textproduct: Medford

KEY MESSAGES

* Rain is likely Wednesday afternoon into Thursday west of the Cascades with lighter rain east of the Cascades.

* Rockslides along highways 38,42 and 138 are possible with this first rain of the season. Less likely in other areas.

* 15 to 20 degrees cooler than normal Wednesday into Thursday.

DISCUSSION

Not much going this morning as some coastal stratus creeps up the coast. Temperatures will trend warmer this afternoon into the lower 90's for highs here in Medford. One could analyze a weak thermal trough over our area this morning and afternoon with inverted 850 mb heights and some light easterly flow aloft. In any case, this brief period of warmer temperatures and dry conditions will come to an end in the next few days.

An upper level wave and embedded short wave will push into northern California and southern Oregon sometime around Tuesday afternoon. The latest forecast has the probability of precipitation increasing into Tuesday afternoon. The precip looks spotty, so it will be more miss than hit. The NBM thunderstorm probability is about 10%, so a few rumbles of thunder are not out of the question.

A deeper wave will eventually move into the Pacific Northwest with what appears to be warm front moving into the coast around 18Z. This should lead to a more widespread lighter rain along the boundary as it moves eastward. A cold front should quickly follow the warm front around 0Z with or perhaps it will come in as an occluded front. In any case, there should be strong synoptic lift and plenty of precip along these boundaries by Wednesday evening. The latest forecast has an inch of rain along the coast from 12Z Wednesday to 12Z Thursday with notably less precipitation farther east. Some areas west of the Cascades could see up to 0.5 inches while locations around Lake, Klamath and Modoc Counties will see significantly less. In fact, Alturas is expected to stay dry into Thursday morning.

There could be impacts from this first rain of the season with rock slides/landslides along the usual spots around highways 42, 38 and 138. The East Evans Creek and Fielder Mountain burnscars could be an issue as well. Some of this is dependent on the severity of the burn areas, although the first light rain will test these burnscars for smaller debris flows.

Lastly, the first rain of the season after longer periods of dry weather can create slick roadways from the oil buildup through the summer months. The threat of accidents can increase after these long dry stretches, so one should use extra caution driving Wednesday afternoon and evening as a lighter rain could push the oil to the surface without running off the road.

Eventually, this upper level wave will move eastwards Thursday and Friday. It looks like another cold front could bring a quick shot of rain to our forecast area with a focus on northern California on Thursday evening. Although ensembles are divided on the amount of rain, almost all guidance brings this low overhead with scattered showers into Friday.

Even though this rain will be uncommon for early September, we're not expecting any rainfall records right now, or the probability for breaking a precipitation record is pretty low. However, we could set a record MINIMUM/LOW temperature in the summer, which seems like a rarity these days. Klamath Falls is forecast to hit 32 degrees on Thursday night and the old record is 32 set in 1912. This seems unlikely with a lot of cloud cover around and the upper low overhead. The NBM/WPC forecast is probably bias correcting lower due to all the clear skies we've had over the previous weeks. The GFS MOS guidance has a low of 40, which seems more reasonable. In any case, this will have to be watched.

Heading into the weekend, it looks like the forecast dries out even though the upper level low remains overhead. Temperatures will remain cooler than normal with highs in the upper 70's with plenty of cumulus cloud cover expected through the day. WPC/NBM does have some PoPs along higher terrain, so a stray shower can't be ruled out. There are a few(3-5) very wet ensemble members Sunday with many staying dry, so quite a QPF spread around day 6-7.

-Smith

AVIATION...31/06Z TAFs

VFR levels under clear skies persist across northern California and southern Oregon. MVFR/IFR ceilings are possible along the coast late tonight into early Monday morning, but a slight easterly component to winds may limit ceiling development. Either way, clouds will increase along the coast through the afternoon and evening as the leading edge of an upcoming system approaches the area and winds become onshore. MVFR/IFR ceilings will prevail along the coast and other areas along and west of the coastal mountains, with potentially some drizzle, by Monday evening. Elsewhere, VFR will continue through the next 24 hours, with some mid level cloudiness expected to develop west of the Cascades by evening.

MARINE...Updated 230 AM PDT Monday, August 31, 2026

Conditions hazardous to smaller crafts will ease this morning with weakening winds across all of the waters. Seas will fall to 4 to 5 feet with a northwest swell around 3 to 4 feet at 10 seconds. The big change will come on Wednesday morning as a warm front first pushes through the waters and kicks up some stronger southerly winds. Conditions will be hazardous to smaller crafts during this time. Eventually, a cold front will move through the waters closer to Wednesday evening. This cold front will likely produce gale force wind gusts around 45 knots. Therefore, we have issued a gale watch between Tuesday night into Wednesday afternoon.

-Smith

FIRE WEATHER...Updated 200 PM PDT Sunday, August 30, 2026

A brief, but strong warming and drying trend will continue on Monday. Winds will increase Monday afternoon as a trough approaches from the west. Wind and humidity conditions will reach critical levels in the Scott and Shasta valleys and east of the Cascades due to gusty south to southwest winds and dry humidities. A Red Flag Warning is in effect for portion of FWZ 280 (Scott Valley) and FWZs 281, 284, 285, and 624.

On Tuesday, gusty winds will again reach critical levels in that area. But, humidities will be slightly above thresholds as temperatures trend cooler. There will also be chances for light showers and a 5%-15% probability of late of day thunderstorms, especially near the Scott Valley in west-central Siskiyou County, and in far northern Klamath County.

A trough dominated pattern will follow for the remainder of the week with a strong cooling trend and increasing chances for rain. Gusty winds, and a wetting rain are likely from the coast to the Cascades, and in northern Klamath County. This will be followed by shower chances Friday into Sunday while slightly warmer temperatures remain below normal. The outlook for day 8-10, early next week, is for warming and drying.

MFR WATCHES/WARNINGS/ADVISORIES

OR...Red Flag Warning from noon today to 8 PM PDT this evening for ORZ624.

CA...Red Flag Warning from noon today to 8 PM PDT this evening for CAZ280-281-284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT early this morning for PZZ350-356-370-376.

Gale Watch from late Tuesday night through Wednesday afternoon for PZZ350-356-370-376.