 degrees above normal. A passing shortwave will bring elevated winds into the Shasta Valley, the Klamath Basin, Christmas Valley, and parts of the Rogue Valley. For western Siskiyou County, Jackson County, and western Cascades foothills, these winds align with ongoing dry conditions to possibly reach critical fire weather conditions. A Red Flag Warning has been issued for Monday afternoon and evening to highlight these concerns. This shortwave is also support slight (15- 20%) thunderstorm chances over eastern Modoc and Lake counties, given its interactions with monsoonal moisture moving over those areas. While the chances for thunderstorms are not high enough to meet Red Flag criteria, any thunderstorms that do develop can still be locally hazardous by bringing lightning strikes or erratic and gusty winds.

On Tuesday, an approaching trough around a low pressure system over the Pacific will shift flow to be more southerly. With dry air aloft precipitation is not expected. Temperatures west of the Cascades will drop a bit, but highs across the area look to stay about 5 degrees above normal. A weak front swinging around that trough may bring marine drizzle and some inland cloud cover On Tuesday morning, but significant impacts are not expected.

For midweek and into the weekend, the upper trough starts to work against high pressure centered around the Four Corners area. The first low will weaken and move off to the northeast but another low follows to keep the trough in place possibly through Saturday. With this pattern, slow and steady cooling would bring generally seasonable warmth across the area by Friday or Saturday. Upper disturbances may bring elevated breezes on Friday, but details that far out are hard to forecast with high confidence. Overall, the forecast through the rest of August looks to be unimpactful. -TAD

AVIATION (00Z TAFs)

Marine stratus with IFR/LIFR will redevelop along the coast this evening and persist through late Monday morning. Otherwise, VFR conditions are expected for inland TAF sites, and typical diurnal winds expected today with some high clouds potentially infiltrating the region overnight. Gusty winds may develop for inland areas late Monday afternoon and evening. Additionally this is a slight chance (20%) for thunderstorms across Modoc and southeastern Lake county Monday afternoon and early Monday evening. Gusty outflow winds may accompany storms on Monday.

MARINE...Updated 230 PM PDT Sunday, August 23, 2026

Gusty north winds and steep wind-driven seas are building steep seas across area waters this afternoon. These winds will persist through Monday morning. The main belt of stronger winds will push into the outer waters Monday afternoon and evening, with a southerly surge of wind and fog along the inner waters Monday night into Tuesday. Generally light winds and calm seas are then expected through Friday with low pressure persisting over the northeastern Pacific.

FIRE WEATHER...Updated 230 PM PDT Sunday, August 22, 2026

With ongoing dry conditions, a passing shortwave will bring elevated winds to areas west of the Cascades. These winds will be southerly in the Shasta and could approach 30 to 35 mph. The Scott Valley could also see southerly winds approach 20 to 25 mph. In the eastern Rogue Valley, westerly winds could reach 20 to 25 mph. With RHs forecast to be in the 10-15% range, this combination represents critical fire weather conditions as any new fires could quickly spread. A Red Flag Warning for gusty winds and low RHs has been issued for California fire weather ones 280 and 281 as well as Oregon fire weather zones 621, 622, and 623. This Warning will be in place from 11 AM through 8 PM on Monday.

Also on Monday, There are some signals for thunderstorm chances across far eastern 285/625, namely the Warner and Hart mountains. 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.

MFR WATCHES/WARNINGS/ADVISORIES

OR...Red Flag Warning from 11 AM to 8 PM PDT Monday for ORZ621>623.

CA...Red Flag Warning from 11 AM to 8 PM PDT Monday for CAZ280-281.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Monday for PZZ350-356.

Small Craft Advisory until 8 PM PDT Monday for PZZ370-376.