What Happened to May? Summer Weather & Cascade Snow Meltdown

May 21, 2018

9pm Monday

The past month has been amazing if you don’t like cool/cloudy/wet springs here in the Pacific Northwest.  It won’t be so “amazing” if we don’t get more typical late May or June weather in the next 4-5 weeks.  Here’s the monthly temperature anomaly map so far…9 days left in May


All of the USA minus Florida and coastal California has been very warm.  Here in western Oregon we’re are in the middle of one of the warmest Mays on record.

May Warm Start Stats

I just planted most of my garden yesterday.  Typically I’m fighting cold/wet conditions, slugs, and not even thinking about watering in mid-May.  But we’ve seen only .25″ in the past 4 weeks.

This is the driest April 21st-May 21st on record at PDX.  We’ve never seen it this dry during this period of time in the past 80 years in Portland.

Typically when we have dry spells this time of year, we see rain on the horizon.  Not this time around as weak ridging continues to remain near the Pacific Northwest.  This weakens systems and/or sends them south into California or up north.  Even though the ECMWF and to a lesser extent the GFS bring rain overhead with an upper-low Friday and Saturday, neither shows a cool/wet weather pattern ahead.  Check out the 24hr QPF forecast from the ECMWF ensembles for the next two weeks:


Looks like about 30 of 50 ensemble members give us at least some light rain early this coming weekend.  Note how dry it is once again next week.  This dry weather is great for outdoor activities of course, but obviously we need some sort of soaking in June or we’ll have water supply issues (dry wells) later in the summer.  Maybe fire season problems too.  One more benefit of the early warming is a rapid meltdown of the Cascade snowpack.  Look at the past 10 years snow depth on this date on Mt. Hood.

Mark Mt Hood Snowpack May

I remember 2009-2012 when campgrounds opened late up in the Cascades.  But now 3 of the past 4 springs we’ve seen a low snowpack this time of year.  The snow water equivalent at this elevation on Mt. Hood is only about 1/2″ of the median for this date.  This Memorial Day weekend many mountain lakes are open for business…you might even beat the mosquitoes!  Gene Blick took this pic at Olallie Lake (5,000′) just today…pretty much snow-free except for some drifts still blocking the last section of the road.  They will be gone soon.


More good news…Skibowl, which was still operating for skiing only 4 weeks or so ago, is mainly free of snow and will have its Adventure Park (Alpine Slide!) open this coming weekend.  What a quick melt this year!  It looked like this from our camera at 5,000′ on Upper Bowl this afternoon:

Live Camera Skibowl Only 2017

Enjoy the warmest/sunniest day of the week Tuesday.  Highs should reach into the lower 80s west of the Cascades.

Chief Meteorologist Mark Nelsen