Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Apr 20 2024 19:53:19 FOUS30 KWBC 201953 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 353 PM EDT Sat Apr 20 2024 Day 1 Valid 16Z Sat Apr 20 2024 - 12Z Sun Apr 21 2024 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR CENTRAL AND EAST TEXAS... East TX will be the main focus for heavy rainfall today. Currently we have ongoing elevated convection based near the 850mb front from west TX into northeast TX. This activity is well into the cool sector of this system, which will impact the degree of instability and rainfall rates associated with it. Given this activity is expected to continue through the day, conditions may saturate enough for a gradual uptick in the flood threat, especially over north central to northeast TX where the duration will be longer. So while exceedance of the current 1 and 3hr FFG is unlikely, some flood risk could eventually evolve warranting a continuation of the Slight risk. The higher rainfall rate potential today will be further south closer to the surface boundary. This is where stronger low level convergence and instability will focus, allowing for the potential of slower moving/training convection capable of 2"+/hr type rainfall. The greatest signal for this is over south central to southeast TX, where 12z HREF neighborhood probabilities of exceeding 3" are over 70% ,and exceeding 5" around 50%. While this indicates 3"+ amounts are likely, EAS 3" probabilities are only ~15%, indicating amounts of this magnitude, while likely, should stay pretty isolated. There is some uncertainty with regards to the organization and coverage of this convection, which makes this Slight risk more conditional in nature...especially given the high FFG. However there is some threat of more organized FFG exceedance should convection grow upscale along this low level stationary boundary. We did remove the Slight risk across most of northern LA into central MS, as this area is well within the cool sector of the system, and thus not anticipating we'll see rainfall rates high enough for flash flooding. With that said, steady rain with embedded higher rates may still cause isolated flooding concerns, which is handled by the Marginal risk. The better chance for higher rainfall rates is actually further south over southern MS. It is here, closer to the front, where heavier rates and 3"+ totals are a possibility. However given the high FFG, currently not expecting enough coverage to justify a Slight risk, but localized flash flooding (especially in any more sensitive urban areas), is certainly possible today/tonight. Chenard Day 2 Valid 12Z Sun Apr 21 2024 - 12Z Mon Apr 22 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard Day 3 Valid 12Z Mon Apr 22 2024 - 12Z Tue Apr 23 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4OW6DViktPjsXeFKWwVtFru3vjbB-lBuLcxmnEnldEle= HrYhCS97Kpaek18JglNVohPhmR5pt3iEB1H-hMdX4CGlpZg$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4OW6DViktPjsXeFKWwVtFru3vjbB-lBuLcxmnEnldEle= HrYhCS97Kpaek18JglNVohPhmR5pt3iEB1H-hMdXw2MyMhU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4OW6DViktPjsXeFKWwVtFru3vjbB-lBuLcxmnEnldEle= HrYhCS97Kpaek18JglNVohPhmR5pt3iEB1H-hMdXFonvpJQ$=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .