While we won’t be without severe weather this week, we’re going to be quieter in a relative sense compared to what is coming. Most models are in agreement of a ‘Prime Time on the Plains’ pattern the week of June 10 -17 or so. But this week? Modest flow will keep the risks on the lower-end of the spectrum.
Pattern Evolution This Week
A lot of this upcoming week will be a week in transition from our highly amplified blocking pattern to a deep western U.S. trough encroaching on the middle of the country. This is a key moment for the atmosphere to set up what might be an epic pattern next week.
On Tuesday a cut off low will be coming onshore on the California coast with solid but not overwhelming flow ahead of it. The flow may make its way over the higher terrain in some areas of New Mexico and West Texas. This would bring just enough shear for a supercell off of the high terrain.
Most models shear this flow out through Thursday, but modest flow will likely exist Tue-Thu over the Southern and Central High Plains with storms forming off of the high terrain each day. There are some indications the dryline could mix east on Wednesday and further on Thursday. This would mean severe weather chances would shift east into the Panhandles and West Kansas.
Regardless, I’m expecting no more than slight risks each day through Thursday.
I pulled this sounding from Tuesday in Eastern New Mexico to show approximately what to expect. 0-6km shear of 20-25kt at best, with effective shear values in the same ballpark. Some reasonable 0-3km SRH values are in place a lot of days (113 m2/s2 in this case), with moderate instability. This type of environment likely results in outflow-dominant clusters, but it’s also an environment that could easily result in a supercell or two each day. This is especially true if you get a SSW moving supercell.
Our first look at convective coverage on Tuesday on CAMs reveals widespread storms expected to come off of the higher terrain in New Mexico, West Texas, and SE Colorado. There’s not a lot of UH being generated by CAMs at this range, but I suspect any supercells that exist will be pretty small and may not look that impressive on UH track maps at this range.
You’ll Notice A Change Next Weekend
I’m writing the following section with a couple of things in mind: 1)There is now broad model consensus of this pattern and 2)This doesn’t mean it can’t change.
Let me repeat that: while the opinions below are the result of broad model consensus at this point, that does not mean things won’t change as data quality improves.
With that said, this next weekend the pattern begins to shift markedly.
By Sunday, a deep upper trough will have come ashore over the Western U.S.
Seasonally strong flow will round its base and we’ll have begun what will be a multi-day severe weather setup that (as modeled now) rivals anything we’ve seen in June in the past two decades on the Central/Southern Plains.
The GFS did something very interesting this morning, splitting the flow into two pretty compact waves that eject over the Plains. From what I’m seeing, we will probably have a string of substantial severe weather risks that will be centered over the lower Plains from Nebraska to Texas from Sunday through Thursday.
Again, this could change, but as modeled right now by multiple models I am seeing more than one day that will generate significant to critical tornado risks over the Plains.
Stay tuned.
