Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 25 2025 23:58:04 AWUS01 KWNH 252356 FFGMPD SDZ000-WYZ000-260555- Mesoscale Precipitation Discussion 0516 NWS Weather Prediction Center College Park MD 755 PM EDT Wed Jun 25 2025 Areas affected...South-central into southwest South Dakota and far northeast Wyoming Concerning...Heavy rainfall...Flash flooding possible Valid 252355Z - 260555Z SUMMARY...Slow moving thunderstorms along a stationary boundary are expected to merge with approaching convection ejecting eastward out of the High Plains this evening, with the potential for 1.5-2"/hr rainfall rates and scattered totals up to 4" across south-central South Dakota. This may lead to a few instances of flash flooding, particularly for areas with soils primed from previous rainfall today. DISCUSSION...A stationary boundary analyzed at 23Z draped across southern South Dakota has been aiding to anchor slow-moving storms in southwestern South Dakota this afternoon and should see convection continue, while also interacting with convection ejecting eastward from northeast Wyoming. MRMS depicts a few of these storms have produced anywhere from 1.5-3.0" this afternoon. Aside from the lifting mechanisms associated with the stationary boundary in the area, this part of the country remains in the RFQ of an upper jet streak and in an area of elevated PWs in the 1.0-1.5" range (above climatology). Instability and effective bulk shear also remain modest with MLCAPE of 1000-2000 J/kg and effective shear of 40-50 kts in western SD. Therefore, thunderstorms should be able to maintain strength for several hours after sunset and should contain efficient rainfall rates to potentially lead to scattered flash flooding. The experimental RRFS and REFS seem to have somewhat better handle on current convection compared to other CAMs. The REFS also happens to have the highest probabilities for 3-hr rainfall amounts greater than 3" by 06z tonight. These greatest chances occur within a region where 3-hr FFG in south-central South Dakota are in the 1.5-3" range. Given atmospheric and soil conditions as well as current radar trends, there exists the potential for isolated flash flooding chances early tonight. Snell ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7xRPBf3tA4vWBos6qybKaeni01YvYhj4ZsBmz2Dah6Yc-Lubk-BOCkDGxRjN5RWGQxdb= hcU_zMR6fE2Q5VXl8c4En-M$ for graphic product... ATTN...WFO...ABR...UNR... ATTN...RFC...KRF...NWC... LAT...LON 45130315 44530143 44009991 43669956 43239990=20 43070141 43200338 43640420 44300447 44890422=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .