Thunderstorm Outbreak This Weekend?
Happy Friday the 13th everyone! As you may have heard, one or two of the local media outlets have mentioned a good chance of seeing a widespread thunderstorm outbreak Saturday afternoon across the Portland / Vancouver area. I have taken a long hard look at both the WRF and NAM and unless something changes dramatically in the next 12-24 hours I see almost ZERO chance for any thunderstorms west of the Cascades this weekend. This mornings slate of models clearly shows an upper level low headed south along the coast today and tonight. What stands out nice and clear to me is a moist return flow around the low pressure center that will feed quite a bit of precipitation back over the metro area from about dusk Saturday night through most of Sunday. Rather than t-storms, I would get ready for more of our famous Pacific Northwest rain. Maybe it is the curse of Friday the 13th? However, for all of you thunderstorm lovers out there, fear not, storms will most likely pay us a visit at some point this spring or summer.
Below are two frames from the 12z run of the WRF and the 12z NAM from the U of W. These maps are what is referred to as C.A.P.E. or Convective Available Potential Energy outputs for Saturday afternoon and evening. This indicates the areas around the Pacific Northwest that are most likely to see instability and the best chances for t-storms. As you can see, there is not much C.A.P.E. on the west side of the Cascades. In fact, none! Eastern Oregon looks like the best location for t-storms Saturday afternoon. With the orientation of the off-shore trough, time of the year and strength of the daytime heating (more like lack thereof), I see no reason to argue with these model outputs. Bottome line — t-storms stay over the Cascades and points east on Saturday.
Have a great weekend! I recommend getting all of that outdoor work done Saturday morning, as Saturday evening and Sunday look wet, as does most of next week. After temperatures near 70 today and mid-60’s tomorrow (Saturday) it looks like we will once again fall below normal for a few days beginning Sunday. It would sure be nice to see some “real” spring weather around here at some point. I guess the wait continues!