Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 01 2023 16:38:02 AWUS01 KWNH 011637 FFGMPD MOZ000-IAZ000-KSZ000-NEZ000-012230- Mesoscale Precipitation Discussion 0612 NWS Weather Prediction Center College Park MD 1237 PM EDT Sat Jul 01 2023 Areas affected...Eastern Nebraska and West-Central Iowa Concerning...Heavy rainfall...Flash flooding possible Valid 011636Z - 012230Z Summary...Slow moving thunderstorms will repeat across parts of Nebraska and Iowa through this afternoon with rain rates of 1-2"/hr. This slow motion could result in locally more than 3 inches of rain and isolated instances of flash flooding. Discussion...The GOES-E visible imagery late this morning clearly indicates an increasingly favorable environment for slow moving convection. An upper low positioned over northeast NE is spinning slowly eastward with clearing to its south, while additional TCu development is draped to the east into IA along the elevated warm front. Beneath the deepest Cu, showers and thunderstorms have developed with radar-estimated rain rates of 1.5-2.5 inches per hour according to KOAX and KDMX. Fueling this efficient rainfall is a deeply saturated column noted on the KOAX 12Z U/A sounding with measured PW of 1.66 inches, above the 90th percentile for the date, a freezing level approaching 13,000 ft, 1100 J/kg of CAPE, and a mean 0-6km wind of just 1 kt. With little change in the overall environment expected, convection should continue to expand and intensify through the aftn. As the upper low drifts just very slowly to the east, it will combine with the LFQ of a 60-70 kt poleward arcing jet streak and weak vorticity impulses rotating through the flow to drive deep layer ascent. This forcing will interact with continued robust thermodynamics to fuel thunderstorms, with renewed development occurring along outflows as weak shear promotes primarily pulse convection. Additional thunderstorms are expected along the elevated front, which may serve to drive a local maxima in rainfall as indicated by higher HREF EAS probabilities. With 850mb inflow in some places aligned anti-parallel to the mean wind, Corfidi vectors will be quite slow, and it is possible some nearly stationary thunderstorms will occur today. This will be most likely along boundaries for regenerating thunderstorms, which through rainfall rates of 2+"/hr could produce more than 3 inches of rain. The HREF probabilities even indicate some low-end potential for locally 5" of rain in some areas. The antecedent soil conditions are generally dry as reflected by USGS streamflow anomalies that are below normal. However, FFG is somewhat compromised in places due to 24-hr rainfall that has been as high as 2-3". Although the greatest risk today should focus around the more saturated soils or less permeable urban areas, any slow moving thunderstorms with these intense rates could result in rapid runoff and flash flooding through this evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9C-YmmajcZ5rRbiTjPxu4DjS1M5bO4CBq_ajMew-WUSSTdhOPH9OakOsJv4xi5r5c-K9= N1ngDIdhEjJGaU3caGnzwig$ for graphic product... ATTN...WFO...DMX...DVN...EAX...FSD...GID...OAX...TOP... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 42619335 42339264 41709222 41149238 40959322=20 40829418 40479491 40089592 40009730 39989828=20 40099898 40549932 41159906 41589843 41649737=20 41969637 42439516=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) .