Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 02 2023 17:54:24 AWUS01 KWNH 021754 FFGMPD OHZ000-MIZ000-INZ000-ILZ000-030000- Mesoscale Precipitation Discussion 0621 NWS Weather Prediction Center College Park MD 153 PM EDT Sun Jul 02 2023 Areas affected...Southern Great Lakes Concerning...Heavy rainfall...Flash flooding likely Valid 021800Z - 030000Z Summary...Showers and thunderstorms moving along a stationary front will continue to produce rainfall rates of 2-3"/hr through this evening. These storms will likely train west to east to produce as much as 5" of rain in some areas. Flash flooding is likely. Discussion...The regional radar mosaic this aftn shows an impressive MCV associated with convection near a surface low skirting near Chicago, IL. This has produced widespread mesonet observations of 3-5" of rain in the last 6 hours over Chicago, resulting in impressive CREST unit streamflow of more than 500 cfs/mi and significant flash flooding. Although this MCV is gradually shifting eastward, a potent outflow boundary has developed to the SW driving additional ascent for convection. This entire system will advect eastward along a stationary front analyzed by WPC, into favorable thermodynamics characterized by PWs above the 90th percentile as measured by GPS, and SPC RAP analyzed SBCAPE as high as 2000 J/kg. 850mb inflow into ongoing convection is generally modest at 15-20 kts, but is originating favorably from even more intense thermodynamics to resupply moisture and instability, while concurrently obliquely upgliding atop the stationary front to drive additional lift. Additionally, a mid-level deformation axis and a collocated TROWAL are helping to increase column moisture and provide stronger deep layer ascent. As this entire system shifts eastward into this evening, the overall environment downstream will remain mostly unchanged as the inflow transports robust thermodynamics northeastward. This should result in continued widespread convection as shown by high-res simulated reflectivity, with most of the development occurring along the stationary front and the outflow boundary due to intense convergence. Efficient warm-rainfall rates as progged by the HREF neighborhood probabilities will exceed 2"/hr at times, with 15-min rainfall on the HRRR reaching above 1" in isolated areas. Thunderstorms developing within the warm sector will generally move northeast at 10-15 kts, but subtle backing of the inflow in response to the approach of the surface wave will help align Corfidi vectors to the mean wind while additionally collapsing to just 5 kts. This will support enhanced training along the front and along the outflow as it gets stretched to the southwest, with additional backbuilding occurring into the greater instability. In this setup, The HREF indicates a 30-50% chance for locally 3 inches of rainfall, and 10-20% chance for as much as 5 inches. These intense rain rates and significant rainfall accumulations will be falling atop soils that are generally dry from below normal 14-day rainfall. This is reflected by below normal USGS streamflow anomalies and high FFG, especially across lower MI. However, FFG in some parts of IL/IN are as low as 1.5"/1hr, and even lower near the urban corridors of Chicago and Detroit. Flash flooding is likely along the outflow boundary and stationary front due to training, and an isolated significant flash flood event is possible should the most intense training occur over any urban areas area again this aftn/eve. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6cpcqxvVSdr1pEut911yp_uW5LbOvBTkmos9429ZTrsKPHvBWBirVe3AobGeVGGnKW5U= GJhsnHSZfMeZjd5CXzwbY1U$ for graphic product... ATTN...WFO...CLE...DTX...DVN...GRR...ILX...IWX...LOT... ATTN...RFC...NCRFC...OHRFC...NWC... LAT...LON 43768340 43608275 43208246 42748259 42498262=20 42098276 41748300 41358345 41288428 41218518=20 40958676 40618752 40358828 40228890 40238939=20 40428978 40738984 41078936 41448897 41748872=20 42258806 42538727 42598664 42768573 43608379=20 =20=20=20=20=20=20=20=20=20=20=20=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) .