textproduct: Medford

KEY MESSAGES

* Temperatures continue to trend lower through the week.

* A dry cold front will push through Thursday with temperatures moving slightly lower.

* Low chance of rain showers in Modoc and Lake Counties Friday.

DISCUSSION

Fair weather cumulus is starting to build over south central Oregon with plenty of high clouds passing through as well. An upper level low off the Oregon and Washington coastline will keep us under a southerly to southwesterly flow this evening into Wednesday morning. Main weather impact is some coastal fog based off the NBM visibility and dewpoint depression forecast. Temperatures will trend slightly cooler into Wednesday as 500 mb heights lower slightly. This will result in normal high and low temperatures for late August with some deeper southerly to southwesterly flow.

The biggest change will be on Thursday as that upper low eventually moves eastwards and a dry cold front pushes towards the coast. The latest WPC frontal forecast has a weakening cold front around 12Z Thursday. Looking at 850mb equivalent potential temperatures, it looks like the front might be moving in a bit later on Thursday. In any case, look for an uptick in winds ahead of the front with some slightly cooler air moving in Thursday night for locations west of the Cascades. Lows will fall into the mid 50's for lows here in Medford, which is pretty typical for late August.

By Friday afternoon and evening, we'll see the chance of showers increase east of the Cascades around Modoc and southern Lake County. The latest rapid refresh ensemble forecast system has around 100-300 J/kg of convective available potential energy, although none of the members are predicting lightning over our area. Therefore, it's looking like plain old convective showers for now.

The active weather pattern continues into the weekend and next week with another trough expected to push through the Pacific Northwest. The latest NBM does have a 15-30% chance of rain mainly north of our area before some of those PoP values move into our area Tuesday. Looking at the 12Z ECMWF ensemble, there are about 8/50 members that do have a cold front with some light rain within southern Oregon. The rest are essentially dry or have the rain more focused to our north near Portland and Seattle. In any case, some hope for rain the extended forecast.

-Smith

AVIATION (18Z TAFs)

Marine layer is stronger today and may provide little relief through the daytime hours for KOTH with IFR/MVFR being common through this cycle. For inland TAF sites, other than high clouds, we are expecting typical summer time diurnal breezes with VFR conditions. There is one thing to consider for KRBG, there is a very small chance (~15% for MVFR) for some low clouds overnight, but confidence was not high to include at this time. This would occur close to sunrise if the low clouds do develop and may be added in subsequent TAFs.

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 200 PM PDT Tuesday, August 25, 2026

While conditions will approach critical fire weather thresholds for both wind and low RH today in the Shasta Valley, we will lack the temporal requirement needed which is 6 hours for zone 281 in California. That said, wind speeds will be 20-25 mph with gusts around 30-35 mph, and humidities will be in the lower teens. This will result in near critical conditions this afternoon, especially through peak heating when the strongest wind speeds and lowest RH are expected.

For tomorrow and Thursday, we are expecting critical fire weather conditions for eastside areas as the pressure gradient increases along with dry conditions. We have issued a Red Flag Warning for tomorrow and a Fire Weather Watch for Thursday. This will primarily be for southern Klamath County, eastern/southern Lake County, and north/eastern parts of Modoc County where the overlap of strong winds and low RH are most likely. In other words, this is for parts of FWZs 624 and 625 in Oregon and 285 in California. This will also be combined with deep mixing through the afternoon/early evening hours which could allow for rapid fire growth. However, there may be high clouds around each day which could limit mixing to some degree. There was enough overlap of variables to increase confidence for the threat of critical fire weather conditions coming to fruition both Wednesday and Thursday.

Friday is sort of a transition day as we see improving conditions becoming more likely through the weekend. However, we may still see some areas of near critical conditions for similar areas as Wed/Thurs.

MFR WATCHES/WARNINGS/ADVISORIES

OR...Red Flag Warning from 11 AM to 8 PM PDT Wednesday for ORZ624- 625.

Fire Weather Watch from Thursday morning through Thursday evening for ORZ624-625.

CA...Red Flag Warning from 11 AM to 8 PM PDT Wednesday for CAZ285.

Fire Weather Watch from Thursday morning through Thursday evening for CAZ285.

PACIFIC COASTAL WATERS...None.