Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Sep 14 2025 00:39:33 FOUS30 KWBC 140039 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 839 PM EDT Sat Sep 13 2025 Day 1 Valid 01Z Sun Sep 14 2025 - 12Z Sun Sep 14 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHERN HIGH PLAINS... ....Central & Southern High Plains... Upper trough over the Great Basin will continue to edge eastward=20 and take on a negative tilt, with a continued influx of moisture=20 (PW anomalies +2 sigma) into the Southern Rockies and points=20 northward. The LLJ (which is on the increase) will support=20 convection over eastern NM that pushes into West Texas. Storms may have enough forward speed to limit flash flooding potential, but there was enough of a signal in the recent high-resolution guidance probabilities and recent radar reflectivity trends to maintain the Slight Risk near the TX/NM border. ....Northern Plains... Southerly flow through the column will maintain a surge of=20 moisture (PW anomalies +3 sigma / 1.50") into the Northern Plains=20 as weaker shortwaves race northward ahead of the main upper low=20 over MT, such as the one transiting central ND currently. It appears that the convection across ND has reached its peak for the day, so lowered the risk to Marginal. Slight Risk impacts are possible in the near term across a couple counties in western ND. ....In and near Indiana...=20 While the primary shortwave has left the scene, some of the mesoscale guidance shows a modest overnight uptick, so left the Marginal Risk in place and shifted it slightly southeast. ....East-central Florida...=20 While daytime convection is beginning to wane across southern FL, activity offshore eastern FL is poised to move inland in the short term within what appears to be a comma head pattern around the periphery of an upper level low. Precipitable water values remain 1.5"+, the low-level flow remains onshore in this region which is keeping 2000+ J/kg of ML CAPE around, and effective bulk shear is=20 high enough to worry about convective organization, which continues concerns about short training bands leading to heavy rain concerns in urban areas before the system moves out to sea Sunday.=20 Mesoscale guidance keeps convective activity close enough to the=20 Space & Treasure coasts to have a Marginal Risk for the region overnight. Roth Day 2 Valid 12Z Sun Sep 14 2025 - 12Z Mon Sep 15 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE WESTERN DAKOTAS... 20Z Update... Extended the Marginal Risk further south from the central Plains into western Oklahoma and the eastern Texas Panhandle, where convection is expected to develop during the afternoon/evening ahead of a low level confluence axis and within a stripe of deeper moisture. While not anticipating a widespread heavy rainfall event, some models do indicate the potential for slow-moving or backbuilding cells, resulting in locally heavy amounts and perhaps isolated flash flooding concerns. Otherwise, no significant changes to the previous outlook. Pereira Previous Discussion... ....Central and Northern Plains... Upper trough exiting the Rockies will split off its southern portion into an upper low over western Nebraska midday Sunday, with southerly flow continuing across the Northern Plains (and ample moisture -- PW anomalies still +2 to +3 sigma). This mid-level low will lift northward and act as a focus for convergence toward the nose of the sfc- based instability gradient just to the east. Storms may repeat over the same area as D1, with the potential for another 1-2"+ of rain. Maintained the Slight Risk outline here with a broader Marginal Risk extending to the south where the guidance shows potential for 2-4" of rainfall, but over areas with higher FFG values (esp. the Sand Hills). Fracasso Day 3 Valid 12Z Mon Sep 15 2025 - 12Z Tue Sep 16 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!__U_fNMniGTBtzn4yvlfOYGsqyReLktn5L0Dutr5YjE8= 32oWido7lRq8LLaYlnOLf_OvCrYJMXUAgoBqMxZvq7-lbLE$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!__U_fNMniGTBtzn4yvlfOYGsqyReLktn5L0Dutr5YjE8= 32oWido7lRq8LLaYlnOLf_OvCrYJMXUAgoBqMxZv97A-NiI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!__U_fNMniGTBtzn4yvlfOYGsqyReLktn5L0Dutr5YjE8= 32oWido7lRq8LLaYlnOLf_OvCrYJMXUAgoBqMxZvu61LNo8$=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .