textproduct: Medford

Updated AVIATION Discussion

AVIATION...25/12Z TAFs

IFR/LIFR conditions under marine stratus will persist along the coast and over the waters through this morning. Conditions will gradually improve to MVFR by this afternoon as the marine layer peels back to the immediate coast, but full clearing is not expected today. LIFR/IFR conditions will return again around sunset. Inland terminals will remain VFR through the TAF period with some mid and high level clouds streaming through the region. Gusty afternoon/evening winds are expected today, strongest east of the Cascades and in the Shasta Valley. These winds will ease after sunset.

PREV DISCUSSION

/Issued 345 AM PDT Tue Aug 25 2026/

KEY MESSAGES...

* Hot temperatures continue today, trending cooler through the week into the weekend.

* Weather pattern largely influenced by upper level troughing, resulting in gusty winds in the afternoons/evenings.

* Heightened fire weather concerns today through Thursday due to gusty winds and low RH. Fire weather concerns highest for Shasta Valley and portions of the East Side.

DISCUSSION...Southwest flow persists over the region today with persistent high pressure over the the Desert Southwest and low pressure just offshore of British Columbia. The upper level pattern doesn't change too much compared to yesterday. Low pressure off the BC coast will drop southward this afternoon and this will be enough to push some drier air into the mid-levels as well as shift the instability slightly eastward today. This will shift any thunderstorm chances into Nevada and Idaho. There could be enough/marginal moisture for some cumulus buildups over the Warners this afternoon, but, along with the lack of instability, it's not sufficient enough for thunderstorm development today. Despite a few degrees of cooling today west of the Cascades, it'll be another hot day across the region with high temperatures (mid- upper 90s West/mid-upper 80s East) peaking around 5 to 7 degrees above normal for late August.

Low pressure offshore this afternoon will be the main weather maker for much of the week as it moves closer to shore today, then gradually inland into the Pacific Northwest Wednesday and Thursday...a pattern quite similar to that of last week. With this trough, temperatures will gradually trend cooler over the remainder of the week, eventually settling into the 80s area wide (except for the coast) for the weekend behind the trough passage. Persistent onshore flow will bring the nightly return of marine layer intrusions along the coast, and eventually into the Umpqua Basin Thursday morning. Expect periods of increased mid and high level cloud cover as shortwaves pass through into southwest flow ahead of this trough today and Wednesday.

Aside from the cooler temperatures, the main concern with this trough will be increased afternoon winds each day through Thursday. This will bring heightened fire weather concerns each afternoon/evening as daily winds increase and RHs remain fairly low. Fire weather concerns diminish some Friday onward as RHs trend higher, but with no precipitation expected anytime soon, fire danger remains very high across the region. Please remember to do your part and prevent a spark. One less spark, one less fire.

The mid-levels will be too dry to support any thunderstorm development this week, and while no widespread precipitation is expected through the forecast period, some of the guidance is showing some tropical moisture being swept into the westerlies on Friday. Current guidance brings this moisture into central CA/northwestern Nevada, which could clip the southeastern portions of the forecast area or remain just south, depending on how it interacts with the trough passing inland at the same time. Overall, the thunderstorm threat is minimal, but it's something worth watching this week.

Broad troughing will remain over the western CONUS over the weekend and into early next week. Dry conditions will continue with temperatures near to a few degrees below normal.

MARINE...Updated 130 AM PDT Tuesday, August 25, 2026...Relatively calm conditions with light winds and low seas are expected through the week. Southerly winds will persist through Wednesday, then turn northerly on Thursday. North winds increase on Friday south of Cape Blanco, but wind driven seas likely hold off until the weekend.

FIRE WEATHER...Updated 300 AM PDT Tuesday, August 25, 2026... Southwest flow will persist over the region through much of the week. The upper level pattern will largely be dominated by an upper level trough over the eastern Pacific that will move closer to shore today, then inland into the Pacific Northwest Wednesday and Thursday. This pattern is quite similar to that of last week, when gusty winds combined with low daytime RHs and brought critical fire weather conditions. This will again be possible today through Thursday as this trough brings gusty winds in the afternoons/evenings. With low daytime RHs expected, near critical conditions are possible each day, with critical conditions also possible in the Shasta Valley and portions of the East Side. Another day of gusty south winds is expected in the Shasta Valley today, which could lead to a period of overlap with gusty winds/low RH, but there is uncertainty on whether the duration requirement is there. For the East Side today, gusty southwest winds will be present, but not quite strong enough and RHs won't be quite low enough for critical conditions to be met. Wednesday and Thursday, however, RHs will trend lower across the East Side as a dry front gradually moves inland. These two days seem most likely for gusty winds/low RH to overlap and result in critical conditions. By Friday, RHs trend upward and remain elevated enough through the weekend to lower the concern for critical fire weather conditions. It'll remain breezy through the weekend, but winds generally trend weaker compared to this week.

Meanwhile, onshore flow will generally maintain moderate to good recoveries with nightly marine pushes for coastal zones. The exception to this could be Thursday morning when poor recoveries are possible along the Warners and southern portions of the Fremont- Winema National Forest. Thunderstorms drop out of the forecast today. Mid-level moisture is marginal enough for some cumulus buildups over the Warners, but along with the lack of instability, it's not sufficient enough for thunderstorm development today. We'll be keeping an eye on the potential for some tropical moisture to get swept into the westerlies later in the week. Current guidance keeps this south of the area, but it's possible it could clip the southeastern zones (285/625) depending on the interaction with the incoming trough. Stay tuned for updates.

MFR WATCHES/WARNINGS/ADVISORIES

OR...None.

CA...None.

PACIFIC COASTAL WATERS...None.