8 Things to Know About South Jersey’s Rainy Forecast
Hopefully your umbrella is ready for a workout, as periods of steady, healthy rainfall will push through the Garden State for both Tuesday and Wednesday.
A strong area of low pressure will track across the Great Lakes over the coming days. Even though the center of that storm system will stay well north of us, it will drag a series of warm fronts and shortwaves through New Jersey. Our atmosphere will tap into a river of moisture stemming from the Gulf of Mexico, spiking dew points and enacting relatively high humidity for the cold season. Therefore, we have a decent chance for healthy, persistent, and occasionally heavy rainfall over the next 36 to 48 hours. It's important to note that temperatures will remain well above freezing throughout this weather event, so we're only talking about wet weather this week - not wintry weather.
2.) Rain Round 1
The rain is passing over the Delaware River as I type, and will continue spreading across the Garden State Tuesday morning. It's going to be a wet day overall, with periods of steady rain expected. Our air is going to become quite warm and humid, with forecast high temperatures in the lower 60s. That could help spawn some thunderstorms and locally heavy downpours. It will be breezy at times on Tuesday as well, with occasional gusts over 20 mph. This "first" round of rain and wind will end between Tuesday late afternoon and Tuesday evening.
Tuesday night, we'll experience a relative lull in the stormy weather. Having said that, scattered showers and some fog will be possible overnight. Due to high humidity levels in the air, temperatures will remain quite mild. Forecast lows are in the mid 50s for most of the state. (North Jersey's atmosphere will likely be a bit drier, and so a few upper 40s will be possible there.)
4.) Rain Round 2
Around late morning on Wednesday, our rain chances ramp up again. Yet again, pockets of heavy rain, thunderstorms, and a brisk wind are in the forecast. Thermometers will climb even higher, topping out in the mid to (maybe) upper 60s by Wednesday afternoon. That is quite unseasonable for late November, about 15 degrees above normal. This second round of persistent rain will potentially last through early Thursday morning.
5.) Rainfall Totals
With 40% of the state currently in "Severe Drought" status, this rain is much-needed (to say the least). It's not quite a "drought-buster," as parts of New Jersey remain almost 10 inches of rain below normal for the year (-9.76, according to the National Weather Service). I believe almost all of New Jersey will pick up at least an inch of rain from this series of storms. Areas that experience a thunderstorm with locally heavy rainfall will see totals of at least 2 to 3 inches - the best chance for heavy rain will be in the northern half of NJ. Good stuff! Especially considering that North Jersey needs the rain the most.
6.) Severe Weather/Flooding?
The ground is very thirsty, given our mounting drought concerns, so it's going to easily and readily "drink up" all the rain that falls. Because of this dry "antecedent moisture condition," the risk for flooding is low. Low, but not non-existent. If it rains hard enough to overwhelm storm drains, brief periods of flash flooding and big puddles will be possible. Never attempt to drive, walk, or swim through flooded areas - Turn Around, Don't Drown!
While the risk for severe wind and hail is also low, the warm temperatures will cause marginal instability and therefore a slight chance for nasty storms. Best chance for isolated severe weather will be on Wednesday, mainly in South Jersey. Additionally, any thunderstorm can pose a danger due to lightning, especially for those outdoors in exposed areas.
7.) Winter Weather?
As I mentioned previously, temperatures will remain well above the freezing mark throughout the state throughout this weather event, so there are no winter weather concerns. But allow me to address a question I'm asked frequently during wintertime rainfall... What if this rain were snow - how much would accumulate?
The easy answer is to multiply the expected rainfall totals by 10, as snow has a frozen-to-water ratio of 10:1 on average. By that math, 2 to 3 inches of rain would translate to about 20 to 30 inches of snow. However, that's not completely accurate. This rain is being fueled specifically by rich moisture and the warm air - conditions would be completely different if this were a winter storm. So I'm sorry to say a direct comparison or calculation is actually impossible and inappropriate.
8.) Beyond the Rain
A cold front will sweep out the rain by early Thursday morning, opening the door to our next area of high pressure. That new air mass will be cooler and drier, so we'll be kissing those 60s goodbye. Highs on Thursday will reach the mid to upper 50s - still above normal. Aside from a brisk wind, it should be a nice, sunny early December day.
Friday's highs will decrease to around 50 degrees, and this weekend will bring back chilly 40s to New Jersey. Our next storm system will hold off until Monday, at the earliest.