GFS model showing a very high amount of CAPE in the Northeast on Sunday.

Medium Range Analysis: Severe Weather Chances this Weekend

Good evening! We hope you all had a great Monday. For the most part, the area had a beautiful, summer day, but some western suburbs of NYC had some strong thunderstorms and flash flooding. These storms quickly weakened as they headed towards NYC, as the pattern right now is generally not favorable for severe weather in our area. But that may change come this weekend, when the general synoptic pattern may start to favor strong to severe thunderstorms.

It’s pretty far out in time, so plenty can change — but at this range we like to look at general features of the pattern and what they signal, since there is inherently less noise in broader signals. One thing we like to look at is a pattern that can favor advection of an EML (Elevated Mixed Layer) into the region. The EML is a layer of very hot and dry air from around 700mb (around 10,000 feet) and up that originates in the desert southwest. This hot and dry air air is not contaminated with moisture and thus it can cool quickly with height, creating a lot of mid-level instability. These EMLs often combine with rich, tropical Gulf of Mexico moisture in the low-levels of the atmosphere in tornado alley and lead to some of the biggest severe weather outbreaks.

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