Here we go again...the atmosphere looks like it will re-load and bring us another shot at severe storms. While we could see an isolated severe storm Monday night into Tuesday morning, there's a better chance for severe storms when a strong cold front plows into town late Tuesday.
The timing will be something I'll focus on in the forecast. Right now it looks like a Tuesday evening or Tuesday night event for St. Louis. But since there's more than 48 hours for the forecast models to change the timing, you'll want to check out our forecasts on News4, kmov.com and the KMOV smartphone app for updates.
Storm setup: A stalled front will exist west to east across the area Monday. Then , a low pressure center will move from Kansas to Northern Illinois Tuesday afternoon to evening and this will force strong southwest winds in the area. As a result the southwest flow will push higher humidity into our area and instability. You can see here that surface based CAPE values from 1500 to 3000. CAPE is "convective available potential energy", and it's one tool we use to see how much potential the atmosphere has for strong updrafts that result in severe storms. Generally values over 1500 indicate enough instability for severe weather, though other factors always come into play too.
Initially storms may be discrete when they rapidly develop late Tuesday afternoon or early evening West of St. Louis. But then the storms should come together in a broken line of storms that move into St. Louis Tuesday evening or overnight into Wednesday morning. Tornadoes will be included in the storm threat, as well as hail and damaging straight line winds.
The bottom line is that it's too soon to be confident about timing, but the ingredients are expected to come together for severe storms along a cold front that pushes through the area late Tuesday and includes the chance for tornadoes.