We’ve been in a “cool” weather pattern for the past two weeks now. By “cool” I mean the extremely warm weather that dominated April and the 1st half of May has taken a break. It’s been replaced by the typical ups and downs we see in May. I think we have 3 more cool days and then meteorological summer arrives right on schedule, either May 31st or June 1st (or both) we may hit 90 degrees for the first time this season. We have hit 89 twice and 88 once, but still no 90 at PDX.
In the meantime, we have a little thing called Memorial Day Weekend to observe. It appears to be similar to last year, maybe a bit warmer. I expect a few scattered light showers tomorrow and possible again Saturday, otherwise the weekend should be dry south of the Columbia River. A little better chance of showers remains up in Washington through Saturday. The Cascades look very chilly tomorrow and Saturday (what else do you expect in May???), then a bit warmer Monday and beyond. Here are 3 forecasts for the mountains, coast, & central Oregon…click on each for a larger view
Over the past few days models have come around to a very warm/hot pattern in the long range. Individual model runs have been all over the place with details like which days will be hot and which are more reasonable. Due to this I am finding ensemble forecasting more and more useful. That’s when any one model is run with many different “perturbed” variations. Here is one example, the ECMWF meteogram from the 12z run has a real heatwave over us next week with 4 days around/above 90 degrees.
That’s because it digs an upper-level trough offshore and keeps a hot ridge over us. I doubted that was correct and sure enough the ECMWF ensemble chart shows that operational run is an “outlier”.
That’s the blue line which is WAY above the red; the average of all the ensembles. Thus I did not warm temperatures up way into the 90s, but kept temps around 90 for now. The ensemble average output numbers are far more reasonable:
The GEFS ensembles (GFS ensemble runs) are similar showing a peak temperature Tuesday or Wednesday, then a secondary peak around Sunday the 5th:
Regardless, there is excellent agreement that after 2+ weeks of the cooler weather we are headed back into a much warmer than normal pattern. After 3 more days of cool-ish weather we’re headed into some unusually warm weather. This time it’ll be June and it won’t be so strange, not like that 85 degree stuff almost two months ago!
By the way, May will end up a bit drier than normal and there is no big soaking on the way through at least the 5th of June. Here’s the GFS precip forecast for each run the last 3.5 days:
Chief Meteorologist Mark Nelsen