West Coast Weather Forecast 10/18/2026; CA Storm system on Wednesday, More Active Pattern for the Northwest towards the end of Oct? Models are still confident in rain showers for most of CA on Wednesday, meaning most of the state will see the first measurable rainfall of the season. Rainfall totals will be tricky. This appears to be a convective cut-off low type system, so some locations could see little rainfall while others see intense downpours and maybe thunder. Models have shown pop-up style rainfall rather than light to moderate rain progressing along a front, and the rain showers could move east to west in Central CA/SF Bay Area. Both are pretty uncharacteristic of CA storms, but not unheard of in October. CAPE (Convective Available Potential Energy) values look kind of decent by CA standards, and are concentrated on the Central/Southern coast at the moment. Isolated thunderstorms could develop there on Wednesday afternoon, particularly south of Monterey on the CA coast. In the long term, the pattern still looks active on the west coast. In fact, the activity may expand northward into the Pacific Northwest. After a hot, dry, and fire-prone autumn so far there, it’s fortunate to see less of a strong ridge signal as we head into November. To be clear, this doesn’t look like an extremely stormy pattern (it’s a bit hard to tell at the moment), but I think they’ll see some rain in the next few weeks, including eastern OR/WA, which desperately needs it given the recent drought and wildfire situation.