The past 3+ weeks have been quite a ride. We've only seen a few sprinkles in much of western Oregon and southwest Washington. Soils are totally dry like what we'd typically see in late June or July. All of us are watering (or should be) lawns, gardens, & crops well ahead of the usual time. But the "outside living" has been spectacular with dependably dry weather as if we're in mid-summer.
This is the 2nd consecutive year we've seen a prolonged dry spell in late spring. In fact this year is record dry.
Maybe more interesting is the lack of wet weather in May recently. We haven't seen a wet May since 2013, although 2016 & 2017 were close to normal.
And of course we've seen quite a stretch of July weather in May. The first 13 days this month have all been above average. We didn't quite hit 90, but were very close with one record high on the 10th.
There has been lots of concern (including from me) that we're repeating the very early fire/dry season from last year and 2015. But there is good news!
A pattern change means the next 10 days will be unusually wet across the region. This is much different than the early dry seasons last year and 2015.
We've been very dry because upper-level high pressure has been just west of us in the Eastern Pacific or right over the Pacific Northwest since mid-April. The 30 day anomaly shows those much-higher-than-average heights well
Now here's the forecast from the ECMWF ensemble run this morning. Both the GFS and Canadian models are similar. In three days (Thursday), a cool upper-level trough will run right into northern California. Heights are below normal all along the West Coast.
Then a 2nd, even deeper low moves inland early next week
This means a stretch of much cooler weather plus widespread rain from southwest Canada all the way down into Southern California. The showers/rain will come in waves and at this point I don't see any "atmospheric river" setting up over the Pacific Northwest. Here's the ECMWF rain forecast for Oregon through Thursday the 23rd, just ahead of Memorial Day Weekend
The GFS model is similar for the next 10 days
I think it's safe to say at least 1.00" is likely in the western valleys, possibly over 2.00" in spots if we get convection (thunderstorms) at some point. In the Coast and Cascade ranges a solid 2-4" is likely in the next 10 days. Excellent news! We can forget about fire issues through late May if this comes to fruition. Notice they both show some rain east of the Cascades as well; good news for "dryland" grain farmers in central & north-central Oregon.
Does this mean all the rest of May will be wet and cool, including Memorial Day Weekend? There's no reason to think that for now. The ECMWF ensembles show at least weak ridging (or lack of cool/wet) arriving between 10-15 days from now. That's over the long holiday weekend...
To wrap it up:
- By sunrise tomorrow (Tuesday) light rain arrives for many of us.
- Finish all dry weather projects this evening; bring in everything that shouldn't get wet.
- Waves of light rain/showers continue for the following 8-10 days.
- EVERY DAY WILL NOT BE A SOAKER. At this point Friday and at least part of Saturday look dry.