Heat & Humidity Returns with Severe Storms Possible Today, Elsa’s Remnants Late Week?

Very hot and humid conditions return for today and Wednesday, as a southwest flow develops. High temperatures will reach the lower and middle 90s throughout much of the region. High dewpoints in the lower 70s will support heat index values reaching into the lower 100s, which will cause the heat to feel more oppressive. For this reason, the National Weather Service has issued Heat Advisories for much of the region, including the New York City metro area. Stay hydrated by drinking plenty of fluids and avoiding strenuous activity outdoors. Keep a close eye on the elderly, children and pets.

There is also potential for strong to severe thunderstorms later this afternoon and evening. An upper-level disturbance approaching the area will likely trigger clusters of showers and thunderstorms over the Upstate New York, Northwest New Jersey and Northeast Pennsylvania. These storms will track southeast into the New York City area by early this evening. The heat and humidity building under an elevated mixed-layer in the atmosphere will result in very high instability, which will support thunderstorms becoming intense.

Therefore, the Storm Prediction Center has placed most of the region under a Slight Risk for severe thunderstorms today. The main threat from these storms is likely to be strong, gusty or damaging winds. Storms are likely TO produce torrential downpours which could cause localized flash flooding, frequent cloud to ground lightning and perhaps some hail.

A lack of strong, deep-layered shear will likely mitigate a tornado risk. But we will need to monitor any localized areas where low-level flow backs more to the south, particularly over parts of Connecticut. That could cause a thunderstorm to rotate and produce an isolated tornado. The model sounding below demonstrates this potential.

On Wednesday, a cold front and upper-level trough will begin approaching from the Great Lakes region and instability will build again. This could trigger scattered showers and thunderstorms during the afternoon or evening hours. With weaker shear and forcing over the region, the risk for strong to severe thunderstorms is likely to be more isolated. Therefore, Storm Prediction Center has currently only placed parts of the region under a Marginal Risk for some isolated severe thunderstorms with damaging wind gusts.

Weather conditions look more unsettled and somewhat cooler on Thursday and Friday. The cold front and upper-level trough will slow down and interact with Tropical Storm Elsa’s remnants from over the Southeast US. This pattern will at least produce more clouds with perhaps some scattered showers or thunderstorms over the region. There is more uncertainty on how much direct impacts there will be from Elsa’s remnants, which will likely track near or southeast of the New York City metro area.

One possibility is that Elsa tracks close enough with it’s tropical moisture and enhances more widespread heavy rainfall and flash flooding over the region. This solution is currently supported by ECMWF model and many of it’s ensembles. Another possibility is that sinking air around Elsa tracking further southeast keeps much of the region drier. This solution has still some support from other model guidance. We will continue to monitor the latest guidance on Elsa remnants and provide more updates this week.

For this weekend, we expect more comfortable temperatures and humidity overall with the cold front to the south. High temperatures will be below normal in the upper 70s and lower 80s. Another disturbance passing by to the south may produce some showers in the region by Sunday.