Insider Blog: An active pattern returns this weekend

Strong storms are possible over the weekend and early next week as a warm and humid air mass pairs with an active pattern.

SETUP

Relatively flat west-to-east flow aloft will send small disturbances and short-wave troughs of low pressure near our region this weekend.

These are embedded in the upper-level jet stream, which is strongest to our north. If there's one limiting factor this weekend, it's that a northern jet stream may keep our overall wind shear relatively low with each event until a deeper dip in the jet stream drives higher storm chances by bringing a deeper trough and stronger wind support on Monday and Tuesday.

At the surface, and at the lower levels of the atmosphere, an area of low pressure will strengthen to our west, and draw warmth and moisture in from the Gulf from Friday through Monday.

In part, these upper-level disturbances will help maximize local lift and wind shear, while our lower-level flow from the south will supply moisture and instability. This flow includes our low-level jet, which aids in storm development and support. This field of winds from the south will intensify each evening, serving as a focus for lift and enhanced wind shear through the weekend.

TIMING

Our first chance for storms will likely come just after midnight Friday morning. Scattered showers and storms may drift into or develop in mid-Missouri, growing more widespread on the nose of our low-level jet early Friday morning. Weak instability and shear may be enough for isolated storms capable of wind and hail.

Storms should clear, leaving us mostly dry on Friday, before the same mechanisms drive another chance for storms Friday night. Dewpoints and temperatures will increase on Friday, driving higher instability across the region. With just enough shear to organize severe storms in the northwest, storms may support severe hail and damaging winds in the evening. Then, rain chances look to linger well into Saturday morning, moslty as showers and weak storms.

Similarly, on Saturday, another intensification of our low-level jet will drive more thunderstorms, with the greatest combination of ingredients for strong storms north of I-70 in the evening.

The warm front and low-level jet are forecast to lift north on Sunday, which should take the focus for storms north of our region, leaving us warmer and drier.

Overall, the weekend will have plenty of dry time between rounds of thunderstorms. Timing and exact placement of storms remain largely uncertain through the weekend.

An upper-level trough is expected to move near, driving better chances for strong storms on Monday and Tuesday.

IMPACTS

Hail and damaging winds are the primary impacts expected from storms on Friday. A low risk looks to come in the evening, after an even lower risk on Friday morning. Friday evening's threat may be mostly isolated and confined north of I-70 and west of Hwy 63. The rest of the weekend remains less certain, but storms may be strong to severe for some again on Saturday night, before the focus for storms shifts north on Sunday. The best chance for strong storms in our region will be on Monday and Tuesday, as the upper trough moves closer.

The weekend will also see near-record warmth alongside added humidity. Heat indexes in the low 90s are possible at some points, especially Saturday and Sunday.