Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Oct 02 2024 19:50:47 FOUS30 KWBC 021950 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 350 PM EDT Wed Oct 2 2024 Day 1 Valid 16Z Wed Oct 02 2024 - 12Z Thu Oct 03 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Sea breeze activity across the FL Peninsula will be the primary area of precip across the CONUS with only modest signals within the CAMs/HREF for >3" at any given point this afternoon and evening. Considering the FFG indices and proposed rainfall rates likely well-below the threshold necessary, the threat was deemed very low probability for flash flooding and did not meet the MRGL risk criteria. The nil ERO was maintained for the D1 forecast. Kleebauer Day 2 Valid 12Z Thu Oct 03 2024 - 12Z Fri Oct 04 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. The consensus for locally moderate to heavy rainfall remains steadfast within the latest ensemble and deterministic interpretations with a bit more emphasis on the Southeast LA Parishes as the 12z CAMs output. Latest HREF continues to signal a focused area of 3-5" potential tomorrow afternoon and early evening in areas along and south of I-10 from near New Orleans through Biloxi towards Mobile. There's still some discrepancy on the placement of the local maxima with the highest potential likely over either St. Bernard or Plaquemines Parishes, both areas that are very difficult to flood due to the swampy land structures and sandier soils that limit flash flood potential. A modest theta-E advection pattern with PWATs running close to 2-2.1" will likely allow for some convective elements promoting rates between 1-3"/hr, but the current FFG indices are very pronounced in those parts, attributing to very low FFG exceedance probabilities in either 1/3/6 hr time frames. Decided against a MRGL addition and maintained the nil forecast across the CONUS, but this will be an area to monitor in the next succession of updates as the threat is non-zero, but currently below 5%.=20 Kleebauer Day 3 Valid 12Z Fri Oct 04 2024 - 12Z Sat Oct 05 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Broad cyclonic flow over the Western Gulf will allow for a modest advection of deeper moisture and accompanying shower/thunderstorms activity to protrude inland of Deep South TX on Friday. Current signature within guidance notes a tongue of elevated instability within a deep moist layer on the western periphery of the low pressure pattern over the Gulf. The area of interest resides across the Lower RGV, mainly within the coastal plain encompassing Brownsville/South Padre Island/Harlingen. Recent trends maintain some rainfall in the area with totals bordering 0.75-1.5" with a few deterministic outputs flirting with the 2"/24-hr marker. The current signal is likely too "light" to allow for any enhanced flash flood concerns, however the threat is likely non-zero. Unless the precip forecast evolves into something greater, this will likely lie outside the MRGL risk threshold, but wanted to make mention as this is an area we will continue to monitor. The nil ERO over the CONUS was carried over in this forecast cycle. Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5kc-E0tpfxorw_eIOJPCMEyUC1MI7dcvdytnrgDDc1ug= xrlyC3qi8VWT0In_9UzOX5tiMOn-EccZIVeBXv4BnFJxRMY$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5kc-E0tpfxorw_eIOJPCMEyUC1MI7dcvdytnrgDDc1ug= xrlyC3qi8VWT0In_9UzOX5tiMOn-EccZIVeBXv4BcIyTuJY$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5kc-E0tpfxorw_eIOJPCMEyUC1MI7dcvdytnrgDDc1ug= xrlyC3qi8VWT0In_9UzOX5tiMOn-EccZIVeBXv4BjNTDZvw$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .