Another serious multi-day threat is expected to begin today in the Southern Plains. This event, although positioned similarly to last week’s event, is somewhat different in terms of the threats it presents. Let’s discuss what to expect for today (Tuesday).
A deep trench currently traversing the southwestern desert will move east today, supporting superiors through days of inclement weather.
In front of this trench, moisture will begin to spill north into the Plains and Deep south from the Gulf of Mexico.
Dew points in the 50s/60s are likely to be as far north as southern Nebraska, setting the stage for some relatively weak destabilization.
The dry line west of TX/OK/KS will be sharp and move East throughout the day. The storm is expected to begin shooting out of this shallow area in the evening.
We can glean something about the expected atmosphere from this forecast sound.
- Humidity return can be quite slow until the overnight hours when the low-level jet ramps up. This leaves us with limited instability. We’ll need mechanical pressure from the dry road or cold front to get things moving.
- A strong limit reversal is expected to continue. Instability is limited, as mentioned above and will require extra force to break the limit. This greatly limits the possibility of forerunner development in warm open areas. Discrete mode is not favored.
- A layer of dry air exists in the middle layers. Strong winds will also be found in this layer, especially as the wind field strengthens during the overnight hours. As dry air sweeps in developing storms, these winds can mix with the surface. Harmful winds are believed to be the main threat.
- Cutting is expected to be more than enough. Although the linear mode is preferred over the discrete mode, supercells or spin-ups embedded in the stream can cause several tornadoes. Winds from SE can enhance rotation, supporting tornado development.
I mentioned that the linear mode is favored, however, there is an area that may present more risk for embedded supercells, albeit in the short term.
As the LLJ actually contracts over the overnight hours, a smaller amount of more abundant moisture is forecast near the north Texas/south Oklahoma border. This more favorable environment may allow storms to strengthen and thus a slightly higher risk of tornadoes.
About time: expect to start convection late afternoon or early evening.
It is expected that there will be rapid growth in luxury goods. Harmful winds are the main threat, although there may be hail and a few swinging areas in the path leading to a few tornadoes.
The line will continue to push eastward through the overnight hours but is expected to weaken somewhat in the early hours of the morning as any instability ahead of the line will lose stability overnight.
This is at least an event that takes place after partial darkness, so make sure there are ways to get alerts that will wake you up. Be prepared to execute your shelter plan, if needed.
While this stream appears weak in the early hours of Wednesday morning, it will enter an environment late in the day allowing it to present a fairly strong serious threat. Look for a blog that discusses Wednesday’s outlook late tonight or early tomorrow. Keep stable!