Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Oct 12 2023 19:25:36 AWUS01 KWNH 121925 FFGMPD NEZ000-130100- Mesoscale Precipitation Discussion 1146 NWS Weather Prediction Center College Park MD 324 PM EDT Thu Oct 12 2023 Areas affected...South-central to Northeast Nebraska... Concerning...Heavy rainfall...Flash flooding possible Valid 121925Z - 130100Z SUMMARY...Slow moving and training thunderstorms just southeast of the Sand Hills support rates over 2"/hr and localized totals of 2-4" possible over the next few hours. Lower FFG values along the eastern side of the Sand Hills may be exceeded resulting in possible localized flash flooding conditions, especially in locations affected by heavier rainfall earlier today/last evening. DISCUSSION...GOES-E WV suite deficits a broad closed low over the central High Plains, starting to consolidate and shift eastward as the nose of the 110kt 3H jet and associated shortwave center crosses E KS becoming increasingly diffluent over central NEB.=20 19z surface analysis denotes the main surface low very close to LXN with strong cold front starting to press eastward across N KS. Solid backed surface to 850mb flow is accelerating toward from the southeast with upper 50s to low 60s (total PWat to 1.3"). A convectively induced surface wave near BBW intersects the west-east stationary front. As such, very strong moisture flux convergence is fueling thunderstorm development in the vicinity of the surface waves with a TROWAL extending northeastward into the Sand Hills triggering more elevated thunderstorms northward and westward. While the main core of the upper-jet and shortwave remain slightly upstream, there is a short-term window (1-2 more hours) of weakened backed steering flow and reduced eastward propagation vectors supporting a more northerly training environment in proximity to the surface wave across south central NEB into central NEB. As such, BBW has recently has seen over 2.5"/hr given the combination of factors. This may be the more extreme of the environment as instability is a bit lower to the east given area has been more socked in with lower stratus clouds limiting temperatures. However, the dynamics should remain strong to support the flux required for 1.5-2"/hr rates before main height-falls start to press eastward and east-northeastward propagation vectors increase substantially. As such, streaks of 2-4" totals are becoming possible over areas southeast of the Sand Hills where FFG values are naturally lower with 1hr/3hr values of 1-1.5"/1.5-2" FFG values, respectively.=20 Currently the main bands remain over areas that have been very dry, but the extreme rates should limit infiltration allowing for spots of flash flooding. As the cells propagate, they will have reduced rainfall totals, but will also track towards areas affected last evening/this morning across northeast NEB, so have included this downstream area in the MPD to account for streaks of 1-3" crossing those recently saturated grounds.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4SNKJViKRVmndW-PN0FT3GuHl6bcy_ah2B_-6lb4BKIEPUT5Wx5LT8Tf69iAJpfLg0xV= QQunfuqDfOJ7czdlA8voSxU$ for graphic product... ATTN...WFO...GID...LBF...OAX... ATTN...RFC...MBRFC...NWC... LAT...LON 42719875 42399760 41729733 40899777 40189925=20 40279997 40770037 41300037 41739973 42159929=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) .