Dangerous heat and powerful storms return to NJ Wednesday

The Bottom Line

Remember last week's taste of fabulous fall weather? 'Tis but a distant memory now, as summer has returned to New Jersey.

Wednesday promises to be an active weather day for the Garden State, for two big reasons: Heat and thunderstorms.

Let me give you a quick rundown of this potentially hazardous weather. With a tease of what's ahead as the Labor Day Weekend approaches too.

Heat

Yes, it's still summer. And summertime in New Jersey is supposed to be hot. But when heat and humidity levels reach certain thresholds, we have to ring alarm bells for dangers to human health.

Temperatures Wednesday morning are starting near 70 degrees — our warmest low temperature in a week and a half.

High temperatures Wednesday afternoon are forecast to reach about 90 to 95 degrees across most of New Jersey. The only potential exceptions, where thermometers may be limited to the 80s, would be the far northwest corner of the state and the immediate coast.

Meanwhile, humidity levels have been steadily creeping up since last weekend. As dew points push into the 70s on Wednesday, the air will become uncomfortably steamy and thick. Remember, the biggest physical impact of high humidity is that your body can not sweat and cool down as efficiently as in dry air conditions.

The combination of heat and humidity gives us the heat index — also known as the "feels like" or "apparent" temperature. The heat index will likely push above 100 degrees on Wednesday, which raises those alarm bells for hazardous conditions.

An Excessive Heat Warning has been issued for the Philadelphia metro area from 11 a.m. to 8 p.m. On the Jersey side of the river, the warning includes Mercer, northwestern Burlington, Camden, and Gloucester counties. The warning specifically cautions the heat index may shoot as high as 105.

A less-severe Heat Advisory blankets almost the rest of New Jersey — excepting Sussex, western Passaic, coastal Monmouth, coastal Ocean, coastal Atlantic, and coastal Cape May counties.

Standard heat safety tips apply: Dress for the heat, stay extra hydrated, and take frequent breaks in air-conditioning.

Cooler temperatures will prevail by Thursday morning, so this is only a "one day heat wave" for New Jersey.

Thunderstorms

Given the soupy atmosphere and an approaching cold front, it should be no surprise that thunderstorms are also in the forecast for Wednesday.

However, I am not convinced that storm activity will be all that widespread. Especially during the daytime hours Wednesday.

There are some isolated showers around southern and coastal New Jersey Wednesday morning. Nothing big — just a smattering of raindrops.

Then, watch for a few popup thunderstorm cells starting around 3 or 4 p.m. Wednesday. These will develop quickly, and will be capable of producing gusty winds, small hail, lots of lightning, and localized downpours. (The tornado threat is low, although not quite zero.)

Again, these will be isolated cells that pack a punch over a small area. According to the latest model guidance, the juiciest atmosphere and highest chance of severe weather will be over the southern half of New Jersey.

If we see a more widespread line of storms, it would not be until late Wednesday night — close to Midnight, perhaps. The same severe weather concerns apply.

Showers may even linger into Thursday morning. However, the threat of severe weather will decrease as time goes on.

Looking Ahead

Thursday will be 15 to 20 degrees cooler than Wednesday, with highs only in the upper 70s. The day will be fairly cloudy and humid though — so not a refreshing breath of beautiful weather. Additionally, I can't rule out some spotty showers or sprinkles around.

The same is true on Friday, although the sky should brighten and high temps should return to about 80 degrees.

That brings us to Labor Day Weekend, the grand finale of the summer season. And the weather forecast is not perfect.

Models have consistently shown a band of rain sweeping through New Jersey in the late Saturday to early Sunday time frame. If that timing holds, Saturday daytime should be nice and warm, Sunday daytime stays iffy, and then Labor Day Monday nice but cooler.

Of course, we will further refine that forecast as time goes on. Let's get past Wednesday's active weather, and then we can focus on the holiday weekend outlook.