Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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832 FXUS63 KLSX 201116 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 616 AM CDT Thu Jun 20 2024 .KEY MESSAGES... - Above normal temperatures through Saturday will continue with dry weather other than an isolated chance (20%) for a shower/thunderstorm across far northeast Missouri and west-central Illinois this afternoon. - The next significant chance (up to 70%) of showers and thunderstorms will be late Saturday through Sunday. - Much above normal temperatures are becoming increasingly likely through the first half of next week, with potential for excessive heat. && .SHORT TERM... (Through Late Friday Afternoon) Issued at 348 AM CDT Thu Jun 20 2024 The mid-level ridge/high dominating the eastern CONUS will slowly advance westward today and result in the anticipated continuous warm- up and largely dry weather across the region. A mid-level disturbance traversing across southern Iowa along with an area of moisture convergence near the surface will result in a chance (20%) for isolated showers and thunderstorms across far northeast Missouri and west-central Illinois this afternoon. Height rises associated with the deep high pressure and the region`s proximity to the center of the mid-level high and substance aloft will suppress precipitation chances and favor increasing temperatures. Temperatures today will be warmer than yesterday with highs in the upper 80s to mid-90s with the region being on the western periphery of the mid-level high. As the mid-level high inches closer to the region, southwesterly low-level flow on Friday will support hotter temperatures than today with highs in the low to mid 90s. MMG/Glass && .LONG TERM... (Friday Night through Wednesday) Issued at 348 AM CDT Thu Jun 20 2024 Little relief of these above normal temperatures is expected through next week. Saturday is forecast to be the hottest day of the weekend as the mid-level ridge remains centered across the Mid-Mississippi River Valley. A shortwave trough will traverse the region late Saturday into Sunday morning and sending a cold front into the area. This cold front will provide the next chance (up to 70%) of showers and thunderstorms. Confidence continues to increase that the greatest precipitation chances will be overnight Saturday into Sunday morning. However, there is uncertainty in the southern penetration of the cold front into the CWA which could affect highs. Should remnant cloud cover persist through the day Sunday, highs could be suppressed. However, with an increase of low level moisture, heat index values could be above 100 degrees Saturday through Sunday. Despite above normal high temperatures into the 90s and peak heat index values between 100-103 degrees in places, these values remain below advisory criteria. Next week, ensemble guidance is in consensus that the mid-level high will be anchored over the western CONUS with the Mid-Mississippi River Valley being in the eastern periphery. The accompanying low- level southwesterly flow will favor hot, and potentially impactful temperatures, and possibly dangerous heat levels. Current ensemble 850 mb temperatures range from 21-24 degrees C on Tuesday, supporting potential highs of 100+ in some places. Further increasing confidence in these extreme temperatures, the upper quartile of the NBM high temperatures is 100+. MMG/Glass && .AVIATION... (For the 12z TAFs through 12z Friday Morning) Issued at 616 AM CDT Thu Jun 20 2024 Dry and VFR flight conditions will persist through the TAF period. Diurnal cumulus clouds will develop this afternoon with light southerly winds. MMG/Glass && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX