Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 18 2023 04:35:48 AWUS01 KWNH 180435 FFGMPD NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-NCZ000-DCZ000-181033- Mesoscale Precipitation Discussion 1205 NWS Weather Prediction Center College Park MD 1135 PM EST Sun Dec 17 2023 Areas affected...large parts of the Mid-Atlantic from eastern North Carolina through eastern Pennsylvania Concerning...Heavy rainfall...Flash flooding possible Valid 180433Z - 181033Z Summary...An intense storm system will continue to migrate northward through the Mid-Atlantic, spreading multiple rounds of heavy rain from North Carolina north through eastern Pennsylvania. Flash flooding remains possible, and this risk will develop northward through the night. Discussion...An extensive warm conveyor extends from the center of a strong surface low over southern North Carolina northward through eastern Pennsylvania per latest radar mosaic imagery. The convection within this warm conveyor continues orient favorably for areas of training and repeating of cells along with a few areas of heavier rain rates (locally exceeding 1 inch/hr and 1.5 inch/3-hr) especially across eastern North Carolina and vicinity.=20 The heavier rain rates were tied to surface convergence near the aforementioned low and appreciable buoyancy/moisture (1.5+ inch PW and 500+ J/kg SBCAPE - focused primarily along coastal areas). Farther north, lower rain rates were noted due to weaker buoyancy, but areas of 0.25-0.5 inch/hr rain rates were observed (especially in Maryland and eastern Pennsylavania). The current rain rates are suggestive of only isolated flash flood potential in the near term, primarily focused in areas that 1) are urbanized/low-lying and/or 2) have received abundant rainfall throughout the day, with prior wetting of soils promoting efficient runoff. The ongoing concern with the active flash flood scenario is that the warm conveyor partially responsible for the widespread precipitation will translate very little, allowing for additional, multiple hours and rounds of rainfall to occur across the discussion area. Instability will gradually build northward into more of the Mid-Atlantic especially along and east of a warm front extending from Wilmington, NC northward through Chesapeake Bay and eastern Maryland. This instability will eventually allow for areas of 2 inch/3-hour rain rates to build northward into more of the northern parts of the discussion area as well. These rates are expected to continue supporting isolated areas of flash flooding across the discussion area as 3-hour FFG thresholds are generally in the 2.5 inch range in most areas (slightly lower from Washington DC northward into Philadelphia). The greatest flash flood potential will exist where heavier rain rates can intersect the lowered FFGs in the discussion area especially near urbanized land surfaces. Additional storm totals of 2-4 inches of rainfall are expected, with locally higher amounts possible. Cook ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_Pa5qJpSmWKi3oty693ggT-E8cClaIg30lNSzVxOYcg53A4_WPWKOdqMabu8Kh7Bijzv= Tr3qrd9lAONpP9xagwmtG_I$ for graphic product... ATTN...WFO...AKQ...BGM...CTP...ILM...LWX...MHX...PHI...RAH... ATTN...RFC...MARFC...SERFC...NWC... LAT...LON 41287513 40827461 39207490 36347576 35207568=20 34317781 34627837 35767852 38047805 39687728=20 40817621=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) .