July 16, 2011: Heat, Humidity Returning

Note: The 5-Day Forecast page was updated tonight. An update discussing Monday’s storms and the long range heat will be posted tomorrow morning.

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With the high pressure previously over the region sliding offshore, a much warmer air mass is spreading into the region, with temperatures warming up as well, reaching the upper 80s inland, upper 80s to lower 90s in the immediate NYC area, and the lower to mid 80s in Long Island and southern Connecticut. Today ended up slightly warmer than expected in the immediate NYC area, though the forecast for Long Island and southern Connecticut verified.

As a warmer air mass continues to spread into the region, temperatures will continue to warm up, reaching the lower 90s over a more widespread area tomorrow. A cold front will move through on Monday, bringing a risk of strong thunderstorms along with increased heat and humidity, with temperatures reaching the mid 90s in parts of the immediate NYC area. Temperatures will slightly cool down on Tuesday/Wednesday, but by the late week, a massive ridge in the central US will spread towards the region, bringing the potential for the hottest temperatures of the year.

Tomorrow’s Outlook:

Warmth will continue to spread into the region tomorrow, with the result being slightly warmer temperatures than those of today. A southwest wind is expected along with partly sunny skies, which will result in temperatures reaching the upper 80s to lower 90s from NYC and further west. Widespread mid 80s are expected in Long Island and southern Connecticut, with lower 80s near the immediate coast and upper 80s closer to NYC.

Monday – Wednesday: Stormy, Then Slightly Cooler

As a cold front approaches the area on Monday, the heat and humidity will only get worse, with temperatures reaching the lower to mid 90s from NYC and further west, though temperatures will be cooler further east, reaching the mid to upper 80s across most of Long Island and southern Connecticut. Combined with dew points near 70 degrees, the heat index may reach the upper 90s in parts of the immediate NYC area.

Along with the cold front comes a risk of thunderstorms. At this time, it appears that this front may bring a better risk of rainfall than most of the previous fronts we’ve seen so far this month, and the parameters on the models are supportive of at least some severe weather, though the best risk of severe thunderstorms will likely stay to the north of the area. Precipitation amounts are more uncertain, and while locally heavy rainfall amounts are possible, widespread heavy rainfall amounts are not expected. The latest operational NAM runs are showing a widespread 1-2 inch area, but is a wet outlier, compared to the other models and the parallel NAM runs as well. More information on Monday’s storms will be posted with an update tomorrow morning.

By Tuesday and Wednesday, a slightly cooler air mass will move in as a high pressure moves into the region. Temperatures will not significantly cool down, but at least upper 80s to lower 90s are expected across the area on Tuesday. Wednesday will bring upper 80s to lower 90s from NYC and further west, but slightly cooler temperatures further east, reaching the mid to upper 80s across most of Long Island/southern Connecticut except for the immediate coast.

Longer Range: Tomorrow morning’s update will discuss the longer range in more details, including potential scenario graphics.

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