Wednesday NJ weather: Heat Advisory, Flash Flood Watch

The Bottom Line

Our weather is about to turn more active, with a 24 to 36 hour period of showers and thunderstorms. Fueled by the abundant humidity in the air, pockets of heavy rain and/or training storms could lead to flash flooding issues. So, unsettled and damp, cloudy and cooler, but still humid. Hopefully we'll trend drier and more pleasant for the weekend, but that's not guaranteed.

Wednesday

Another summer morning in the steamy 70s and in the fog (along the coast). As a frontal boundary slows to a crawl over central New Jersey, we have seen a few little thunderstorm cells. Any isolated pockets of rain should fizzle out by about 8 a.m.

Then, sizzling sunshine will heat up thermometers to about 85 to 90 degrees. Factor in the high humidity, and the heat index (the "feels like" or "apparent" temperature) will push into the mid to upper 90s. A Heat Advisory continues until 8 p.m. for 5 NE NJ counties in the NYC metro area — Bergen, Essex, Hudson, Passaic, and Union.

The aforementioned frontal boundary will be the spark for another round of strong thunderstorms starting in the early afternoon hours — let's say along the NJ Turnpike corridor around 1 p.m. These will be slow-moving soakers, with the potential for training thunderstorms. (Where storms form over and over again in the same spot.) With several models suggesting localized 3+ inch rainfall totals somewhere in New Jersey, we have to ring alarm bells for potential flash flooding.

Remember, we're only a week and a day removed from Tropical Storm Isaias, which dumped 7+ inches over SW NJ. So it totally makes sense that a Flash Flood Watch has been issued for the 12 NJ counties with the soggiest soil. Morris, Warren, Hunterdon, Somerset, Middlesex, Mercer, inland Monmouth, NW Burlington, Camden, Gloucester, Salem, and Cumberland counties fall under the watch from 11 a.m. to 11 p.m. It wouldn't take much downpour action to cause ponding and flooding, so please stay alert and be careful. Never attempt to drive, walk, or swim through flooded areas.

With little to no steering mechanism, the threat for showers and thunderstorms will continue Wednesday evening into Wednesday night.

Thursday

And more scattered rain is in the forecast for Thursday, with that front still in the neighborhood. I don't think the day will be a total washout, but generally damp and unsettled. The combination of raindrops and clouds will keep temperatures cooler, with a high only around 80 degrees. It will still be very humid though.

Friday

A drying trend should kick in Friday, but a few thunderstorms are still possible at some point. If everything falls into place (timing-wise and location-wise), we'll get some late-day clearing. High temperatures will be slightly below seasonal normals, around 80 to 85 degrees.

Saturday & Sunday

There are many question marks surrounding the weekend forecast, largely swirling around an area of low pressure just off the coast. The latest model guidance suggests that off-shore storm system will be just far away enough to miss New Jersey. I'm not totally convinced though — so I'm keeping a chance of rain in the forecast for both Saturday and Sunday.

Best case scenario, we'll enjoy partly sunny skies, a stiff east breeze, and not-hot temperatures in the lower 80s for the weekend.

The Extended Forecast

No 90s on the horizon. Following one or two more rounds of stormy weather in the Monday-Tuesday time frame, high pressure should allow for an extended period of seasonable, reasonably pleasant weather through late next week.

Finally, we continue to watch Tropical Depression 11 chugging through the tropical Atlantic Ocean, about 2,700 miles southeast of New Jersey. It is expected to become a tropical storm soon — the next name on the list is Josephine. Most models turn Josephine out to sea before reaching the U.S. East Coast. But it's still pretty far out there — just worth watching for now.

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