Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 31 2023 01:05:00 AWUS01 KWNH 310104 FFGMPD NEZ000-SDZ000-WYZ000-310645- Mesoscale Precipitation Discussion 0817 NWS Weather Prediction Center College Park MD 904 PM EDT Sun Jul 30 2023 Areas affected...far eastern WY into southwestern SD and northwestern NE Concerning...Heavy rainfall...Flash flooding possible Valid 310103Z - 310645Z Summary...Localized rainfall totals of 2 to 3+ inches are expected across portions of southwestern SD into far northwestern NE over the next 6 hours, but with most of that falling in 1-2 hours. Due to recent heavy rain and lowered FFG values, flash flooding will be possible through 06Z. Discussion...0030Z infrared satellite and regional radar imagery showed scattered thunderstorms over the central to northern High Plains, mostly along and north of a stationary front analyzed from south-central NE into northeastern WY. Large CAPE values were in place over central and western portions of SD and NE with the 00Z soundings from UNR and LBF showing 1500 and 3900 J/kg MLCAPE, respectively, with some dry air present in the UNR sounding between 850-700 mb. Precipitable water values at UNR and LBF ranged from 1.2 to 1.6 inches, both showing sufficent speed shear for organized cells. Using 850 mb winds as a proxy for the low level jet, RAP forecasts show an increasing magnitude through 06Z from 10-20 kt into the 20 to 30+ kt range. The southeastward advancing thunderstorm cluster moving into western/northwestern SD will likely continue its current movement over the next 2-3 hours while the increasing isentropic ascent near the existing frontal boundary and any outflow boundaries that are produced will likley support an increased coverage of thunderstorms into the overnight. While deeper layer mean winds and forecast Corfidi vectors suggest movement of thunderstorms toward the southeast at 20-40 kt, a hindrance to flash flooding, organized cell motions have been observed in the 5-10 kt from the NE Panhandle into southwestern SD. Organized cells, cell mergers and brief training will support rainfall rates of 1-2 in/hr and 2-3 inches in 2 hours or less, allowing for an increased flash flood threat acorss the region, focued over southwestern SD into northwestern NE, where recent heavy rainfall over the past week has lowered FFG values to 1-2 inches in 3 hours. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8iufS0PWihUPhNrGaHi2kje6J8VnSJKvWRIR3AuEZjf7CaLcOQY7F6Pfhs6DUDugqC5N= SP2oa23GowQIh8szIZLSZk8$ for graphic product... ATTN...WFO...CYS...LBF...UNR... ATTN...RFC...MBRFC...NWC... LAT...LON 44680394 44250214 43350059 42820054 42780172=20 42040283 42230401 43240448 44220461=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) .