Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 28 2023 16:01:25 AWUS01 KWNH 281601 FFGMPD MEZ000-MAZ000-NHZ000-VTZ000-282200- Mesoscale Precipitation Discussion 0600 NWS Weather Prediction Center College Park MD 1200 PM EDT Wed Jun 28 2023 Areas affected...Parts of New England Concerning...Heavy rainfall...Flash flooding possible Valid 281600Z - 282200Z Summary...Showers and thunderstorms will train from south to north across central and northern New England through this evening. Rainfall rates may exceed 2"/hr at times, and instances of flash flooding are possible. Discussion...The regional radar mosaic early this aftn shows showers and isolated thunderstorms increasing in coverage from Upstate New York though much of central New England. This convection is blossoming in response to increasing deep layer ascent downstream of mid-level height falls accompanying a trough axis and increasing upper divergence as a jet streak pivots northward. At the surface, low-level flow is nearly unidirectional from the south on morning U/A soundings, transporting PWs northward that were measured at 1.64 inches at OKX and 1.41 inches at GYX, nearing the 90th percentile according to the SPC sounding climatology. While the GYX sounding indicated some mid-level dry air to overcome, the column was deeply saturated at OKX with modest lapse rates and 12000 ft freezing levels, indicating efficient rain processes. Clouds beginning to break has allowed SBCAPE to reach 1000 J/kg according to the SPC RAP, furthering the convective intensity, reflected by estimated rainfall rates of 1.5"/hr from KBOX last hour. The mid-level trough will continue to pinwheel to the east today while a modest shortwave noted in WV imagery swings through its base. These together will impinge into an increasingly favorable thermodynamic environment as the unidirectional southerly flow drives PWs to as high as 1.75 inches and MUCAPE to around 2000 J/kg. This impressive overlap of forcing and moisture will produce widespread convection this aftn/eve with rainfall rates likely eclipsing 2"/hr as shown by HREF probabilities. Despite 0-6km mean winds of 15-20 kts indicating fast forward propagation, aligned Corfidi vectors suggest an enhanced threat for training and even some backbuilding into the greater instability. With deep unidirectional flow in place, any weak convergence signatures could also produce more coherent lines of convection, and the HRRR sub-hourly fields indicate a threat for up to 1" of rain in just 15 minutes today. Where these lines train most efficiently, a few areas could receive 2-4" of rainfall. Much of New England has been wet recently noted by 14-day rainfall departures that are 150-300% of normal according to AHPS. This has pre-conditioned the soils resulting in extremely anomalous stream flows well above the 90th percentile, and FFG as low as 1"/3hrs which has a 20-40% of being exceeded. These antecedent conditions combined with sensitive terrain suggest an enhanced runoff risk today, so training of any intense rainfall could produce flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!62IlrRhY8cKNFNUQbq-j4_Q4i0uBRixUGbp_dX-Qe6xSKIF7c_DcnaJF1sVyPiNb4lLN= 41hWVtN0UXn0gXKisfQk6RU$ for graphic product... ATTN...WFO...ALY...BOX...BTV...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 45367189 45357098 45057049 44677045 44127050=20 43487067 43417069 42967087 42637107 42577113=20 42397157 42347215 42517260 42807284 43197306=20 43797309 44257310 44687301 45097275=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) .