Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jan 20 2023 20:25:17 FOUS30 KWBC 202025 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 324 PM EST Fri Jan 20 2023 Day 1 Valid 16Z Fri Jan 20 2023 - 12Z Sat Jan 21 2023 ....16Z Update... The probability of rainfall exceeding flash flood guidance is less than 5 percent.=20 Wegman Day 2 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... ....2030Z Update... The biggest change from inherited was to remove essentially the entire Florida Peninsula from the Marginal Risk area for the Southeast. Otherwise no changes were needed. The front that will be producing the potential for isolated flash flooding from excessive rainfall will produce multiple rounds of rain across the Marginal Risk area. Associated rainfall is unlikely to extend across the Florida Peninsula, and any rain that impacts northern areas is unlikely to amount to enough to cause an isolated flash flooding risk. Soil moisture depictions from NASA SPoRT indicate that much of the Marginal risk area is drier than normal, so any storms that have the potential to cause flash flooding will have to be training storms, move over a particularly sensitive area, such as urbanized areas, or merge with other storms over the same area. Thus, the threat is definitely on the lower end of the Marginal Risk scale. As with the previous discussion, the addition of a Marginal Risk for RI and far eastern MA was considered with this update. The combination of a slight eastward shift in the axis of heaviest rainfall into higher FFG areas on Cape Cod and similar rainfall totals forecast for this area as inherited once again precluded this. This area will continue to be monitored. Wegman ....Previous Discussion... 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 The Day 3 outlook will be updated by 2030Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_327-LwS2wD9nACdac7VhPs2q22Z3GkehR_lwK3WFR_u= h6BoHkcQeRvoNMil7S8MidO5d7Mv-KYdxFhDt_ujM38nAd8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_327-LwS2wD9nACdac7VhPs2q22Z3GkehR_lwK3WFR_u= h6BoHkcQeRvoNMil7S8MidO5d7Mv-KYdxFhDt_ujvpF8OwA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_327-LwS2wD9nACdac7VhPs2q22Z3GkehR_lwK3WFR_u= h6BoHkcQeRvoNMil7S8MidO5d7Mv-KYdxFhDt_ujRKHQqiU$=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) .