Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jun 20 2023 21:03:52 AWUS01 KWNH 202103 FFGMPD SDZ000-NDZ000-210300- Mesoscale Precipitation Discussion 0541 NWS Weather Prediction Center College Park MD 502 PM EDT Tue Jun 20 2023 Areas affected...Central Dakotas Concerning...Heavy rainfall...Flash flooding possible Valid 202100Z - 210300Z SUMMARY...Repeated rounds of thunderstorms along a frontal boundary producing maximum hourly rainfall rates up to 2.5"/hr may result in flash flooding. DISCUSSION...20Z surface analysis showed a slow moving cold front tracking across the Dakotas this afternoon with a growing field of towering cumulus ahead of and along the front. GOES-16 water vapor imagery and RAP mesoanalysis depicted a 500mb vorticity maximum over eastern CO tracking towards the northern Plains. As daytime heating peaks, instability will become maximized over the central Dakotas where temperatures have soared into the mid-90s and dew points into the mid 60s in some areas. RAP forecasts by early evening show as much as 2,500-3,000 J/kg worth of MLCAPE and PWATs between 1.5-1.75". The bubbling field of cumulus towers will soon erupt into intense thunderstorms this afternoon and continue into the evening hours. RAP forecasts indicate as much as 30-50 knots worth of effective bulk vertical wind shear will be present with the higher values likely to reside in ND. There will also be effective SRH values of 100-200 m2/s2, of which both parameters support the potential for supercells and multicell clusters. Warm cloud layers are not overly deep, making the flash flood threat more confined to areas where thunderstorms track NNE and parallel to the front. Despite the sufficiently deep warm cloud layers, the mesocyclones born out of the available shear and storm relative helicity values can still be efficient rainfall producers and any training storms would increase the flash flood potential. Storms in this environment can produce 1.5-2.0"/hr rainfall rates (locally higher possible) and the repeated segments could make for 2-3" in just 2 hours. 3-hr FFGs are 1.5-2.0" in some areas, making some parts of the Dakotas susceptible to flash flooding. The most at-risk areas are in poor drainage areas and urbanized settings that feature a greater concentration of hydrophobic surfaces. Some portions of central ND have also witnessed 300-400% of normal rainfall over the past 7-days according to AHPS, making this area also susceptible to flash flooding. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Wn07rRT-mvJAXRfaDu7R5U61pw0Pv4hIoeZl0Dpoh7hf-9N63h1LeL9a40oHFWpJ8C9= AqOkGvGVxJSI73bgDME2AP4$ for graphic product... ATTN...WFO...ABR...BIS...FGF...UNR... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 49079938 48859873 47609889 46559927 45489966=20 44370002 43440064 43470154 44180189 45230187=20 46840155 48080081 48870031=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) .