Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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597 FXUS63 KLSX 260745 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 245 AM CDT Wed Jun 26 2024 .KEY MESSAGES... - Thunderstorms this morning will exit off to the southeast early in the day, giving way to a much nicer day with cooler temperatures than we`ve seen in a while. - The heat returns this weekend, but not as intense. Heat index values around 100 are expected on Saturday. We`ll also have more opportunities for thunderstorms Friday and Saturday ahead of the next front. && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 245 AM CDT Wed Jun 26 2024 Multiple convective complexes pushing south this morning have made it pretty hard to identify where the surface cold front is, but we will be seeing a change in air mass today as cooler and drier air moves in. The morning thunderstorms should exit to the southeast fairly early in the day, although some of the CAMS do keep some showers lingering into the afternoon. This just reinforces the idea that it will be significantly cooler today, especially if the clouds and showers linger into the afternoon. Temperatures tonight drop well into the 60s as the surface high pressure axis approaches. We`ll see the temperature warm a few degrees on Thursday with more sun, but still at or a little below normal for this time of year, mostly in the mid 80s. Kimble && .LONG TERM... (Thursday Night through Tuesday) Issued at 245 AM CDT Wed Jun 26 2024 Ridging over the western US moves east and flattens as it does so. So while we will see another warm up, it shouldn`t be as intense as our last heat episode. Friday and Saturday warm back into the 90s with increasing humidity as well. Heat index values over 100 are most likely on Saturday. Troughing moving onshore in the Pacific Northwest today will continue to push slowly eastward near the US/Canada border through the weekend. We`ll see a surface front developing out in the Plains and pushing southeast through our area as the upper trough axis moves into the Great Lakes on Saturday. Ahead of the front, multiple rounds of thunderstorms are possible beginning on Friday. Much of the lift stays north of our area on Friday, but the northern part of Missouri into western Illinois may be close enough to get in on some thunderstorms. The better lift moves through on Saturday ahead of the cold front with more widespread thunderstorms possible. With a southerly low level flow and a modest westerly flow aloft, there`s just enough shear available for some storm organization, so we`ll have to keep an eye on the potential for strong to severe storms both days, especially as heat and humidity peak leading to a peak in instability as well. A progressive upper pattern continues with a shift toward cooler temperatures behind Saturday`s trough, but warming back up again next week as ridging moves in to replace it. How hot we get will depend on how well established the ridge becomes over our area and whether we are affected by daily thunderstorms on the northern periphery of the ridge. Kimble && .AVIATION... (For the 06z TAFs through 06z Wednesday Night) Issued at 1221 AM CDT Wed Jun 26 2024 Main concern for the TAF forecast is timing of thunderstorms at each location. Confidence has grown relative to prior forecasts that the final round of storms will be moving through overnight. The best instability, and most confidence for thunderstorms, is in central Missouri, but most of the area will see rain and some embedded thunder. Winds are variable as downdrafts are coming from many directions with all the convection around, but the general trend will be toward northerly winds by morning. There`s a low chance we could develop some MVFR ceilings behind the main line of convection, but so far this has not materialized and confidence has decreased in it occurring. We should see a trend toward VFR clearing during the day Wednesday. Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX