Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 21 2023 02:20:48 AWUS01 KWNH 210220 FFGMPD NYZ000-NJZ000-PAZ000-MDZ000-WVZ000-210718- Mesoscale Precipitation Discussion 0775 NWS Weather Prediction Center College Park MD 1018 PM EDT Thu Jul 20 2023 Areas affected...Southern NY and the Northern Mid-Atlantic Concerning...Heavy rainfall...Flash flooding possible Valid 210218Z - 210718Z SUMMARY...A strong to severe line of convection will continue to advance through much of southern NY and adjacent areas of the northern Mid-Atlantic going through the overnight hours. A localized and mainly urban flash flood threat will exist. DISCUSSION...The latest satellite and radar imagery continues to show a strong to severe line of thunderstorms advancing across areas of southern NY and down through much of central to southwest PA. The convection continues to be associated with a strong shortwave trough dropping down across the Great Lakes region along with a cold front. Strong forcing associated with the height falls will advance downstream and cross much of the northern Mid-Atlantic region going through the overnight hours, and this energy will be interacting with a moist and moderately unstable airmass. MLCAPE values across much of southern and eastern PA are as high as 1000 to 1500 J/kg with PWs locally as high as 1.5 inches. The latest HRRR guidance and the 18Z HREF suggests some of the stronger cells will be capable of producing rainfall rates of as much as 1.5 inches/hour, with some spotty storm totals going through 06Z that could reach 2 to 3 inches where any brief cell-training occurs. Generally the heaviest rains should tend to be over areas of southern and eastern PA, with lesser amounts farther north closer to the NY border and into adjacent areas of southern NY. The MCS activity is highly progressive in nature and this will temper the overall excessive rainfall threat. However, the rainfall rates will be such that there could certainly be some urban flash flooding concerns as this line of convection advances east-southeast overnight through the northen Mid-Atlantic region. FFGs are also notably lower across portions of southern NY and down through the eastern half of PA given more moist antecedent conditions, so these areas also may tend to have more efficient runoff concerns from these heavier rains. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_2-aPuKkP2qs8qsg2Gv8A3rcbKAJ_jRRkkgDS8NYl8yt7Gs0M6BRTq6RuWmOpy5YEECf= C9jX_kUOUdFbw9uKfgzHIMI$ for graphic product... ATTN...WFO...ALY...BGM...CTP...LWX...OKX...PBZ...PHI... ATTN...RFC...MARFC...NERFC...OHRFC...NWC... LAT...LON 42737601 42497495 41687454 40647485 39817638=20 39647842 39847999 40278054 40658034 40678011=20 40847948 41317814 42187719 42527690=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) .