Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Oct 26 2025 23:31:39 FOUS30 KWBC 262331 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 731 PM EDT Sun Oct 26 2025 Day 1 Valid 01Z Mon Oct 27 2025 - 12Z Mon Oct 27 2025 ....THERE IS A SLIGHT RISK OVER PORTIONS OF THE CENTRAL GULF COAST AND CENTRAL FLORIDA... ....Central Gulf Coast... Shortwaves rotating beneath a mid-level low centered over the=20 Middle Mississippi Valley are forecast to reignite convection near the FL Panhandle overnight at the leading edge of an instability pool moving across the central Gulf Coast presently, with some=20 heavy rain possibility inland closer to the southernmost Piedmont=20 of the Appalachians. Precipitable water values, instability, and effective bulk shear are sufficient to support organized convection which could reach hourly rain amounts to 2.5" and local totals to 5" where storms train, backbuild, or merge. Even though recent convective trends have been significantly downward, the Slight Risk area was maintained for portions of the the Florida Panhandle since the ingredients appear to be there for issues. Impacts would be more significant in urban areas. ....Eastern Florida...=20 A signal for continued heavy rainfall persists in the mesoscale guidance through at least 06z along the FL coast, and early Monday morning for the Georgia coast. An approaching upper level trough is helping to aid divergence/difluence aloft. Onshore flow is allowing for sufficient moisture and instability to move ashore, and the low-level flow and upper level flow are nearly balanced, implying storms with heavy rainfall shouldn't go terribly far inland overnight. Effective bulk shear is sufficient for organization, whether in the form of occasional mesocyclones, backbuilding, or cell training. Cell mergers are also possible where organized convection runs into less organized thunderstorms.=20=20 Storms today have been capable of hourly amounts to 3" and local=20 totals to 7", which is a reasonably assumption for the overnight=20 period. The Slight Risk was extended southward to account for the 18z HREF guidance, which appears to be doing a better job than the 12z REFS at this time. Roth 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!7iJz0U6PedejTBC39wCCcBKbAIi_CV6h_LQtEhjV9YWQ= -W8x7TqL7UrOMFkHpvfvrkhXyPRafneMS_25zbObfirqp1Q$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7iJz0U6PedejTBC39wCCcBKbAIi_CV6h_LQtEhjV9YWQ= -W8x7TqL7UrOMFkHpvfvrkhXyPRafneMS_25zbObWfT-orE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7iJz0U6PedejTBC39wCCcBKbAIi_CV6h_LQtEhjV9YWQ= -W8x7TqL7UrOMFkHpvfvrkhXyPRafneMS_25zbObw_VGFK0$=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) .