Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 05 2023 05:03:19 AWUS01 KWNH 050503 FFGMPD SDZ000-NDZ000-MTZ000-WYZ000-051100- Mesoscale Precipitation Discussion 1036 NWS Weather Prediction Center College Park MD 102 AM EDT Tue Sep 05 2023 Areas affected...western SD into southwestern ND Concerning...Heavy rainfall...Flash flooding possible Valid 050500Z - 051100Z SUMMARY...Areas of heavy rain with rainfall rates occasionally exceeding 1 in/hr are expected to impact portions of western SD into southwestern ND through 11Z. Areas of flash flooding will be possible as a result. DISCUSSION...0430Z water vapor imagery from GOES East showed a well defined upper level vorticity max and associated negatively tilted trough axis over the northern High Plains, advancing northeastward. While the western Dakotas were in a post-frontal environment, CIRA LPW imagery showed anomalous moisture in the 850-700 mb layer advecting northward through the central Plains and wrapping cyclonically around into the northern High Plains. Regional radar and ENTLN lightning imagery has shown a recent increase in the coverage and intensity of slow moving showers with embedded thunderstorms just north of the Black Hills, immediately north of the mid to upper level vorticity center. This increase was due in part to a developing deformation zone beneath an increasingly diffluent and divergent flow regime aloft, located south of a strengthening 70-80 kt jet max near 250 mb over southern Manitoba (measured by GOES East DMVs). SPC mesoanalysis data through 04Z indicated MUCAPE values dropping off markedly over the western Dakotas over the past 3 hours, but with 100-500 J/kg remaining. Short term forecasts from the RAP showed that weak instability will linger over eastern portions of the MPD threat area but continue to lower to insignificant levels for western areas. Meanwhile, the developing deformation axis is expected to support a slow moving stratiform region of moderate to heavy rain with embedded convective elements, where overlap with weak instability occurs, from northwestern SD into southwestern ND over the next couple of hours. Pivoting of this axis may allow for the heaviest rain in the vicinity of the western ND/SD border where occasional rain rates over 1 in/hr and storm total rainfall of 2-3 inches will be possible through 11Z. With 3-hr FFG values of 1.5 to 2.5 inches in 3 hours in place across a good portion of the western Dakotas, areas of flash flooding will be possible. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!569_8jUGsFrje-rYPSZjMeFiUsqI7feCE3ibkrw1JT72T0cPwsBZxZUObcbhDVWATXQq= paVyg1A2BmvmuPik8q5Wt4o$ for graphic product... ATTN...WFO...ABR...BIS...BYZ...UNR... ATTN...RFC...MBRFC...NWC... LAT...LON 47330100 47010043 46020069 45040132 44090246=20 44080386 44580430 45200431 45980353 47070224=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) .