Increased humidity, severe storms this weekend

Low clouds have created a bit of a wrinkle in the forecast early Friday morning, owing to a southeasterly flow which developed late Thursday night. The low level inversion allowed for these clouds to push inland and develop, as seen on visible satellite imagery from Eastern Pennsylvania into much of New Jersey and New York. These clouds will eventually thin and break later Friday afternoon, as southwesterly winds take over.

Temperatures, as a result, will rebound with highs expected to reach into the upper 80’s. Rising humidity will also make it feel much more uncomfortable. The atmosphere won’t be able to efficiently mix out — so temperatures won’t rise into the 90’s on Friday and seabreezes may develop. These seabreeze boundaries could serve as a focal point for the development of some isolated storms Friday afternoon.

HRRR model forecasting highs in the 90's away from the coast on Friday, with cooler air near the shore.

HRRR model forecasting highs in the 90’s away from the coast on Friday, with cooler air near the shore.

The bigger threat for storms will come on Saturday. A mid level disturbance is forecast to approach the area, with some vigor. Southwesterly winds will help to build instability with increasing mid and low level temperatures. The approach of moderately favorable wind fields will juxtapose with this instability to create a kinematic and thermodynamic environment favorable for the development of thunderstorms.

The Storm Prediction Center issued a Slight Risk for severe storms for much of the Northern 1/2 of New Jersey, the NYC Metro, Long Island and Southern New England on Saturday. In this area, organized thunderstorms will be capable of producing some strong gusty winds. In addition, dangerous lightning is possible in storms as well as heavy rain and localized flooding. The threat for severe weather is expected to initially develop to our west-northwest over the interior Northeast, and eventually push toward the coast.

Storm Prediction Center outlook for Saturday.

Storm Prediction Center outlook for Saturday.

Much of the severe weather threat depends on timing, not only with the disturbance and cold front itself, but with the passage of favorable wind fields. These wind fields and shear are important in the development of organized thunderstorms. If they can juxtapose with moderate instability at the right time, organized severe thunderstorms could push towards the coast. But if the timing changes slightly as Saturday approaches and they are misaligned, the threat will be more marginal.

We’ll keep a close eye on the threat for severe thunderstorms as Saturday approaches. For now, warm and humid conditions are expected throughout the remainder of Friday. Be sure to stay tuned to our social media accounts for updates on isolated storms which, again, are possible as early as Friday afternoon.