Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 04 2023 22:25:40 AWUS01 KWNH 042225 FFGMPD MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-PAZ000-050330- Mesoscale Precipitation Discussion 0864 NWS Weather Prediction Center College Park MD 624 PM EDT Fri Aug 04 2023 Areas affected...Eastern Upstate NY...Much of New England into Northwest ME... Concerning...Heavy rainfall...Flash flooding likely Valid 042230Z - 050330Z SUMMARY...Scattered areas of intense rain-rates and potential training likely to continue instances of flash flooding through early overnight period. Second line of thunderstorms, may also cross areas already flooded earlier, reaggravating conditions as well. DISCUSSION...GOES-E WV suite depicts a subtle inflection at the base of the large scale trof crossing the central St. Lawrence Valley nearing far NE NY/VT dropping another cold front across the Valley into the Interior northeast. Convergence along the front continues to spur some lingering thunderstorms across the Adirondacks across SE Quebec within a narrow corridor of enhanced deeper layer moisture and modest remaining instability. Rates are likely to be limited, but will slide southward across areas in NE NY/VT as instability wanes, to potentially add an additional 1-1.5" in spots that have already been flooding today. Further north into NW ME, increased angle of surface to 850mb convergence and modest 1000-1500 J/kg of CAPE remain to spark scattered updrafts that will be slower moving given deeper steering flow more parallel to the slowly advancing cold front. Updrafts appear to be more narrow given slightly reduced moisture (1.25" total PWat), suggesting less efficiency, but still may pose spots of 1-2" totals, though this window is closing quickly with the slow reduction of daytime heating and instability source, but flash flood risk is low, but still non-zero. Further south, 21z surface analysis suggested a wave near Rome, NY with increased oblique angle to ongoing convection/outflow boundary across S VT into far SW ME from ongoing thunderstorms.=20 CIRA LPW and RAP analysis suggests a confluence of moisture streams in the low levels along/ahead of the cold front across S central NY angling through central to western PA, as well as a coastal moisture stream through the Delaware valley into the Hudson and southern New England. Weak but effective warm advection/confluence of these moisture streams appears to be favorably orienting to the deeper mean flow to suggest continued thunderstorm development through the late evening into early overnight period across central to southern New England.=20=20 Untapped CAPE up to 1000-1500 J/kg remains forecast across the region with this increase of moisture toward 1.5", combined with 20-25kts of 850mb confluence flow, should support strong updrafts with rates of 1.5-2"/hr. Spots of 2-3" along this band are possible and align with saturated soil conditions per 7-14 day AHPS precipitation anomalies in the region. As such, spots of flash flooding remain likely through 04z especially across central New England.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9ruorvGmI_ecDsA7txhzyrZZkVjzpusv99f7pe-XViUg_rrbgTNSn76hfjfxf6SOGZsk= qANqXPx7B22iBR9nMnVHW_A$ for graphic product... ATTN...WFO...ALY...BGM...BOX...BTV...CAR...GYX...OKX... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 46896925 46436878 45686893 44966949 44346985=20 43816978 43227039 42857056 42287090 41837160=20 41517336 41697522 42067581 42547575 43357501=20 43757472 44337391 45337141 46027050 46756999=20 =20=20=20=20=20=20=20=20=20=20=20=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) .