Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Oct 07 2023 16:59:14 AWUS01 KWNH 071659 FFGMPD MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-072200- Mesoscale Precipitation Discussion 1139 NWS Weather Prediction Center College Park MD 1258 PM EDT Sat Oct 07 2023 Areas affected...Eastern Upstate New York, Western New England Concerning...Heavy rainfall...Flash flooding possible Valid 071657Z - 072200Z Summary...Training showers with embedded heavier rates will continue across eastern Upstate New York into western New England this afternoon. Rainfall of 2-3" with locally higher amounts above 4" is likely. This could cause isolated instances of flash flooding, especially in sensitive terrain. Discussion...The GOES-E WV imagery this afternoon clearly indicates the remnants of Philippe southeast of New England, with a drying cold front also easily recognizable moving into central PA. Between these two features, an anomalous theta-e ridge is advecting westward as moisture off the Atlantic surges PWs to 1.3-1.5 inches as far west as the Hudson Valley of NY. Although instability is modest, generally less than 250 J/kg, a pocket of 500 J/kg SBCAPE is analyzed by the SPC RAP over MA/CT/southern VT, which may transport northward at least subtly this aftn on S/SE flow ahead of the front. These thermodynamics are being acted upon by intense ascent through low-level convergence ahead of the front, especially along a potent surface inverted trough which is also laying beneath a strengthening deformation axis. Additionally, a poleward arcing jet streak is placing its favorable RRQ over the region, overlapping with the approaching height falls to additionally enhance lift. Through the aftn, this front is progged to move more progressively and eventually sweep the heavy rain off to the east. However, ahead of this front, the overlapping deformation axis/inverted trough should remain a focus for rounds of heavy rainfall. Showers that develop along this axis should train northward on 0-6km mean winds parallel to the front, so despite modest rainfall rates limited by weak instability to generally 0.5"/hr, slow translation of this band will likely produce 2-3" of rain with locally higher amounts possible noted by HREF probabilities reaching 20% for 3"/6hrs. With impressive moist inflow ahead of the remnants of Philippe pivoting northwest from the Atlantic Ocean converging efficiently into this axis, some heavier rates are also possible, especially in upslope regions. This is reflected by the HRRR depicting some 0.5-0.75" 15-min rainfall accumulations. Rainfall today has been measured by MRMS and observations as high as 3-4" in some areas, which has resulted in saturated top-soil conditions becoming increasingly vulnerable to runoff. This is despite 14-day rainfall, before today, that has been less than 10% of normal, except across the lower Hudson Valley, Berkshires, and southern Greens which have experienced more recent rainfall. FFG across the region is generally 2-2.5"/3hrs, which has a limited potential for exceedance on the HREF. However, locally heavier rain rates, or axes of the most intense training, especially atop any sensitive terrain, could result in rapid runoff and isolated flash flood instances into the evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9AJJQLClTmnpx6cHNQbsJtFtusEbKg2aWdEO6IN0fBA41Sv2OZgkXhlicQjtyaaLPswy= nmZwqKMnZrI-E5cXZvmclwc$ for graphic product... ATTN...WFO...ALY...BGM...BOX...BTV...GYX...OKX... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 45097312 44637258 43837272 42887254 42427267=20 42157298 41967351 41837379 41637410 41597447=20 42477454 44037444 45017410=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) .