Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 08 2025 00:51:25 AWUS01 KWNH 080050 FFGMPD SDZ000-NDZ000-MTZ000-080645- Mesoscale Precipitation Discussion 0881 NWS Weather Prediction Center College Park MD 848 PM EDT Thu Aug 07 2025 Areas affected...Eastern MT...Western and Central ND Concerning...Heavy rainfall...Flash flooding possible Valid 080048Z - 080645Z SUMMARY...Clusters of heavy showers and thunderstorms should gradually grow upscale going through the evening hours. Locally high rainfall rates with this convection will support at least an isolated threat for flash flooding. DISCUSSION...The early evening GOES-E IR satellite imagery shows an upper-level trough gradually impinging on the northern High Plains, and this energy will be interacting with an increasingly moist and unstable environment pooling near a frontal zone that will be conducive for upscale growth of heavy showers and thunderstorms over the next several hours. Already there are a few well-organized clusters of convection noted over areas of central to northeast MT and far northwest ND as stronger forcing/DPVA begins to overspread the region ahead of the upstream shortwave energy/height falls. However, there is a well-organized pool of extreme instability and much stronger low-level moisture transport/convergence noted farther east over areas of western and especially central ND near this front. MLCAPE values are on the order of 4000 to 5000 J/kg, and with a strongly sheared environment characterized by 40 to 50+ kts of effective bulk shear, the convective mode evolution going into the evening hours will likely be dominated by supercells and bowing line-segments. However, as the convection grows upscale and gradually into a more organized MCS evolution later this evening, there will likely be a number of cell-mergers and at least some periodic cell-training concerns. The environment is very moist across areas of western and central ND near this front, with surface dew points locally in the lower 70s. This is supporting PWs of 1.3 to 1.5 inches in the pre-convective environment which are a solid 1 to 2 standard deviations above normal. A combination of this moist environment along with a gradually strengthening low-level jet and the aforementioned pool of instability should favor high rainfall rates with the organizing convective clusters. Earlier 12Z/18Z HREF guidance and the 12Z REFS suggested rainfall rates with the stronger cells reaching well into the 2 to 3 inch/hour range. The enhanced low to mid-level shear profiles will further aid these higher rates and especially within these supercell mode thunderstorms. Given the localized cell-merger and cell-training considerations, some storm total rainfall amounts going through midnight may reach as high 2 to 4 inches (spotty 5+ inch amounts possible). The 90th percentile 6-hour QPF data from the 00Z WoFS (along with previous runs) supports this over north-central ND in particular. Therefore, with these totals and at least relatively moist antecedent conditions, there will be concerns for at least isolated areas of flash flooding over the next several hours. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_to1yPtjwTf_G0ikOcol7kU_eps8aJyOoMcezA0syRmUYnW5yNr2KKFCITIASE9apH3l= VA7mJCCh7_71oKXUApAgguQ$ for graphic product... ATTN...WFO...BIS...BYZ...FGF...GGW...UNR... ATTN...RFC...KRF...MSR...NWC... LAT...LON 49170084 49059876 48559801 47629810 46679976=20 46020244 45720400 45430630 45650775 46510812=20 47240769 47940668 48540514 48940326=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) .