Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 13 2023 18:46:54 AWUS01 KWNH 131846 FFGMPD MNZ000-IAZ000-SDZ000-140045- Mesoscale Precipitation Discussion 0289 NWS Weather Prediction Center College Park MD 246 PM EDT Sat May 13 2023 Areas affected...IA into adjoining portions of MN and SD Concerning...Heavy rainfall...Flash flooding likely Valid 131845Z - 140045Z SUMMARY...Slow-moving thunderstorms are expected to produce rainfall rates of 1 to 2+ in/hr across IA through 00Z which should lead to a few areas of flash flooding. 6-hr totals of 2-4 inches with locally higher totals will be possible. A lower end flash flood threat will also exist into adjoining portions of SD and MN. DISCUSSION...Widely scattered thunderstorms were ongoing across portions of central and northwestern IA as of 1815Z within a moist (1.2 to 1.4 PWATs) and fairly narrow axis of MLCAPE estimated by the 18Z SPC mesoanalysis to be 500-1500 J/kg. Low level easterly winds over central IA were converging into southerly winds in place over southwestern IA near an occluded and stationary front over the region, supporting lift on the southeast side of a closed mid-level low located in eastern SD. Storm motions over northwestern IA were ~10-20 kt from south to north while cells near/southeast of Des Moines were tracking toward the northeast at similar speeds. Thunderstorm coverage is expected to increase over the next few hours within the uninhibited instability axis, connecting locations from central IA into northwestern IA and portions of southwestern MN/southeastern SD. Slow movement and repeating of cells are likely to produce rainfall rates of 1-2 in/hr and 2-4 inches in 2-3 hours, and perhaps locally higher than that across the region. Despite lower instability to the north and west, upper level diffluence will help to enhance lift to the immediate southeast of the upper low, possibly boosting rainfall intensity amid the lower CAPE values in MN and SD. Heavy rainfall over the past 3 days has produced wet antecedent conditions and low FFG, especially across northwestern IA into southwestern MN. Considering the low FFG values and favorable setup for heavy rain, flash flooding is considered likely across portions of IA and possible for adjoining MN/SD, although coverage may remain isolated to widely scattered. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_v7uBodMK-1tMnc35D0htE-Q9jlZjIzllsi9BFVjKVRSa52U79H7ZeRD0MxRZixRPoDM= xcub_Uj-4AIL0hl2z-4C1BE$ for graphic product... ATTN...WFO...ABR...ARX...DMX...DVN...FSD...MPX... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 44659655 44609557 44189459 42939300 42009227=20 41339241 41089327 41419412 41799457 42339537=20 42849621 43169694 43909726=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) .