A new week, a new serious threat. However, unlike previous weeks, where the focus was on the southeast, this threat will persist over the central US for several days before a strong cold front pushes it further east.
Today’s threat is not quite as widespread or as strong as tomorrow’s expected. However, when convection begins to occur, conditions will somewhat support significant weather extremes.
Before we go any further, I will share an explanation for limiting the inverses. Caps will play a role in this week’s inclement weather, especially tomorrow. So for those who don’t know:
Hopefully my homemade pictures help you visualize the process.
Limit inversion occurs when there is a layer of warmer air overhead. Warm air rises from the surface and undergoes condensation – at least if moisture is present.
This ascending air eventually hits the limit inversion, which is warmer than the ascending air. Air cannot enter another layer of air warmer than it, so it is forced to sink. This process continues until there is enough instability or a lifting mechanism (such as a cold front) appears to force air through the lid. Additionally, the air underneath the lid can warm to a greater temperature than the air overhead and the lid will disappear. Either way, deep convection is possible now.
In situations where there is not enough added stability or no forcing mechanism, the cap stays in place and no deep convection occurs.
Limit reversals will play a role in setting today’s extreme weather.
The focus of today’s event is across the Mid-South – from northeastern Texas to as far south as Illinois. A cold front sinking southeast this morning will return north as a warm front this afternoon/evening as a much stronger system begins to form west of it.
While there is cap inversion this morning, the cap section is expected to slowly erode as moisture is introduced from the south throughout the day. However, it is expected that there is still enough cap to centrally classify storms, allowing discrete cells to form instead of a large, multicellular mess.
The usual disclaimers apply to this audio: It’s GFS and therefore has a lower resolution – but we can still collect information about the state of the atmosphere.
- The very high average lapse rate will not only allow for increased strength of any storm forming, but also the threat of large hail.
- Good shear force (both speed and direction) is sufficient to organize and sustain the supercells as well as the tornado threat.
- The mild dry upper layer with ~35 kts winds within it is sufficient to translate into a damaging wind threat to some species, particularly if high-grade growth occurs later in the event.
- There is enough limitation to only allow more powerful updates to pass through. This leads to a discrete mode rather than multicellular or linear.
As far as time goes:
Storms are forecast to start forming in the late afternoon and early evening.
Flow boundaries from morning showers and storms will be key here. They can help provide a little extra impetus to get things going where they used to lie.
Since this event is a late-start event and will continue into the evening hours, make sure there are multiple ways to receive alerts, including at least one that will wake you up. Be prepared to enact your shelter plan if you need to do so.
Severe weather threats continue into Tuesday, but we’ll look at that in tomorrow’s blog.