82 in Portland Today: Possible Thunder Tomorrow Evening

May 3, 2017

10pm Wednesday

What a day!  Temperatures reached into the lower 80s today with our first real taste of late spring/early summer weather.  PDX officially hit 82, the warmest day since late September

It appears that Medford was the warmest spot in Oregon (of the official METAR sites) with a high of 90 degrees

We did this with a relatively humid atmosphere, morning clouds in the valleys, and very little offshore flow.  You can see how we could be close to 90 in this pattern with dry offshore flow.  That happened on this date in 1992.  We hit 89 on that day and the following one.  I remember that hot weather spell; my first spring living in Portland and sitting on a very sweaty MAX train coming home from a downtown job.

The warm weather means we hit our first 70 AND first 80 degree day together, which hasn’t happened in the past in Portland.  Here are a few other weather facts for you:

Tomorrow we start sunny except in the southern Willamette Valley where some low clouds might come in off the Pacific Ocean.  Then things get interesting in the afternoon.  Models have consistently been showing convection breaking out over the Cascades & Coast Range, then popping up over the valleys too.  Each model is slightly different, but they ALL show very low lifted indexes, abundant CAPE, and precipitable water values well above 1″.  This means we have a POSSIBILITY of seeing a strong thunderstorm anywhere from the Coast Range to the Cascades, but not everyone will see one.  They are always tough to forecast.  The evening WRF-GFS and our RPM imply most of the action stays near/over the Cascades in the south-southwest flow aloft.  I’m not sold on that, but I also don’t see a setup like the June 4th, 2009 event which brought damaging wind to the metro area from a line of thunderstorms.  That event was the last time we saw a Severe Thunderstorm Watch west of the Cascades.


Yes, that’s 8 years back.  We don’t get damaging thunderstorms west of the mountains very often!  In early August 2014 severe storms developed over the North Cascades and north-central Oregon, but a watch only extended up to the Cascade crest as you can see on this image:


For now SPC has part of our area under a MARGINAL threat for severe thunderstorms tomorrow:

Beyond tomorrow evening/night, we’ve got a cold front coming through Friday morning followed by light showers the rest of the day and Saturday today.  Sunday through Tuesday looks pretty nice with typical May clouds and sun mixed.  Note the ECMWF ensemble precipitation product shows little/no rain from Saturday through early next Wednesday.  This is quite an improvement over last week!

We’ll be watching the radar and trends closely tomorrow and I’ll keep you updated.  Don’t forget to follow us on Twitter and Like us on Facebook.  I update info more frequently there.  You see those posts over to the right.

Chief Meteorologist Mark Nelsen