I’m still waiting on the 00Z NAM to come out, so I may make a brief update later tonight after I get a chance to go over that. For now I’m just working off of the 12Z and 18Z runs. I also skipped over Thursday’s threat for this forecast post. I want to wait until the NAM to pick up on it tomorrow before I start talking about the extent of any tornado threat. So for now, the focus is all on Tuesday’s setup.
A dryline will already be in place over the western plains Tuesday morning. The moisture gradient should tighten along the dryline through the afternoon (see afternoon dryline location drawn on the map above), with dewpoints in the mid 60’s expected ahead of the dryline in Kansas and Oklahoma. That’s a little better moisture quality then what it was looking like we may get a couple days ago. Telling when storms will fire is still a bit tricky this far out (it’s tricky even a couple hours before it happens to be honest lol), but my best guess is 4-5pm. It appears as if discrete storms will develop along most of the dryline from SW Oklahoma up into northern Kansas. The area of greatest interest for me though is going to be any storms developing along the corridor I boxed in green on the above map. I like this area for a couple reasons. One is that the area downstream of that area is where the best CAPE/shear overlay should be. Another reason is there may be a bit of a dryline bulge somewhere in that area/moisture gradient may be a bit tighter. This area has also been the most consistent in showing precip with the models for quite some time now.
The environment should be quite favorable for supercells with moderate instability and 45-50kts of deep layer shear. Storm motions will be northeasterly so discrete supercells should be the favored mode of convection so long as the dryline has a north-south orientation to it. The NAM has been wanting to put more of a NE-SW orientation to the dryline farther north in Kansas while keeping more of a N-S orientation farther south. The GFS keeps a N-S orientation. Either way, storms should get off the boundary just fine over the area I’m interested in. Low level shear doesn’t really pick up until around 7pm. Before 7pm conditions are only marginally favorable for tornadoes, but once shear ramps up around 7pm hodographs enlarge dramatically and will be quite supportive of tornadic supercells. There has been a VBV tendency to hodographs after 00Z with the models, which is a bit of a concern, but I’ll wait until tomorrow to get into that. Anyway, as it gets close to dark 0-1km SRH is forecast to be around 300 with 1km shear improving dramatically. As that happens, any discrete supercell tracking through the area I boxed in red on the map could pose a threat of strong tornadoes.
I need to call my mom for mothers day right now, so I’m going to leave it there for now, but I may update again here in a bit once I see the 00Z NAM. I still feel like this is an upper end enhanced risk or possibly a moderate risk over the area I boxed in red. I’d probably go 10% or 15% hatched on the tornado probability map, depending upon moisture quality and low level shear. Right now I’m planning on targeting a storm developing along the dryline somewhere between the Meade, KS and Pampa, TX area. I’ll probably target somewhere in the far eastern Oklahoma panhandle initially. I want to place downstream from where I think the storm I want will fire so that I don’t get my pants pulled down if something goes farther north. It’s easy to catch a storm coming at you, not so easy to catch one going away from you. Alright, gotta call mom so that’s it for now. If I don’t update again here in a couple hours check back tomorrow for update.