Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 02 2025 00:13:54 AWUS01 KWNH 020013 FFGMPD SDZ000-020612- Mesoscale Precipitation Discussion 0847 NWS Weather Prediction Center College Park MD 813 PM EDT Fri Aug 01 2025 Areas affected...portions of SD Concerning...Heavy rainfall...Flash flooding possible Valid 020012Z - 020612Z Summary...A reinvigorated MCV continues to move eastward across northwest SD. Hourly rain amounts to 2.5" with local amounts to 5" are possible, which would be most problematic in urban areas.=20 While this flash flood threat is conditional and potentially small scale, the risk could elevate if its feeder band backbuilds for 2+ hours. Discussion...Convection formed earlier today in association with a pre-existing MCV and has since evolved into an occluded appearance on radar imagery with the MCV itself resembling a weak bounded weak echo region/mid-level eye around 6:15 pm CDT. Convection has had a tough time getting going otherwise, with limited and occasional activity south of Deadwood. Other showers and thunderstorms are moving through the High Plains of WY towards the region. Precipitable water values are over 1.5". ML CAPE is 500-2500 J/kg in its vicinity, with the CAPE gradient oriented northwest- southwest to the southwest of the MCV. This is leading to a feeder band within its southern and eastern peripheries which is trying to broaden the heavy rain footprint in association with this system. The mesoscale guidance has had a handle on convection near the system's center so far, but has struggled on the details outside of its immediate environment. Because of the MCV moving eastward into an environment of lesser instability, both the 18z HREF and 12z give the impression that the feeder band will increasingly become the heavy rain producer with this system which then tries to move southeast down the instability gradient, which conceptually fits the environmental parameters. Hourly rain amounts to 2.5" are expected at times within the feeder band with local amounts to 5", particularly if storms backbuild on the westermost end of the feeder band, cell mergers occur from the incoming WY activity, or storms haunting the area south of Deadwood merge in. These amounts would be most problematic in urban areas.=20 The flash flood threat is conditional, and could become concerning if the tail end of the feeder band shows any prolonged backbuilding character towards the instability pool in any specific location. This would both increase the hourly and overall rain total potential stated above from this system. The uncertainty regarding this possibility kept this MPD in the Possible category. Roth ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Xqa13rU3ZzT_5C5TcXv7r6P3z1XgzSzB8kdmrWj3XLhdq6MqEYK0JgVVAR3bH8ytKpC= _KooFB_YxOYBtvPCfFhse7k$ for graphic product... ATTN...WFO...ABR...UNR... ATTN...RFC...KRF...NWC... LAT...LON 45870272 45610059 44789937 43650002 43710178=20 44760301=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .