Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Oct 03 2025 16:02:15 FOUS30 KWBC 031602 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1202 PM EDT Fri Oct 3 2025 Day 1 Valid 16Z Fri Oct 03 2025 - 12Z Sat Oct 04 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF EASTERN FLORIDA AND THE INTERMOUNTAIN WEST... ....Florida's East Coast... For the 16Z Update, the Slight Risk centered along Florida's Treasure Coast was removed. While easterly flow is still expected to support showers and storms, with isolated heavy amounts possible=20 along Florida's East Coast, the consensus of the HREF/RRFS has=20 trended down along the Treasure Coast -- showing the focus for=20 deeper moisture and heavier amounts further south. Probabilities=20 from the HREF/RRFS now indicate the greatest chance for heavy=20 amounts through the remainder of Day 1 is across Southeast Florida, which may result in runoff concerns, especially if they set up=20 over the urbanized areas. However, confidence in the details is=20 limited, with some indication that the heaviest amounts may set up west of the urbanized areas over the Everglades. Therefore,=20 maintained just a Marginal Risk for now. ....Great Basin... Additional rainfall is forecast to occur beneath the upper low, which will continue propagating through the interior West today. Recent heavy rainfall over portions of the Great Basin will likely prime surfaces for runoff from additional precipitation. Burn scars in central and southern Idaho continue to be of concern from today's storms, the bulk of which should occur this morning into afternoon before the upper low moves directly over the Great Basin and instability weakens. HREF EAS exceedance probabilities of over 1 inch are between 15-35% over northern/central Nevada where PWATs will be between 2-3 standard deviations above normal. Pereira/Kebede Day 2 Valid 12Z Sat Oct 04 2025 - 12Z Sun Oct 05 2025 ....THERE'S A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF FLORIDA'S EAST COAST... ....Florida's East Coast... Thunderstorms are expected to continue to develop along the inverted trough axis oriented north-south along Florida's east coast on Saturday. Moisture will lift north along with the mid- level disturbance. The inherited slight and marginal risk areas were maintained due to a mostly consistent signal for excessive rainfall over the east central coast. Ensemble exceedance probabilities of 2 inches are between 5-10% across the marginal risk area. 48 hour totals between 3-5 inches (local 6") will likely make overcoming flash flood guidance a bit easier. ....Central Gulf Coast... The same moisture regime impacting the Florida peninsula will focus over the central Gulf Coast this weekend. Mid-level vorticity will lift into the area on Saturday, providing forcing for convection along the immediate Louisiana/Mississippi coast. Anywhere between 4-6 inches of rain may occur over far southeastern Louisiana through Saturday night. Despite 2" ensemble exceedance probabilities being relatively low (5-10%), the multi day nature of the rainfall could still produce isolated instances of flash flooding. Kebede Day 3 Valid 12Z Sun Oct 05 2025 - 12Z Mon Oct 06 2025 ....THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL GULF COAST AND THE SOUTHEAST COAST... ....Central Gulf Coast... The mid-level disturbance continues propagating westward toward the positively tilted upper trough centered over the West on Sunday. Thus, the heavy rainfall threat will likely bleed over from Saturday evening into Sunday morning for portions of the Central Gulf Coast, before dissipating beneath diminished support aloft. PWATs of 2-2.5" and instability between 500-1000 J/Kg MUCAPE could churn out rain rates between 1-1.5"/hr Saturday morning into afternoon. Ensemble exceedance probabilities of 2 inches are between 5-15% along the far southeastern Louisiana to Florida panhandle corridor, which supports the marginal risk area in place. ....Southeast Coast... Inverted troughing continues along the Florida/Southeast Coast through the latter part of this weekend. Anomalous moisture (2-3 stndv) will continue interacting with the surface boundary to generate scattered to isolated thunderstorms across the Florida/Georgia coast. Rainfall totals of 1-3" are likely along the Florida/Georgia/South Carolina coast on Saturday. The latest guidance has trended away from tropical moisture making its way inland, therefore a marginal risk was maintained for much of the Southeast Coast. Kebede Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4W0WTOsZBXy7bIn50nQYOd9hE61R1hNw9pyfn6wACvrt= kINYEAYL_efBcfQO7vY3575CIscAmdX-SnGA4ejP47iUn1A$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4W0WTOsZBXy7bIn50nQYOd9hE61R1hNw9pyfn6wACvrt= kINYEAYL_efBcfQO7vY3575CIscAmdX-SnGA4ejPL2Jz_AY$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4W0WTOsZBXy7bIn50nQYOd9hE61R1hNw9pyfn6wACvrt= kINYEAYL_efBcfQO7vY3575CIscAmdX-SnGA4ejPfgJlpzM$=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) .