It’s been a very “normal” Memorial Day Weekend. Cool and cloudy Saturday, then warm and sunny Sunday. Of course a weak weather system lingering overhead the first half of today left us damp through noon or so. We expected that. We eventually warmed into the upper 60s in the Willamette Valley.
Portland ended up with .07″ rainfall, about what models were showing last night at this time. A mix of sun, clouds, & showers are perfectly normal for this “beginning of summer” weekend. Take a look at Memorial Day Weekend weather the past 10 years (click for a better view)
We are in flat “westerly flow” right now. That means a weak late May jet stream is overhead. That’s why a wet weather system is lingering so close this evening.
But that warm upper-level high pressure to our south pushes north and east the rest of this week. By Thursday/Friday it’s centered right over Nevada
A heat wave is coming for California this week. Excessive heat warnings are up for the Central Valley. Highs reach upper 90s to upper 100s tomorrow through Thursday!
How warm for us this week? Tomorrow we’ll be back into the 70s; lots of clouds leftover from today will keep temps under control. But then weak offshore flow Wednesday/Thursday plus 100% sunshine warms us dramatically. 850mb temps reach +14-16 Wednesday, then +17-19 Thursday-Friday. With good offshore flow, there’s no reason we couldn’t hit 90 in Portland both Thursday and Friday. But I see “flat” upper-level ridging, plus most models are not showing a sharp thermal trough. So I’ll go a bit more conservative with the highs. 85-90 is a good forecast for those days. Anything over 87 would be the warmest day so far this spring in Portland. Enjoy another taste of summer, but without the record heat. By the way, record highs at PDX for Wednesday-Friday are 95-100-90.
I’ll be watching Saturday closely since a “cutoff” upper-level low is forecast to swing north along the West Coast. Sometimes this can give us a good soaking and/or thunderstorms as it passes by. That southeasterly upper-level flow just ahead of the low (shown) is great for steering some thunderstorms west of the Cascades.
Models are in very good agreement that we move into a wetter/cooler pattern again after Saturday. Check out the ECMWF ensemble rain forecast. Each line on this chart (upper part) represents one of the 51 ensemble members from this morning’s run. Great agreement that we’re dry through at least Saturday morning. Then every member shows showers later Saturday through sometime Sunday. Get your deck staining done this week and wrapped up Friday. Or early Saturday would be a good time to put out some warm weather veggie transplants; they will get watered over the weekend.
That’s it for now…enjoy the warm weather this week!
Chief Meteorologist Mark Nelsen