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Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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284 FXUS63 KLSX 080350 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1050 PM CDT Sun Jul 7 2024 .UPDATE... Issued at 840 PM CDT Sun Jul 7 2024 The threat for strong thunderstorms this afternoon has largely ended as outflow has raced well out ahead of the thunderstorms, and even the newer updrafts are starting off elevated and behind the gust front. That gust front is moving through the St Louis area as of 830PM. We still expect some showers and thunderstorms overnight as the low level jet picks up, but coverage is expected to decrease over the next few hours and may be relatively sparse overnight as well. There should be a lull Monday morning before renewed thunderstorms develop Monday afternoon, this time more likely in the central and southeast portions of the forecast area. We`ve made some updates to try to show the hourly progression of precipitation chances, but we really can`t rule out some activity showing up on our radar anytime during the next 48-60 hours or so. The best threat window for strong to severe storms (marginal risk) is Monday afternoon, and the best threat for flooding (slight risk) is on Tuesday. Kimble && .KEY MESSAGES... - Scattered to numerous showers and thunderstorms will impact the area, expanding eastward across the CWA tonight through Monday. - An isolated strong-severe storm is possible into early evening across parts of northeast Missouri and west-central Illinois, and across southeast Missouri and southern Illinois on Monday afternoon. - The remnant circulation of Tropical Cyclone Beryl is expected to track across southeast Missouri and southern Illinois on Tuesday and Tuesday evening. There remains some uncertainty in the exact track, but a swath of heavy rain from 2-4 inches will likely accompany the track which could pose flooding concerns. && .SHORT TERM... (Through Monday Afternoon) Issued at 238 PM CDT Sun Jul 7 2024 A series of vort maxes across western MO along with a weak boundary in western MO have already lead to the development of showers and thunderstorms from northeast through west-central MO this afternoon. There is some pretty decent instability ahead of the storms into northeast MO and this along with effective shear of 25-30 kts could result in a few strong to severe storms into early evening with one inch hail and damaging winds the main threat. Otherwise these vorticity maxima along with an increasing southwesterly LLJ and the advancing boundary should lead to scattered to numerous showers and storms impacting primarily northeast and central MO and west-central IL tonight. The upstream longwave trof is forecast to steadily deepen and progress eastward on Monday with additional disturbances in the flow aloft and the aforementioned boundary providing the impetus for scattered to numerous showers and thunderstorms. The exact convective trends are a bit unclear but there should be some combination of ongoing activity in the morning and then newer development across east-central and southeast MO and southern IL in the afternoon where the best instability will reside. Isolated strong to severe storms would be possible with the afternoon storms and this has been supported by a few of the CAMS. Glass && .LONG TERM... (Monday Night through Next Sunday) Issued at 238 PM CDT Sun Jul 7 2024 The latest guidance shows the southern portion of the progressive upper trof will have a greater interaction with TC Beryl and will be deeper, leading to a more northward track following the recurvature. The latest NHC forecast along with latest superensemble track guidance suggests the center of the remnant circulation will track across southeast MO and southern IL Tuesday and Tuesday night. Rain will spread into southeast MO and southern IL late Monday night associated with the initial surge of mid-high level moisture and the interaction with an ULJ to the north. Present indications are a band of locally heavy rain, 2-4 inches, will accompany the remnants of Beryl as it tracks through the CWA. At this time and given the current track, it appears this band will be centered through southeast and east-central MO and southwest IL. If there is favorable overlap where we saw heavy rain in early July across eastern MO and southwest IL where soil moisture is high, then there could be some flash flood concerns. The additional rainfall will certainly add to the mainstem river flooding and potentially produce river flooding in smaller basins south of St. Louis. Depending on the exact low track and timing, there could be tornado threat across parts of southeast MO and southern IL closer to the low but this is highly conditional on the low track. After the remnant low exits to the east-northeast on Wednesday it appears that all-in-all we should see a tranquil period. We might see an isolated diurnal thunderstorm across parts of the area on Thursday afternoon, but it looks predominately dry heading late week into next weekend. Temperatures on Tuesday will be well below normal due to clouds and rain, but rising heights late week into the weekend signal a return to more summer-like heat with highs in the 90s. Glass && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1046 PM CDT Sun Jul 7 2024 For the rest of the night we`ll see light winds and abundant mid cloud cover. A few showers and storms are possible overnight as the low level jet tries to bring in more moisture, but coverage is expected to be relatively low and confidence in this affecting any TAF location is low. There will be a clear lull in activity Monday morning before additional development occurs in the afternoon with a greater chance of impacting the St Louis metro where VCTS continues to be included for this possibility. This threat wanes in the evening. Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX