PORTLAND, Ore. (KOIN) – A large area of low pressure is going to be our weather troublemaker Sunday night though Monday.
As the sun set for the first time this season at 4:52 p.m., our first weather punch arrived as pounding rain. Many neighborhoods encountered temporary street flooding after nearly a half-inch of rain fell in less than an hour.
More wet, turbulent weather is in our immediate forecast. Your best chances for severe thunderstorms Sunday night will be along the Oregon coast, coast range, and a small portion of the central Willamette Valley. Portland and the rest of the valley may encounter anything from punishing rain to thunderstorms producing hail and gusty winds.
This is the (SPC) Storm Prediction Center's convective outlook issued for Sunday. Notice the dark green area highlighting western Oregon with the letters MRGL. That means there's a marginal risk of severe thunderstorms in that dark green zone. The remaining light green area indicates general or non-severe thunderstorms.
All thunderstorms are capable of producing lightning, gusty winds and hail. Severe thunderstorms get their classification when hail, damaging wind or tornadoes are possible, even the smallest percentage, as is the case with the marginal risk.
'Marginal' doesn't mean the thunderstorm is no biggie. Marginal is used to describe the limited organization of storms, duration or very low coverage and marginal intensity. We see this classification in our forecast across the Pacific Northwest from time to time. It's no guarantee of a twister or Dorothy-type winds. However, there is a less than 5% chance these severe thunderstorms could produce a tornado. Nevertheless, when the SPC does put out a forecast for marginal risk thunderstorms we pay attention.
Timing the exact location of thunderstorms can be like walking into a crowded restaurant without reservations. You never know exactly when that table will clear.
Here's what you need to know: be ready for rumbles of thunder overnight anywhere in the Willamette Valley. If you're along the Oregon coast, be aware you are in the zone with an increased chance for severe thunderstorms.
Storms are building and moving onshore through early Monday morning. The chance of severe thunderstorms diminishes Monday, however, we all know that thunderstorms with damaging wind and/or EF-0 tornadoes can happen even when there is no green shade on the forecast map.
All the right ingredients are there for strong wind shear, thunderstorms, and generally disruptive weather overnight which could spill over into Monday.
Monday's weather will be most notable for the strong southerly winds. A wind advisory goes into effect Monday from 7am to 10pm for the Portland/Vancouver greater metro areas and Willamette Valley. Gusts could reach 40-45 mph. Downed tree limbs and power outages are possible.
Don't be a sitting duck. Be prepared for severe weather by staying aware of your surroundings. Do you have your phone charged? Are you set up to get weather text alerts from KOIN6 and the National Weather Service? Reach out to your local NWS office or follow the prompts here to ensure you're up to date with the latest news and weather.
