Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 05 2024 14:17:07 AWUS01 KWNH 051417 FFGMPD WIZ000-MNZ000-SDZ000-NDZ000-052000- Mesoscale Precipitation Discussion 0810 NWS Weather Prediction Center College Park MD 1016 AM EDT Mon Aug 05 2024 Areas affected...southeast ND, northeast SD, central MN Concerning...Heavy rainfall...Flash flooding possible Valid 051415Z - 052000Z Summary...Showers and thunderstorms will regenerate through the afternoon along a convergence axis and ahead of a shortwave. Rainfall rates of 1-2"/hr are likely, which through training could cause 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this morning shows a narrow corridor of showers and thunderstorms aligned NW to SE from near Minneapolis, MN back into far southeastern ND. This convection is regenerating along the nose of an 850mb LLJ analyzed by the SPC RAP to be 25-35 kts surging into a surface stationary front positioned across southern SD. This LLJ is then rising isentropically into central MN, drawing PWs as high as 1.5-1.8 inches, and elevated MUCAPE of 500-1000 J/kg, northward. The 12Z U/A sounding out of KMPX indicated a steep EML above 800mb reflective of the elevated convection, with tall skinny CAPE and moist adiabatic lapse rates above 700mb. This warm/moist environment will continue to support warm rain processes, and convection is progged to expand in coverage and intensity the next several hours as a shortwave over ND moves eastward to produce downstream ascent overlapped with modest diffluence in the RRQ of a jet streak moving across Ontario, Canada. The CAMs may be somewhat under-doing the current activity along the LLJ nose, but confidence is still high that convection will expand and train into the afternoon. The LLJ will likely try to veer more to the W than S over the next few hours in the typical diurnal cycle, but as this occurs the shortwave impinging from the west should help offset that with local backing of the flow, leading to a generally continued S/SW LLJ ascending the surface front into the area. This will result in showers and thunderstorms regenerating along this elevated boundary, and both the HREF and REFS neighborhood probabilities suggest rain rates of 1-2"/hr becoming common. This is also supported by HRRR 15-min rainfall accumulations reaching 0.25-0.5 inches at times. With mean 0-6km winds forecast to be generally from the west and aligned to the front, this indicates a strong likelihood for training as storms regenerate and expand ahead of the shortwave and then move to the E/SE. Where training is most pronounced, 2-3" of rain is possible with locally higher amounts. This area has been extremely wet recently as reflected by AHPS 7-day rainfall departures as much as 300-400% of normal leading to elevated 0-10cm soil moisture and compromised FFG as low as 1.5"/3hrs. The HREF exceedance probabilities are modest, likely due to the models struggling with current activity, but the setup should support FFG exceedance leading to instances of flash flooding through the afternoon. The greatest risk appears to be over urban areas or the most sensitive soils this afternoon, and additional heavy rainfall is possible this evening which could necessitate additional MPDs across these same areas. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9QAvUlIuNM6O-hzhWOX_HVRBvcqC851hB6D_sS6Y2s24AxMQpoFDMckAY3smMmuYvswx= vl0L9M_DZRsoXBasH1muTB4$ for graphic product... ATTN...WFO...ABR...BIS...DLH...FGF...MPX... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 46889655 46229377 45999312 45559243 44669203=20 44329278 44609436 44969645 45119863 45189936=20 45499979 46019967 46729845=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) .