Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 13 2025 20:20:39 AWUS01 KWNH 132020 FFGMPD COZ000-UTZ000-140130- Mesoscale Precipitation Discussion 1082 NWS Weather Prediction Center College Park MD 420 PM EDT Sat Sep 13 2025 Areas affected...Southeast Utah...Western Colorado... Concerning...Heavy rainfall...Flash flooding likely Valid 132020Z - 140130Z SUMMARY...Expanding slow moving, rotating cells capable of quick 1"/hr rates and localized scattered incidents of flash flooding in arid, rugged terrain likely to continue through the evening. DISCUSSION...GOES-E WV suite shows core of strong base of larger scale trough is centered across south-central UT, slowly lifting ENEward. Strong DPVA and broad divergence along the UT/CO border, along and east of the 3H trof and west of the 50-80kt 3H jet is providing strong vertical ascent across much of the area of concern. Deep layer moisture has been pressed further east in the warm conveyor belt, but sufficient lingering westward wrapping of the western branch of the TROWAL has maintained a solid moisture gradient across SE UT into SW and south-central CO, all while the strong, well defined dry slot under-cuts the circulation across NE AZ/NW NM. CIRA LPW denotes this evolution very well, with still some lingering enhanced moisture to feed the strong vertical development noted in Visible and 10.3um EIR loops.=20 Total moisture, mainly loaded from 850-700mb only totals about ..75" but with north to northeast flow fluxing into the stronger cells along the northwest edge of the dry slot; sub-cloud evaporation is helping to moisten the full profile while intra-cloud processes slowly increase rainfall generation/efficiency. Effective bulk shear to 40kts, also helps to keep updrafts rotating, increasing moisture flux convergence through the lower profile and supporting rates up to 1"/hr.=20 Additionally, being north of the stronger southwesterly steering flow also will slow northeastward cell motions up to 5-10kts and with Bunker's right moving propagation vectors near 15-20kts further aides residency of the stronger/broader up/downdrafts allowing for some localized 1-2" totals. Given the naturally arid, rugged geological formations, little infiltration is expected resulting in high run-off and localized flash flooding.=20 Remaining pockets of 1000-1500 J/kg of MLCAPE and favorable slow northeastward drift across W CO, will likely maintain the risk for these local flash flooding incidents through the remainder of the evening. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_bPJikECOFoz7t_FqR15qvJnvKlZ_gNlH3pkWnDu-kfYcwOwDLomGTM72Qlc3cJUYaDz= wBX5SN7TiTql8DAoNowygyk$ for graphic product... ATTN...WFO...GJT...PUB...SLC... ATTN...RFC...FWR...STR...TUA...NWC... LAT...LON 40340733 40070676 39140640 37990599 37110609=20 37000708 37040849 37090964 37511045 38231041=20 39000967 39880847=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) .