Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed May 15 2024 17:45:23 AWUS01 KWNH 151745 FFGMPD PAZ000-VAZ000-NCZ000-WVZ000-SCZ000-OHZ000-TNZ000-KYZ000-152345- Mesoscale Precipitation Discussion 0271 NWS Weather Prediction Center College Park MD 144 PM EDT Wed May 15 2024 Areas affected...Portions of the Upper Ohio Valley and Central/Southern Appalachians Concerning...Heavy rainfall...Flash flooding possible Valid 151745Z - 152345Z SUMMARY...Developing slow-moving and isolated to widely scattered cells could contain rainfall rates of 1-2 in/hr over a region with relatively low flash flood guidance. Localized flash flooding may result where isolated 1-3 inch rainfall totals occur. DISCUSSION...A stacked sfc-500mb low pressure system analyzed via GOES-East water vapor imagery over the Upper Ohio Valley is sliding eastward this afternoon while diurnal heating increases surface instability into the region. However, the SBCAPE is only expected to reach towards 750-1000 J/kg per the RAP and recent 12z CAMs due to plenty of cloud cover, which should limit the updraft potential somewhat. This heating also increases the thermodynamic gradient between areas east of the Appalachians and north of a stationary front located over North Carolina, where a wedge of very stable air is in place. Any developing thunderstorms across the upper Ohio Valley and central Appalachians will remain west of the central Appalachian crest due to this boundary and weak mid-level flow. The weak flow throughout the column was noted by ILN's 12z sounding, which depicted 5-10kt winds from the surface to 300 mb. Precipitable water values of 1-1.3" are also found in this region and per ILN's 12z sounding was near the 90th climatological percentile on SPC's sounding climatology web page. Better instability exists farther south near a triple point in southwest North Carolina and should lead to the potential for rainfall rates up to 2" as storms form along the southern Appalachians and slide east into the western half of North Carolina, but these storms will likely exhibit faster forward propagation due to westerly flow through the column. Otherwise, most storms are expected to be highly localized with rainfall rates of 1-2"/hr covering even less real estate. CAMs depict a scenario into the early evening with scattered storms continue to develop and maintain through the early evening hours. Most storms won't produce flash flooding concerns and exhibit a pulse nature due to the weak flow aloft and low instability, but certain clusters of thunderstorms containing 1-2"/hr rates could linger over areas long enough to exceed the 1-2.5"/3-hr flash flood guidance. Long skinny CAPE profiles in forecast soundings are a feature that could support the maintenance of updrafts. The 14z HRRR highlights localized totals of 1-3" within 3 hours and 12z HREF neighborhood probabilities of 30-60% for at least 2" in 6 hours by 00z tonight. Additionally, it's worth noting that areas of northern Kentucky and Indiana early this morning over preformed with the associated system as localized totals exceeded 3". ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!46S_Usqatoxbr9rIZQOUfo5lPYtCx-lSusG3LuE2sMpHtNoXdjVZNCQE4XAIOumC1gze= Vs77SJHD0s8Q8KoLZW0YnXw$ for graphic product... ATTN...WFO...GSP...ILN...JKL...LMK...LWX...MRX...PBZ...RAH... RLX...RNK... ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 40598119 40498041 39408083 38968064 38677993=20 37977962 36647994 35528078 35038163 35198253=20 36528161 37388194 38078379 38908404 39638315=20 40208215=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) .