Forecast radar reflectivity showing storms in our region Friday evening. (Pivotal Weather)

The siege of moist air, torrential rain and flooding is about to come to something of a pause in time for the weekend. But it does so with a grand finale of sorts, from strong to severe showers and thunderstorms ahead of an approaching cold front on Friday.

The most likely time for strong to severe thunderstorms should focus on Friday afternoon into early evening. Some of the storms could be intense, with the threat of flash flooding, intense lightning, large hail and damaging wind gusts.

Additionally, given the overabundance of rainfall and fully saturated soil across the region, many tree root systems are stressed and weak. Already in recent days, there have been news reports of trees toppling over in the muddy, wet ground, with nothing more than mild breezes pushing against them. Thankfully, these reports have been spotty.

Nonetheless, the odds for significantly more widespread and powerful winds come along Friday as these storms pass. Of great concern is an unusual susceptibility to trees falling.

One of the reasons for highlighting this threat is to raise general awareness: If a storm approaches, it may be prudent to leave the upper story of residences. If driving, you may want to remain clear of forested or tree-lined areas until the storm passes. Odds still remain low that you may suffer consequences from the storm, but it pays to be wary, considering the current conditions.


Amount of rain needed in three hours to cause flash flooding. (Middle Atlantic River Forecast Center)

Additionally, residents should be prepared for one final round of flash flooding, partly since it won’t take much rainfall.

Heavy showers and storms will be capable of delivering another half inch to one inch of rain to many areas, places already teetering on the edge of more flooding. The timing of these storms may be such that the rush hour may face major impacts in some spots.

The Storm Prediction Center (SPC) has outlooked the region extending from Washington to New York for a “slight risk” of severe storms. This is considered a 2 out of 5 in terms of actual threat (Level 5 being the greatest), and this translates more precisely into about a 15 percent probability that anyone will experience a severe weather event within a radius of 25 miles.


Thunderstorm outlook for Friday from the Storm Prediction Center. (NWS)

Our best short-term and storm-focused weather models suggest a broken or solid line of storms will try to congeal west of our region during mid-late afternoon and quickly sweep through between 5 and 8 p.m., give or take. There should be enough instability (because of strong heating by the sun), combined with significant wind shear, to organize some of these storms into longer-lived and more intense clusters and bowing line segments.

As is typically the case, the risk of damaging wind is highest in bow-shaped radar echoes. Some of that is certainly possible Friday.

If the pre-storm environment experiences especially strong destabilization or wind shear is stronger than currently predicted, it’s possible the SPC could elevate the risk category further. Friday is no doubt a good day for extra vigilance, given the scenario in front of us. We’ll have the latest as it unfolds.