Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jun 11 2023 18:47:03 AWUS01 KWNH 111846 FFGMPD COZ000-NMZ000-WYZ000-120030- Mesoscale Precipitation Discussion 0463 NWS Weather Prediction Center College Park MD 245 PM EDT Sun Jun 11 2023 Areas affected...Central Rockies & High Plains Concerning...Heavy rainfall...Flash flooding possible Valid 111845Z - 120030Z SUMMARY...A blossoming field of thunderstorms this afternoon will contain rainfall rats as high as 2"/hr. Flash flooding is possible, especially in burn scars, low lying spots, and urbanized areas. DISCUSSION...An upper low tracking over southern California is responsible for a 250mb jet streak placing its diffluent left-exit region over the central Rockies and High Plains this afternoon and evening, providing ample large scale support for vertical ascent aloft. At low levels, a stalled frontal boundary along the Rockies and easterly low level winds will act as a source of lift at the surface. Daytime heating is well underway and is quickly destabilizing the environment. RAP forecasts suggest MLCAPE by mid-late afternoon will range between 500-1,000 J/kg from the Front Range of the Rockies east into the heart of the High Plains of CO and southeast WY. In terms of moisture, PWs will surpass 0.75" east of the Front Range, which is close to the 90th climatological percentile. One of the factors supporting a flash flood threat today is low-level vertical wind shear. As storms develop along the Front Range and the Palmer Divide, winds in the surafce-1km AGL layer are out of the northeast while winds in the 2-3km AGL layer are strengthening out of the southwest. This is creating curved surface-3km hodographs that would entice storms to develop organized mesocyclones. Storm relative helicity (SRH) in the surface-3km layer are as high as 125-175 m2/s2 this afternoon and would support potential supercell thunderstorms. Area averaged HRRR soundings from the Front Range to the southern Denver metro area around 21-22Z were remarkably saturated, averaging 90% in the low-mid levels and classic "skinny CAPE" profiles. RAP guidance this afternoon suggests warm cloud layers could become as deep as 7,000 feet. Steering flow within the cloud layer topped out at 10 knots as well, suggesting storms will not be overly fast movers. According to the RAP, bulk effective wind shear will be around 40 knots in central CO, lessening to 30-35 in southern WY and increasing to 40-45 knots in southern CO and northern NM. These are all favorable levels for organized covnection. Thunderstorms with healthy mesocyclones in a highly saturated environment can be exceptional rainfall producers. 12Z HREF probabilities showed as high as 60-80% probabilities for >1"/hr rainfall rates within these cells, with 20-25% probabilities for >2"/hr rainfall rates. It has also been a rather wet 7-14 days in central CO and southern WY. AHPS 7-day rainfall totals have been as high as 400-600% of normal for much of the highlighted region. Given the potential for up to 2"/hr rainfall rates and overly saturated soils, flash flooding is possible this afternoon and evening. In addition to saturated soils, burn scars in the Rockies, rugged terrain, and urbanized metro areas are also susceptible to flash flooding. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9rD1s1QAL6kuEWbdBchCcHMcxUTjm6rcU84lcewkU6rNaT1xHbaD96MrAA-cEvFmvYCM= zD1pgbZDTILmZqzfZy44svM$ for graphic product... ATTN...WFO...ABQ...BOU...CYS...PUB... ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC... LAT...LON 41870518 41250419 39490350 38270317 37140302=20 36280411 35960526 36120583 38120574 38740613=20 39400603 39870611 40670638 41140698 41800684=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) .