Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue May 09 2023 04:21:50 AWUS01 KWNH 090421 FFGMPD TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-090900- Mesoscale Precipitation Discussion 0242 NWS Weather Prediction Center College Park MD 1216 AM EDT Tue May 09 2023 Areas affected...Western KY...Northern West and Middle TN...Adjacent Portions of IL/MO Concerning...Heavy rainfall...Flash flooding likely Valid 090410Z - 090900Z Summary...Hourly rainfall rates up to 2.5" will likely result in localized totals of greater than 3". Isolated instances of flash flooding are likely, and scattered instances of flash flooding (with a considerable event or two) are possible. Discussion...A complex evolution of pre-frontal convection is expected across the MO Bootheel into western KY and northern portions of West and Middle TN over the next couple of hours. To the west (across Southwest MO), convection has organized into a mesoscale convective system (MCS) with the storm motion of the leading bow generally following the Corfidi downshear vector (~35 kts to the east-southeast), producing rainfall rates of up to 1-2"/hr along the path of the favorable northern bookend vortex. Out ahead of this MCS (over western KY), an isolated discrete cell has managed to take advantage of available instability (ML CAPE 2000-2500 J/kg) while tracking at a much slower ~15 kts towards the southeast (following the expected Bunkers right vector). While the low-level jet (925-850 mb) and associated moisture transport remains modest from the west-southwest, there has been a notable uptick (from 15 to 25 kts) over the past 4 hours (per SPC mesoanalysis). Precipitable water values range from 1.3-1.5 inches (near the 90th percentile, per BNA sounding climatology) with effective bulk shear of 25-30 kts supporting continued storm organization. Given this favorable environment, convection ahead of the approaching MCS is expected to continue to grow upscale, as short-term radar trends already show new updrafts attempting to form in the vicinity of the isolated supercell (which continues to show healthy signs of strengthening, with still-cooling cloud tops and a distinct above-anvil cirrus plume signature). While CAMs (new 00z HREF and subsequent HRRR runs) are rather unimpressive in their depiction of QPF through 09z (generally showing localized totals capping out around 2"), the experimental WoFS has occasionally show more concerning totals in the vicinity of the ongoing discrete convection. The 50th percentile has depicted localized totals closer to 3", and the 90th percentile has actually had a few runs closer to 5-6". Given the ongoing realized rates already (with MRMS estimating localized hourly totals approaching 2.5" in association with the aforementioned supercell), think these WoFS solutions are much closer to reality than the other CAMs. Given the recent proliferation of convection out ahead of the MCS, there are also concerns for backbuilding and repeating of rates of 1-2"/hr over a larger area of western KY (and possibly into portions of northern West and Middle TN). Considering that locally in the vicinity of the supercell Flash Flood Guidance (FFG) is as low as 1.0-1.5" (over 3-hr), localized instances of flash flooding are considered likely. Should the backbuilding/training scenario unfold, more scattered instances of flash flooding are possible (with a considerable instance or two of flash flooding unable to be ruled out).=20 Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_fVSDxr1FcZU0qFRSg8N437I08BkwSCwISsZJ5TP-G49ZqfAD2rWz7Hkf38brV4KDIgx= ibqXKuZzDlkEOmkd2sT2sBU$ for graphic product... ATTN...WFO...JKL...LMK...LSX...MEG...MRX...OHX...PAH... ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC... LAT...LON 38198915 37818757 37708641 37558536 37318490=20 36578474 35868548 35828725 35928864 36008958=20 36109000 36559019 37408988 37988978=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) .