Discussion: Before we talk about Debby remnants today, a reminder that the most beautiful weekend of the summer starts in about 18-24 hours. Reasonably warm temperatures, sunny skies, refreshing breeze, and low humidity. It’s going to feel magical as reflected in the daily breakdown further below.
At this point, Debby’s remnant impact on NJ has become annoying. Earlier in the week, inches of rainfall were promised. Some models even showed up to 10 inches of rainfall and worse, a few media outlets ran with it—getting a lot of people worked up about flooding. Some even combined the Tuesday frontal system with this weekend’s original rainfall amounts to make it seem even scarier re. I initially held off on rainfall amount predictions but still had a “from the hip gut feel” of about 1-3 in NWNJ (maybe 2-4) and even less for SENJ. Now it looks like that will even be an overestimation. Had Debby tracked directly over NJ, then NJ would have seen the higher rainfall amounts from more of a widespread slug of moisture. But as detected a few days ago, Debby tracked/is tracking well W of NJ and along with that went the heavier rainfall into PA.
Debby’s remnant circulation, now into SW PA, has become weaker and unorganized. It is currently meeting up with the trough that’s eventually going to carry her out to the N and NE. The frontal boundary that pushed N to S through NJ on Tuesday, is now back to the N of NJ as a warm front that pushed through NJ from S to N overnight/this morning. This warm front is now attached to Debby’s circulation and a cold front has formed to the S of Debby—currently moving W to E through SW PA, W VA, W MD, and VA. This cold front is what will usher in the amazing weekend conditions. But first, it must pass through NJ between this afternoon and late-tonight/early Saturday AM. Given everything said above, NJ is now in a warm sector (between the warm front to our N and cold front to our W). Air is rushing in off the ocean, mainly from the S/SE, to move towards the center of Debby’s former circulation (now just a mid-latitude low). That’s why we are currently windy (windiest along ECNJ/SNJ coasts). I expect sustained winds today of 15-25mph with gusts to 40mph. Tropical air mass will remain over NJ as long as we’re in the warm sector. That’s why it’s still humid as heck right now.
Even though the flow is still considered onshore, it is very much out of the S/SE. This wind direction is beneficial for coastal flooding interests because it is more perpendicular to the inlets rather than parallel (like an E flow would be). Therefore, I still believe coastal flooding will remain in the minor category at most with only some water in the streets (for people who normally see water in the streets). For the most part, coastal flooding should be a non-issue for NJ. Very different from some of the NE MD imagery I saw today (S/SE winds pushing Chesapeake water northward).
As far as remaining rain and storms today, there should be some activity but not widespread. We have some linear segments of downpours and storms starting to form over VA and MD (as of 1130am Friday) that should push through NJ. But they should be very thin strips of precipitation meaning short durations of rainfall. These segments could certainly dump water in a short amount of time. But all of NJ should step away from widespread rainfall expectation today. Skies should be sunny between these narrow areas of precipitation bands feeding into Debby’s remnant circulation. Winds, however, will be more of a steady occurrence today. For areas that get hit by the thin bands, these areas have the best chance to see either a severe thunderstorm form (for wind) or an isolated tornado. A tornado was confirmed for Delaware last night and I saw another just now for NE PA (warned but not confirmed). Everything should clear out sometime between midnight and 6am Saturday morning. I am leaning earlier than later at this point. Now let’s discuss the weekend.
From an upper-level perspective, the jet appears rather zonal across the US this weekend into early next week. There’s a flat upper low near the N Great Lakes that will eventually absorb Debby’s remnants entirely before the trough pushes through the E US. But for Saturday and at least Sunday, the back side of an Atlantic ridge will push in over NJ before the trough does move through. This will contribute to the amazing weekend conditions. At some point (as early as tonight/by early Saturday AM), winds will switch from S to W/NW as the cold front pushes through NJ from W to E. From that point forward (well into next week), NJ will see a flow varying between W and N (cooler and drier flow). By noon on Saturday (at the latest – likely by late-morning), this flow will push all the humidity out of NJ. Dew point temperatures will fall from 70s into the 50s and we’ll have our phenomenal feel that should last through possibly Tuesday. Here’s the breakdown:
Friday (Aug 9) high temperatures should reach the low-to-mid 80s for most NJ locations. Skies should be mixed with periods of sun and tropical rain/storm bands (afternoon-evening). Some storms could be severe with an isolated chance of a tornado. Otherwise, conditions should be humid and breezy/gusty out of the S/SE (gusts to 40mph possible statewide). Conditions begin to significantly improve overnight (after 2am) into Saturday morning. Unless you’re a Navy Seal or an animal seal, stay out of the ocean today (Friday). It’s going to be rough through Saturday morning.
Saturday (Aug 10) high temperatures should reach the mid-80s for most NJ locations. Rainfall should end by 6am but humidity could linger as late as noon. By early afternoon, there should be an entirely new pleasant look and feel across NJ as humidity levels dive and cool W/NW breeze takes over. I hope this happens earlier than noon. Then get ready for possibly the best summer night to be outside of the year. Overnight lows should range from 55-65 from NNJ elevations to SNJ coasts with clear skies and low humidity.
Sunday (Aug 11) high temperatures should just break 80 statewide. Skies should be mostly sunny with a very pleasant feel. Winds should be light out of the W/NW. Overnight lows should range from 55-65 from NNJ elevations to SNJ coasts.
An early look at next week (Aug 12-Aug 16) indicates the less hot, less humid, and nice conditions lasting for a while. A small rain chance Tuesday night and then another Thursday into Friday. I wouldn’t be doing my job if I didn’t mention that some long-range models are seeing another tropical event for the E US around Aug 18-20. Just a long-range storm signal for now. I’m sure we’ll be discussing next week if the storm signal doesn’t drop off of model guidance. Otherwise, everyone please have a great weekend and be safe! JC
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Jonathan Carr (JC) is the founder and sole operator of Weather NJ, New Jersey’s largest independent weather reporting agency. Since 2010, Jonathan has provided weather safety and forecasting services for New Jersey and immediate surrounding areas through the web and social media. Originally branded as Severe NJ Weather (before 2014), Weather NJ is proud to bring you accurate and responsible discussions ahead of high-stakes weather scenarios that impact the garden state. All Weather. All New Jersey.™