Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 21 2025 16:58:25 AWUS01 KWNH 211656 FFGMPD MOZ000-IAZ000-KSZ000-NEZ000-212300- Mesoscale Precipitation Discussion 0772 NWS Weather Prediction Center College Park MD 1256 PM EDT Mon Jul 21 2025 Areas affected...southeast Nebraska, northeast Kansas Concerning...Heavy rainfall...Flash flooding possible Valid 211700Z - 212300Z Summary...Showers and thunderstorms developing north of an outflow boundary will expand through the afternoon. Rainfall rates of 1-3"/hr are likely within these storms, which through training could produce 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The GOES-E WV imagery this afternoon indicates a shortwave lifting across northwest Kansas, with downstream convective development rapidly occurring over southeast Nebraska. This convection is blossoming in response to both subtle height falls/PVA downstream of this shortwave, but more impressively thanks to the resultant acceleration and backing of the 850-700mb flow lifting across KS. Recent observations from KTWX VWP indicate 850mb winds have become due south at 15-20 kts, lifting isentropically atop a low-level boundary analyzed from west to east across KS and into MO. This 850mb-700mb flow will continue to intensify through the afternoon, surging elevated moisture northward as reflected by the 850-700mb ALPW product, with a subsequent easterly push of moisture within the 500-300mb layer helping to raise PWs to as high as 2.25 inches, which would set a daily record for the region. This moisture combined with MUCAPE that is already 2000-3000 J/kg is supporting the convective expansion with radar-estimated rain rates of 1.5-2"/hr. As the afternoon progresses, moisture and instability will continue to be drawn northward to resupply thermodynamics favorably to support thunderstorm development. At the same time, a jet streak positioned to the north will create additional lift, helping to further enhance the intensity of thunderstorms. The CAMs have struggled to capture the ongoing activity, although the RRFS seems to have the best handle so far today, with the recent HRRR runs starting to catch on to a similar idea. Using these as proxy, it is likely that convection will persist north of the surface trough/outflow boundary, and intensify through the aftn as HREF neighborhood probabilities for 1"/hr (2"/hr) rise to 40% (15%). As this occurs, training from west to east is expected as mean 0-6km winds align west to east, north of the trough, and along the nose of the 850mb inflow. Although there may be a push southward of thunderstorms by this evening, until that occurs a narrow corridor of heavy rainfall of 2-3" with locally higher amounts is likely. FFG across this area is generally 1.5-2"/3hrs, for which the HREF/REFS exceedance probabilities reach 15-25%. This may be somewhat under-forecasting the true risk due to the struggle of the CAMs today. However, it appears likely that training of these heavy rainfall rates will become more common through the afternoon, which could result in instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5vsY2E4PrYqRLAcSTL0IREwAClFj07sYBEFS1TlFcXK2ceoMSnepIPf_qcEg0sGAFJUv= nlC3VxRy0Z-K3Ds6HsowrL4$ for graphic product... ATTN...WFO...EAX...GID...GLD...LBF...OAX...TOP... ATTN...RFC...KRF...NWC... LAT...LON 40919649 40649536 39969450 39299416 38739408=20 38449465 38939621 39069672 39329779 39369881=20 39329947 39590017 40140060 40470041 40809949=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .