Steep Lapse Rates
Wednesday, August 19, 2026 · 6:49 PM
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Slight risk level two out of five for severe storms tonight in the northwest. Damaging winds and heavy rain are the main concerns. There is a very low tornado and large hail threat as well. Scattered thunderstorms develop again Thursday afternoon and evening with a low severe weather threat for areas south of Interstate forty. Near normal temperatures are expected this weekend. Southern Missouri sends the shortwave down! Thirty to forty knots of effective bulk shear tearing through heat indices of one hundred five! The surface inversion is shallow, it cannot hold the night! After eight P.M. the atmosphere tears wide open! Moisture pooling across the draped boundary! Precipitable water values approaching two inches! Heavy downpours drowning the localized grid! It loses steam after midnight but the sky is already broken! Steep lapse rates! Steep lapse rates! Steep lapse rates! Steep lapse rates! Steep lapse rates! Steep lapse rates! Steep lapse rates! Steep lapse rates! STEEP LAPSE RATES! STEEP LAPSE RATES! STEEP LAPSE RATES! STEEP LAPSE RATES! STEEP LAPSE RATES! STEEP LAPSE RATES! STEEP LAPSE RATES! STEEP LAPSE RATES!
The forecast discussion
KEY MESSAGES
Updated at 641 PM CDT Wed Aug 19 2026
- Slight risk (level 2 out of 5) for severe storms tonight in the northwest.
Damaging winds and heavy rain are the main concerns.
There is a very low tornado and large hail threat as well.
- Scattered thunderstorms develop again Thursday afternoon and evening with a low severe weather threat for areas south of I-40.
- Near normal temperatures are expected this weekend.
SHORT TERM
(Rest of today through Thursday Night) Issued at 1121 AM CDT Wed Aug 19 2026
A slowly decaying complex of storms is trying to push into the area late this morning with the main consequence being some cloud cover for the western half of the area.
Some scattered storms may make it into the area through the early afternoon.
If you've been outside this morning, you may have noticed it is a little more humid.
Temperatures this afternoon will top out in the low to mid 90s with heat indices around 100-105 degrees.
The main focus of the forecast is tonight as storms are expected to develop ahead of a shortwave in southern Missouri this afternoon and push southeastward.
The environment ahead of that line will be characterized with steep mid level lapse rates and 30-40 kts of effective bulk shear.
In addition, there will be some low level curvature in the hodographs with a shallow surface inversion in place.
With that said, there is a Slight Risk (Level 2/5) for the northwestern part of the CWA.
Damaging winds are the main threat, but given the steep lapse rates and low level curvature, there is a very low threat for a tornado or large hail.
The timing for the severe threat will be after 8 PM through 2 AM. As the overnight hours progress, the storms will lose some of their steam but showers and storms will persist into Thursday morning.
The overnight wave will dissipate by midday but a surface front will be draped across the area.
Additional storms will develop late in the afternoon and evening as another shortwave swings through the mid level flow.
Moisture will pool across the front during the day on Thursday with PWAT values approaching 2" which will lead to some heavy downpours and possible localized flooding.
The shortwave will push the weak surface front through the area Thursday night.
LONG TERM
(Friday through next Wednesday) Issued at 1121 AM CDT Wed Aug 19 2026
The upper troughing will remain in place on Friday with another wave swinging through the flow.
This may spark some additional showers and storms on Friday mainly along the plateau.
Some slightly less humid air will move in behind Friday's wave with temperatures staying around normal through the weekend and into early next week.
Rain chances look very low for the weekend as well.
The upper high will push eastward toward the end of the weekend and into early next week which means temperatures will start to creep up toward mid next week.