textproduct: Medford

UPDATE

Updated Aviation Discussion.

AVIATION...31/23Z TAFs

LIFR is present along the coast in low stratus and fog. These conditions will persist through this morning, gradually lifting and clearing in the early afternoon. However, areas of IFR/MVFR may persist along the immediate coast. Then, IFR/LIFR will return in the early evening.

Inland, conditions will remain VFR through the TAF period. The only exception may be areas of MVFR visibilities due to wildfire smoke, which may affect Klamath County (mainly north of Klamath Falls) and western Siskiyou County at times.

PREV DISCUSSION

/Issued 249 AM PDT Sun Aug 31 2025/

DISCUSSION...An upper low has moved northward and is located off the Washington coast near 47N 129W. Meanwhile over inland areas, an upper level ridge is present, centered just east of the area. This is bringing continued warm and dry weather to the area today. Temperatures will be similar to yesterday. Breezy afternoon and early evening winds are expected again today. This pattern continues on Monday as the upper low gradually shifts further north and the ridge remains in place. Temperatures are forecast to be similar or slightly warmer on Monday.

Smoke from area wildfires will continue to impact the region, especially across western Siskiyou county and into Klamath and northern Lake counties. With southwest to southerly flow aloft, the bulk of the smoke impacts from the Emigrant fire should remain north of the forecast area. The HRRR Smoke model continues to indicate a pattern of higher smoke concentrations moving into Klamath County and northern Lake County in the evening and overnight as northerly winds bring smoke from the Emigrant fire. This is followed by improvement in the afternoons as southwest winds increase east of the Cascades and help to clear out the air. The Oregon Department of Environmental Quality has issued a Air Quality Alert for Klamath County that is in effect through at least Tuesday morning. Meanwhile, smoke impacts from the Dillon fire in western Siskiyou County will continue to bring impacts across western Siskiyou County, with higher smoke concentrations settling in the Scott/Shasta/Klamath River Valleys in the evening and overnight, then improving in the late morning and early afternoon. The HRRR models also indicates that smoke will filter into central Siskiyou County, including the Shasta Valley. In the Rogue Valley, less but still significant impacts are expected. The HRRR model shows smoke from the Dillon Fire drifting into the Illinois/Applegate Valleys, then being carried eastward into the Rogue Valley in the afternoons, before shifting east in the early evening. Expect periods of hazy conditions and degraded air quality for the foreseeable future.

The pattern changes heading into Tuesday and Wednesday with a strengthening upper level ridge, resulting in hotter temperatures, and an upper level disturbance moving into the area from the south. Models continue to indicate sufficient mid level moisture and weak instability on Tuesday to allow for a slight chance (15-20%) of thunderstorms across northern California and from the Cascades east. West of the Cascades in Josephine and Jackson counties, the potential for thunderstorms is lower (5-10%). There is a low chance (5-15%) for some isolated overnight thunderstorms or showers Tuesday night, mainly east of the Cascades. The slight chance for thunderstorms persists on Wednesday for these same areas as the disturbance tracks northward over the area. The exact timing and location for thunderstorms will be dependent of the track and strength of this disturbance. Ensembles continue to show variability on this feature, so confidence is low the details. We will continue to monitor and update as needed. For additional details on the upcoming heat and thunderstorms, please see the previous discussion below.

MARINE...Updated 200 AM PDT Sunday, August 31, 2025...A weak thermal trough develops along the coast today, bringing northerly winds. North winds increase Monday into Tuesday, resulting in low end advisory level steep seas south of Cape Blanco. These conditions may persist through mid-week, with winds easing below advisory levels for the latter half of the week.

FIRE WEATHER...Updated 200 AM PDT Saturday, August 30, 2025...The area will remain under southwest flow today and Monday with an upper low off the Washington coast and a upper level ridge centered inland over the region. This will bring a warm and dry pattern to the area. Temperatures will trend slighter hotter going into Monday. Breezy to gusty winds and dry humidities are expected across inland valleys through Monday. Overall, winds and humidities are not expected to reach critical conditions. However, some locally, brief near critical conditions are possible in the late afternoons, mainly in the Shasta Valley and east of the Cascades. So, we have continued to headlined the gusty winds and dry humidities.

The upper level ridge will continue to strengthen on Tuesday and Wednesday with hotter temperatures expected. Additionally, there is a slight chance for thunderstorms (15-20%) across northern California and form the Cascades east as an upper level disturbances moves up from the south and into the area.

Tuesday the position of the upper low is such that it could result in at least isolated thunderstorms for portions of northern California, and Cascades east. Conditions could be favorable for nocturnal storms Tuesday night. However, there is more evidence that does not support storms Tuesday night. We'll continue to monitor this.

Wednesday, the operational models differ with the progression of the upper low. The ECMWF has the low positioned in northern California as it becomes cut off from the main flow. The GFS also hints at the low becoming cut off from the main flow, but progresses the upper low through our area by Wednesday afternoon which would put the best chance for storms north of our forecast area. In contrast the ECMWF solution would at least maintain the chance for thunderstorms Wednesday afternoon and evening. Gut feeling is the slower progression of the low makes more sense given both models show the upper low becoming cut off.

If the upper low does end up progressing slower, then we could be dealing with the potential for nocturnal storms Wednesday night, but much will depend on the timing and location of the upper low. If nothing else, another thing we may have to consider, but there's still plenty of time to address this.

Isolated storms could still be a part of the equation Thursday afternoon and evening, but right now there's nothing in the forecast and much will depend on the track of the upper low.

It's also worth noting, the upper ridge will remain in place Tuesday and Wednesday with afternoon temperatures around the triple digit mark for the interior westside valleys, and upper 80s to low 90s east of the Cascades.

PREV DISCUSSION... /Issued 1027 PM PDT Sat Aug 30 2025/

DISCUSSION...Tuesday through Thursday will be the time period worth watching for two reasons: thunderstorm potential and heat. First, the thunderstorms...models remain consistent in showing a weak low that takes on a negative tilt as it moves northward through the region Tuesday through Thursday, bringing increasing moisture and instability. We've ventured away from the NBM to add a slight chance of thunderstorms for Tuesday and Wednesday afternoons/evenings, focused in the typical areas along and east of the Cascades as well as for portions of western Siskiyou County. There is some question as to whether storms develop west of the Cascades on Tuesday and Wednesday. Guidance the potential for storms as far west as the Illinois Valley, but not so much north of the Rogue-Umpqua Divide. This is still 4-5 days out, so details are likely to change once this time frame is covered by the models that help us hone in on timing and location.

Meanwhile, the upper level ridge amplifies over the intermountain west as energy dives southward into the mid-west. As this ridge amplifies, the low pressure offshore this weekend, gets pushed northwestward (retrogrades) into the Gulf of Alaska. We'll see a warming trend beginning Monday, but models show the ridge axis being centered over the West Coast States by mid-week, which will result in another warm up across the region for the Tuesday-Thursday timeframe. Upper 90s into the triple digits for the West Side (low 90s/upper 80s for East Side) is expected for this warm up. While it seems fairly certain that it'll be hot again for mid-week next week, with the aforementioned low drifting around during the same time, cloud cover could end up being a mitigating factor in the extent of the heat. Additionally, smoke from area wildfires could also play into how warm temperatures get. HeatRisk values are indicating a moderate to locally major risk for heat related illnesses Tuesday through Thursday, primarily for the valleys west of the Cascades, so we'll be evaluating the need for any heat related headlines over the coming shifts. The ridge starts to break down and shift eastward on Friday, so temperatures are expected to trend cooler but still remain above normal for early September.

MFR WATCHES/WARNINGS/ADVISORIES

OR...None.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 11 AM Monday to 5 PM PDT Tuesday for PZZ356-376.