Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Apr 15 2024 08:20:07 FOUS30 KWBC 150819 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 419 AM EDT Mon Apr 15 2024 Day 1 Valid 01Z Mon Apr 15 2024 - 12Z Mon Apr 15 2024 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF THE PLAINS... A deepening low and amplifying jet will pivot into the Upper=20 Midwest creating broad areas of ascent while increasing low-level=20 southerly flow from the Gulf of Mexico. Precipitable water values=20 will surge to 1.25/1.5 over the Plains with moisture anomalies=20 peaking around 2.5 standard deviations. The environment will be=20 conducive for convection to develop ahead of the front that will be capable of multiple hazards like very large hail, destructive=20 winds(possible tornadoes) and heavy rainfall. The nature of these=20 storms will be progressive which may somewhat limit the threat for=20 flooding however with the support of mixed-layer CAPEs of at least=20 1000-2000 J/Kg over the southern portion of the Marginal Risk area, there will be a higher probability of more intense 1-3hr rainfall=20 rates compared to areas farther north. Higher FFGs (lower soil=20 moisture percentiles lower) over the southern portion of the=20 outlook area will maintain a Marginal or localized flash flood=20 risk. Meanwhile, lower FFGs/wetter antecedent soils over the northern portion of the outlook area, along with a better chance for more prolonged activity along/north of the surface warm front, will be offset by decided lower deep-layer instability (even elevated). So even here, again the flash flood risk remains marginal. Campbell/Hurley Day 2 Valid 12Z Mon Apr 15 2024 - 12Z Tue Apr 16 2024 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS EASTERN=20 PORTIONS OF THE NORTHERN PLAINS SOUTHWARD THROUGH MUCH OF THE=20 MISSISSIPPI VALLEY... The closed low and trailing cold front will advance from the High Plains into the Upper Mississippi Valley while an west-east orientated warm front extends across the Upper Midwest to the Mid- Atlantic region. An axis of anomalous precipitable water values up to 2 standard deviations above the mean, will persist along and ahead of the well defined cold front while pooling along the warm front. Organized convection will likely fire up in proximity to this=20 anomalous moisture axis. Like the previous day, the convection is expected to be fairly progressive that continues to limit the potential for heavy rainfall and associated areas of localized flooding. Locations along and north of the warm front have the greater potential for organized precipitation to span from the Northern Plains to the Upper Mississippi Valley/Upper Midwest. Heavy rain will likely spread across locations north of the warm front and maintain for longer durations as the moisture surging northward from the Gulf of Mexico over the frontal boundary persists. Consensus suggests broad areal averages of 1 to 2 inches with locally higher amounts certainly possible. This region has=20 been relatively dry over the past few weeks, resulting in dry soils and below average stream flows.=20 Campbell Day 3 Valid 12Z Tue Apr 16 2024 - 12Z Wed Apr 17 2024 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE GREAT LAKES, OHIO VALLEY AND WESTERN PARTS OF THE NORTHEAST... Showers and thunderstorms will shift east as the closed low and fronts advance through the Ohio Valley toward the Mid-Atlantic. Much of the guidance has 1 to 2 inches for this period for parts of the Great Lakes, eastern Ohio Valley and portions of the Northeast. This part of the country has much lower FFG guidance from antecedent rain thus are more sensitive to additional rainfall. A Marginal Risk spans from Michigan/Wisconsin south to Kentucky and east into western New York, Pennsylvania and Maryland. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4ZdXJTHELtyPFjC29SsTWlicUrunjfihZQqBp5V4U1nS= JWQekkzsIF3s8yquzudEMALQxji-1-adN7v66l-YL_WUzXg$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4ZdXJTHELtyPFjC29SsTWlicUrunjfihZQqBp5V4U1nS= JWQekkzsIF3s8yquzudEMALQxji-1-adN7v66l-YZ0AFpAY$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4ZdXJTHELtyPFjC29SsTWlicUrunjfihZQqBp5V4U1nS= JWQekkzsIF3s8yquzudEMALQxji-1-adN7v66l-YykR3DM0$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .