FNUS73 KLSX 201507 FWSLSX Spot Forecast for Grasshopper Hollow RX...Forest Service National Weather Service Saint Louis MO 1007 AM CDT Fri Mar 20 2026 Forecast is based on ignition time of 1000 CDT on March 20. If conditions become unrepresentative, contact the National Weather Service. .DISCUSSION... UPDATE: No major changes made to this forecast, as current trends are following the previous forecast closely. One slight change to the discussion below is that wind speeds near and behind the cold front are expected to be very light this evening and overnight, and we may not see a notable northerly push as a result. Instead, very light and variable winds are expected overnight, with terrain-driven downslope winds dominating. PREVIOUS DISCUSSION: Well above normal temperatures will continue today with RH values hitting their minimum in the low 20s this afternoon. Initially light southwesterly winds will become westerly and increase in speed to approximately 5-7 mph at 30 ft. There is only a 10% chance that winds will increase above 12 mph in the burn area, increasing confidence that elevated fire danger criteria will not be met. Mixing will reach above 1,000 ft between 11 AM and 12 PM today and continue to mix into the afternoon, reaching a maximum between 4,000-5,000 ft by 3-4 PM. Winds between 10-15 mph within the mixed layer this afternoon will promote smoke dispersion. A weak, dry cold front will move into the area this evening between 11 PM-1AM, 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. .REST OF TODAY... Sky/weather.........Sunny (0-5 percent). CWR.................0 percent. Chance of thunder...1 percent. Temperature.........66 at ignition...Max 87. RH..................55 percent at ignition...Min 21 percent. Eye level winds.....Winds southwest at 1 to 2 mph at ignition...otherwise Southwest winds around 2 to 4 mph with gusts to 5 mph. Wind (20 ft)........Winds southwest at 3 to 5 mph at ignition...otherwise Southwest winds around 4 to 8 mph with gusts to 11 mph. Mixing height.......1200 ft AGL at ignition...otherwise max 7100 ft AGL. Transport winds.....West 8 to 14 mph. Smoke dispersal.....Poor /2260 m/s-m/ at ignition. Max...good /12240 m/s-m/. TIME (CDT) 10 AM NOON 2 PM 4 PM 6 PM 8 PM Sky (%).........1 2 1 2 13 18 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............66 79 85 87 84 75 RH..............55 40 25 21 26 37 20 ft wind......W 3 SW 4 SW 5 SW 5 SW 4 SW 3 20 ft wind gust.12 9 9 11 9 7 Eye level wind..W 1 SW 2 SW 2 SW 2 SW 2 SW 1 Eye lvl wnd gst.6 4 4 5 4 3 Mix hgt (kft)...1.2 2.5 5.4 7.1 1.4 0.5 Transport wind..W 14 W 10 W 10 W 13 W 9 SW 8 Vrate kt-ft/1K..14 22 48 78 12 4 Ventrate Cat....POOR POOR FAIR GOOD POOR POOR .TONIGHT... Sky/weather.........Mostly clear (10-20 percent). CWR.................1 percent. Chance of thunder...4 percent. Temperature.........Min 55. RH..................Max 80 percent. Eye level winds.....Light, variable winds. Wind (20 ft)........Light, variable winds. Mixing height.......Min 400 ft AGL. Transport winds.....West 8 to 12 mph. Smoke dispersal.....Poor (490 m/s-m). .SATURDAY... Sky/weather.........Sunny (0-10 percent). CWR.................1 percent. Chance of thunder...4 percent. Temperature.........Max 88. RH..................Min 23 percent. Eye level winds.....Light winds becoming west around 1 to 3 mph early in the afternoon. Heavy terrain influence. Wind (20 ft)........Light winds becoming northwest around 3 to 6 mph early in the afternoon. Heavy terrain influence. Mixing height.......Max 8200 ft AGL. Transport winds.....Northwest 5 to 8 mph shifting to the west 7 to 9 mph. Smoke dispersal.....Poor (440 m/s-m) early in the morning increasing to good max (10260 m/s-m) in the afternoon. $$ Forecaster...19 Requested by...Chad Randolph Type of request...PRESCRIBED .TAG 2606655.1/LSX .DELDT 03/20/26 .FormatterVersion 2.0.0