Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 09 2023 21:03:50 AWUS01 KWNH 092103 FFGMPD MEZ000-MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-NJZ000-100300- Mesoscale Precipitation Discussion 0680 NWS Weather Prediction Center College Park MD 502 PM EDT Sun Jul 09 2023 Areas affected...Eastern NY...Western MA...Western CT...Vermont...Western NH...Northwestern ME Concerning...Heavy rainfall...Flash flooding likely Valid 092101Z - 100300Z SUMMARY...Widespread slow moving storms with high rainfall rates are expected to continue through the evening hours from the greater New York City metro area northward across central and northern New England. Multiple instances of flash flooding are likely through 11 pm local time given wet antecedent conditions and slow cell motions. DISCUSSION...Regional Doppler radars are indicating an increase in intense convection within a plume of enhanced low-mid level moisture with PWs generally within the 1.7 to 2.0 inch range based on recent SPC mesoanalysis. There is also enhanced 300 mb right entrance region divergence which is helping to aid deep layer ascent. The surface to 850 mb flow is generally out of the SSE and this is resulting in enhanced orographic ascent from the Berkshires to the White Mountains, and some of the cells that have developed have become somewhat anchored to the terrain and thus leading to longer duration of rainfall rates exceeding 2 inches per hour. Some back-building cells are also likely to develop, and this will tend to lengthen the duration of the higher rainfall rates. Mixed layer CAPE on the order of 1000-1500 J/kg will also support strong updrafts with resulting very heavy rainfall.=20 The latest CAM guidance suite has a good overall depiction over the next several hours with patchy QPF maxima of 2-4 inches, and isolated 4+ inch totals are within the realm of possibility. The 18Z HREF neighborhood probabilities have up to 60% exceedance of 3-hourly flash flood guidance across portions of western New Hampshire. Rainfall over much of the outlook area has been well above normal over the past week, with over 400% of normal values from the greater Hartford metro area northward to central New Hampshire, which also had excessive rainfall yesterday. These areas will be more vulnerable to additional heavy rain, and flash flooding is considered likely through 11 pm local time. There is very slow general eastward motion, but slow enough to likely warrant additional MPDs beyond 11 pm. Hamrick ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4hwMGrL18XI_0iJcMn4PqIDG1w3bAo9_DWT5irstvAVPY1-a7giJPn2uVVVG-X4vCxnA= uc3xvXzidEDKSOyVaZwl3kk$ for graphic product... ATTN...WFO...ALY...BOX...BTV...CAR...GYX...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 46597021 46526966 45496991 44887046 44257086=20 43537133 42987160 42517185 41917223 41447259=20 41037298 40657326 40507359 40437398 40437417=20 40557430 40887404 41257383 41657371 41957357=20 42367343 42637339 42887352 43017371 43077395=20 43267419 43717413 44567417 45027391 45077314=20 45047249 45057192 45357139 45597088=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) .