The latest on Debby: Day-by-day heavy rain forecast for NJ

The Bottom Line

Up and down the U.S. East Coast, all eyes are on Tropical Storm Debby. The center of the storm is hovering over coastal Georgia as of Tuesday morning. And the storm is stuck — barely moving to the northeast at just 7 mph.

Tropical Storm Debby's forecast as of 8 a.m. Tuesday. Centered about 600 miles southwest of Cape May, N.J. It is still expected to fly directly over New Jersey as a tropical depression or post-tropical storm on Saturday. (NOAA / NHC)

And it will stay stuck throughout tomorrow. And Wednesday. And Thursday. Probably dumping feet of rain over the Carolinas, sparking catastrophic level flooding.

New Jersey faces two big bursts of active, stormy, wet weather over the next five days.

First is a round of thunderstorms late Tuesday into Wednesday. This is not a direct impact of Debby — it is another storm system swinging through. But our atmosphere will tap into a flow of rich tropical moisture, raising concerns for heavy rain and flooding. Gusty winds are possible too.

Next will be Debby itself, after the system finally unhinges itself. The center of that remnant low is forecast to pass directly over New Jersey from Friday into Saturday, driving in another round of tropical rainfall.

Forecast model tracks for the center of Debby, many of which show it passing directly over New Jersey on Saturday. (Tropical Tidbits)

Note: I am really not worried about tropical storm force winds or significant coastal flooding at this time. (If the storm track shifts a bit to the east, closer to the coast, we may have to talk about such impacts.) For now, this forecast is all about rain.

Most likely scenario is between 2 to 4 inches of total rainfall over the next five days. Worst-case scenario raises that possibility to 6 or even 8 inches. That is a lot of water.

The 5-day total precipitation forecast, showing a huge swath of 3+ inch rainfall from Georgia to Maine. (NOAA / WPC)

Yes, we need the rain. But we could do without the flooding.

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Tuesday Morning to Early Afternoon

Tuesday begins as Monday ended: Very warm and humid, with a bright sky and dry weather. Morning temperatures are firmly in the sticky 70s. Afternoon highs will range from the mid 80s (north) to lower 90s (south).

We should enjoy bright summer sunshine through the morning, before clouds increase in the afternoon. No weather problems through at least 2 or 3 p.m.

A storm system will drive rain into New Jersey late Tuesday, with gusty thunderstorms possible. (Accuweather)

Tuesday Mid-Afternoon to Night

As a storm system approaches from the west, a few thunderstorm cells could pop up in the northern half of New Jersey through the mid to late afternoon hours.

Then, after about sunset, thunderstorm activity looks to become a more widespread, almost-statewide concern. Southern New Jersey could miss out on this round of thunderstorms.

HRRR model forecast as of around Midnight Tuesday night. Note the pockets of very heavy rain and strong thunderstorms driving through northern and central New Jersey. (College of DuPage Meteorology)

Given the heat and humidity of the day and the strength of the impending storm system, any storms that form will likely be capable of producing heavy downpours and gusty winds.

Tuesday's severe weather outlook paints much of inland New Jersey in an elevated risk area for damaging thunderstorm-driven wind gusts. (NOAA / SPC)

Again, this is not actually Debby. But there is a direct connection between Debby's rich moisture and Tuesday night's thunderstorms. So I am calling it "tropically-enhanced" rainfall. It is a precursor rain event — an appetizer of the main course coming later this week.

The NAM precipitable water model forecast shows a direct connection between Tropical Storm Debby's rich pool of moisture (at the bottom) and New Jersey's increased humidity and rain chances. (College of DuPage Meteorology)

Parts of New Jersey could pick up 1 to 2+ inches here. Big puddles — a.k.a. flooding — could slow travel through the overnight hours.

Tuesdays excessive rainfall outlook from the Weather Prediction Center puts New Jersey in an elevated risk of flooding rains. (Although not quite in the same category as the SE US.) (NOAA / WPC)

A Flood Watch has been issued from 2 p.m. Tuesday to Noon Wednesday for 18 of New Jersey's 21 counties. (All but Atlantic, Cape May, and Cumberland.)

Wednesday

Wednesday will not be a pretty day. But it is not necessarily a washout either.

Spotty rain will continue through at least the first half of Wednesday. There could be some pockets of heavier stuff and rumbles of thunder along the way. But the threat for flooding and/or severe weather should be much lower than Tuesday night.

Wednesday will be wet, cloudy, and miserably cool. Temperatures are expected to run 15 to 20 degrees below seasonal normals. (Accuweather)

Meanwhile, thick clouds will prevent temperatures from rising much. High temperatures will only reach the the lower 70s, at best. Parts of North Jersey in particular could be stuck in the 60s all day. Wednesday could very well be New Jersey's coolest day since early June.

Thursday

I have to admit that Thursday is a bit of a question mark. We will be in between storm systems. But again, Debby's deep tropical moisture is just down the road.

I am leaning toward a dry or "mainly dry" forecast on Thursday. I think we could even see a peek of sun.

Once again, high temperatures will stay well below seasonal normals. Expect only mid 70s at the warmest.

Friday

Friday will mark the arrival of Debby's primary storm system. A mere shadow of its former self, it may no longer show tropical characteristics.

Periods of rain are likely on Friday. If I had to guess, I would say we'll see one in the morning, then a brief break, then another in the late afternoon through overnight hours.

This is where tropical rainstorm concerns really start to ramp up. Even when it is not actively raining, it will feel deep. And incredibly humid too.

Flash flooding and river flooding will become big concerns by the end of the week, as Debby's remnants dump several inches of rain on New Jersey. (Accuweather)

Saturday

According to the latest model guidance, the heaviest rain, the greatest risk of flooding, and the worst weather will be Saturday. Specifically Saturday morning through midday.

This GFS model forecast shows the heaviest deluge of rain this week arriving around late morning Saturday. (College of DuPage Meteorology)

Rainfall rates may exceed an inch per hour, leading to ponding and flooding issues very quickly. Wind-driven rain could make for poor visibility and traction too — sloppy driving conditions.

So if you have outdoor plans or traveling plans on Friday or Saturday, you may run into trouble. We could start to see some clearing Saturday afternoon, but I would not bet on it.

To be clear, I am not ringing Ida-level alarm bells at this time. (Or Irene, or Floyd, etc.) But this situation needs to be monitored closely — especially if you live, work, or travel through areas that tend to flood in big rainstorms.

Sunday & Beyond

By Sunday, it's all over. As Debby's remnant low pushes away to the northeast, New Jersey's skies will clear. And a new, dry, refreshing air mass will build in. Heralding a new period of pleasant weather through next week.

Highs in the 80s, with low humidity, and practically zero rain chances? Next week will be a vast improvement compared to this week! Our next widespread rain chance is not models to arrive until late next week.

5 DAY FORECAST: New Jersey Weather Center