A deep southwesterly flow has developed this morning, allowing for increasingly warm mid level temperatures to advect into the area. Surface temperatures, as a result, are expected to rise much higher today than they did on Wednesday. Temperatures in the low 90’s are anticipated by early afternoon throughout much of New Jersey and New York City. Humidity will be on the rise as well. An Air Quality Alert is in effect for parts of NJ and NYC today, which means you should avoid prolonged exposure to the heat and humidity as air quality will be subpar.
A wind shift boundary, sitting just to our north over the Lower Hudson Valley, will serve to enhance the development of instability to its south. Models are in good agreement that upward of 2500 joules of Surface Based CAPE will develop from Eastern PA into New Jersey and New York City during this afternoon. These numbers are quite high for our area — especially during this time of year.
This obviously raises some eyebrows for the potential development of strong and severe thunderstorms. The question, then, becomes whether or not there will be enough atmospheric lift to trigger these storms. Thunderstorms need instability to develop, but they also need lift, forcing, or ascent to allow the updrafts to initially form. And then they need the right amount of atmospheric shear to mature and survive.
Forecast soundings don’t lend much increased confidence, as they show some “capping” in the mid levels of the atmosphere during the late morning and early afternoon. This means that storm development will be somewhat mitigated initially, waiting for forcing to, well, “force” the development of the storms. The most likely location for these storms to develop will be along the twice mentioned wind shift boundary, which will push southward from New England into the Mid Atlantic on Thursday afternoon. Prolific instability exists just south of this boundary, with northerly winds and stable air to its north.
If updrafts do develop, storms could become severe quite quickly. A juicy and unstable atmosphere would support very heavy rain, dangerous lightning, and the potential for small hail and gusty winds in any storms. These storms would likely ride along the wind shift boundary from northwest to southeast as it pushes southward this afternoon, initially developing in Northern NJ and pushing south into NYC, LI and Central NJ later tonight.
The Storm Prediction Center has placed our area in a “Marginal Risk” for severe thunderstorms, also citing the lack of lift for storm development as a potential mitigating factor. We’ll be closely monitoring this afternoon for storm development. This thread will become a live blog at 12:00pm — so stick around!