Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 18 2023 20:12:07 AWUS01 KWNH 182012 FFGMPD COZ000-WYZ000-UTZ000-190210- Mesoscale Precipitation Discussion 0942 NWS Weather Prediction Center College Park MD 411 PM EDT Fri Aug 18 2023 Areas affected...Northeast UT...Western/Central CO Concerning...Heavy rainfall...Flash flooding possible Valid 182010Z - 190210Z SUMMARY...Expanding clusters of showers and thunderstorms may produce some instances of flash flooding this afternoon given intense rainfall rates and considerations of rugged terrain and burn scar locations. DISCUSSION...The latest GOES-W satellite imagery in conjunction with dual-pol radar shows shower and thunderstorm activity expanding in coverage over the higher terrain of the central Rockies including much of central and western CO and also over into areas of northeast UT. The convection is being driven by a moderately buoyant airmass characterized by SBCAPE values of 1000 to 1500 J/kg with a substantial amount of monsoonal moisture entrenched over the region. PW anomalies are running as high as 1.5 to 2 standard deviations above normal across northwest CO and northeast UT in particular with strong moisture concentrations seen in the 700/300 mb layer from the latest CIRA ALPW data sets. This pooling of moisture through the column coupled with the level of instability will favor convective cells with efficiently high rainfall rates that may reach 1 to 2 inches in as little as 30 to 45 minutes, and the latest GOES IR satellite imagery has been showing some locally rapidly cooling convective tops with some of the cells over the last hour which is indicative of strong updrafts and subsequent increase in rainfall rates. The 12Z HREF guidance supports some localized storm total amounts of 2 to 3 inches going through the afternoon hours, but given the anomalous moisture environment, slow-moving cells, and orographic forcing that will be in place, some spotty heavier amounts cannot be ruled out. In fact, the HREF does show some low-end probabilities of seeing enough rainfall for the 100-year ARI to be exceeded going through 00Z. Some areas of flash flooding will be possible for the remainder of the afternoon, and some of the burn scar locations and areas of rugged terrain in particular will be susceptible to these impacts. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9bZ7Yutx1N52QtyYmv8hZNLnghN_rkRevyWGGn-j3bCnM0w4aRaqQNE8Sm27WCQBdSH6= 1JoFDjqmRVry0U2AH4VVoI4$ for graphic product... ATTN...WFO...BOU...CYS...GJT...PUB...RIW...SLC... ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC... LAT...LON 41170785 40940646 40440567 39780525 39160505=20 38720511 38490550 37770607 37460682 37350777=20 37660839 38030859 38800898 39161007 39721021=20 40071114 40231144 40721101 41150976=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) .