Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 30 2023 19:15:15 AWUS01 KWNH 301915 FFGMPD NYZ000-PAZ000-010113- Mesoscale Precipitation Discussion 0218 NWS Weather Prediction Center College Park MD 314 PM EDT Sun Apr 30 2023 Areas affected...south-central NY & northeast PA Concerning...Heavy rainfall...Flash flooding possible Valid 301913Z - 010113Z Summary...Rainfall intensity should increase over the next few hours as some limited instability moves in from the west/southwest and 850-650 hPa frontogenesis increases over an area of saturated soils/low flash flood guidance values. Excessive rainfall is possible. Discussion...Rain has overspread south-central NY and northeast PA, with hourly rain totals close to 0.1" as of late near the northern end of an inverted trough extending poleward from a pair of low pressure systems in VA and NC. Precipitable water values of ~1.1" lie in the region per GPS data, which when combined with 1000-500 hPa thickness values near 5580 meters suggest a nearly saturated atmosphere. MU CAPE of 100+ J/kg has been edging eastward across western PA and occasionally appearing across western NY per SPC mesoanalyses, which has led to some warm topped convection edging towards the area. An area of overlapping 650-850 hPa frontogenesis is moving in from the southwest, associated with the incoming frontal system. Divergence aloft is being aided by the Carolinas upper level low and a shortwave moving across the southeastern Mitt of MI from the west around an upper level low in eastern WI. With both low- to mid-level frontogenesis associated with the incoming occluded front phasing into the inverted trough and some limited instability moving into the region, expect the hourly rain totals to increase, particularly starting in the 20-21z time frame and continuing for several hours. The ingredients in place could support hourly totals up to 0.5", which if they occurred over 2+ hours could lead to exceedance of the low flash flood guidance values across the area. The mesoscale guidance suggests that local amounts to 1.5" are possible over the next six hours, with some overlap of these amounts and the area of saturated soils.=20 Moderate to heavy rainfall in most areas should be longer duration, but excessive rainfall is possible. Any heavy rain-related issues are expected to be isolated to widely scattered. Roth ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5BKiE7a9FQ7VX97d8KUof99hyyx8Hh-lW2sR5gn9tommljoNKDx8JSimjhSIGqrE6C0B= 972GlpjdvsSQcKLQ6QBx1DY$ for graphic product... ATTN...WFO...ALY...BGM...CTP... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 42917606 42917475 42087452 41797457 41527574=20 41267630 41527683 42187722=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) .