Flash Flood Guidance
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Issued by NWS
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440 AWUS01 KWNH 141926 FFGMPD MAZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-150125- Mesoscale Precipitation Discussion 0437 NWS Weather Prediction Center College Park MD 325 PM EDT Fri Jun 14 2024 Areas affected...Portions of the Northern Mid-Atlantic...Southeast NY...Far Southern New England Concerning...Heavy rainfall...Flash flooding possible Valid 141925Z - 150125Z SUMMARY...Showers and thunderstorms advancing across central PA should gradually expand in coverage over the next couple of hours and should impact portions of the I-95 corridor with heavy rain heading into the early evening hours. An isolated and mainly urban concern for flash flooding will exist. DISCUSSION...The latest GOES-E WV suites depicts a shortwave trough crossing the northern Mid-Atlantic currently which will be interacting with a relatively moist and unstable boundary layer pooled up across the coastal plain from the Delmarva northward through southeast PA, NJ and into southeast NY. SBCAPE values with the aid of strong diurnal heating have risen to 1000 to 1500 J/kg, and surface dewpoints across the MPD are generally in the mid to upper 60s. Overall, the PWs are on the order of 1.4 to 1.6 inches. Over the next couple of hours, some additional uptick in boundary layer instability and some modest increase in convergent low-level flow will combined with the arrival of the shortwave energy to foster the further development and expansion of shower and thunderstorm activity. Already there is a fairly organized cluster of stronger thunderstorms crossing through central PA where stronger vort energy with the shortwave trough is noted, and this convective cluster will continue to advance generally off to the east as new storms ahead of it also begin to develop. Rainfall rates with the stronger storms heading into this evening may reach into the 1 to 2 inch/hour range, and the 12Z HREF guidance suggests that some areas of the northern Mid-Atlantic and especially areas along and east of the I-95 corridor may see some of the convection get locally concentrated with some periodic cell-merger and cell-training concerns. This may result in a few spotty 2 to 4 inch rainfall totals with areas of southeast PA, central and northern NJ, and perhaps far southeast NY including the New York City metropolitan area at greatest risk for these heavier totals. An isolated and mainly urban flash flood concern may evolve where these heavier totals materialize heading into the early evening hours. Orrison ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ALY...BGM...BOX...CTP...LWX...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 42267228 41667211 40537330 39847393 39377462 38967566 39157666 39717682 40527604 41037536 41537461 42207332