Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 30 2023 08:47:37 AWUS01 KWNH 300847 FFGMPD MIZ000-WIZ000-MNZ000-301345- Mesoscale Precipitation Discussion 1116 NWS Weather Prediction Center College Park MD 445 AM EDT Sat Sep 30 2023 Areas affected...East-Central MN...Northwest and Central WI Concerning...Heavy rainfall...Flash flooding possible Valid 300845Z - 301345Z SUMMARY...Heavy showers and thunderstorms may continue to expand in coverage a bit more over the next few hours before gradually weakening after dawn. Some localized training of cells may produce at least an isolated threat for runoff problems and flash flooding. DISCUSSION...The GOES-16 IR satellite imagery has been showing an increasing level of convective organization with the showers and thunderstorms that were traversing areas of central and eastern MN and are now advancing into northwest WI. The convection is elevated in nature and is being driven by a low-amplitude shortwave trough crossing the Upper Midwest in conjunction with a well-defined frontal zone and nose of a 30 to 40 kt southwesterly low-level jet out ahead of a surface low center. PWs are on the order of 1.25 to 1.5 inches in connection with the surge of stronger low-level jet energy, and there is a pool of MUCAPE values of 500 to 1000 J/kg that should persist over the next few hours in close proximity to a warm front draped across areas of western and southern WI. This coupled with some very modest shear profiles should tend to maintain the current MCS activity going through dawn, with a gradual weakening trend thereafter as the low-level jet begins to wane. The 00Z HREF guidance has not had a particular good night in handling this convection with some members tending to be underdone and also too far northwest with their overall convective footprint. The HRRR guidance in particular has been way underdone with its QPF. IR satellite imagery has been showing an uptick in cooling convective tops over the last hour and reflective of some very strong updrafts. Consequently, MRMS data has been showing an increase in rainfall rates which are occasionally reaching 1.5+ inches/hour. The orientation of the convection ahead of the surface low center and north of the warm front to its east suggests some increased potential for some cell-training over the next few hours as the activity crosses northwest WI and potentially loses some latitude into areas of central WI. Expect as much as 2 to 4 inches of rain along the path of the MCS early this morning, and this may drive at least an isolated threat for runoff problems and flash flooding. This will include some urban flooding considerations. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4LoA57FURyrWa3DQcGrfU75llOn-0sqO0p4tssJ1vH46OYGXE8QuF935XslVnJrs8CGl= 1SfJvZbnHFb_gHXVmNxDB6E$ for graphic product... ATTN...WFO...ARX...DLH...GRB...MPX...MQT... ATTN...RFC...NCRFC...NWC... LAT...LON 46679111 46158924 45338842 44438883 44439064=20 45289261 45999290 46559240=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) .