Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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571 FXUS63 KLSX 151943 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 243 PM CDT Wed May 15 2024 .KEY MESSAGES... - Unsettled weather returns to the region late tonight through Friday. Isolated strong to severe thunderstorms are possible Thursday afternoon and evening. - Portions of southeast Missouri and southwest Illinois could see locally heavy rainfall that could produce minor flooding on Friday. - Warmer weather returns to the region late in the weekend and through next week. Temperatures will be around 10 degrees above normal by Monday and Tuesday. && .SHORT TERM... (Through Late Thursday Night) Issued at 237 PM CDT Wed May 15 2024 A weak surface ridge will continue to slide off to the southeast tonight as the next system over the Northern/Central Plains moves into western MO by 06z Thursday. A warm front will develop along the MO/AR border this evening and lift northward as an upper level shortwave associated with the system lifts northeastward out of the Southern Plains. Still some uncertainty on the exact location of the warm front through the period and where the main axis of showers and storms will develop. The latest deterministic model runs range from across northern MO (NAM) to across southern MO (GFS), while the majority of the HREF ensembles have the main axis along and south of I-70 tonight through Thursday. So kept the highest POPs along and south of I-70. Since the activity will take awhile to reach the region, still have high confidence that it will be weakening as it moves into the area due to weakening instability and veering low level jet. There is still some uncertainty on how much the atmosphere will recover by Thursday afternoon due to the morning rain and cloud cover. However, as a remnant MCV, associated with the morning activity, slides along the MO/AR border Thursday afternoon combined with MU CAPEs between 1000-2000 J/kg and 0 to 6km bulk shear of 30 to 40 kts, could see isolated severe storms develop over southeast Missouri and southwest Illinois, as well as a small portion of east-central Missouri. The main threats will be damaging winds and large hail between 2 pm and 8 pm Thursday. The activity will taper off by late evening Thursday with the boundary stalling out along the MO/AR border. This boundary will be the focus for additional activity developing after 06z Friday as the main shortwave/trough over the TX panhandle slowly slides east northeast towards the region. Byrd && .LONG TERM... (Friday through Next Wednesday) Issued at 237 PM CDT Wed May 15 2024 The shortwave with associated surface low will continue to slide east northeast on Friday towards the forecast area. With the surface boundary lingering across southern Missouri, the combination of a southerly low level jet (25 to 35 kts), PWATS in excess of 1.5 inches and deep layer ascent at the left exit region of the upper jet will generate widespread showers and storms. Thus portions of southeast Missouri and southwest Illinois could see locally heavy rainfall that could produce minor flooding on Friday. The latest ensembles as well as deterministic models still have differences in timing, strength and location of the system as moves through the region this weekend. For now still expect low chances (20-40%) of showers and a few storms Friday night through Saturday, especially across portions of east-central/southeast Missouri and southwest/south-central Illinois. Otherwise, a majority of the region will be dry this weekend. Beyond the weekend, warmer weather is expected with above normal temperatures by Monday and Tuesday. Otherwise, there is the potential for another active period as multiple shortwaves move across the region. Byrd && .AVIATION... (For the 12z TAFs through 12z Thursday Morning) Issued at 105 PM CDT Wed May 15 2024 IFR/MVFR ceilings will lift and scatter out by mid afternoon. Otherwise, showers and storms will move into portions of central Missouri by 07z Thursday and spread eastward, moving into St. Louis metro area TAF sites by 14z Thursday. As for KUIN, the main area of rain will stay south, so just have vicinity shower mention after 13z Thursday. Expect MVFR ceilings and visibilities with the stronger storms. Light and variable winds will veer to the south and pickup by mid morning on Thursday. Byrd && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX