Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 29 2024 03:22:11 AWUS01 KWNH 290322 FFGMPD ILZ000-MOZ000-IAZ000-290900- Mesoscale Precipitation Discussion 0752 NWS Weather Prediction Center College Park MD 1121 PM EDT Sun Jul 28 2024 Areas affected...Central & Southeastern Iowa... Adj. NW IL & NE MO... Concerning...Heavy rainfall...Flash flooding possible Valid 290320Z - 290900Z SUMMARY...Increasing isentropic ascent for backbuilding thunderstorms that may repeat/train behind initial bowing segment. DISCUSSION...Regional RADAR mosaic denotes a mature accelerating bow echo across central IA moving east with a well defined MCV in Franklin county. While the bow is progressive, the strong moisture flux and supported sub-hourly 1"+ totals in/along its path. Spots near the northern bookend may have a bit longer residency for up to 1.5" but still at or slightly below the hourly FFG values, but it is wetting the grounds for trailing convection. GOES-E WV suite notes that the MCV is aligned with the parent mid-level shortwave which continues to drift eastward into a broad col in the mid to upper-level flow. This is providing some upper-level divergence to maintain the strength of the MCV, as well as strengthen low level wind response. And that is the key for further upstream development over the next few hours. 03z surface analysis denotes the wake anticyclonic rotor to the bow echo has placed a WNW to ESE outflow boundary from just east of SUX to CIN to DSM. VWP suite upstream shows strengthening LLJ response with broad 25-40kts across E NEB/NW MO at 850; orthogonal to the outflow boundary. The air over SW IA through E IA remains conditionally unstable with MUCAPE values of 2000-2500 J/kg. Deep moisture has pooled near the MCV/shortwave through depth supporting enhanced pocket of deep layer moisture up to 1.75-1.9" but CIRA LPW and RAP analysis show upstream moisture tongue through the Missouri Valley is angling northward with the LLJ and so moisture flux values are increasing to sizable values. The leading edges of the LLJ have ascended to develop thunderstorms along the 'arrow' portion of the mid-level rear-inflow jet upstream of the 'bow' of the MCS. Deep layer flow in the wake of the MCV is fairly parallel to the orthogonal LLJ ascent providing 850-700mb convergence while also supporting parallel cell motion vectors. As the main core of the LLJ reaches the outflow boundary, expect convection to increasing in coverage and intensity with 1.75-2"/hr rates. As such, a swath of an additional 2-4" is becoming increasingly possible across the area of concern across central to SE IA. While southwest IA remains relatively dry; central to southeast IA is a bit wetter through depth with 0-40cm soil saturation ratios in the upper 40s to mid 50s percent per NASA SPoRT and generally match the FFG where 1.5-2"/hr or 2-3"/3hr align with the area of concern. Given this, flash flooding is considered possible tonight.=20 A bit of uncertainty remains in the placement of the training axis, dependent on the LFC; greater surface rooting would place the axis further south and west but with also greater moisture flux and depth for more intense rates maybe even spots of 4"+.=20 However, this evolution is not well known and will be contingent on the next few hours. There are some hints this may becoming more of reality based on recent agitated low level cu field and arched status noted in SWIR 3.9um across south-central IA into N MO. However, there is limited guidance to support that evolution with the exception of the FV3CAM. HRRR/ARW solutions remained a bit more capped over north-central MO until the MCS is in full maturity later into the morning. Will be watching the evolution closely, in case an area to the south does convect a bit earlier. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5a0E-DfkoL5aAVqlCLrnLciRqUXpcNlADXNq-UPGBhmdd1O8ySoSSqbzbU4Xhq1jo99f= oPb9JueUg7GWZxYa_1fV2Ys$ for graphic product... ATTN...WFO...DMX...DVN...EAX...FSD... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 42989456 42659223 42449097 42009010 41049051=20 40409111 40329232 40669340 41599466 42279541=20 42929539=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) .