Heat, Humidity, and Powerful Thunderstorms Today
A Heat Advisory and an elevated risk for severe thunderstorms will make for an active weather day for New Jersey.
UPDATE as of 2:45pm on Tue 6/23...
Our primary band of thunderstorms has started to move into the state, and we have now had our first Severe Thunderstorm Warning of the day. For the latest warnings information, see the map embedded below.
A Severe Thunderstorm Watch continues until 4 p.m. for Bergen, Essex, Passaic, and Union counties. That Watch goes until 7 p.m. for the rest of the state EXCEPT Salem, Cumberland, and Cape May counties. A Watch simply means that severe weather, including gusty winds, hail, and an isolated tornado will be possible.
Our forecast for powerful storms holds for this afternoon. The HRRR model continues to show an aggressive line of thunderstorms pushing through central and southern New Jersey from 4 p.m. to 8 p.m. The NAM also shows thunderstorms spreading southward, but keeps the intensity a little lower for all but South Jersey. The GFS also indicates the deepest pocket of instability to setup around the Pine Barrens later this afternoon and this evening.
A few reminders of what to expect:
- The strongest storms will likely happen in the 4 p.m. to 8 p.m. window.
- Storms are likely to grow and move quickly. We've already seen thunderstorm movement clocked at 75 mph today.
- The primary severe weather threat is potentially damaging wind gusts. Pockets of heavy rain, hail, frequent lightning, and an isolated tornado are also possible.
Original Post from 6:00am on Tue 6/23...
Summertime in New Jersey is all about hot temperatures, high humidity, and thunderstorms... And your forecast for today will include them all. The heat and the high probability of severe storms will present a double threat today, and it will be very important to prepare for the weather and monitor changing conditions carefully. Here's the rundown...
Heat & Humidity
Today will likely be the hottest day of 2015 so far, as widespread 90s are expected this afternoon. Additionally, dew points soar to about 70° today, which is the cusp of the "oppressive" zone. (Dew point is a measure of moisture in the atmosphere, expressed as the temperature at which dew or condensation forms... 50s are comfortable, 60s are sticky, 70s are yucky...) For some spots in the state (including Newark Airport), today will mark the third consecutive day of 90+ degree temperatures, making it our first "official" heat wave of the year.
The hottest temperatures today will be found in the southern half of the state. Heat waves are particularly fierce in and around urban centers, so the National Weather Service has issued a Heat Advisory for the Philadelphia metro area and I-95 corridor. On the New Jersey side of the Delaware River, that advisory includes Mercer, Northern Burlington, Camden, and Gloucester counties. A Heat Advisory means heat index ("feels like") values will be at or above 95 degrees, and prolonged exposure to the heat and humidity could be dangerous. Even if you don't live in the advisory area, it's still going to be an unusually hot day... Wear light clothing, drink plenty of water, take frequent breaks, and watch for signs of heat exhaustion and heat stroke.
An approaching cold front will fire off a line of thunderstorms, that are expected to sweep through the state from northwest to southeast between about 2pm and 9pm. Because of our hot and moist atmosphere, these thunderstorms are expected to pack quite a punch.
The Storm Prediction Center has placed New Jersey (and much of the Northeast U.S.) in an "Enhanced Risk" area for today. That's the 3rd highest of 5 categories of severe weather risk, and it's the spot on the scale where we need to really take the thunderstorm risk seriously. The biggest potential danger from today's storms will be gusty winds, typical of linear "squall line" type thunderstorm setups. Here's a further breakdown of the severe weather threats today...
- Wind: The most significant severe weather threat for today. Damaging wind gusts in excess of 70 mph will be possible, both within and near the storms. The gusts that happen out in front of the storms (outflow) will be especially dangerous, as the wind will pick up dramatically without much warning. That makes it especially important to go inside a sturdy building as soon as skies begin darkening up and/or as soon as you hear thunder.
- Heavy Rain: Yes, there will be locally heavy downpours. But because these storms are expected to move very quickly, I'm not overly concerned about flash flooding. Storm drains could still become clogged, and low-lying areas could be temporarily inundated, so I'll state my usual advice... never attempt to drive, walk, or swim through flooded areas.
- Lightning: The flashes of lightning and booms of thunder will likely be frequent or almost constant within the strongest storms. While lightning isn't technically "severe" weather, it makes every thunderstorm potentially dangerous.
- Hail: Hail is formed within very strong updrafts, which will only be present in the strongest storms today. Small hail will be no big deal, but anything bigger than quarter-sized hail (1" in diameter) could potentially cause damage to cars, houses, trees, etc.
- Tornadoes: The risk for a tornado is low today, but not zero. Tornadoes are far more likely to occur in cellular storms than linear storms, and today's storms should take a linear characteristic fairly quickly. But again, and isolated tornado is not impossible today... Just another reason to keep a close eye on the sky today.
Just to make this forecast crystal clear, here are the answers to some anticipated questions regarding today's forecast...
- Will everyone in New Jersey see a storm today? Probably not... The models indicate the storms will be broken/scattered as they sweep through. I think *most* New Jerseyans will see *something* today, but some areas may remain dry.
- Will everyone in New Jersey see a severe storm today? Nope... It is likely, but not guaranteed, that any storms today will reach strong or severe limits. Also, see above.
- Is it going to rain all day? No. You'll experience, at most, an hour or two of rain and thunderstorms in the Noon to 9pm neighborhood. The only exception would be far North Jersey (around Sussex Co.), where we might see more sustaining rain through the late morning and early afternoon.
- Is the weather really going to be dangerous? If you stay smart, take the threat seriously, and monitor the weather closely, you should have nothing to worry about. If you try to drive through a Tornado Warning, Severe Thunderstorm Warning, or Flash Flood Warning, you're probably going to have a bad time.
Remember the cold front I mentioned as the spawn point for these storms? That will sweep through the Garden State tonight, and usher in a slightly cooler and significantly less humid air mass. With weak high pressure in control of our weather on Wednesday, we'll enjoy a beautiful day featuring abundant sunshine and warm, seasonable high temperatures in the mid 80s.
Thursday will start off OK, with sunny skies and highs in the lower 80s. But clouds and showers will arrive later in the day, marking the beginning of a fairly unsettled period of weather.
Friday will be cloudy and a bit cooler, with highs held to the 70s. Additionally, the forecast for Friday includes occasional showers and a brisk wind.
Unfortunately, the upcoming streak of unsettled weather looks to press into this weekend. Saturday looks downright wet... cloudy, breezy, and cool with rain for most of the day and highs only in the 60s. (That's pretty chilly for late June!) Sunday starts with rain, but we'll hopefully see some late day clearing. There's still a lot of time for this forecast to evolve and chance, as the weekend is still five days away... so, stay tuned!