Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jan 21 2023 08:31:29 FOUS30 KWBC 210831 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 330 AM EST Sat Jan 21 2023 Day 1 Valid 12Z Sat Jan 21 2023 - 12Z Sun Jan 22 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE GULF COAST AND SOUTHEAST... A southern stream trough will amplify as it moves through the Great Plains today. A surface wave will glide across the Gulf Coast and direct moisture up the eastern seaboard through Sunday. Modest southerly mid-level flow will support PWATs in the 1-2" range with 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 the Gulf system moves ashore. Fortunately, 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 within convective cells, therefore a broad marginal risk is in place. Kebede Day 2 Valid 12Z Sun Jan 22 2023 - 12Z Mon Jan 23 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHEAST... A southern stream system will phase with a northern stream trough over the Ohio/Tennessee Valley on Sunday. Mid-level flow out of the South will continue to supply moisture advection into the Southeast and eventually up the East Coast later into Monday morning. There's a decent signal for a line of convection to develop along a strengthening cold front and deepening low pressure system moving from the central Gulf Coast to Southeast coast late Sunday afternoon into the evening. PWATs between 1.5-2" and rainfall rates between 0.25-0.5in/hr may form along the axis of enhanced frontogenesis linked to convection/instability Sunday evening. The latest deterministic guidance is in reasonable agreement with the orientation and magnitude of the maximum qpf stripe extending from the Florida Panhandle to the Carolina coast. The GFS and EC have had great run-to-run consistency with respect to their 24 hour totals along the East Coast. The 00z NAM and 00z UKMET appear to be on the northern and southern extent, respectively, of the 00z suite of guidance with respect to their axis of greatest qpf. Kebede Day 3 Valid 12Z Mon Jan 23 2023 - 12Z Tue Jan 24 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF Texas... An upper-level low will swing from the four corners region into the Southern Plains on Monday. The primary rainfall threat won't begin until late Monday evening when the mid-level low arrives and starts pumping moisture into the Southern Plains. Mid-low-level southerly flow of around 50kts and shallow instability could support strong thunderstorms and enhanced rain rates, but a marginal severe risk will suffice for now according to the Storm Prediction Center. PWATs between 0.5-1in and rain rates between 0.1-0.25 over portions of north-central Texas could cause isolated flash flooding. Some of this early evening rainfall over northwestern Texas may turn The latest deterministic qpf guidance diverged a bit from continuity given a signal for the upstream ridge to flatten a bit over the Pacific Northwest. The resulting 00z GFS and ECMWF guidance have trended drier and farther south with their respective to their 24hr qpf footprints. Ensemble mean 2 inch exceedence probabilities remain low while 1 inch exceedence probabilities are modest at around 5-20%. High FFG and dry soils support this marginal risk area on day 3. Kebede Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-TAefE7YkBZtNHmsr8eCrqrA5tZU_v5glglzr02B4uIG= gfjdNJM-xweMMAvnq-G1dA8n2DiyE6ZQnTCwsXYFNRvebfc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-TAefE7YkBZtNHmsr8eCrqrA5tZU_v5glglzr02B4uIG= gfjdNJM-xweMMAvnq-G1dA8n2DiyE6ZQnTCwsXYFfsIKLYQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-TAefE7YkBZtNHmsr8eCrqrA5tZU_v5glglzr02B4uIG= gfjdNJM-xweMMAvnq-G1dA8n2DiyE6ZQnTCwsXYFKndIMTg$=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) .