081 FXUS63 KLSX 140454 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1154 PM CDT Sun Apr 13 2025 .KEY MESSAGES... - A cold front passing tonight/early Monday will bring a slight chance (15 - 20%) of showers to areas mainly north of I-70 (MO)/I-64 (IL) tomorrow morning. Highs in the 60s are forecast for Monday and Tuesday as cooler air filters in behind the front. - There is a potential of elevated fire danger in northeast Missouri and west-central Illinois on Tuesday. - There is a chance (30 - 60%) of showers and thunderstorms beginning late Wednesday and lasting through the weekend. The highest probability of rain is focused on Wednesday night into Thursday morning. && .SHORT TERM... (Through Late Monday Night) Issued at 206 PM CDT Sun Apr 13 2025 Marginal elevated fire conditions have been observed in portions of central and northeast Missouri this afternoon due to gusty winds, warm temperatures, and under-performing dewpoints. These areas are more susceptible to fire danger than the greener, more rain soaked Ozarks. Although humidity is marginal, those burning today should still use caution due to the gusty winds. Elevated fire danger conditions are expected to continue through the rest of the afternoon. Today`s gusty winds will come to an end tonight as a cold front passes through the area. Dry conditions are expected along the front, but mid-level frontogenesis behind the front is expected to provide enough support for isolated showers late tonight through tomorrow morning despite the dry air the rain will be falling into. Otherwise, the front will usher in cooler air with highs on Monday peaking in the 60s for all but the far southern CWA. Jaja && .LONG TERM... (Tuesday through Next Sunday) Issued at 206 PM CDT Sun Apr 13 2025 Elevated fire danger is possible in northeast Missouri and west- central Illinois Tuesday afternoon. Despite highs in the 60s, the dry airmass in place is expected to tank relative humidity values, allowing them to reach criteria. Additionally, fuel moisture in these areas is much lower and more conducive for fire danger than in the Ozarks due to less antecedent rain and less greenup having occurred. If temperatures are cooler or the airmass is more moist than expected, elevated fire danger may not be realized. An active pattern will establish itself on Wednesday and last through the end of the week. A surface low pressure system will develop in the High Plains in response to a passing shortwave. Our first and currently highest potential for showers and thunderstorms will occur late Wednesday into Thursday morning as the low`s warm front pushes northeast over the CWA. Ensembles and the NBM remain consistent in a 50 to 60% chance of precipitation during this timeframe. Since most locations will be within the warm sector for most of the day Thursday, temperatures will be allowed to climb back into the 70s for most. The exception to this will be locations in Illinois that either remain on the cool side of the front or enter the warm sector too late in the day to warm up. These locations will likely not reach 70 degrees. The potential for strong to severe thunderstorms increases on Friday ahead of the system`s cold front. LREF MUCAPE and bulk shear values in the neighborhood of 1500 J/kg and 50 kts are more than sufficient for the production of severe thunderstorms. However, this solution represents the cold front nearly bisecting the CWA at 7pm on Friday. Deterministic guidance still varies with respect to frontal timing, which will impact the amount of daytime instability we are able to gain before the frontal passage or the amount of daytime instability we lose before it. These parameters also don`t consider the orientation of the front and shear vectors. The front appears to have a more horizontal component than vertical with bulk shear vectors parallel to the front. This would result in a line of thunderstorms along the front with cells interacting with one another as it pushes southeast. This isn`t favorable for severe thunderstorm development and maintenance. With that said, there is still plenty of time for these details to change for the better or worse. In short, the potential for severe weather on Friday is present, but uncertainty is high. The potential for showers and thunderstorms will continue into the weekend as the cold front stalls just south of the CWA and interacts with passing vorticity lobes. Jaja && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1151 PM CDT Sun Apr 13 2025 VFR flight conditions will persist through the end of the TAF period. Scattered high clouds will stream across the region during the first few hours of the TAF period, becoming more broken as a cold front approaches the region between 06-09Z. The cold front will pass largely dry, though there is a 15-20% chance for showers through the day. Winds will become northwesterly and gusty (around 20-25 kts) behind the front and remain so through the end of the period. Delia && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX