Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 29 2023 11:18:16 AWUS01 KWNH 291118 FFGMPD KYZ000-INZ000-ILZ000-291700- Mesoscale Precipitation Discussion 0601 NWS Weather Prediction Center College Park MD 717 AM EDT Thu Jun 29 2023 Areas affected...Illinois, Indiana, Kentucky Concerning...Heavy rainfall...Flash flooding possible Valid 291116Z - 291700Z Summary...Thunderstorms will increase in coverage and organize into clusters this morning. These clusters will train to the southeast with rain rates exceeding 2"/hr. Flash flooding is possible. Discussion...The regional radar mosaic this morning shows convection rapidly blossoming across eastern IL and far western IN. These thunderstorms are developing along the nose of a 20-25 kt LLJ that is locally backed to the S/SW driving additional convergence for ascent. This LLJ is also acting to transport impressive thermodynamics into the region characterized by PWs of nearly 2 inches measured by GPS, above the 90th percentile for the date, and SPC RAP analyzed MUCAPE of 3000 J/kg. These intense thermodynamics are fueling rain rates that are already estimated via KILX WSR-88D to be 1.5-2"/hr, resulting in FLASH response in the QPE:FFG ratio of around 100%. The high-res guidance is in good agreement that this convection will expand through the morning, but is highly variable in the location. Convergence along the backed LLJ will continue to be the primary driver of ascent, resulting in this expanding coverage of thunderstorms, with intensification also likely for the next few hours before the LLJ begins to weaken. 0-6km bulk shear of 30-50 kts will allow these storms to organize into clusters, and possibly an MCS, which will then dive southward into the better inflow and along a sharp CAPE gradient. While Corfidi vectors are progged to be 20-25 kts to the SE, suggesting fast motion, aligned mean winds indicate an increasing likelihood for training of cells. With convection repeatedly developing along the LLJ, this could result in an elongated area of thunderstorms which will train repeatedly to the southeast over some areas. Antecedent conditions are relatively dry which has raised FFG to 2-2.5"/1hr, and lowered streamflow anomalies to below the 25th percentile. However, rain rates forecast by the HREF neighborhood probabilities will exceed 2"/hr, and the HRRR indicates that 15-min accumulations could exceed 1" in the most intense or organized convection which could overwhelm even these dry soils. Additionally, although the exact placement of the heaviest rain axis remains somewhat uncertain, training of these rain rates could produce 3-5" of rain, producing instances of rapid runoff and flash flooding through late this morning Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9y1Gsz4T5BKD_EUAZLdhEs5SgH_W4Q0_3UiHUmlCOVLFnKs3V7hOMCGN-lQpfTyxnaQ4= daqhfgCxxG4GZmtoC-85Zlw$ for graphic product... ATTN...WFO...ILX...IND...LMK...LOT...LSX...PAH... ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC... LAT...LON 41218899 40918757 40188665 39548605 38868587=20 37868600 36968661 36678743 36808797 37438883=20 37968928 38708970 39858986 39888986 40628968=20 40848947=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) .