Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 25 2023 07:52:17 FOUS30 KWBC 250752 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 250 AM EST Mon Dec 25 2023 Day 1 Valid 12Z Mon Dec 25 2023 - 12Z Tue Dec 26 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHERN APPALACHIANS... Upper level difluence will increase during this period as a mid-level closed low slowly moves over the Southeast. Moisture transporting in from the Gulf/Atlantic will be around +2 sigma (PW values of 1-1.25 inches) will override a warm front/stationary boundary over Georgia and Carolinas. This as the strengthening SE-SSE low-level flow provides some upslope enhancement, as most of the models show a heavier rainfall footprint across this region with areal-average totals between 1.5 and 3.0+ inches. The favored location for the highest amounts and the greatest threat for flooding concerns will by along/east of the extreme Northeast corner of Georgia/South Carolina/North Carolina border in the higher terrain. However, any elevated instability will be relatively weak/shallow, with MUCAPEs generally under 500 J/Kg. This will limit the 1 and 3 hourly rainfall rates somewhat, which along with the current low 0-100 cm soil moisture percentiles (less than 20% per NASA SPoRT), will likely lead to a more marginal excessive rainfall threat with the expectation of at most localized short-term runoff issues. Also limiting the potential for a Slight or better risk over much of the Southeast region will be the faster progression of the leading cold front, thus increasingly transient quasi-linear convective segments over most areas. ....Washington... Model guidance continue to depict 3 to 5 inches of rain, with snow levels remaining high enough to only impact the highest peaks of the eastern Olympics. While the event is only expected to be 24 hours long, the forecast rainfall amounts are high enough (and have been increasing) such that flash flooding and riverine flooding of the rivers that drain the Olympics are possible. Some isolated locations could see maximum values approach the upper single digits in accumulations. The Marginal Risk that was already in a effect was adjusted a bit further east while reducing the north some to remove the mostly snow areas. Campbell/Hurley Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!77uTXn1X_U_wnj1Ka6PkXan5Xqarjw2vWr-hHadVGjM2= lx2aza2Dw5FxUFZFA0NYkf1PSOrxx3dwWnG4iyhfrCQuHdw$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!77uTXn1X_U_wnj1Ka6PkXan5Xqarjw2vWr-hHadVGjM2= lx2aza2Dw5FxUFZFA0NYkf1PSOrxx3dwWnG4iyhfFKGGEho$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!77uTXn1X_U_wnj1Ka6PkXan5Xqarjw2vWr-hHadVGjM2= lx2aza2Dw5FxUFZFA0NYkf1PSOrxx3dwWnG4iyhf4VsHZrM$=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .