Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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680 FXUS63 KLSX 201740 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1240 PM CDT Fri Sep 20 2024 .KEY MESSAGES... -Scattered showers and thunderstorms (20 to 30% chance) are possible through this evening. An isolated strong to severe storm over southeast Missouri and southwest Missouri is possible this afternoon and this evening. -Several rounds of showers and thunderstorms (50-90% chance) and locally heavy rainfall are expected between Saturday and Monday night, with the best chance north I-70 between Saturday night and Monday morning. Isolated strong to possibly severe storms and locally will be possible on Sunday. -Temperatures are expected to be above normal through tomorrow, but then back to near normal starting on Monday. && .SHORT TERM... (Through Late Saturday Afternoon) Issued at 405 AM CDT Fri Sep 20 2024 The latest surface analysis is showing a front extending from central Iowa through northwest Missouri into northwest Oklahoma. Thunderstorms that had earlier developed across Iowa have shown a gradual weakening trend as they have moved southeast into less instability early this morning. I have continued with lows PoPs (20- 30%) through today as the front will continue to move east across the CWA including early this morning when convergence increases on the nose of the low level jet. Chances will continue this afternoon into this evening over southwest Illinois into southeast Missouri when MLCAPES are expected to climb into the 2000-3000 J/kg range with deep layer shear up to 30 knots. This would support one or two strong to severe storms capable of producing downburst and perhaps some large hail. There will be a better chance (40-70%) on Saturday morning when showers and thunderstorms develop along a warm front that will move through the area during the day. Both the NAM/GFS are showing a 35 knot low level jet developing over the Plains late Friday night that will bring the best chance for showers and thunderstorms into central Missouri on Saturday morning. High today will once again be around 90 degrees with 850mb temperatures around 20C and sufficient sunshine. Highs tomorrow will be mainly 80s and with the coolest reading where there be the most clouds and rain. Britt && .LONG TERM... (Saturday Night through Thursday) Issued at 405 AM CDT Fri Sep 20 2024 The unsettled weather pattern will continue into early next week as the medium range models are showing the upper ridge that has been over the central CONUS shifting to the east and the low in the Southwest lifting out and moving across the Midwest. The highest PoPS (70-90%) will be Saturday night into Sunday when a initial shortwave trough will move out across the area as cold front moves back southeast across the area. There will be a few strong to possibly severe storms given CAPE/shear parameter space and some locally heavy rainfall is also possible as PWATS will be near 2". There will also be likely PoPs (60-70%) going Sunday night into Monday night as the main upper trough and attendant cold front moves across the area. Chances for rain the rest of the week are low as the LREF is showing a large area of high pressure moving across the area with most members (<15%) not producing any precipitation after Monday night. Temperatures will fall back closer to normal behind the cold front beginning on Sunday and staying there most of next week. Britt && .AVIATION... (For the 18z TAFs through 18z Saturday Afternoon) Issued at 1240 PM CDT Fri Sep 20 2024 The largest changes to the TAFs this issuance are the removal of thunderstorms at the St. Louis metro terminals this afternoon and the addition of rain at all terminals tomorrow morning. This afternoon`s/evening`s thunderstorm potential has fallen, and any thunderstorms that do develop are expected to remain further south and east than previously forecast. Showers will ramp up overnight, with the Mid-Missouri terminals having the highest likelihood at seeing precipitation. Elsewhere confidence decreases in whether a terminal will see rain and when exactly it will occur. Therefore, the 4 hour VCSH window is a best estimate. Rain may start sooner and/or end later, but rain will not be falling during the entire duration. Otherwise, winds will be variable during most of the TAF period as a cold front sinks south today and buckles back northward overnight and into tomorrow. Jaja && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX