Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jan 20 2023 08:38:58 FOUS30 KWBC 200838 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 337 AM EST Fri Jan 20 2023 Day 1 Valid 12Z Fri Jan 20 2023 - 12Z Sat Jan 21 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent.=20 Kebede Day 2 Valid 12Z Sat Jan 21 2023 - 12Z Sun Jan 22 2023 ....A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE GULF COAST & SOUTHEAST... A southern stream trough will amplify as it moves through the Great Plains on Saturday. A surface low pressure system will glide across the Gulf Coast and direct moisture across the region and the eastern seaboard through Sunday. Modest southerly mid-level flow will support PWATs in the 1-2" range and hourly rates of around 0.25-0.5in/hr over portions of the central Gulf Coast and Southeast. Increased frontogenesis is expected in the late afternoon hours of Saturday as diurnal heating potentially spawns convection. Fortunately, the soils in the Southeast are relatively dry so the 1-2" of forecasted rainfall won't cause widespread flash flooding concerns. There's still a chance for isolated flash flooding, therefore a broad marginal risk is in place. Kebede Day 3 Valid 12Z Sat Jan 21 2023 - 12Z Sun Jan 22 2023 ....A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE SOUTHEAST... A southern stream trough will phase with its northern stream reflection and amplify over Ohio/Tennessee Valley on Sunday. Mid-level flow out of the South will continue moisture advection into the Southeast and eventually up the East Coast later into Monday morning. There's a decent signal for heavy rainfall to develop over the Southeast Coast along a strengthening cold front and out ahead of a deepening low pressure system. PWATs between 1.5-2" and rainfall rates between 0.25-0.5in/hr may form along an axis of enhanced frontogenesis Sunday evening. The latest ECMWF trends have suggested a QPF footprint that is closer to the coast and inland areas while the GFS has been more consistent in this regard as well as the potential for enhanced rainfall tracking up the East coast and into New England. A marginal extending up into the Northeast was considered, but 24hr amounts between 0.5-1" aren't high enough to extend it northward at this time. Kebede Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7wj8XwrGAQT08--ZmmAUNym2LDcbKu44wDRrOVptOH7Z= EIv-fLrHK-Ch7NBZ0b4PnJBgayBiePxk5fLL6RA2TYMTgt0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7wj8XwrGAQT08--ZmmAUNym2LDcbKu44wDRrOVptOH7Z= EIv-fLrHK-Ch7NBZ0b4PnJBgayBiePxk5fLL6RA2GKi-EVo$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7wj8XwrGAQT08--ZmmAUNym2LDcbKu44wDRrOVptOH7Z= EIv-fLrHK-Ch7NBZ0b4PnJBgayBiePxk5fLL6RA2uVGvrcU$=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) .