Ridge riders tonight?

It's coming to the season where once in a while we can get overnight thunderstorms. Not necessarily severe, and not necessarily exciting but a yearly occurrence nonetheless. They sometimes get called ridge riders because they tend to occur on the edge of the cap, usually overtop the 500 mb ridge.



I look at both the GEM-REG and NAM output and both hint at thunderstorms overnight or tomorrow morning. So will they happen?

Well, moisture is kind of there: not great but good. Dewpoints in the mid teens.

As a result of that, instability will be there. Again, not great but good.

Lift? Well, there seems to be a diffuse front draped near the international border.

Shear? Actually, not too bad. 30 knots west at 500 mb and 10 knots east at the surface.

So what is missing? Well, the LLJ is nothing if not unimpressive. I'm talking 10 knots here, and it is forecast to increase to 20 knots. Woo.

And with the unstable air parcels originating in a southerly flow instead of an easterly one, I think the deep bulk shear will be on the order of 25 to 30 knots.

So what do I think will happen tonight? Scattered organized multicells with pea-sized hail and rainfalls up to 25 mm. Nothing huge.

What do you think?