BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Sun, 22 Mar 2026 15:50:21 +0000 ----------------------------------------------------------- FOUS30 KWBC 221550 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1150 AM EDT Sun Mar 22 2026 Day 1 Valid 16Z Sun Mar 22 2026 - 12Z Mon Mar 23 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE UPPER OHIO VALLEY TO THE NEW YORK CITY METRO... ...16z Update... Forecast remains on track for isolated flash flooding potential=20 from the Ohio Valley to the northern Mid-Atlantic/Northeast as=20 thunderstorms form and track along an approaching cold front beginning this afternoon. 12z CAMs continue to highlight the best environment for training thunderstorms and localized rainfall totals up to 2 inches (20-40% chances per the 12z HREF) across=20 central/southwest PA through tonight, but with most locations=20 within the MRGL risk receiving less than an inch of rain. Steep=20 mid-level lapse rates and limited low-level moisture will lead to=20 the presence of hail in many of the stronger updrafts, which could=20 actually further limit impacts associated from heavy rain. Snell Previous Discussion... A strong cold front, supported by a passing upper level shortwave, will press southward from the Great Lakes towards the upper Ohio Valley and the mid-Atlantic. The warm air mass ahead of the front is characterized by dew points in the lower 60s across the Ohio Valley and upper 50s across the mid-Atlantic. These are hardly great amounts of moisture. Nonetheless, especially over the Ohio Valley, instability will increase Sunday afternoon to between 1,000 and 2,000 J/kg. This will be enough to support widespread thunderstorm development ahead of the front. The flow of warm air will be out of the WSW, essentially parallel to the front. This will support cells within the SSE-ward moving line moving east, allowing for some opportunity for some training. The combination of better upper level support from the aforementioned shortwave, greater instability, and available moisture will begin to counter the much drier-than-normal soils and rather fast movement of the cold front. Organized convection will break out across Pennsylvania in the late afternoon, then "zip" southwestward across the upper Ohio Valley during the evening, with storms persisting well into the overnight hours. The inherited Marginal Risk area was expanded south and west to include more of southeast Ohio and northern West Virginia, where the threat for training storms could result in isolated instances of flash flooding. Further east, across much of Pennsylvania, wetter-than-normal soils from recent rains could support enough rainfall from storms to result in isolated instances of flash flooding. East of the Appalachians, however, instability rapidly decreases the closer to the ocean you go. This will result in decreasing rainfall rates for any storms that move east off the mountains. The front will also be slower to move south than the same front further east. Thus, while any rain rates from mostly stratiform precipitation will be low, a longer period of time of rain along with wetter soils could also prove enough to result in isolated flash flooding. The inherited Marginal Risk from central Pennsylvania east to the New York City Metro is unchanged from inherited. Wegman Day 2 Valid 12Z Mon Mar 23 2026 - 12Z Tue Mar 24 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Wegman Day 3 Valid 12Z Tue Mar 24 2026 - 12Z Wed Mar 25 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Portions of western Washington State, specifically the Olympic and Cascades Mountains, will be monitored for a potential Marginal Risk introduction with future updates. A front moving into the area will make for a brief time (12-hour) of heavy rain Tuesday morning. While this would normally not be nearly long enough to result in flash flooding, given there is ongoing river flooding from the last event, and both soils and streams/creeks are full, this round of heavy rain may be enough to cause renewed isolated flash flooding. Wegman Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4AhuYKT8BjQyfzh6cR3RPxorbjxIkbnK3zEZyeb44yOd= luxUHNJ0mjmuzb2Nz-4scSCVJw6u21h-xFn1mb-SfAfXNcI$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4AhuYKT8BjQyfzh6cR3RPxorbjxIkbnK3zEZyeb44yOd= luxUHNJ0mjmuzb2Nz-4scSCVJw6u21h-xFn1mb-Si1rkmqI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4AhuYKT8BjQyfzh6cR3RPxorbjxIkbnK3zEZyeb44yOd= luxUHNJ0mjmuzb2Nz-4scSCVJw6u21h-xFn1mb-Saavvqe8$=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 3.28-Linux * Origin: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]