Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 30 2023 17:45:09 AWUS01 KWNH 301745 FFGMPD KSZ000-NEZ000-COZ000-WYZ000-302330- Mesoscale Precipitation Discussion 0606 NWS Weather Prediction Center College Park MD 144 PM EDT Fri Jun 30 2023 Areas affected...Central High Plains Concerning...Heavy rainfall...Flash flooding possible Valid 301743Z - 302330Z Summary...Thunderstorms will expand and organize into clusters across eastern Colorado this afternoon. These thunderstorms will generally be progressive to the east, but 1-2"/hr rates may cause flash flooding atop sensitive soils. Discussion...The GOES-E WV imagery this aftn clearly indicates a shortwave lifting northeast across CO downstream of a mid-level trough axis oriented NE to SW over the Intermountain West. The associated height falls are driving deep layer ascent, aided by modest upper diffluence in the LFQ of a pivoting jet streak. This synoptic lift is occurring within extremely favorable thermodynamics for heavy rain characterized by PWs of 0.6 to 1.1 inches, around the 75th percentile for the date, and SBCAPE increasing within clearing sky conditions to 1000-2000 J/kg. This overlap of ascent and moisture/instability has allowed convection to develop already, with radar-estimated rain rates of 1-1.5"/hr according to KFTG. As the shortwave continues to lift northeast in conjunction with the mid-level trough axis, forcing is expected to intensify through the aftn. This will result in widespread thunderstorm development across much of the High Plains of CO and southern WY, with storm organization likely thanks to bulk shear of 30-50 kts. The simulated reflectivity from the high-res indicates multiple clusters of storms will form in this environment, with HREF neighborhood probabilities suggesting 1-2"/hr rain rates will be common. Despite mean 0-6km winds that should remain progressive to the E/NE at 20-25 kts, HRRR 15-min rainfall forecasts reach as high as 0.75 inches, further reflecting the potential intensity of rainfall. Additionally, the Corfidi vectors are progged to become increasingly aligned to the mean wind, so some training is possible as storms move from WSW to ENE. This could result in stripes of heavy rainfall reaching 2-3". These amounts could be locally higher in a few locations where storm development occurs, possibly along terrain features, to initially slow storm motions. The antecedent soils across this portion of the High Plains are quite saturated from 14-day rainfall that is in many places more than 300% of normal and leading to widespread 90th-percentile or greater streamflow anomalies. This has reduced 3-hr FFG to 1" or less in some areas, which has a 20-40% chance of exceedance according to the HREF. This indicates an increasing threat for flash flooding today, with the greatest chance occurring when any storms repeat over the most sensitive soils including burn scars. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-p7ev5alf6AxaCPvDQAjiP25ng2a-mh4l--Q48cHgJcMhhoCK7u89BeyXU0xlLCjvPCc= iROBF0emCXQcM2bCDUv1i08$ for graphic product... ATTN...WFO...BOU...CYS...GLD...LBF...PUB... ATTN...RFC...ABRFC...CBRFC...MBRFC...NWC... LAT...LON 41920498 41910345 41690248 41340159 40700066=20 40140030 39780057 39480098 38900220 38690307=20 38700414 39040508 40320586 41540605=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) .