Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 09 2023 15:06:13 AWUS01 KWNH 091506 FFGMPD MEZ000-MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-092100- Mesoscale Precipitation Discussion 0674 NWS Weather Prediction Center College Park MD 1104 AM EDT Sun Jul 09 2023 Areas affected...Interior Northeast Concerning...Heavy rainfall...Flash flooding likely Valid 091505Z - 092100Z SUMMARY...An increasingly unstable and highly saturated atmosphere will give rise to widespread thunderstorms today. Flash flooding is likely and could become significant, particularly in areas with highly saturated soils. DISCUSSION...Similar to their neighbors in MPD 674, a robust 250-500mb trough axis near the central Appalachians will work in tandem with a strengthening jet streak to the northwest to generate strong vertical ascent within the atmospheric column. The region lies beneath the divergent right-entrance region of the jet streak, while a near by stationary front and surface based heating spark numerous thunderstorms this afternoon. The atmosphere is already supportive of convection to develop in short order. RAP mesoanalysis already shows >1,000 J/kg of MLCAPE in the Hudson Valley and as far north as Lake Champlain. With the aid of surface based heating and low level moisture advection, MLCAPE should rise to >1,500 J/kg this afternoon. RAP forecasts show PWATs rising to 1.5-1.75" by mid-afternoon, values that eclipse the 90th climatological percentile according to NAEFS. As winds strengthen aloft and storms form, atmospheric profiles will grow highly saturated. 1000-500mb RH values are forecast to rise above 90%, especially in the southern half of the highlighted region this afternoon. Sampled RAP soundings in northern NY, central VT, and central NH around 21Z all show roughly the same thing-- highly saturated, skinny CAPE profiles, and warm cloud layers as deep as 10,000-12,000ft deep. Hodographs in the area show increasingly sheared soundings this afternoon (thanks to increasing speed shear with height), but winds will be primarily out of the SW. Some RAP soundings show Corfidi upshear vectors as low as 10 knots, suggesting the potential for backbuilding convection that can be aided by persistent upslope flow in topographically-favored locations. Not only is the atmosphere primed to produce Excessive Rainfall rates, but most soils are highly saturated from the past 7-days worth of rainfall. AHPS 7-day rainfall shows totals in southern NH/VT that are 300-400% of normal, with much of the Lower Hudson Valley and the Adirondacks seeing similar amounts. Some of these areas, most notably south-central VT, have already dealt with washed out roads and culverts from the heavy rainfall on July 7. These atmospheric parameters, along with the sensitive soils in place, will likely result in flash flooding this afternoon. Hourly rainfall rates are likely to range between 2-3"/hr in the most intense thunderstorm activity. Water will have the potential to rise rapidly in poor drainage areas, in urbanized communities, and may even result in mudslides in steep terrain. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5b-9EVSzM4HeYOPH7jWsfCh66vZ84bkvEAhQjiUYRwa9bw1Hkn_SjPoB-C5sfleQL2R_= Snpb-uB_n6z1u5YsX3eMHE4$ for graphic product... ATTN...WFO...ALY...BOX...BTV...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 45897075 45577011 43407129 42197208 41727326=20 41917363 42417373 43057429 43977431 45017388=20 45327162=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) .