Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 09 2023 17:29:42 AWUS01 KWNH 091729 FFGMPD INZ000-ILZ000-092328- Mesoscale Precipitation Discussion 0895 NWS Weather Prediction Center College Park MD 128 PM EDT Wed Aug 09 2023 Areas affected...Central IL...Southern IN Concerning...Heavy rainfall...Flash flooding possible Valid 091728Z - 092328Z Summary...Thunderstorm activity is beginning to deepen across portions of western IL, ahead of a well-defined MCV over central MO. Periods of high rainfall rates (possibly exceeding 1" in 15 minutes) as these storms intensify will support instances of localized flash flooding this afternoon. Discussion...Recent radar mosaic this afternoon shows an expansion of thunderstorms between LSX and ILX ahead of a well-defined MCV along the I-70 corridor in central MO. This activity appears somewhat disorganized, although recent estimates from LSX and MRMS suggest hourly rainfall rates are approaching 1.5"-2"/hour within the most robust updrafts over western IL. Warm cloud tops are noted with these storms on IR imagery along with relatively reduced lightning activity to suggest efficient warm rainfall processes ongoing in these storms. The mesoscale environment ahead of the MCV continues to improve for heavy rainfall. Recent blended TPW shows continued moistening of the column across the Midwest ahead of the MCV along an axis of low-level moisture transport at the 925-850 mb levels. In fact, by 18z PWATs 1-1.5 sigma above climatology are forecast to nose into the area with warm cloud layers of 4000-4500 meters. Meanwhile, filtered insolation combined with the moisture transport should support MLCAPE around 500-1500 J/KG along an east-west axis, distributed in a "tall-skinny" profile (NCAPE~.1). Effective shear is also forecast to strengthen ahead of the MCV, around 30-40 kts which will aid in convective longevity and organization. Thus, the concern is for quick hitting and efficient thunderstorms to expand ahead of the MCV and exceed the 1-3 HR FFGs, which vary from 1.5-2"/hr and 1.5-2.5"/3hr, respectively. Owing to the increasingly favorable environment, recent runs of the HRRR sub-hourly show some particularly heavy 15 minute rainfall totals later this afternoon within the strongest storms (.75-1"/15 minutes) which could quickly breach some of the lower FFGs. By 0Z tonight, the 12z HREF suggests heightened probabilities (20-50%) of 10 year ARI exceedance across a narrow swath of IL and IN (including Indianapolis), where spotty 3-4" appears reasonable.=20 Asherman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9ASRbMRFUrnvMocpZaoVtf4N7vH4tMUY79Tns6_c6b3_7qXNWCURh82V2eIpuQeHEkfV= tK603S1WDvZJ8URtjVNALBQ$ for graphic product... ATTN...WFO...ILN...ILX...IND...LMK...LOT...LSX... ATTN...RFC...NCRFC...OHRFC...NWC... LAT...LON 40528895 40048524 38748528 38878804 39048986=20 39449071 40229069=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) .