Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 21 2023 19:40:11 AWUS01 KWNH 211940 FFGMPD NEZ000-COZ000-WYZ000-220140- Mesoscale Precipitation Discussion 0552 NWS Weather Prediction Center College Park MD 338 PM EDT Wed Jun 21 2023 Areas affected...Central High Plains Concerning...Heavy rainfall...Flash flooding possible Valid 211940Z - 220140Z SUMMARY...Strengthening thunderstorm activity this afternoon containing max hourly rainfall rates up to 2"/hr may lead to flash flooding. Areas with lingering saturated soils are most susceptible to flash flooding. DISCUSSION...19Z surface analysis showed an elongated frontal boundary stretching from northern CO on northeast into the northern Plains. There was also an analyzed outflow boundary from 15Z that has worked its way into southeast WY and eastern CO. These two features are set to help initiate strong-to-severe storms this afternoon and evening. RAP forecasts later this afternoon suggests MLCAPE will rise to as high as 2,000-3,000 J/kg and PWATs as high as 1.0-1.25". The amount of low level moisture is impressive with dew points in the mid 60s and NAEFS shows 850mb mean specific humidity percentiles in western KS and NE that are above the 99th percentile at both 18Z and 00Z this evening. This is well represented in the HRRR area averaged soundings within the highlighted region. As thunderstorms develop (along the aforementioned boundaries and off the Front Range of the Rockies), low level RH values could approach 90%. The unusually high dew points are also leading to unusually low LCLs, which combined with freezing levels as high as 14,000-15,000' AGL, would allow for up to 9,000-10,000' deep warm cloud layers. There will also be an impressive amount of vertical wind shear (RAP forecasts show up to 55 knots of effective bulk shear) and storm relative helicity (>100 m2/s2 of effective SRH). These kinds of parameters support thunderstorms becoming well organized and containing mesocyclones, which can be highly efficient rainfall producers. Southern WY and northeast CO still feature some sensitive soils after picking up as much as 400-600% of normal rainfall over the past two weeks. These areas, along with more urbanized metro areas, are most prone to possible flash flooding this afternoon. The threat for strong-to-severe storms may linger deeper into the evening hours depending on the speed/propagation of the developing clusters of storms in the central High Plains. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6nDLF5Cw0t2OnQ922dHr9dMyDPM1jAZB7oOGM3DXqMBiTPQi3m9mtd59lO1zv1_8nMxO= ZrWntqksIQXbxXmLp-raaTM$ for graphic product... ATTN...WFO...BOU...CYS...GLD...PUB... ATTN...RFC...ABRFC...CBRFC...MBRFC...NWC... LAT...LON 43300470 43040421 42560361 41410277 40270248=20 39440279 38760405 38820517 40160579 41000589=20 41720616 42630595 43270558=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) .