Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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831 FXUS63 KLSX 031138 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 638 AM CDT Wed Jul 3 2024 .KEY MESSAGES... - The combination of heat and humidity will allow heat index values to climb to around 105 degrees over parts of southeast Missouri where a Heat Advisory is in effect this afternoon into early this evening. - There will be additional rounds of thunderstorms through Thursday night. A few of the storms could be severe this afternoon and this evening and again on Thursday afternoon and evening. - In addition to the severe weather potential, locally heavy rainfall is possible with these thunderstorms. && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 422 AM CDT Wed Jul 3 2024 Highs will reach the lower 90s over southeast Missouri and dewpoints are forecast to be in the mid to upper 70s over much of the area. Peak heat index readings will reach around 105 over parts of southeast Missouri, so I have issued a Heat Advisory for Reynolds, Iron, and Madison counties from 11 am through 8 pm today. I have gone ahead and canceled the flood watch early as the heavy rainfall threat has ended over the northern CWA. We are continuing to see showers and thunderstorms over the central part of the CWA early this morning. These were occurring on the nose of the LLJ and they should gradually weaken and move east over the next few hours as the LLJ veers and weakens. The associated outflow boundary will move south into the southern part of the CWA this afternoon. The most likely time for additional thunderstorm development today will be this afternoon over southeast Missouri into southwest Illinois along this effective front where MLCAPES will be 2500+ J/kg with deep layer shear of 30+ knots. This could is favorable for producing a few organized multicell clusters that could produce damaging winds through early this evening. The coverage of showers and thunderstorms will increase across the area late this evening and overnight as a shortwave trough approaches the area and the low level jet kicks back warranting 60- 90% PoPs. We are still looking at PWATS between 2-2.5" and very high warm cloud depths, and the HREF LPMM has some small spots with with totals exceeding 3" tonight into tomorrow morning. Will continue to look at the potential for locally heavy rainfall tonight into early Thursday. Then there will be another risk for severe thunderstorms Thursday afternoon and evening as yet another shortwave trough move across the area where the warm front will intersect the incoming cold front. The combination of CAPE/shear favors a few supercells/ organized multicells capable of producing damaging winds and large hail. Britt && .LONG TERM... (Thursday Night through Tuesday) Issued at 422 AM CDT Wed Jul 3 2024 Available guidance is still favoring the front moving through the area on Thursday night with showers and thunderstorms moving out of the southeastern part of the CWA on Friday. Friday night into Saturday look dry as large surface high moves across the area. The next upper trough moves through the area early next week bringing a chance of showers and thunderstorms as early as Sunday. Britt && .AVIATION... (For the 12z TAFs through 12z Thursday Morning) Issued at 633 AM CDT Wed Jul 3 2024 Complex of showers and thunderstorms currently affecting the St. Louis area terminals is expected to move out of the terminals by 14Z. Low clouds with MVFR and IFR ceilings will affect UIN/COU/JEF through 17Z. There will be the chance for additional showers and thunderstorms through the day into the evening, but coverage will be too low to include in the TAF. A better chance for thunderstorms will occur later this evening and overnight with the potential for MVFR and and IFR ceilings and visibilities in heavy rain. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Heat Advisory from 11 AM this morning to 8 PM CDT this evening for Iron MO-Madison MO-Reynolds MO. IL...None. && $$ WFO LSX