textproduct: Medford

Updated AVIATION Discussion

AVIATION...20/18Z TAFs

Marine stratus will persist through much of the TAF period along the coast and over the marine waters. Current LIFR/IFR conditions will likely improve to IFR/MVFR this afternoon, but confidence is low on full clearing to VFR. Expect the marine layer to lower again by early evening to LIFR/IFR.

Inland, VFR conditions will prevail with high clouds streaming overhead today and overnight. Expect some slightly enhanced afternoon breezes today, with gusty winds expected in the Shasta and Scott Valleys this afternoon. Winds will ease after sunset, but mid and high level clouds will persist overnight into Friday as an upper level trough approaches the region. /BR-y

PREV DISCUSSION

/Issued 435 AM PDT Thu Aug 20 2026/

KEY MESSAGES...

* Some westside valleys will be around 100 degrees today so some HeatRisk exists today, but temperatures are back closer to seasonal normals starting tomorrow

* Friday and Saturday will see enhanced breezes, with Saturday having the stronger gusts, and when combined with low RH we will see elevated to critical fire weather conditions both days

* Isolated thunderstorms are possible Friday afternoon along the Cascades and possibly eastside areas through the evening hours

* Areas of smoke and poor air quality remain possible across western Siskiyou County and parts of Klamath and Lake counties due to nearby wildfires

DISCUSSION (Today through Wednesday)...

Overall, very typical summer-like pattern is slated to continue. The general pattern continues to be noted by high pressure over the Desert Southwest and a closed low off the coast around 134W and 37N. This will maintain south to southwesterly flow aloft through much of the next 7 days, even as the low gets absorbed into the mean flow. This pattern will likely play a large role on our fire weather conditions (wind/low RH) and thunderstorm chances starting tomorrow. The signal is currently weak for thunderstorm chances, but we do have moisture and weak instability across the region, so the added dynamics aloft could help produce a thunderstorm or two Friday afternoon/early evening. Thunder potential has decreased compared to 24 hours ago. There will be mid/high clouds around through peak heating on Friday, so this may limit mixing and overall thunderstorm potential will be subdued as instability is limited. If the closed low is allowed to push farther eastward before its north/northeast trajectory, we might see more coverage on the eastside. That said, still only expecting very isolated thunderstorms if any form. Confidence is high for pressure gradients to increase on Friday and further increase on Saturday which will ultimately lead to increased fire weather threats from strong gusts and low RH. The overall takeaway is that we will see increased risk for fire weather conditions from either lightning potential (lower threat) or the combination of winds and low RH (higher threat) starting tomorrow and peaking Saturday.

As the low pushes north and east, we will remain under south/southwesterly flow through early next week. This pattern will keep us overall dry with the main weather hazard revolving around fire weather potential which is typical for this time of year.

MARINE (Updated 330 AM Thursday, August 20)...

Conditions are expected to continue improving today with relatively lighter winds and lower seas through Saturday. A thermal trough will redevelop along the coast Sunday bringing a return of strong north winds and steep seas for areas mainly south of Cape Blanco.

FIRE WEATHER (Updated 330 AM Thursday, August 20)...

Still keeping an eye on Friday and Saturday for conditions approaching critical thresholds. Friday we have an approaching upper level low that will start our enhanced pressure gradients resulting in strong gusts coupled with low RH for eastside areas and parts of northern California. In addition to the low RH and winds, we will have increased chances for thunderstorms on Friday as well, mainly along the Cascades and north, potentially spreading to eastside areas. On Saturday, the thunderstorm threat likely shifts north and east of our area, but we will have those enhanced breezes sticking around for another afternoon/early evening. In fact, Saturday will likely have the stronger gusts of the two days. This combined with another dry afternoon will bring elevated to critical fire weather conditions. Coverage wise, Friday and Saturday will be the most noteworthy days regarding fire weather concerns. That said, the threat of elevated to perhaps critical fire weather conditions will continue through the weekend and into early next week.

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 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.