EARLY SPRING SYNOPSIS

Please dive in with me to think about what weather might grace us in the next few weeks. Quite a lot has been going on lately, which is typical for early-to-mid Spring as increasing sunshine causes warmer air masses to battle with pools of cold air ejected from the polar regions in late Winter and early Spring. But this Spring has been quite unusual and I will try to delve into the primary reasons below.

Increased instability also causes springtime to be more unpredictable than the other seasons, especially looking long-term. Thus, while I’ve also added some peeks into what late Spring through late Summer might look like, please keep this “Spring predictability barrier” in mind, though it’s already breaking down to some degree.

THREE-WEEK FORECAST

Although April 14 marked a temporary shift towards warmer, drier weather, that’s also helping to prime April 20–27 for increasing atmospheric instability.

The 2025 winter polar vortex is also refusing to depart peacefully. Due to the downstream effects of the March 5–15 polar vortex disruption, the next eight days should generally be on the cool side, with mostly cloudy skies.

(That disruption, known as the “Final Warming”, was the second earliest such event of the past several decades and has prevented us from having a significant heat wave, so far.)

Temperatures this weekend should be relatively mild compared to the last several cold spells, with overnight lows in the 39–42° range. But Monday and Tuesday night could reach 36–38°.

Wed. afternoon April 23 could reach 67–72°.

Then, the chance of precipitation increases significantly Thursday night into Saturday April 24–26 just as tropical convection activity increases and sends a frontal system towards Oregon, and the (likely) final impact of the aforementioned polar vortex disruption arrives here, dropping our temperatures *well below average for this time period.

This should be followed by a generally normal period, but still with some potential for precipitation as we head towards early May.

After about May 3–4 there are signs of an extended warming trend, particularly around May 9–11.

LATE SPRING INTO LATE SUMMER SEASONAL TRENDS

As of April 19, the El Niño Southern Oscillation Index (ENSO) is slowly moving into cool neutral conditions which are expected to persist into Autumn, with the possibility of an early 2026 El Niño.

The C3S Met Office (UK) seasonal precipitation model posted April 1 predicted a 40%+ above average rainfall for parts of western Oregon in May-June-July.

But most seasonal prediction models are then pointing towards unusually hot and dry conditions in the Northwest by mid-July, through August, and possibly much of September.