Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 06 2024 15:51:31 AWUS01 KWNH 061551 FFGMPD NYZ000-PAZ000-OHZ000-062100- Mesoscale Precipitation Discussion 0818 NWS Weather Prediction Center College Park MD 1151 AM EDT Tue Aug 06 2024 Areas affected...eastern Great Lakes through central Pennsylvania Concerning...Heavy rainfall...Flash flooding possible Valid 061550Z - 062100Z Summary...Expanding coverage of showers and thunderstorms downstream of a shortwave will emerge from the Great Lakes into the western Mid-Atlantic States. Rainfall rates of 1-2"/hr will become common, which through repeating rounds could produce 2-3" of rain with potentially locally higher amounts. Flash flooding is possible. Discussion...The GOES-E visible imagery this afternoon shows a large area of cloud cover exiting from the Great Lakes associated with a large area of showers and thunderstorms. This convection is developing in response to a shortwave noted in WV imagery and present in the RAP analysis moving across Lake Huron. At the surface, a stationary front is analyzed by WPC from near Albany, NY to near Lima, OH, and the interaction of the shortwave with this boundary is helping to drive rapid Cu development within clearings and along differential heating boundaries. Additionally, a jet streak moving across southeast Canada is strengthening to place favorable RRQ diffluence aloft, to further enhance ascent into robust thermodynamics characterized by PWs of 1.5-1.8 inches, and a ribbon of MLCAPE approaching 1500 J/kg south of the front. Radar-estimated rainfall rates within ongoing convection have already reached 1.5-2 inches per hour. As the shortwave continues to advect east, it will interact with even more impressive thermodynamics thanks to continued destabilization south of the stationary front. SBCAPE may exceed 2000 J/kg this afternoon from far eastern OH into central PA, with a very intense cape gradient likely to develop due to the front and pronounced cloud cover. This should result in an expansion and intensification of convection as shown by most of the available high-res CAMs, and the HREF neighborhood probabilities for 1"/hr (2"/hr) rates increase to 60-70% (30-40%). Storm motions will likely remain quick on 0-6km mean winds of around 30 kts, but aligned Corfidi vectors suggests training or repeated rounds of cells containing these intense rates in some areas. The presence of the sharp instability gradient and impressive convergence of moisture transport vectors additionally supports storms that will train primarily along the vicinity of the front, and where the most pronounced training occurs the HREF neighborhood probabilities suggest some areas could receive in excess of 3" of rain. This region has been active recently, and AHPS 7-day rainfall anomalies are in general 150-300% of normal, leading to elevated 0-10cm RSM from NASA SPoRT and FFG compromised to as low as 1-1.5"/3hrs. The HREF 3-hr FFG exceedance probabilities peak above 50% this afternoon, further indicating the potential for instances of flash flooding despite the fast motion of individual cells. This additionally indicates the probability of repeating rounds of storms through the afternoon which could cause flash flooding impacts. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7Pd0FPhKKF5Bx3BFerKgLjsBjNeaVnBvCzz0KmntoSSZPkkiVKYh2YZOtX950YIuToHn= cMDIGLcXQkPNu9PQRJ80ns0$ for graphic product... ATTN...WFO...BGM...BUF...CLE...CTP...PBZ... ATTN...RFC...MARFC...NERFC...OHRFC...NWC... LAT...LON 42587898 42447736 42207636 41647591 40827643=20 40337772 40377885 40437912 40648015 41078119=20 41598147 42078120 42448014=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .