Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 07 2023 06:10:41 AWUS01 KWNH 070610 FFGMPD INZ000-ILZ000-MOZ000-IAZ000-071200- Mesoscale Precipitation Discussion 0230 NWS Weather Prediction Center College Park MD 209 AM EDT Sun May 07 2023 Areas affected...Far Southwestern IA and Northeastern MO...North-Central IL...Western IN Concerning...Heavy rainfall...Flash flooding possible Valid 070600Z - 071200Z Summary...Localized rainfall rates of 1-2"/hr expected to continue across portions of the central MidWest, which may lead to localized totals as high as 3-6" through the early morning hours. Isolated instances of flash flooding are possible. Discussion...Semi-discrete convection is continuing to slowly proliferate across portions of far southwestern Iowa, far northeastern Missouri, and into much of north-central Illinois at this hour. Regional radar imagery depicts a messy mixture of storm modes, with cell mergers forming a decently organized bow echo across central Illinois (which has the best chance of leading the formation of an MCS), with mini supercells forming behind the still-developing bow (into IA/MO). Some of these supercells are also splitting, with a spatial depiction of hodographs (via SPC mesoanalysis) indicating a high degree of variability over relatively short distances across the frontal zone (with a veer-back-veer signature clearly visible in some of these hodographs, which is likely limiting the upward potential of overall proliferation). The mesoscale enviornment is characterized by SB CAPE gradient of 500-3000 J/kg (highest towards the southwest, but generally advecting northeastward with the low-level jet), precipitable water values of 1.2-1.5 inches (between the 90th percentile and the max moving average, per DVN and ILX sounding climatology), and effective bulk shear of 40-50 kts. Upscale growth of convection is generally expected to continue along the quasi-stationary front, with bunkers right storm motion vectors favoring easterly progression. This should allow for some training and repeating of 1-2"/hr rainfall rates, given the parallel orientation of the frontal feature. Corfidi vectors would also continue to allow easterly (to southeasterly) motion as well, which may allow for additional repeating of high rainfall rates along the southwestern flank of a developing MCS. All-in-all, this may allow for localized 6-hourly totals to approach 4-6 inches across portions of central IL (and possibly downstream into south-central IN), as advertised by several HRRR runs since 23z (though the 00z HREF signal is less impressive with 3" neighborhood exceedance probabiltiies peaking near only 20%). Corresponding 6-hr Flash Flood Guidance (FFG) average near 2.5", so any realized totals of 3"+ are expected to lead to isolated instances of flash flooding (with much of those totals occuring over a period of 3-hr or less, where FFGs average closer to 2"). Considering the overall uncertainty in ultimate MCS formation and the placement of cells to allow for idealized training and repeating, isolated instances of flash flooding are considered possible. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7avWTIA3kfShPaKXCF1gLEwO9owsBqlr2WVZULVz9Jxqk3JLNtkvJvUm15rnx_Z4mSi5= zDuxEYOeya4UGynCitR2uMg$ for graphic product... ATTN...WFO...DVN...ILX...IND...IWX...LMK...LOT...LSX...PAH... ATTN...RFC...NCRFC...OHRFC...NWC... LAT...LON 41449026 40808694 39808626 38628670 38398801=20 39379077 40319221 41339202=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) .