NYC Area Forecast: Strong storms possible later today

In what seems to be becoming a bi-weekly occurrence, strong thunderstorms are again possible throughout the Northeast later today. In all seriousness, another frontal boundary approaches this part of the country today – the second this week to do so with some vigor. The airmass ahead of it is once again expected to be humid and unstable, and the lift associated with a pre-frontal disturbance will be significant enough to aid in thunderstorm development later today. SPC has placed parts of the Northeast in a Slight Risk for severe storms later today and tonight. 

As is often the case with thunderstorm events, the devil is in the details – and the details are uncertain. The latest observations this morning suggest that forecast models were a bit over-aggressive with their depiction of morning showers and thunderstorms across the Northeast. This is both good and bad news; it means a drier and more pleasant morning, but it allows the atmosphere to become more unstable later today.

Instability increases across the area later today – fuel for thunderstorm development.

As southerly winds increase and warmer, moist air is drawn into the Northeast, CAPE will increase area-wide. CAPE, or Convective Available Potential Energy is a measure of the atmospheric instability that thunderstorms can act upon. Higher values typically (in simple terms) support stronger, more intense thunderstorm activity. When lift in the atmosphere develops storms near an axis of CAPE (and sufficient wind shear), you get thunderstorms that can become organized and strong or severe. That’s what we are expecting today.

Forecast model guidance, in the short term, is split on exactly how storms develop. Big shock there! Most agree that a pre-frontal trough (or a trough ahead of the main cold front) will help develop storms over Central and Eastern PA as well as Southeast New York by the early to middle afternoon hours. These storms could become severe and begin tracking eastward into Pennsylvania by the middle afternoon, with the potential to produce dangerous lightning, gusty winds and heavy rain.

After that point, some guidance suggests storms weaken and become showers before approaching the coast. Others suggest a continued threat for strong and severe storms into New Jersey, Southeast New York and Western New England. Us? We give up. Kidding – but while wind shear is not strong enough for widespread/significant severe weather today, it does appear sufficient to keep storms organized – and so our opinion is that that the potential for strong storms will continue eastward towards the aforementioned areas this evening.

NAM model simulated radar near 8pm. It’s stormy.

In the immediate NYC Area, the best potential for strong storms will be after 7pm, and may largely remain to the cities north and west. However, storms are still expected – right between 7 and 9 pm – as the pre-frontal trough makes its move past the region. So you may want to think about: A) Moving happy hour inside during this time frame or B) Turning happy hour up and notch, not telling anybody that the storms are coming, and getting soaked (in all seriousness, go inside if you see a storm approaching, they can be dangerous).

For Northern New Jersey, the NYC Metro, Southeast New York and Western New England, the main threats with these storms will be gusty winds, heavy rainfall, and lightning. As always, pay close attention to warnings and local information. We suggest following us on Twitter for minute-by-minute updates later today.

The Storm Prediction Center maintains a Slight Risk (Level 2 of 5) for parts of the Northeast today where the threat for strong to severe thunderstorms is expected to be focused. A Marginal Risk (Level 1 of 5) remains in effect elsewhere, where storms are possible but not expected to be overly organized or impactful.

Further updates are on the way today – so enjoy your morning and we’ll check back in later. PS – Slack is back up, so there’s no excuse not to be working!