BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Sun, 29 Mar 2026 08:20:34 +0000 ----------------------------------------------------------- FOUS30 KWBC 290820 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 420 AM EDT Sun Mar 29 2026 Day 1 Valid 12Z Sun Mar 29 2026 - 12Z Mon Mar 30 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard Day 2 Valid 12Z Mon Mar 30 2026 - 12Z Tue Mar 31 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. An uptick in convective activity is expected Monday night into Tuesday morning across portions of MI into western PA/NY. There is a strong surge of moisture and instability, and thus locally heavy rainfall is possible. Overall it seems like the better chance of localized flash flooding is after 12z Tuesday as the duration of rain makes hydrologic conditions more sensitive by then. So we=20 will hold off on introducing any day 2 risk area and let the day 3 Marginal cover the threat. But we will continue to monitor trends=20 as the event gets more in range of the high res models today. Chenard Day 3 Valid 12Z Tue Mar 31 2026 - 12Z Wed Apr 01 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE OHIO VALLEY INTO NEW YORK AND VERMONT... A stationary front positioned over NY will likely be a focus for=20 scattered convection to start the period Tuesday morning. The=20 front is not forecast to move much during the day, likely=20 supporting periodic rounds of scattered showers and thunderstorms. An area of low pressure riding along the front should increase=20 forcing and convergence by Tuesday evening, resulting in an uptick=20 in rainfall coverage. Moisture parameters are impressive with this system...PWs are forecast to be near late March to early April max values, and IVT increases above the climatological 90th percentile. Instability is more marginal, and will likely reduce max rainfall rate potential and act as a limiting factor for flash flooding. However, there is some instability forecast in the morning, and by evening the increasing forcing/convergence could help offset decreasing instability. Thus while not widespread, some localized hourly rainfall around 1" seems plausible.=20 Model consensus rainfall magnitudes are generally in the 1-2" range, although with multiple rounds likely, there is a potential for more localized swaths getting into the 2-4" range. These=20 higher amounts are most likely over portions of far northeast OH,=20 far northwest PA and into southwest NY...near the stationary front and within a corridor where instability has a better chance of=20 persisting. A bit farther northeast into upstate NY and VT, some=20 snow melt contribution could also aid in minor runoff concerns.=20 Farther southwest over IN and OH instability is higher supporting=20 greater rainfall rates, but duration should be shorter with a=20 quicker frontal progression. Soil and streamflow conditions are=20 more conducive for flood impacts over portions of OH and IN, but=20 dry out with southwest extent into IL and MO. Thus while convection will extend into these latter areas as well, for now we will stop=20 the Marginal risk near the IL/IN border. Overall the primary threat is for localized flooding in areas=20 where training, or multiple convective rounds, occur near the=20 stationary front...or where higher short duration rates intersect=20 sensitive urban areas. Chenard Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8aoz4vPJkRtLeQk5gZk52-IZpaAX2xFUSC5w-nsxSrdw= ighh8TORp4zXmeWRokv4_uGj0tjn6kRRORVKCb42bWiV2ik$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8aoz4vPJkRtLeQk5gZk52-IZpaAX2xFUSC5w-nsxSrdw= ighh8TORp4zXmeWRokv4_uGj0tjn6kRRORVKCb42ofWEm-I$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8aoz4vPJkRtLeQk5gZk52-IZpaAX2xFUSC5w-nsxSrdw= ighh8TORp4zXmeWRokv4_uGj0tjn6kRRORVKCb42tS7Uujo$=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 3.28-Linux * Origin: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]