SPC day 1, May 22, 2010

I'm out of town so can't chase but if I were able to go, I would hit up somewhere in central South Dakota.

But curiously, on the 6Z issue SPC issued a 5% tornado risk extending into southern Manitoba.



Could this be real?

Moisture:



Okay, this isn't bad. 850 mb dewpoints in the teens. Juicy.

Shear:



40 to 50 knots. Sweet.

Instability:



Oops. Not even close. In fact, let's take a look at a prog sounding from farther south. This is from west of Grand Forks:



So there must be some fudging going on here, as the surface-based instability isn't forecast anywhere near the southern prairies. And as any meteorologist worth his salt will tell you, tornadoes ingest surface-based air parcels.

What's the fudging for? It looks like model variations is the reason. Check out this forecast for 00Z from the GEM-regional.



It has SBCAPE over 1000 J/kg over parts of southern Manitoba.

Anyhow, as of the 13Z update, SPC has decreased the risk extending into southern Manitoba.



And based on the surface plot, I have to agree:



Notice the good dewpoints (60+) are still down in Nebraska. Maybe another day and they'd make it but not this time, I don't think.

My virtual target: Pierre, SD. Today is an edge-of-the-cap play.

A note to chasers: Lake Oahe is a pain. Essentially you have to decide which side you're going to chase on, as the crossings are few and far between: Bismarck, ND, Mobridge, SD or Pierre, SD.