Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 02 2023 12:18:20 AWUS01 KWNH 021218 FFGMPD MIZ000-INZ000-WIZ000-ILZ000-IAZ000-021800- Mesoscale Precipitation Discussion 0620 NWS Weather Prediction Center College Park MD 817 AM EDT Sun Jul 02 2023 Areas affected...Upper Midwest and Great Lakes from eastern Iowa to lower Michigan Concerning...Heavy rainfall...Flash flooding possible Valid 021217Z - 021800Z Summary...Showers and thunderstorms developing along a warm front will expand in coverage while moving very slowly through early this afternoon. Rainfall rates may climb above 2"/hr at times, resulting in 2-3" of rainfall with locally higher amounts. Flash flooding is possible. Discussion...Closed 500mb low positioned over northern IL is clearly evident in the GOES-E WV imagery this morning. The associated warm conveyor belt is surging moisture and instability into the Ohio Valley, which is then wrapping cyclonically back into the low within an intensifying TROWAL. This TROWAL is positioned above a sharp 700mb deformation axis, and nearly collocated with a surface low and warm front analyzed by WPC. Low-level inflow from sfc-850mb is from the SW at 10-20 kts, producing modest isentropic upglide to aid in ascent, while coincidentally supplying PWs of 1.7 inches and MUCAPE above 1000 J/kg into the region. Within this overlap of forcing and thermodynamics, showers have shown a steady increase in intensity on the regional radar mosaic this morning leading to pockets of FLASH response of 100+% QPE:FFG ratio and unit stream flow of 100-200 cfs/mi. Although the high-res models differ modestly in their evolution, there is some consensus in the simulated reflectivity the next several hours. The surface wave will move only gradually east, while the associated front wavers in the vicinity before gradually advecting as well. This will result in continued moist low-level flow into the front while the TROWAL aids in keeping PWS over 1.75 inches, even as SBCAPE climbs towards 2000 J/kg. This setup suggests that convection will continually redevelop along the warm front and expand in coverage, with additional storms occurring along the lake breeze and any resultant outflows. Storm motions are progged to be just 5-10 kts, with anti-parallel Corfidi vectors of 5 kts or less indicating nearly stationary or backbuilding storms into the better instability to prolong heavy rainfall. With rainfall rates forecast by the HREF probabilities to exceed 2"/hr, and the HRRR indicating some areas of around inch of rainfall in 15 mins, where storms slow or regenerate more than 3 inches of rain is possible. This region has been generally dry as of late noted by below normal rainfall the last 7 days and generally normal to below normal streamflows. However, these intense rates could still overwhelm 1-hr FFG, especially in more sensitive or less permeable locations. This suggests there is at least an isolated risk of flash flooding, especially in urban areas, through this aftn. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5E5b3az0rZGrY_BdmQKR659zrkO6e2v6n4esrHfLdy_0gtMdp3zgVSQ2Evv4rIDrWSUm= fAZHLGFu6tL907RjtnZdI9M$ for graphic product... ATTN...WFO...DTX...DVN...GRR...ILX...IWX...LOT...MKX... ATTN...RFC...NCRFC...OHRFC...NWC... LAT...LON 42508777 42498675 42458558 42258435 41918342=20 41738369 41778456 41658573 41168680 40698803=20 40378928 40328972 40259095 40389145 40709173=20 40989159 41359128 41749093 42049039 42318979=20 42448880=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) .