Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Oct 26 2025 19:40:30 FOUS30 KWBC 261940 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 340 PM EDT Sun Oct 26 2025 Day 1 Valid 16Z Sun Oct 26 2025 - 12Z Mon Oct 27 2025 ....THERE IS A SLIGHT RISK OVER PORTIONS OF THE CENTRAL GULF COAST AND CENTRAL FLORIDA... ....Central Gulf Coast... Energy rotating beneath a mid-level low centered over the Middle Mississippi Valley will help propel a convective complex through the Southeast. Storms will move into a moisture and instability rich environment across the immediate Mississippi/Alabama/Florida coast this afternoon/evening. Along the immediate coast, precipitable water values will be between 1.5-2", which will be in the 90th percentile of PWATs for this time of year. MUCAPE between 1000-1500J/Kg should provide enough instability to support 1-3in./hr rain rates in some places. Urban areas will be especially susceptible to runoff from excessive rainfall. THere continues to be a growing consensus for slower cell motions and backbuilding storms over the immediate coast Sunday night. The Slight was maintained for the Gulf Coast spanning from far eastern Louisiana to the Florida Panhandle, however the northern boundary was expanded further north into southern Mississippi and Alabama. A broad Marginal remains in place from the central Gulf Coast to southeast Missouri, southern Illinois and southwest Kentucky. ....Central Florida... A strong signal for heavy sustained rainfall has emerged in the CAMs this morning. Mid-level vortices propagating through the southern periphery of a strong low, and beneath modest upper-level divergence should contribute enough forcing to generate convection from Florida up through coastal Georgia this afternoon/evening. Bulk shear between 30-40kts with weak low-level winds out of the south should also support supercell development and slow cell motion. Easterly on- shore flow from the Atlantic should advect over an inverted trough, and quasi- stationary front draped east- west across the central part of the state. Therefore, westerly mid- level flow over easterly low level/surface flow will likely support backbuilding convection over central parts of the state beginning this afternoon. Ample low level moisture is in place (1-2" PWATs) across the marginal risk area. ML CAPE values between 500-1000J/Kg should be sufficient enough to generate 1-3"+ rain rates within the slight risk area. The 12z HREF 40km neighborhood probability of 6hr qpf exceeding 100 year ARI for this afternoon and evening is between 30-60% from the Orlando metro area to the coast. 3 and 5" exceedance probabilities are also well over 25-30%. Kebede Day 2 Valid 12Z Mon Oct 27 2025 - 12Z Tue Oct 28 2025 .... THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHEAST AND SOUTHERN APPALACHIANS... ....2030z update... Guidance has trended wetter across the Southern Appalachians/western Carolinas for Monday. 40km neighborhood probabilities of 24hr qpf exceeding 5" is between 15-25% over portions of far western Carolinas, while EAS neighborhood probabilities of exceeding 3" is up to 5%. Localized amounts of over 2" are possible especially in the terrain. Kebede ....Previous Discussion... Low pressure tracking through the southern tier will pivot to the northeast allowing for convection to spread across the southern Appalachians and Southeast. The low level flow will enter a relatively more stable environment that will reduce the the risk for excessive rainfall; however guidance continues to depict isolated maximums near 2 inches across the region. A Marginal Risk area remains in effect across eastern Tennessee, eastern Georgia, western South Dakota and western North Carolina. Campbell Day 3 Valid 12Z Tue Oct 28 2025 - 12Z Wed Oct 29 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Kebede Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8hErAnaxTpu2WlpYeBEkdzQIc-vqhH4OkBcuWbqtdtpD= _SuQdMvLw_2KORhEbZx_TCTbQV0Jqw7e2z_kecVgq_A68Ts$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8hErAnaxTpu2WlpYeBEkdzQIc-vqhH4OkBcuWbqtdtpD= _SuQdMvLw_2KORhEbZx_TCTbQV0Jqw7e2z_kecVg-yoVQYo$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8hErAnaxTpu2WlpYeBEkdzQIc-vqhH4OkBcuWbqtdtpD= _SuQdMvLw_2KORhEbZx_TCTbQV0Jqw7e2z_kecVg-ZJa9sI$=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) .