Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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416 FXUS63 KLSX 020345 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1045 PM CDT Sat Jun 1 2024 .KEY MESSAGES... - Showers and isolated thunderstorms will diminish by early this evening, with areas of fog possible overnight into early Sunday morning. - Unsettled weather returns late Sunday night and persists into midweek with nearly continuous chances for showers and thunderstorms, however no all day rains. Temperatures will largely be above normal during this period. - A pattern change will result in cooler temperatures, near to perhaps slightly below normal, during the later part of the week and into early next weekend. && .SHORT TERM... (Through Sunday Afternoon) Issued at 157 PM CDT Sat Jun 1 2024 The axis of the mid level trof and attendant surface trof were near the MS River early this afternoon. The best coverage of showers were along and to the east of them, with scattered showers back into the cyclonic flow west of the MS River. Despite SBCAPE of 750-1500+ J/KG centered in roughly the same region across far eastern MO and western IL we have yet to see any thunder, seemingly owing to the lack of more vigorous updrafts. The threat of showers and perhaps still a rumble of thunder will persist across eastern MO into western IL through the remainder of the afternoon into early evening, sliding east with time in concert with the advancement of the upper and surface trofs with activity dissipating in IL this evening with loss of heating. For the remainder of tonight we will see diminishing clouds across portions of central and eastern MO, while clouds should persist longer along and to the east of the MS River. The clearing clouds in the western CWA along with light winds and the recent rainfall seem like a pretty good recipe for fog overnight into Sunday morning. We will need to monitor this tonight as it`s certainly possible we could see some locally dense fog. Weak surface ridging will generally dominate on Sunday. After the dissipation of the morning fog, we should see cumuliform clouds and warmer temperatures that will be closer to normal. There is a small chance of showers and thunderstorms in central MO late in the afternoon associated with a weak impulse in the quasi-zonal flow and perhaps an old boundary originating in the Plains. Glass && .LONG TERM... (Sunday Night through Next Saturday) Issued at 157 PM CDT Sat Jun 1 2024 A more unsettled pattern will unfold late Sunday night and persist into midweek. Sunday night through Tuesday, a series of weak migratory short waves in the quasi-zonal flow will bring thunderstorm chances to the area. On Sunday night we actually could see precipitation in two ways: Scattered WAA LLJ driven showers and thunderstorms late across parts of eastern MO and western IL, and/or a decaying Plains MCS and associated boundary moving into the area late. This remnant boundary or re-energized MCS seems like it will be a catalyst for additional showers and thunderstorms on Monday and perhaps into Monday night, especially as the day progresses and it interacts with an increasingly unstable air mass. Otherwise a more prominent northern stream short wave trof that will be the impetus for a pattern change will bring a threat of showers and thunderstorms as it and the associated cold front traverse the region late Tuesday- Wednesday. While there are some timing differences in the cold front passage on Wednesday, present indications are the highest POPs will be centered on Tuesday afternoon and night. The deterministic and ensembles are coming into better agreement later next week and into next weekend with the ensuing pattern change and development of an upper low in the vicinity of the Great Lakes with a broad trof extending southeastward through the Middle Atlantic. As mentioned yesterday this will result in northwest flow across our area during the later half of next week and into early next weekend. The above normal temperatures for the Monday-Wednesday period will be replaced by near to perhaps slightly below normal temperatures Thursday-Saturday as a series of weak short waves in the northwest flow bring periodic surface trofs or weakly defined cold fronts through the region. There are a lack of strong signals for precipitation during this time frame but the flow regime suggests that it certainly can`t be ruled out. Glass && .AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1039 PM CDT Sat Jun 1 2024 Ample low-level moisture thanks to recent rainfall will allow for fog and low stratus development tonight and early Sunday morning. Locally dense fog is possible, but confidence on where this will occur relative to the local terminals is low. The low stratus is expected to move into the region from the east-northeast and impact KUIN, KSUS, KSTL, and KCPS. The latter three terminals are expected to be on the western edge of this stratus, so sudden changes from VFR to MVFR are possible during the early morning hours. IFR flight conditions are looking less likely at these three terminals compared to earlier. Any fog and/or stratus will dissipate later in the morning, with VFR flight conditions expected through the remainder of the TAF period. Elmore && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX