The pattern seems to be continuing with the mild overnight temperatures before transitioning to hot afternoon temperatures. Today is set up almost exactly like yesterday, and the day before. However, there is one key difference. A low pressure system sitting off the coast of Northern California is pushing in moisture out of the south. There is also a lot of heat being pushed in as well. Add on to that some instability, and we get thunderstorms. Light and isolated showers started the morning off in Northern California. The first lightning strikes occurred around 6:30 a.m. showing that there is enough moisture content in the air to fire up some lightning.
We started out the morning with clear skies inland and a marine influence at the coast. Visibilities at coastal locations were down to as little as a mile throughout the early morning. As the sun heats up the surface, the fog will lift and mostly cloudy skies will remain through today. Cloud coverage has already started to increase in Douglas County, and looking at the visible satellite imagery cirrus are already moving in as far north as Salem. Cumulus will build as the air heats up and eventually, updrafts will be strong enough to produce some cumulonimbus. The bulk of the thunderstorm activity will be in the Basin, Cascades and Central Oregon. However, there seems to be enough instability to bring some storms into the valley as well.
A RED FLAG WARNING is in effect for the Umpqua Basin until 6 p.m. Friday. Between now and then, abundant lightning and dry fuels have the ability to spark new wildfires. Winds picking up in the afternoons can also spread any new ignitions.
Saturday will remain mostly dry, with the exception being the Cascades. Low pressure will continue to send impulses into the region and another wave on Sunday will bring an elevated chance for thunderstorms in all regions (excluding the coast) again. If you plan to head out to the Oregon County Fair, bring plenty of water, as it will be hot! After Sunday, high pressure will, once again, back-build into our region and dry us out. This will also bring in air from the desert southwest allowing for temperatures to get well above averages. Roseburg, and surrounding areas could reach the triple digits by Tuesday.
Thanks for logging on, and stay cool out there!
Meteorologist Seth Phillips