Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 08 2023 05:39:46 AWUS01 KWNH 080538 FFGMPD MIZ000-INZ000-ILZ000-MOZ000-IAZ000-081130- Mesoscale Precipitation Discussion 0660 NWS Weather Prediction Center College Park MD 138 AM EDT Sat Jul 08 2023 Areas affected...eastern Iowa, Illinois, northern Indiana Concerning...Heavy rainfall...Flash flooding possible Valid 080537Z - 081130Z Summary...Clusters of showers and thunderstorms will train across the area overnight. Rainfall rates may exceed 1"/hr at times resulting in 1-3 inches of rain. Flash flooding is possible. Discussion...The regional radar mosaic tonight shows an expanding area of showers and thunderstorms spreading out of Iowa and into Illinois. These thunderstorms are developing downstream of a modest shortwave impulse noted in the GOES-E WV imagery, and along the nose of a surging SW 20-25 kt LLJ. The approach of the shortwave is causing local backing of the LLJ to enhance advection of robust thermodynamics characterized by PWs of around 1.7 inches and MUCAPE of 500-1000 J/kg. The backing/surging of this LLJ is more impressively advecting these thermodynamics northward, helping to enhance the coverage and intensity of ongoing convection, which has resulted in recent radar-estimated rain rates above 1"/hr from KILX. The weak shortwave moving eastward will continue to be the primary forcing mechanism for ascent, interacting with the backing LLJ to expand convection tonight. The high-res guidance is in good agreement that thunderstorms will continue to expand and intensify in response to the surge of more favorable thermodynamics. Mean 0-6km winds are progged to remain generally due east at around 15 kts, with aligned Corfidi vectors indicating a likelihood for training, with backbuilding to the W/SW into the greater instability also possible, especially along a trailing convergent zone/elevated front just south of the shortwave. This suggests that multiple rounds of convection are possible in some areas, and with rain rates progged by the HREF to exceed 1"/hr at times, this could produce 1-3" of rain with isolated higher amounts. There is some uncertainty as to the axis of heaviest rain, but a general west-to-east trajectory of clusters is likely, with just some subtle southeast motion possible farther east in response to better thickness diffluence and the continued backing of the LLJ downstream of the driving shortwave. 14-day rainfall from eastern IA through much of northern and central IL has been 200-300% of normal, resulting in compromised FFG of around 1.5"/1hr. While exceedance probabilities from the HREF are generally modest, around 20%, there exists at least an isolated flash flood risk tonight, especially if the most efficient training can overlap any more impermeable/urban areas. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8k2PXB4rPrpimpTVyyLHVCrIC9TcXiCborDvj1yUtD4qgXMISd9CWr-r5c_k09Zxs4Yj= zN8Fqt_ZOBF_S3CAjAJfxIk$ for graphic product... ATTN...WFO...DMX...DVN...ILX...IND...IWX...LOT...LSX... ATTN...RFC...NCRFC...OHRFC...NWC... LAT...LON 41998803 41938701 41878617 41688593 41268590=20 40888594 40528618 40188651 39748750 39488849=20 39488973 39719050 40049121 40479204 40659236=20 40939274 41249274 41469201 41669099 41918949=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) .