Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jan 12 2024 08:30:56 FOUS30 KWBC 120830 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 330 AM EST Fri Jan 12 2024 Day 1 Valid 12Z Fri Jan 12 2024 - 12Z Sat Jan 13 2024 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MID-ATLANTIC AND NORTHEAST... ....Mid-Atlantic and Northeast U.S.... Surace low pressure is expected to form over the Mid-Atlatic regiom later today along a boundary associated with deepening low presure over portions of the Ohio Valley. The resulting inflow of low level moisture is maximized at about the same time that upper level divergence increases through a deep layer due to the approach of an upper level jet especially during the afternoon/evening over the Mid-Atlantic region and moreso into parts of the Northeast U.S. from this evening into the overnight hours. QPF amounts are not blockbuster values...due to the relatively short window of opportunity given the progressive nature of the system. However...models are beginning to pick up on a period of elevated convection and associated increase in rainfall rates which may prove to be problematic in areas still draining off water from the heavy rainfall earlier in the week.=20 Amounts alone are such that a Slight Risk area in parts of the Mid-Atlantic would probably not have been entertained had it not come on the heels of the heavy rainfall earlier in the week across an area that has been wet for at least 4 weeks. Confidence is higher for impacts farther north into parts of the Northeast U.S. where higher amounts from this event will overlap areas soaked a few days ago...in part given the higher magnitude afforded by strengthening low level flow and increasingly deep moisture.=20 ....Mid Mississippi Valley to the Lower Ohio Valley... Expanded a portion of the Marginal Risk area...mainly over northeastern Arkansas into adjacent areas of Tennessee...where convection from overnight looks to perist into the early portion of the Day 1 period. There has been some training of cells overnight and high-resolution guidance has shown that threat to linger beyond 12/12Z. As previously mentioned...very dry soil conditions remain prevalent across much of the Marginal Risk area will mitigate the flash flooding threat...as well as increased cell motion later today. Maintained the Marginal Risk along the corridor of highest expected rainfall totals. Substantive rainfall should be done in most of the Marginal Risk area by 12/18Z Friday in the wake of the cold front which ushers in very cold air. ....Pacific Northwest... The Marginal remains largely the same, but in following with the latest guidance shifting a bit southward in response to the latest guidance. Locally enhanced rainfall rates are expected from later today into early Saturday morning with several bouts of heavy rainfall within the coastal plain extending from northwest CA up through central OR given steepening low- and mid-level lapse rates. There could be some localized flooding with the urbanized corridors along the coast, but nothing too extraordinary in the grand scheme. Bann 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!7LamcunFMcLC6I1hbfqFeZmt3A-UNm1MemJo6-9f7TND= BDZrIDG-57P9WO5vEz27J4t7YlSUXo_eMyWt4oZlVCH2g0Q$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7LamcunFMcLC6I1hbfqFeZmt3A-UNm1MemJo6-9f7TND= BDZrIDG-57P9WO5vEz27J4t7YlSUXo_eMyWt4oZltD2gBDw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7LamcunFMcLC6I1hbfqFeZmt3A-UNm1MemJo6-9f7TND= BDZrIDG-57P9WO5vEz27J4t7YlSUXo_eMyWt4oZl6KBdqaU$=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) .