Weather Alert Day for afternoon chance of thunderstorms

UPDATE:

We're starting to see the juicy atmosphere fire off some thunderstorms. As of this update, they're down in Central Oregon, but for a huge chunk of territory we'll see unstable air pair up with today's peak daytime heating.

The area highlighted in the darker color is where there's a marginal chance of thunderstorms across NE Oregon and into Idaho. A slight chance of thunderstorms exists for a lot of Puget Sound down to the Portland Metro and Willamette Valley. The best time for these to start happening in our area is still between noon and 8p.

Our morning continues to be dry as forecasted, but the clouds are starting to start looking pretty tall around our cameras this morning. The puffy growing towering cumulus clouds indicate an atmosphere that has some lift and that lift will produce some on/off showers for this afternoon and evening. The first one went through yesterday and delivered a few isolated t-storms around Olympia yesterday afternoon and then overnight around Spokane. The second one is offshore and heading across our region today.  

So, few of these showers could blossom into small thunderstorms with small hail, brief downpours, gusty localized winds, and dangerous cloud to ground lightning. These also don’t have much upper air support so it is unlikely any of these t-storms will become officially NWS defined severe thunderstorms.  

It's all thanks to a dip in the jet stream called a trough and embedded in that flow we're seeing two smaller areas of circulation called shortwaves. Let's compare the imagery of the Monday water vapor satellite view (above) with the one today/Tuesday (below). I've highlighted the jet stream too so you can see how deep the trough was on Monday compared to today.  Notice how the trough isn't as deep today, that second shortwave will help pull the trough to the east to allow us to dry out and warm up quickly tomorrow. 

High temps similar to yesterday mid to upper 60s for most of us. But we’ll be much warmer soon. We should be out of the showers taper off completely by mid-morning on Wednesday and sunshine takes over the afternoon. We'll be significantly warmer as we wrap up spring and say hello to summer.  Normal is 71 for this part of late spring. 

Sunday is the Summer Solstice. The new season officially begins at 8:32p in our time zone. Solstice is latin for "sun standing" and the sun will arc through the same spot in our northern skies for several days and from the 18th to the 25th. Seattle has our longest days of the year during that time period. Give or take a few seconds-- each day is about 15 hours and 59 minutes long! -Tim Joyce

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