Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 17 2025 16:40:02 AWUS01 KWNH 171638 FFGMPD NHZ000-VTZ000-NYZ000-172230- Mesoscale Precipitation Discussion 0282 NWS Weather Prediction Center College Park MD 1238 PM EDT Sat May 17 2025 Areas affected...northeastern NY into VT/NH Concerning...Heavy rainfall...Flash flooding possible Valid 171636Z - 172230Z SUMMARY...Localized to widely scattered instances of flash flooding will be possible from northeastern NY into north-central New England through early evening. While the majority of cells are expected to be progressive, cell alignment will occasionally favor areas of short term training, capable of producing 1-2 inches of rain in an hour or less. DISCUSSION...16Z visible satellite and radar imagery showed scattered thunderstorms from eastern Lake Ontario into the Adirondacks, in the wake of a preceding swath of showers/thunderstorms advancing through VT. The storms over northeastern NY were located just downstream of the leading edge of a mid-upper level closed low centered over Lake Huron, within the diffluent left exit region of a 90-110 kt upper level speed max located just south of the closed low. The environment over northeastern NY into VT contained 500-1000 J/kg MLCAPE and 1.1 to 1.4 inches of precipitable water per 16Z SPC mesoanalysis data. Daytime heating in the wake of overcast skies departing toward the east from VT (and eventually parts of NH) should allow for an expansion of CAPE across the region with 500-1500 J/kg likely from eastern NY into central/north-central New England over the next 2-4 hours. Forecast stalling of a warm front over southern NH should limit the northeastward extent of instability and therefore rainfall intensity over eastern NH at least through late afternoon. A mixture of storm types will be possible given sufficient shear and instability but individual cells are expected to average 25-35 kt from the southwest. The concern for flash flooding will come from multiple rounds of cells over the same location and/or brief alignment of cells with the mean wind to support short term training. These scenarios could allow for 1-2 inches of rain in an hour, or even as short as 15-30 minutes, given the strong ascent ahead of the upper low. 1-2 inches of rain (perhaps localized 3 inch totals) will be capable of localized to widely scattered flash flooding through 22Z. However, the coverage of these higher rainfall totals should stay somewhat limited across the region. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-7EM3pHbT7goWxmX10YGl1NPzHOPV8cGSEUpYB-UnBbR_Yct8s7eVOu09P55KJnodLJs= jsL5Un_9piRR3fgAOEN0WF4$ for graphic product... ATTN...WFO...ALY...BGM...BTV...BUF...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 45217212 44987141 44247144 43467192 42777243=20 42747308 42967348 43157380 43177476 43227535=20 43217581 43417609 43667612 43967584 44407513=20 45057386=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) .