Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 10 2025 22:30:58 AWUS01 KWNH 102230 FFGMPD IAZ000-NEZ000-SDZ000-110430- Mesoscale Precipitation Discussion 0639 NWS Weather Prediction Center College Park MD 629 PM EDT Thu Jul 10 2025 Areas affected...Eastern Nebraska and Western Iowa Concerning...Heavy rainfall...Flash flooding possible Valid 102230Z - 110430Z SUMMARY...Showers and thunderstorms initiating along a surface trough across eastern Nebraska are growing upscale with some backbuilding, leading to an increasing flash flood threat. DISCUSSION...GOES-East satellite imagery indicates that the earlier line of elevated convection that moved through northeastern Nebraska left behind several hours of clearer skies, leading to enough daytime heating to initiate a new round of surface-based thunderstorms. A surface trough extending through eastern Nebraska from a surface low centered near northwest Kansas and southwest Nebraska is providing a zone of convergence that will serve as a focal point for continued convective initiation. MLCAPE values of 2000-3500 J/kg across the region, combined with 30-40 knots of 0-6 km Bulk Shear, supports the development of severe convection. Convection should begin as scattered thunderstorms with some isolated supercells, then steadily growing upscale into an organized MCS later in the period as the upper-level shortwave energy rotates through and the existing convection across eastern Colorado and western Kansas eventually merges with the convection over eastern Nebraska as a larger MCS. Although the 850 mb low-level jet of 20-30 knots is relatively weak, there is significant moisture convergence occurring along the axis of the surface trough, with a 19Z sounding at LBF indicating a PW of 1.27" which is close to the 90th percentile relative to climatology. Combined with a deep-layer mean southwesterly flow of only 20-25 knots, relatively slow storm motions and propagation vectors into the weak low-level jet suggests that backbuilding and upscale growth over the next few hours will lead to an increased risk for flash flooding. CAMs guidance is in good agreement with this flash flood potential, with HREF probabilities at 50-70% of 3-hr QPF exceeding 2". Flash flood guidance values also drop off significantly from west to east across Nebraska, given the moist antecedent conditions across eastern Nebraska and western Iowa, so FFG is less than 2" across the area of concern. Shieh ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-UIYUdV548phRFqGcgYF6WTtP_p6Rt0cfwtD1dROZqkwxw0pd6rbLWD7oPxeUW-4mRgC= PIP4Mlo06IhfV0RRw26qNlc$ for graphic product... ATTN...WFO...DMX...FSD...GID...LBF...OAX... ATTN...RFC...KRF...MSR...NWC... LAT...LON 42909505 42259411 40979618 40269822 40269822=20 40329939 41559969 42529753=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) .