Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 26 2023 17:02:07 AWUS01 KWNH 261702 FFGMPD MAZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-262245- Mesoscale Precipitation Discussion 0589 NWS Weather Prediction Center College Park MD 101 PM EDT Mon Jun 26 2023 Areas affected...Northern Mid-Atlantic Concerning...Heavy rainfall...Flash flooding possible Valid 261700Z - 262245Z SUMMARY...Rounds of strong-to-severe thunderstorms containing hourly rainfall rates of 2-2.5"/hr may produce areas of flash flooding this afternoon. DISCUSSION...GOES-16 visible satellite showed a cluster of potent thunderstorms in eastern PA, northern NJ, and Upstate NY tracking northeast with a growing field of agitated cumulus over the Lower Susquehanna Valley and central PA. These soon-to-be storms that are in their infancy stage in east-central PA are forming along a warm front lifting north and at the nose of a 500mb vorticity maximum tracking north through the Shenandoah Valley. The region also lies at the nose of the diffluent left-exit region of a 250mb jet streak, further aiding in the strong vertical ascent atop the atmosphere. These storms have a good moisture source to work with thanks to a southerly 850mb moisture transport that is both intersecting the warm front and leading to some upslope enhancement along the Appalachians in central PA and the Poconos. The 12Z OKX sounding featured PWATs (1.78") and sfc-850mb mixing ratios that were above the 90th climatological percentile and dew points have steadily increased into the low 70s from the northern DelMarVa to the NYC metro area. PWATs will generally range between 1.5-1.75" for most of the highlighted region. There is also plenty of MLCAPE available with values ranging between 1,000-2,000 J/kg this afternoon. Effective bulk vertical wind shear is likely to range between 25-35 knots this afternoon. In addition, curved hodographs at low levels thanks to the veering wind profile from ESE to WSW with height will allow for some storms to develop mesocyclones, which can be efficient rainfall producers. Speaking of "efficient", warm cloud layers are likely to be as deep as 10-11kft this afternoon, further giving support to these cells containing excessive rainfall rates. The vort max will act as another source of synoptic scale lift as it moves northeast, and as additional storms form this afternoon, they will track over areas that have already received rainfall earlier this morning. 1-hr FFGs in some of these areas are now as low as 1.0", particularly in areas with saturated soils and in the more urbanized metro areas. Look for areas with overly saturated soils, urbanized metro centers, and low-lying/poor drainage locations to be most susceptible to flash flooding this afternoon. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!61T3L2RopvqL-BQ6hzbsU0PfZzrxD7L3rOmxA1EEC3SWHiWiXQq0n4zzXgRyRHXO_JCK= QRVRyli4T-B9lvVeolcTWoI$ for graphic product... ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 43097494 42687262 41067403 40227451 39927489=20 39787565 40057689 40427701 40957693 42187648=20 =20=20=20=20=20=20=20=20=20=20=20=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) .