Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jan 19 2023 15:42:28 FOUS30 KWBC 191542 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1041 AM EST Thu Jan 19 2023 Day 1 Valid 16Z Thu Jan 19 2023 - 12Z Fri Jan 20 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent.=20 An intense line of convection is expected to develop over OH this afternoon/evening, but severe weather is expected to be the main hazard, not flash flooding. Cells will be quick moving and it is a colder environment without anomalous moisture. Nonetheless, some localized swaths of 0.5"-0.75" of rain within an hour is expected. This may result in some ponding of water and minor runoff, but the flash flood risk remains below 5 %. Rain over southern New England will increase this afternoon/evening as well. Current model consensus is for up to 1-1.5" of rain, and hourly totals peaking around 0.5" along the south coast of New England. Neither these rates or totals appear high enough to warrant a Marginal risk, with the threat of flash flooding remaining low. Chenard Day 2 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 Roth Day 3 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... An upper low moving into the southern High Plains is expected to phase with a northern stream trough in the Northern Plains and progress eastward into the Mississippi Valley by Sunday morning.=20 This feature will aid divergence aloft across portions of the Gulf Coast and Southeast. Ahead of its associated cold front, precipitable water values rise to 1.25-1.75", which is high for late January. Any surface based CAPE is expected to be close to the Gulf Coast. However, MU CAPE of up to 500 J/kg should sneak somewhat inland across areas of the eastern Gulf coast.=20 Compensating for the minimal CAPE intrusion from the Gulf of Mexico is overlapping low- to mid-level frontogensis which should aid precipitation production from central MS eastward into central GA Saturday night into Sunday morning. Hourly rain totals to 2" along the Gulf Coast and 1" across the Interior Southeast appear the most probable at this junction. Inflow at 850 hPa is fairly strong -- approaching 50 kts -- and broadly cyclonic, so that progressive nature of the upper trough and cold front may not have much impact on QPF magnitude along and ahead of the long warm front. In the presence of enough instability, convection should attempt to organize The guidance generally agrees on narrow swaths of 2-4". Precipitation over the past week has been generally below average. The region is in the process of getting some precipitation at the present time, though the expected totals in the very short term shouldn't change the soil saturation very much between now and then. Overall, feel the inherited Marginal Risk from experimental day 4 continuity seemed reasonable so let it ride for day 3 with minimal changes. Roth Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6RifJCbgvp9E8qCIV88wLpdhqhRwFaaTdAY5HG-GIBnr= nT_apKttwLUU7nsHpLiFE4TDEabrJOkX-LrzopV2IeY3Nis$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6RifJCbgvp9E8qCIV88wLpdhqhRwFaaTdAY5HG-GIBnr= nT_apKttwLUU7nsHpLiFE4TDEabrJOkX-LrzopV2I_zsJBg$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6RifJCbgvp9E8qCIV88wLpdhqhRwFaaTdAY5HG-GIBnr= nT_apKttwLUU7nsHpLiFE4TDEabrJOkX-LrzopV2bzdM5dY$=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) .