Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 17 2024 18:55:45 AWUS01 KWNH 171855 FFGMPD AZZ000-UTZ000-NVZ000-180000- Mesoscale Precipitation Discussion 0892 NWS Weather Prediction Center College Park MD 255 PM EDT Sat Aug 17 2024 Areas affected...Much of Utah, far eastern Nevada, far northern Arizona Concerning...Heavy rainfall...Flash flooding likely Valid 171854Z - 180000Z Summary...Showers and thunderstorms will increase in coverage and intensity through the evening. Rainfall rates of 1"/hr will become increasingly common, leading to hourly rainfall accumulations of up to 0.75" and instances of flash flooding. Discussion...The GOES-E visible satellite imagery late this morning shows expanding low and high cloud associated with a potent shortwave and accompanying convection moving across much of Utah. ENLTN lightning density continues to increase across the area, reflective of the strengthening environment which is now characterized by PWs of 1.2-1.5 inches as measured by GPS, well above the 90th percentile, and MLCAPE which has rapidly increased to above 1000 J/kg away from the clouds. Expanding and deepening thunderstorms are accompanying this overlap of ascent (aided by a strengthening jet streak to the north) and thermodynamics, with recent rainfall rate estimated from KICX reaching 1.5"/hr. The morning convection associated with the potent shortwave somewhat struggled to intensify, but as instability continues to climb through daytime heating and a surge of low-level flow to draw higher CAPE/PW northward, rain rates have become more impressive in the fresher updrafts. This is likely to continue as reflected by simulated reflectivity in the recent high-res CAMs, including the 15-min HRRR and UA WRF. The HREF neighborhood probabilities reach above 20% for 1"/hr rates this evening, and both the UA WRF and HRRR 15-min rainfall accumulations suggest 1-hr rainfall could reach 0.75" in some areas. This is despite progressive storm motions which are likely to remain around 25-25 kts, as aligned Corfidi vectors suggest an enhanced training risk. The ingredients suggest that storms will continue to develop to the south within the axis of more intense thermodynamics, and then lift north/northeast to produce multiple rounds of storms in some areas. The terrain of the Wasatch could also be a focus for convection, and it is likely several areas will receive 1-2" of rain, with a 10-20% chance of locally as much as 3" in some locations. This region is exceptionally vulnerable to heavy rain rates due to the variety of sensitive terrain features. However, some of this region has experienced more than 300% of normal rainfall the past 7 days which has led to 0-40cm soil moisture that is in some places above the 90th percentile and 1-hr FFG below 0.5 inches. This suggests that while heavy rain moving across any burn scars, slot canyons, or dry washes will have the greatest potential to produce flash flooding, any location that receives multiple rounds of these intense rain rates could experience impacts due to flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5_XqXu9T36hHr-Gzq2iuo62iqHYYuzjaOuPZ-LwXXnfgSPverOZ2azRtYoznWWeLz-b_= MVRRNi_zXtnmZhuyW9eiGAc$ for graphic product... ATTN...WFO...FGZ...LKN...SLC...VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 40931175 40501068 40081047 39091067 38011059=20 37291092 36711160 36511213 36451222 36241301=20 36371363 36761398 37261435 38251439 38951408=20 40191366 40701275=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) .