Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 20 2023 19:33:10 AWUS01 KWNH 201933 FFGMPD KSZ000-NEZ000-COZ000-WYZ000-210001- Mesoscale Precipitation Discussion 0772 NWS Weather Prediction Center College Park MD 332 PM EDT Thu Jul 20 2023 Areas affected...Central High Plains Concerning...Heavy rainfall...Flash flooding possible Valid 201931Z - 210001Z Summary...Thunderstorm development is underway along much of the Front Range. 2-4" of rainfall through 0Z tonight (some of which could fall in a very short period of time) could support instances of flash flooding prior to upscale growth tonight. Discussion...Radar and visible satellite imagery show increasing thunderstorm coverage along much of the front range in response to strengthening DCVA, left exit forcing, and diurnal heating atop the terrain. Additional agitated cumulus was also noted along a cold front southeast of Denver. 1000-2000 J/KG MUCAPE estimated in the vicinity of this initial pulse activity supported rainfall rates approaching 1" per hour, which prompted a Flash Flood Warning west of Fort Collins as a cell lingered over the Cameron Peak Burn Scar. As the convection moves off of the terrain, the storms are expected to organize and intensify into intense multi-cells and supercells as they interact with an axis of higher theta-e air prompted by easterly upslope flow, and cyclonically curved shear profiles containing 40-45 kts of effective bulk shear. Proximity soundings to the convection depict favorable vertical profiles this afternoon for excessive rainfall, including 1000-1500 J/KG MLCAPE, PWATS of 1-1.5" (in the 90th-95th percentile for the area), warm cloud layers around 10,000 feet (especially over northeast CO), and 100 mb mean mixing ratios of 12-14 g/kg. The strong flow aloft will prompt fairly progressive storm motions (mean flow ~20 kts and BRM ~20-25 kts) which will limit residence times of heavy rainfall. However, recent runs of the 15 minute HRRR depict some intense 15 minute rainfall rates upwards of .75-1"/15 minutes along and east of the Front Range this afternoon within the axis of higher theta-e air as cells mature into supercell clusters prior to their eventual upscale growth tonight. This could easily overwhelm the 1 HR FFGs which are as low as .5-1"/hr across much of the area, not including vulnerable burn scar areas. Through 0z tonight, the 12z HREF suggests elevated chances of 5-10 year ARI exceedance (60% & 50%, respectively) focused atop northeast CO, with some signal for 100 year ARI exceedance depicted (5%) as CAMS show 2-4" of rainfall are possible. Asherman=20 ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4saB5kGzW1Kt3chkABdpmRKhe5Fl1SobHB3rBbcYAw1AmS2SNTlgiaI8Jo1D93ELQYKU= uHuzCEBygUBae27Xf8MKylE$ for graphic product... ATTN...WFO...BOU...CYS...DDC...GLD...PUB... ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC... LAT...LON 41820545 41470357 40720227 39770172 38410184=20 37610261 37050392 37430528 38890580 40980660=20 =20=20=20=20=20=20=20=20=20=20=20=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) .