Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 07 2023 17:40:07 AWUS01 KWNH 071740 FFGMPD NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-072330- Mesoscale Precipitation Discussion 0654 NWS Weather Prediction Center College Park MD 138 PM EDT Fri Jul 07 2023 Areas affected...Northern Mid-Atlantic Concerning...Heavy rainfall...Flash flooding possible Valid 071735Z - 072330Z SUMMARY...Thunderstorms currently unfolding across the region, as well as additional storms that are expected to develop later this afternoon, will be slow movers that produce 2-3"/hr rainfall rates. Flash flooding is possible, especially in the more urbanized metro areas and spots with saturated soils. DISCUSSION...Doppler radar and GOES-16 satellite imagery showed a corridor of thunderstorms along a surface trough oriented N-S from the DC metro area to as far north as the Poconos. A cold front is also approaching from the west and may act to trigger more storms in the Appalachians this afternoon. Strong surface based heating and dew points that are in the low-mid 70s are fostering a tropical air-mass with MLCAPE values that are ranging between 1,000-2,000 J/kg. Some parts of northeast MD and the Lower Susquehanna Valley are forecast to see MLCAPE >2,000 J/kg. The ongoing cluster of storms are packing a punch with MRMS instantaneous rainfall rates reaching as high as 3.0-4.0". PWATs are playing a big role as well as values range between 1.8-2.0" throughout the afternoon. As daytime heating continues, more storms will form as far south as Richmond. Visible satellite also shows a burgeoning field of towering cumulus in the central Appalachians. Mean 850-300mb winds are not much stronger than 15 knots, so any storms along the Appalachians and Blue Ridge could reach the more urbanized corridor later this afternoon, or any associated outflows from thunderstorm activity could act to trigger additional storms as well. Storms will reside in an environment with low-mid level RH values up to 80% and warm cloud layers between 11-12kft deep. In the Delaware Valley, the approaching cells from the west and the advancing sea breeze from coastal NJ could be a focus for strong thunderstorms this afternoon. The past 14 days have been rather wet along the I-95 corridor from central VA on north into the Delaware Valley. AHPS shows as much as 300-400% of normal rainfall for much of the area. The greater concentration of hydrophobic surfaces along the I-95 corridor also conflates the flash flood potential this afternoon. West of I-95, some locations feature <2"/hr FFGs in the central Appalachians, Susquehanna Valley, and into northern NJ. Flash flooding is possible this afternoon with the urbanized metro areas and poor drainage areas most at-risk. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7H5VRHmyYHmjIU62bjSs7ivpJCcDVMOFTxvbOqtCYTlG9WI7V-ApDi5EKl8bpM16RpHr= hSbROkst9M1uiGK2ZjgwxXI$ for graphic product... ATTN...WFO...AKQ...ALY...BGM...CTP...LWX...OKX...PHI... ATTN...RFC...MARFC...NERFC...SERFC...NWC... LAT...LON 42137440 42097408 41607400 40757453 39687517=20 38687596 37267683 37167767 37927842 38107898=20 38647915 39667877 40117825 40337787 40437713=20 40807579 41557488=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) .