Keeping an eye on thunderstorm potential Tuesday afternoon

Weather

PORTLAND, Ore. (KOIN) – A crack of thunder and a downpour may be in the forecast Tuesday afternoon.

Instability is to set grow after lunch, and if we have enough sun breaks this afternoon, we may have a thunderstorm develop around Portland.

Before we get to the afternoon, the morning clouds are keeping conditions mostly stable west of the Cascades. Thunderstorms have developed in central and eastern Oregon and we haven’t even hit the peak heating hours of the day. Those storms will slowly move to the north and northeast during the life cycle of the storm and will burst with downpours and lightning, which may also be the case for the valley heading into the afternoon.

THUNDERSTORM POTENTIAL ZONE

The Storm Prediction Center (SPC) has placed the Willamette Valley in a thunderstorm risk today, with a marginal risk for counties of Umatilla and Union (surrounding areas in darker green shade). This is the main area of focus on Tuesday, although a stray storm may develop outside of this zone of concern. The delineation isn’t going to be as strict as the graphic is implying, meaning, just because you may be right outside the shade of green, it doesn’t mean you’re completely out of the risk today.

TIMING & GENERAL LOCATION

Weather models are pointing at a northern Willamette Valley spread of storms this afternoon. The timing has been around 2 p.m. to 5 p.m., with the ability for a few more isolated t-storms into the evening hours into counties of Clark and Cowlitz counties. Notice that there are some massive cells forming over the high terrain of the mountains in the aforementioned marginal risk zone above. However, storms may generate through mid-day for central Oregon. Areas of Deschutes, Jefferson and Wasco counties (and east), may be dealing with storm development through the day until the sun sets.

Just to reiterate, we will be watching for the potential of strong storms, bringing downpours, hail, gusty windy and lightning in the afternoon for the Greater Portland Metro Area. In scenarios like this, storms form from the coast range and carry over into the western areas of the Willamette Valley first. There tends to be a redevelopment of storms around the west hills, which may drag those storms over the city and into Clark county. I wouldn’t be surprised if we have some small hail around the Bethany area or through the west hills today. Communities riding northwest off of US30, will also be a target for storms this afternoon. Be prepared for moments of heavy rain and small hail.

Here is another weather model coming from the KOIN 6 Weather graphics, which shows a similar scene to the model generated above. We will keep an eye out for you this afternoon as we tap into the radar and post on social media.

This final graphic is a depiction of instability in the atmosphere. That large area of purple and pink, is letting us know that we have the ability for rising air and storm development. When you factor that in to all the other ingredients that we have in place, like the colder air aloft and the strength of the wind for eastern Oregon, we are keeping an eye out for the development of storms. This is all part of the weather story today.

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