Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Oct 29 2023 20:15:32 FOUS30 KWBC 292015 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 414 PM EDT Sun Oct 29 2023 Day 1 Valid 16Z Sun Oct 29 2023 - 12Z Mon Oct 30 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF CENTRAL ARKANSAS...=20 ....16Z Update... Quite a few trimmings to the previous ERO risk areas with this update. Instability has been meager across all of the ERO risk areas...with a few hundred J/kg noted across southern/western TX. This lack of instability throughout the atmosphere has prevented the showers and a few storms that have developed from producing heavy rainfall rates. Given the front is essentially stationary, it's unlikely too much instability will be added through daytime heating...partially from time of year, and mostly because of overcast skies. The rain is training because of the stationary front, but it's almost all light rain, other than a few convective elements that develop from time to time, allowing briefly moderate rainfall rates of up to 1 inch per hour. These rates so far have fallen well short of enough to cause flash flooding. Through this afternoon, expect a few more convective elements to the overall broader rain shield to develop across central Arkansas, where the Slight risk area remains. Even here the Slight is a low-confidence and lower-end Slight, as the ground in the area has done well at absorbing the rain that has fallen up to this point. Elsewhere, rates have also been coming down across western Texas and most of Oklahoma, so the Marginal was trimmed there, as well as for much of the middle and upper Ohio Valley due to dry antecedent conditions and poor rainfall rates.=20=20 Wegman ....Previous Discussion... =20=20 ....Southern Plains into the Ohio Valley...=20=20 Precipitable water values will be in slow decline this period, maximizing in the 1.75-2" range early on before falling into the 1.25-1.5"range by Monday morning. A positively-tilted upper level trough will be approaching the region from the west and north causing some forward progression to the front across Texas and the Lower Mississippi Valley with time. The degree of low-level inflow and effective bulk shear available could organize convection into training bands Sunday morning, assuming sufficient instability, as the flow is fairly uniformly out of the west-southwest with height. MU CAPE of 250-500 J/kg should be sufficient to achieve hourly rain totals of 1-2" at times early on, which would be a problem across area terrain and places that rained heavily thus far, but the 00z NAM indicates the instability fades with time on Sunday and Sunday night. Local amounts in the 2-4" range are indicated by the available guidance overall. The size/extent of the Slight Risk area has as much to do with current soil saturation and ongoing heavy rainfall as it does with the possibility of additional heavy rainfall. There was some temptation to raising the threat level to a Moderate Risk, but the minimal/declining instability forecast remains the biggest drawback.=20 =20=20 Roth Day 2 Valid 12Z Mon Oct 30 2023 - 12Z Tue Oct 31 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent.=20 =20 Wegman Day 3 Valid 12Z Tue Oct 31 2023 - 12Z Wed Nov 01 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Wegman Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!72o3pXaQfDTvdGcJQ935BQMhZOEIRiieTu4Yp-xyk0ou= CMVBkhAdZQfEnpBYHnt9UgjJnfHLp5UcHxiJNtQNmlUKxE4$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!72o3pXaQfDTvdGcJQ935BQMhZOEIRiieTu4Yp-xyk0ou= CMVBkhAdZQfEnpBYHnt9UgjJnfHLp5UcHxiJNtQNXYE0IVw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!72o3pXaQfDTvdGcJQ935BQMhZOEIRiieTu4Yp-xyk0ou= CMVBkhAdZQfEnpBYHnt9UgjJnfHLp5UcHxiJNtQNwnqUa_o$=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .