Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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797 FXUS63 KLSX 270527 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1227 AM CDT Mon May 27 2024 .KEY MESSAGES... -Significant severe thunderstorms are likely through this evening, along and south of I-70. The main threats are very large hail (2"+), damaging winds (70-80+ mph), and strong tornadoes (EF2 or higher). -Locally heavy rainfall, up to 2-5 inches, is possible with this round of storms. -Dry and mild weather expected through the work week with temperatures near normal. && .SHORT TERM... (Through Late Monday Night) Issued at 316 PM CDT Sun May 26 2024 Latest visible satellite and radar imagery indicates that a cu field is developing between I-70 and I-44, as well as scattered storms as of 20z. In the meantime, strong heating is occurring in this area with steep LR (8-8.5C/km), MU CAPEs 2000-3000 J/kg, as well as decent deep layer shear (50-60kts). So thunderstorms will continue to develop in this area within the strongly sheared environment. Supercells will be the dominant convective mode then transition to a more linear structure as the activity exits the forecast area later this evening. There is a risk for all severe hazards including very large hail (2"+), damaging winds (70-80+ mph) and strong tornadoes (EF2 or higher), especially along and south of I-70. Otherwise, there is still the possibility of locally heavy rainfall as the storms move through. With west-east shear parallel to the outflow boundary, could see training storms through this evening. The latest HREF probability matched mean indicates the potential for rainfall up to 2" over a 3 hour period. Areas that have already seen modest rainfall in the past two days will be at higher risk for flash flooding. So the Flood Watch remains in effect until 06z Monday. Surface ridge will build in behind the cold front late tonight with dry and pleasant weather returning on Monday. Lows tonight will be in the mid 50s to low 60s. In the meantime, a secondary shortwave will rotate around the system and sink southeast through the forecast area during the day on Monday. Will see increasing cu field, but the best chances for showers will be just north of the forecast area. Highs will be in the upper 70s to mid 80s. Byrd && .LONG TERM... (Tuesday through Next Sunday) Issued at 316 PM CDT Sun May 26 2024 Upper level ridge will build over the western CONUS while troughing lingers over the eastern half. Therefore the forecast area will be in northwest flow aloft with temperatures a bit below normal through the end of the work week. Otherwise, the pattern begins to change late in the work week with chances of rain returning by next weekend. Byrd && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1218 AM CDT Mon May 27 2024 By and large convection has ended across the region, and the remainder of the TAF period is expected to be dry. A largely sky and recent rainfall increases the potential for patchy fog tonight, particularly in the valleys and river bottoms where winds will be more sheltered. However, given the lingering cloud cover still around, I don`t yet have enough confidence to include a mention of visibility reduction at any of the TAF sites just yet. If fog does develop it will clear by 12-13Z with sunrise. Winds will remain from the northwest through the period, becoming strong (sustained winds above 10 kts) and gusty (near 20 kts) during the afternoon hours tomorrow. MRM && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX