Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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069 FXUS63 KLSX 210906 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 406 AM CDT Sat Sep 21 2024 .KEY MESSAGES... -Several rounds of showers and thunderstorms are expected through Monday night will bring some beneficial rainfall to some areas. The best chance (70-90%) will be late tonight into Sunday morning. -There is the potential for some locally heavy rainfall late tonight into Monday. Isolated strong to severe storms are also possible over parts of central and southeast Missouri on Sunday afternoon and evening. && .SHORT TERM... (Through Late Sunday Afternoon) Issued at 405 AM CDT Sat Sep 21 2024 Latest radar mosaic was showing a complex of showers and thunderstorms over western Missouri on the nose of the low level jet early this morning. The latest runs of the CAMS continue to show that this complex will weaken as it moves east into the CWA early this morning as the LLJ veers and weakens. Have lowered PoPs to 40- 60% over southeast and central MO early this morning based on the recent trends. Chances for showers and thunderstorms the rest of the day into the evening will be dependent on developing along a warm front moving over the area or any residual outflow boundaries underneath an upper level ridge. Will keep chances in the 20-40% range for now. Better chance is still late tonight into Sunday as the axis of the aforementioned upper ridge will begin to shift to the east and an upper low currently over the southwestern CONUS will lift out and move into the Plains. Lift associated with an initial shortwave trough will move into the area late tonight at the same time that a cold front will move southeast out of Iowa. The increase in the low level jet will bring added moisture with PWATS around 2". Will continue with high PoPs (70-90%) late tonight into Sunday morning as the front will move slowly southeast as it will be aligned with southwesterly flow aloft. There may be an isolated strong to severe storms capable of producing damaging wind gusts on Sunday afternoon and evening ahead of the slow moving front. MLCAPES will be in the 1000-2000 J/kg range with deep layer shear range ahead of the front before it moves south of the area early on Sunday evening. Highs will be in the 80s to near 90 where the clouds can clear out. There will be a contrast in temperatures from north to south based on the front moving through with 70s in the north and 80s in the south. Britt && .LONG TERM... (Sunday Night through Friday) Issued at 405 AM CDT Sat Sep 21 2024 Will continue with the high PoPs Sunday night into Monday night (50- 80%) as all of the available guidance is showing one or two additional troughs moving through the area along with an attendant cold front, though with different timing and strength. The LREF does match these high PoPs, with some lower chances on Tuesday before going dry Tuesday night into Wednesday night as a surface high moves through the Midwest. Will continue with slight chances for showers at the end of the week as some of the guidance is showing an upper low over the central CONUS. Temperatures will be below normal to start next week, with Monday having highs in the 60s over northwest half of the CWA where there will clouds, rain, and CAA. Temperatures will gradually climb back to near normal Wednesday into Friday. Britt && .AVIATION... (For the 06z TAFs through 06z Saturday Night) Issued at 1043 PM CDT Fri Sep 20 2024 VFR conditions will continue through much of the overnight period with the focus shifting westward to eastern Kansas. A decaying complex of showers and thunderstorms continue to move east into western Missouri with broken/overcast mid to high clouds reaching as far east as the Mississippi River. The main question heading into Saturday morning will be how much of this complex survives as it approaches KCOU/KJEF/KUIN. The stalling surface front lifts northeastward with scattered showers and a few thunderstorms expected along the boundary. This northward shift is limited with precipitation generally expected to track northwest to southeast, also leaving in question just how far east activity makes it before total decay. Therefore, much of the prevailing groups maintained VCSH/SHRA mention with VCTS over central Missouri terminal and VCSH near metro terminals. While VFR is favored through much of the period, isolated and intermittent MVFR cigs/vsby cannot be entirely ruled out if a lingering thunderstorm directly impacts a terminal. There could be a lull Saturday late morning into the afternoon with isolated showers/thunderstorms. The better potential holds off until late in the period when a more vigorous shortwave support more widespread showers and thunderstorms late Saturday night into Sunday. Much of this lies in the tail end or beyond the period, which will be addressed in later updates. Maples && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX