textproduct: Medford

DISCUSSION

An upper level closed low will stay spinning over the Sierra Nevada will be the main weather-maker today and Thursday. This system will produce an active pattern of showers and thunderstorms, some of which will become strong (and perhaps even severe) this afternoon/evening and again Thursday afternoon/evening.

Multiple shortwave disturbances will rotate around the low and since the low is located to our southeast, the showers/storms will move in a general east-west fashion across NorCal and SW Oregon. Currently, radar is showing an area of showers moving east-northeast to west-southwest over Siskiyou County, which put out a few lightning strikes as it crossed over Lake county earlier this morning. These showers will move out of the forecast area over the next hour or so.

Meanwhile, another strong mid-level disturbance will develop over NW Nevada and move over the area this afternoon/evening. As the first shortwave moves away, this should allow for good destabilization late this morning and this afternoon with MUCAPE of 250-500J/KG. Good forcing, shear and steep lapse rates should support the convection this afternoon. In fact, a few showers have already formed up around Winnemucca and McDermitt, NV, with a handful of lightning strikes, as of noon. The shortwave will be within a belt of strong mid- level easterly flow of 35-45 kt, so storm motions will be very fast. Hi- res guidance shows cells developing early this afternoon around Modoc/southern Lake County and then potentially developing into a line of storms that will move east- west across NorCal & southern Oregon reaching Klamath Falls/Mount Shasta regions ~2-5 pm. By then, storms should have the ability to bring strong, gusty outflow winds of 40-50 mph, small hail and a good amount of cloud to ground lightning. This would also normally cause increasing concern for fire starts, but wetting rainfall across a good portion of the area yesterday significantly muted this potential. Showers/storms will continue to move quickly off to the west to the Cascades/Siskiyou Mountains 3-6 pm. The main uncertainty with storms this afternoon is if they will hold together once they move onto the west side during the evening. Models are showing much more stable air over here, but there is still some elevated instability/forcing that could maintain the storms at least until mid evening (8 pm or so). HRRR (a bit of an outlier) is showing the convection moving all the way to the coast by around 10pm- midnight. We think by then, it will mostly just be leftover showers. Tonight, while there is still a chance of showers, the thunder risk should end for a while.

It won't last long though as another shortwave moves into the area Thursday. Convection could get going Thursday morning in portions of Klamath/Lake counties, where instability is greatest. Models are showing 500-1000J/KG CAPE, steep lapse rates and good forcing, resulting in the potential for another round of gusty wind/hail producing storms. Mid-level flow isn't as strong as it will be today, so storm motions will be slower and this could add a heavy rainfall risk, especially for storms that tend to form consistently over the same locations. While just about anywhere could see strong storms (except the coast), the most likely area for possible severe storms is up the Cascades (near/north of Crater Lake) and also over northern Klamath/Lake counties. This is where the Storm Prediction Center has a marginal risk. An inverted trough will maintain an area of forcing for showers to continue Thursday night focuses near the Cascades, but also over portions of the east side.

On Friday, coverage of showers is greatest through the morning hours, but should diminish some as upper ridging noses in from the Pacific. Even so, there is still enough instability for a slight chance of thunder of the far east side. The next upper trough swings through the area on Saturday, but most areas likely remain dry (outside of S&E sections, where there's still a chance of showers/t-storms). Sunday, PoPs are low (generally 10% or less), so most areas should be dry. Temperatures remain around normal this weekend.

Models are consistently showing a warmup early next week -- the degree of which is uncertain. The majority of the guidance shows highs here in Medford in the upper 80s to near 90F Mon-Wed (peak of warmth on Tuesday) and about 5-10F lower at Klamath Falls. The range of solutions for Medford for Tuesday is 82-97F with a 50% chance of 90F or higher. A reasonable worst-case (90th percentile) would be 96F. -Spilde/BPN

AVIATION...27/18Z TAFS

A mix of VFR/MVFR conditions with higher terrain obscurations prevails across the region this morning. Conditions improve to VFR by early afternoon, but expect another round of showers, thunderstorms and gusty winds this afternoon/evening, especially east of the Cascades. Guidance continues to show storms forming into a line that moves east-west across the region later this afternoon/evening. Initially impacting Klamath Falls between 23z-01z, then moving west of the Cascades around 02z, possibly reaching the Rogue Valley around 02-03z. Storms probably weaken as they move westward, with showers possibly reaching as far west as Roseburg/Grants Pass this evening before dissipating late this evening. -Spilde/BR-y

MARINE...Updated 1200 PM PDT Wednesday, May 27, 2026

Gusty north winds will persist today, maintaining very steep wind-driven seas through tonight into early Thursday. There could be a brief period of gale force north winds this afternoon, south of Gold Beach and beyond 1-2 nm from shore. Otherwise, the strongest winds and highest seas will be from Gold Beach south. North winds will ease Thursday, but a long period west-northwest swell will build into the waters tonight into Thursday. This will maintain steep seas through Thursday, but seas will transition to swell dominated with the easing of winds.

Conditions briefly improve early Friday, but this improvement will short lived as north winds increase again Friday afternoon, then persist through the weekend. Initially, advisory level winds and steep seas (possibly very steep seas) are expected south of Cape Blanco by Friday afternoon, but are likely to spread north of the Cape over the weekend. /BR-y

BEACH HAZARDS...Updated 1200 PM PDT Wednesday, May 27, 2026

Long period northwest swell, originating from recent storms near the Kamchatka and western Aleutian Islands, will build into the southern oregon coastal waters today. Initially arriving as 2 to 3 feet at around 20 seconds, swell will peak at 6 to 8 feet at around 17 seconds during the day Thursday. The threat will be highest during periods of incoming tides, which will be during the morning, and during the late afternoon and evening on Thursday.

Sneaker waves can run up significantly farther on beaches than normal, including over rocks and jetties. These waves can suddenly knock people off of their feet and sweep them into the ocean. The waves can also move logs or other objects which could crush or trap anyone caught underneath. Avoid climbing on rocks and jetties. Stay away from the ocean and remain out of the water to avoid hazardous conditions. Never turn your back on the ocean!

MFR WATCHES/WARNINGS/ADVISORIES

OR...Beach Hazards Statement from this evening through late Thursday night for ORZ021-022.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT this morning for PZZ350-356-370-376.

Hazardous Seas Warning until 5 PM PDT Thursday for PZZ350-356- 370-376.