Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 26 2024 18:38:05 AWUS01 KWNH 261838 FFGMPD MNZ000-SDZ000-NDZ000-270030- Mesoscale Precipitation Discussion 0930 NWS Weather Prediction Center College Park MD 237 PM EDT Mon Aug 26 2024 Areas affected...Central Minnesota... Concerning...Heavy rainfall...Flash flooding possible Valid 261840Z - 270030Z SUMMARY...Increasingly unstable deep moist air along the front ahead of approaching MCV/shortwave should support slow cell motions and potentially training/repeating environment over the late afternoon into evening with potential for localized 3-4" totals and possible incidents of flash flooding. DISCUSSION...GOES-E and RADAR depict incipient thunderstorm development across western MN at the apex of the deep layer moisture return axis/deep layer stationary front across northern MN into Ontario along the NW coast of Lake Superior. Satellite suite also shows decayed but still compact MCV, upscaled shortwave over SE SD lifting north. At the surface a low has developed downstream of the approaching DPVA near KAQP with a cold front dropping south into another surface low in northeast NEB. Ample insolation and well above/near record low level moisture with Tds in the upper 70s and low 80s is supporting very unstable profiles, while moisture is pooled along an effective comma head/TROWAL in the sfc to 700mb layers per CIRA LPW extending downstream along the stationary front.=20=20 Aloft, steering flow is weak between the exiting synoptic wave in Ontario and the approaching shortwave (with much stronger synoptic closed low well upstream into the northern High Plains. As such, flow is 15-20kts through depth but also fairly unidirectional with propagation vectors also parallel to backed slightly to reduce forward cell motions. The approaching shortwave is increasing effective bulk shear to support some organized structures and support low level moisture flux into individual storms, but overall cell motions will be slow with additional development propagating on maturing outflow boundaries. Given the strong updraft strength from CAPE over 3000 J/kg, but ingested localized moisture vertically converging in the low levels, efficient rainfall production is possible along with some of the severe parameters expected; and any rotating updrafts will further enhance flux. As such, rates of 2-2.5"/hr are possible. Slow motions, upstream redevelopment may allow for localized 3-4" spots given 1-2 hour residency.=20=20 Initially, larger scale convergence has only been sufficient near/north of the surface low and confluent portion of the 850mb deformation zone/TROWAL across Otter Tail county. Eventually, with further backing/strengthening of low level winds, agitated cu field across the area of discussion will experience increased convective coverage toward the later evening, expanding potential for spots of 3-4" and localized flash flooding concerns especially across the southern reaches of the Red River Valley into the Minnesota River Valley where FFG values are a bit lower naturally (1.5-2"/hr & 2-2.5"/3hr) and are in reach of rainfall potential. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-FAReQDrBfXzzVqRYgvuoNik8lyZx7YMqgyPbr7pzNTA02zUFpCU6rc9b9nChi52c1Xe= spNOxu49vlIMACjbxArOexs$ for graphic product... ATTN...WFO...ABR...DLH...FGF...MPX... ATTN...RFC...NCRFC...NWC... LAT...LON 47349405 47279305 46689270 45829315 45069363=20 44489406 44209487 44769566 45169663 45689691=20 46089679 46429658 46819600 47179506=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) .