UPDATE as of 10:45 a.m. Wednesday...

A Severe Thunderstorm Watch has been issued until 3 p.m. for the following 14 counties in central and southern New Jersey: Atlantic, Burlington, Camden, Cape May, Cumberland, Gloucester, Hunterdon, Mercer, Middlesex, Monmouth, Ocean, Salem, Somerset, and Warren. A "watch" serves as a formal heads-up to potentially hazardous weather.

A Severe Thunderstorm Watch (pink) is in effect until 3 p.m. for all the counties in pink.
A Severe Thunderstorm Watch (pink) is in effect until 3 p.m. for all the counties in pink.

A line of strong thunderstorms is sweeping through Pennsylvania at this time. While there is nothing on radar in New Jersey yet, forecast models continue to suggest an early afternoon arrival time. The atmosphere in the watch area is "fully charged," with temperatures well into the 80s (even at the Jersey Shore).

Are you guaranteed to see a thunderstorm today? Not necessarily.

If you see a thunderstorm, is it likely to be strong or severe? Yes. (Especially in the watch area.)

Biggest concerns? Wind and rain. (See below.)

Best place to be during a severe thunderstorm? Inside a sturdy building. (Really, that's true of any thunderstorm.)

ORIGINAL POST FROM 6:16 a.m. Wednesday...

Wednesday Overview

Steamy and stormy — a familiar story here in New Jersey in the warm weather months. Over the next four days, we face unseasonably and uncomfortably warm conditions, along with some unsettled weather. Several rounds of thunderstorms are likely — and given the heat and humid (energy and moisture), those storms will almost certainly reach strong to severe limits.

We already had a round of loud, soaking thunderstorms early Wednesday morning. As of this writing (5:30 a.m.), we have a few spotty showers in southern New Jersey, but nothing to write home about. We'll get an hours-long stretch of dry weather through the morning, before things turn active later.

Meanwhile, high temperatures will reach the lower to mid 80s for most of the Garden State. Inland South Jersey could very well register the first 90-degree day of the year. It's not a heat wave. And we should remain below the threshold for "dangerous" heat.

Keep an eye on the sky from Wednesday midday through Wednesday early evening — let's say Noon to 7 p.m. That is when two or three rounds of scattered to isolated strong thunderstorms will impact the state, progressing from northwest to southeast. I expect northern and central New Jersey to experience (widespread) scattered thunderstorms. Southern New Jersey will see more isolated thunderstorms later on, with scattered showers at night.

Wednesday's severe weather outlook from the Storm Prediction Center paints almost all of New Jersey in an "enhanced" risk of dangerous thunderstorms. (NOAA / SPC)
Wednesday's severe weather outlook from the Storm Prediction Center paints almost all of New Jersey in an "enhanced" risk of dangerous thunderstorms. (NOAA / SPC)

A Taste of Storm Science

For severe weather to occur, you need three primary ingredients: energy, moisture, and a spark. As temperatures heat up into the 80s (at least), the atmosphere will become quite unstable — there's the energy. Humidity will rise, with dew points in the 60s (at least) — abundant moisture. And a weak front will drift through New Jersey — the lift from that front boundary will be the spark for thunderstorm initiation.

(There's a 4th ingredient we also consider — convective inhibition, or the "cap" — which is required for the formation of the most powerful supercell thunderstorms, but isn't totally necessarily for stormy weather here in New Jersey.)

Biggest Concerns

Let's talk about our five biggest concerns to come from the sky from Wednesday's storms, in order of likelihood:

1.) Cloud-to-ground lightning... Guaranteed. By definition, a thunderstorm contains thunder and lightning. So by definition, every thunderstorm is potentially dangerous.

2.) Torrential rain... Highly likely. The atmosphere will be incredibly juicy, evidenced by the thick humidity you'll feel all day. Plenty of water vapor to form rain droplets and provide a thorough soaking. Downpours may cause localized flooding issues.

3.) Damaging winds... Likely. As heavy rain falls, it cools air and causes it to blow out ahead of a line of thunderstorms. It's called outflow. And it can be pretty destructive, as we have seen several times this year already. The forecast strength of these storms will almost certainly be high enough to produce wind gusts above strong (40+ mph) or severe (60+ mph) limits.

4.) Hail... Possible. Hail requires a layer of very cold air at the top of a thunderstorm cloud, where chunks of ice can congeal and grow. Even though surface temperatures will be in the 80s, it will be subfreezing about 3-4 miles overhead. Good enough for small (pea-sized) hail. And with strong enough updrafts, larger hail stones can't be ruled out.

5.) Isolated tornado... Slight chance. These thunderstorms will be primarily linear, however models are suggesting a few discrete storm cells which would be more conducive to a quick spin-up. A tornado is a very specific weather phenomenon, that requires very specific parameters from a very powerful thunderstorm. The risk is not zero today. (In fact, the Storm Prediction Center codifies it as a 2% threat for NJ.)

The Extended Forecast

After sunset Wednesday evening, things will calm down. We'll see see some showers around, especially in South Jersey. And it will definitely be sticky, with low temperatures only dipping into the upper 60s or so.

Thursday's forecast reads similarly to Wednesday's, but I think it will be slightly less steamy stormy. Skies will be partly to mostly cloudy, with highs in the mid 80s. Spotty showers and thunderstorms are probably, especially Thursday night.

Friday could be a mainly dry day. Clouds and sun will accompany temperatures again in the mid 80s. I'll just include a chance of a shower or thunderstorm for now.

Eventually a cold front will put an end to the heat, humidity, and daily thunderstorms. But we will move into the weekend facing another steamy, active daySaturday. Look for highs in the 80s, with elevated humidity levels for most of the day. At it stands now, expect one final push of scattered thunderstorms around midday Saturday.

By Sunday, our weather turns drier, cooler, less humid, and brighter. Looks like a great back half to the weekend, with mostly sunny skies, a fresh northwesterly breeze, and high temperatures in the upper 70s.

Long-range models suggest the pleasantry will continue through Monday and Tuesday too. Good news all around!

With both the heat and the storms in play, please be smart and stay safe out there today.

Dan Zarrow is Chief Meteorologist for Townsquare Media New Jersey. Follow him on Facebook or Twitter for the latest forecast and realtime weather updates.

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