textproduct: Medford

Updated AVIATION Discussion

AVIATION...01/18Z TAFs

IFR/MVFR ceilings persist along the Oregon coast and Umpqua Valley this morning with VFR elsewhere. The lower ceilings should tend to lift/break up later this morning/this afternoon, but may be more persistent along the coast. Expect marine stratus to return again late tonight, bringing another round of IFR/MVFR ceilings.

Meanwhile, we expect convective activity to begin this afternoon with some cumulus buildups during the mid-late afternoon. Isolated showers and thunderstorms should develop late afternoon/evening near and just west of the Cascades, including around the Rogue Valley. The chance of thunderstorms is about 20-30% around the MFR terminal this afternoon, so gusty outflows are possible with cloud to ground lightning. Confidence is lower for thunderstorm activity north of the Rogue-Umpqua Divide for this afternoon/evening. However, model guidance shows some elevated instability up that way overnight tonight, and there's about a 10-20% chance for some lightning activity near the Roseburg terminal between 10z-15z Saturday.

PREV DISCUSSION

/Issued 449 AM PDT Fri May 1 2026/

KEY MESSAGES... -Marine layer stratus on the coast and in the Umpqua Basin this morning. -Isolated thunderstorms late this afternoon and evening, mainly Siskiyou County northward to the Siskiyous/Cascades and also west side valleys along I-5. -Thunder potential continues this weekend into Monday. -High pressure brings warmer, drier weather again Tuesday and Wednesday. -Shower/thunder chances could increase again late next week.

DISCUSSION...Satellite imagery is showing a bit deeper of a marine push this morning with low stratus for all coastal areas and also portions of the Umpqua Basin. Clear skies (with some high cirrus) persist elsewhere. The lower clouds should gradually break up/lift this afternoon. With the upper ridge axis shifting to the south and east, an upper trough will close off just off the PacNW coast and move southward (inside 130W, but just offshore). Increasing southerly flow in advance of this disturbance will bring higher moisture (PWs of 0.5-0.8") and instability (CAPE 200-500 J/KG) over the area late this afternoon/evening. Hi-res guidance shows decent some cumulus building during the late afternoon/evening over the mountains, especially from western Siskiyou County, up across Jackson County and into the Cascades. A capping inversion does exist, so it'll likely take most of the day before we see much activity (it may hold off til evening). Even so, these areas stand a decent chance (20-40%) of showers along with a slight chance (15-20%) of thunderstorms. While convective parameters aren't bullish on severe potential (bulk shear only in the 20-30kt range), any cells that do form could produce gusty winds, cloud to ground lightning and small hail. Some activity (mostly just showers) could linger near and west of the Cascades into tonight since the core of the closed low will be just off the Oregon coast at that time.

Showers and storms will be in the same general areas Saturday, but with the flow becoming more SSE as the closed low heads down the coast, activity could become more widespread and include east side areas during the afternoon/evening. Latest guidance shows the highest probabilities near the Cascades and over the higher terrain of the East Side. The low settles southward to a position about ~300 miles WSW of San Francisco Saturday night into Sunday morning and showers should wind down over our area with the loss of instability.

Sunday into Monday, the low is forecast to elongate and shift eastward -- moving onshore into California just south of SF Bay during this time. The focus for showers and storms will be directed into NorCal, but also still into portions of southern Oregon. We'll probably start off sunny Sunday and it will remain quite warm/even humid. There should be enough moisture, instability and forcing for more widespread showers and thunderstorms during the afternoon/evening. Highest PoPs and thunder chances will be across NorCal and up the Cascades with lower chances in NW sections (northwest of Roseburg). By Monday, we'll be decidedly on the northern periphery of the low with upper ridging to the north and mid-level flow around the low from the ENE. Most areas will be at least slightly cooler, but especially NorCal where clouds/showers will be most persistent. There's still a chance of thunderstorms, but best chance is east of the Cascades. Rain amounts with this entire system will likely vary quite a bit due to the showery nature of the precipitation (and also the potential for thunderstorms). Some places could end up with nothing at all, while those that get under more persistent showers could have 0.25-0.50 of an inch (most likely in Siskiyou County of NorCal) with up to an inch in areas that manage to get beneath a thunderstorm core for a while.

Tuesday into Wednesday, the upper ridge to the north will win out as the closed low settles into the Great Basin and Desert Southwest. This will allow things to warm up again, with shower/thunder chances staying mostly to our south and east. Long range guidance is hinting at the potential for another trough to arrive sometime late next week (Thu/Fri) with perhaps an increase in shower/thunder chances again. -Spilde

MARINE...Updated 230 AM PDT Friday, May 1, 2026....A thermal trough pattern will bring gusty north winds into Saturday evening. The strongest winds and very steep seas are expected south of Ophir again today. Seas will be steep elsewhere. Winds diminish while a longer period northwest swell builds late Saturday night, then becomes dominant later Sunday into Monday.

BEACH HAZARDS...A short period northwest swell and a building long period northwest swell may combine their energy to produce unpredictable waves washing up on area beaches. The risk will be highest around sunrise on Sunday morning.

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. Never turn away from the ocean!

MFR WATCHES/WARNINGS/ADVISORIES

OR...Beach Hazards Statement from Saturday evening through Sunday morning for ORZ021-022.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Saturday for PZZ350-356-370-376.

Hazardous Seas Warning until 11 PM PDT this evening for PZZ356- 376.