May 16, 2025
A 500mb shortwave trough moved across the Upper Midwest with height falls across the Quad State during the afternoon and evening of the 16th. The exit region of a strong (125kt) upper level jet was positioned across the area as well. Low-level winds strengthened during the afternoon to 50kts at 850mb. Following the early AM convection, ample sunshine allowed for a very unstable airmass to develop with CAPE of 3000-4000J/kg with deep layer shear of 65-70kts. Late afternoon, STP peaked at 9 near t
Source: NOAA National Weather Service Storm Events Database (event 1274290). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Massac County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.