In theory, everything appears to be nicely setup for a thunderstorms in the next 7-8 hours over the lowlands of northwest Oregon and maybe extreme SW Washington too. That’s the theory based on an unstable atmosphere, increasing moisture overhead (precipitable water) and warm temps. Upper level winds are light from the east, so we’re already getting a slow drift of showers developing over the Cascades and moving westward. You can see that in the radar imagery here. It helps that we are getting full sunshine in the valleys as you can see on the 1pm visible satellite image:
which should eventually get us into the mid 70s. We don’t have offshore flow which is often helpful in these situations to push us to 80 or so. I would have liked to see a nice thermal trough over the western valleys.
Now numerical weather prediction models don’t handle very small details well, like whether you get a thunderstorm but your friend that lives 5 miles down the road doesn’t get one. But, they do give us general ideas of where convection will be and right now they sure don’t like developing much action from the metro area northward. Here is the total precipitation through 9pm this evening from the 18z (11am) RPM model:
and the latest HRRR:
Not real encouraging eh? The 12z (6 hours earlier) RPM model had shown a few good thunderstorms from Portland to Salem, but now they appear weaker on the current run.
So here’s the big picture as of 1:30pm…
- Thunderstorms are beginning to pop over the Cascades
- A few will drift into the Cascade foothills the next few hours (Sandy, Estacada, Mill City, Sweet Home etc…)
- A few may also pop up around maximum heating time (4pm-7pm) in the lowest elevations, that includes the entire I-5 corridor.
- But the chance appears to be relatively small that any one location in the Salem, Portland/Vancouver, Longview metro areas get a storm
- Best chance is south of the Portland metro area in the lowlands
- Of course I could be wrong, but this doesn’t appear to be a great setup where we get widespread storms all over the lowlands.
Keep an eye on the radar! Movement will be very slow with these storms so if you get one you could really get soaked! I’m hoping for that at home for my garden because we sure don’t see much rain in the next week or so.
Chief Meteorologist Mark Nelsen