FNUS73 KLSX 201039 FWSLSX Spot Forecast for Weldon Spring NA burn...Missouri Department of Conservation National Weather Service Saint Louis MO 539 AM CDT Fri Mar 20 2026 Forecast is based on ignition time of 1200 CDT on March 20. If conditions become unrepresentative, contact the National Weather Service. .DISCUSSION... Well above normal temperatures will continue today with RH values hitting their minimum in the mid 20s this afternoon. Initially light southwesterly winds will become westerly and increase in speed to approximately 10-12 mph at 30 ft, resulting in elevated fire conditions within the burn area, promoting efficient spread. There is a 60-70% chance winds will gust intermittently into the upper teens to low 20s this afternoon. Mixing will reach above 1,000 ft around noon today and continue to mix into the afternoon, reaching a maximum between 4,000-5,000 ft by 3-4 PM. Winds between 10-25 mph within the mixed layer this afternoon will promote excellent some dispersion. A weak, dry cold front will move into the area this evening between 6-8PM, and winds will become northerly behind it. Cooling temperatures with sunset will cause RH to increase and the mixed layer to collapse, trapping any lingering smoke at the surface. **Please call the office to request a smoke dispersion model that starts from the burn and shows how the smoke plume will change over time under the forecast atmospheric conditions.** .REST OF TODAY... Sky/weather.........Sunny (15-25 percent). CWR.................0 percent. Chance of thunder...1 percent. Temperature.........77 at ignition...Max 85. RH..................40 percent at ignition...Min 27 percent. Eye level winds.....2-3, gusting to 6mph, using an adjustment factor of 0.3. Wind (20 ft)........Winds west at 8 mph at ignition...otherwise West winds 6 to 8 mph. Gusts up to 20 mph early in the afternoon. Mixing height.......2000 ft AGL at ignition...otherwise max 5000 ft AGL. Transport winds.....West 18 to 21 mph. Smoke dispersal.....Marginal /4950 m/s-m/ at ignition. Max...good /14230 m/s-m/. TIME (CDT) NOON 2 PM 4 PM 6 PM 8 PM 10 PM Sky (%).........11 17 21 30 33 34 Weather cov..... Weather type....NONE NONE NONE NONE NONE NONE Tstm cov........ CWR.............0 0 0 0 0 0 Chc of thdr (%).0 0 0 0 0 0 Temp............77 84 85 82 72 67 RH..............40 30 27 32 44 54 20 ft wind......W 8 W 8 W 8 NW 6 N 3 N 2 20 ft wind gust.16 16 16 12 9 7 Eye level wind..W 4 W 4 W 4 NW 3 N 1 N 1 Eye lvl wnd gst.7 7 7 6 4 3 Mix hgt (kft)...2.0 3.8 5.0 1.1 0.4 0.4 Transport wind..W 18 W 21 W 21 NW 13 N 10 N 8 Vrate kt-ft/1K..32 68 91 12 4 3 Ventrate Cat....POOR GOOD GOOD POOR POOR POOR .TONIGHT... Sky/weather.........Partly cloudy (20-30 percent) then becoming mostly clear (5-15 percent). CWR.................1 percent. Chance of thunder...3 percent. Temperature.........Min 49. RH..................Max 93 percent. Eye level winds.....1-2 mph using an adjustment factor of 0.3. Wind (20 ft)........Northwest winds around 6 mph early in the evening becoming light. Mixing height.......Min 300 ft AGL. Transport winds.....North 9 to 13 mph shifting to the east 7 to 8 mph overnight. Smoke dispersal.....Poor (310 m/s-m). .SATURDAY... Sky/weather.........Sunny (5-15 percent). CWR.................1 percent. Chance of thunder...3 percent. Temperature.........Max 82. RH..................Min 34 percent. Eye level winds.....Light winds. Wind (20 ft)........Light winds. Mixing height.......Max 4100 ft AGL. Transport winds.....Southeast 7 to 8 mph shifting to the west 5 to 10 mph in the afternoon. Smoke dispersal.....Poor (310 m/s-m) early in the morning increasing to marginal max (5750 m/s-m) in the afternoon. $$ Forecaster...Delia Requested by...Raenhard Wesselschmidt Type of request...PRESCRIBED .TAG 2606563.0/LSX .DELDT 03/20/26 .FormatterVersion 2.0.0