Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 31 2024 06:40:55 AWUS01 KWNH 310640 FFGMPD ILZ000-MOZ000-IAZ000-311230- Mesoscale Precipitation Discussion 0763 NWS Weather Prediction Center College Park MD 240 AM EDT Wed Jul 31 2024 Areas affected...Much of Southern IA...Northeast MO...Far Northwest IL... Concerning...Heavy rainfall...Flash flooding likely Valid 310640Z - 311230Z SUMMARY...Increasing convective activity with increasing rates of potential of repeating/training and spots of 2-4" crossing recently wetted ground conditions resulting in possible flash flooding through daybreak. DISCUSSION...GOES-E WV suite depicts a quick moving shortwave along the SD/NEB border moving into W IA currently at the apex of the larger mid-level ridge scale ridge. At the surface a pair of weaker surface waves can be seen along the central KS/NEB border with a bowed warm front peaking in latitude near OLU to OMA before the sharpened theta-E gradient defines the stationary front across SW IA, north-central MO into SE MO. Given the movement of the shortwave, low-level jet has responded with slightly veering but accelerating to 25-35kts per VWP across SE NEB enhancing nearly orthogonal isentropic ascent/convergence with the frontal boundary across SW IA. CIRA LPW in the sfc-850mb layer (given low to mid 70s Tds at the surface) has risen to .85" in the layer and moisture flux values are nearing 200 kg/m/s which places those ranks in the 95th to 99th percentiles; this continues into the 850-700mb layer, but the 700mb moisture axis is a tad narrower, but focused over SW IA within the southeast quadrant of the shortwave. Total PWat values are starting increasing from 1.75 to near 2". RAP analysis shows highly conditionally unstable environment with CAPE values over 4000 J/kg but remain strongly capped generally west of the Missouri River. This weakens a bit to the east and give the deep layer moisture flux convergence, convective activity has perked up with numerous updrafts starting to congeal into a more traditional looking WAA convective arc. Deep layer flow is not as ideally unidirectional through the steering layer to be parallel to the boundary, but should be sufficient for training/repeat elements particularly concerning for upstream redevelopment near/along the frontal zone as the LLJ veers more westerly with time. This places west-central to central/south-central IA broadening across E/SE Iowa into Northeast MO in greatest potential for 2"/hr cells with training. Cell motions should be fast too, limiting any given cell's residency. So potential is greater for 2.5-3.5" totals but an isolated 4"+ is still at a lower probability but not to be unexpected through the early morning hours. Flash flooding is considered likely given current trends, looks like areas that have seen recent heavier rainfall and increased soil saturation from Dallas/Warren to Wapello, Des Monies counties have another higher potential, further increasing potential for limited infiltration and increased run-off. NASA SPoRT 0-40cm saturation ratios are in the mid 60s to upper 70%; and so FFG values of less than 1.5"/hr and less than 2"/3hrs. Drier grounds to the south and west, should be able to handle increased rainfall up to 2.5"/hr and 3.5"/3hrs, so if cells become more surface rooted near the front, better training and higher rainfall generation potential (deeper cloud depth) still could pose a risk for some spots of flash flooding and have been included in the area contingent on further south and west development near the surface front.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5uiAnc6ibMoA3wKFp4LkKt0H7Dp1-RIzM1DJOjgI4_oPg4Dj_LUlPhitpHd2DlwKdhOb= XR8ay27huKGVEZYkOJjRERY$ for graphic product... ATTN...WFO...DMX...DVN...EAX...ILX...LSX...OAX... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 42379338 42209197 41839107 41209026 40319031=20 39779107 39729194 39899274 40699402 41109476=20 41329540 41769572 42219518=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) .