July 15, 2013: Highs Approach 100 Degrees

Forecast Highlights:

Hot and humid conditions continue across the region as a massive ridge continues to build overhead, with mostly to partly sunny skies and highs in the mid to upper 90s away from the coast persisting throughout the week as heat index values reach the upper 90s to mid 100s. A slow moving cold front will bring an end to this heat wave by next weekend, but with the possibility of strong to severe thunderstorms as well.

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Sunday, July 14 Observations:

The upper level low that produced widespread showers on Friday and isolated storms on Saturday evening left the region on Sunday as a ridge built in, providing the area with mostly sunny skies, light winds, and warmer temperatures. Most of the area started the heat wave on Sunday, with highs reaching the upper 80s to low 90s. The hottest temperature in the area was 94 degrees in LaGuardia airport.


This Week: Hot, Humid

A strong, widespread ridge with 500mb heights as high as nearly 600 dm continues to sit overhead while expanding across the Northeast and Ohio Valley regions, continuing the hot and humid conditions that started yesterday with the departure of an upper level low, currently over Texas. Widespread 850mb temperatures of 16-20C, combined with NW winds and mostly sunny skies, will continue the heat wave through the rest of this week as well, resulting in a stretch of 6-7 consecutive days of highs over 90 degrees.

As of 11 AM, temperatures have already warmed into the upper 80s to low 90s across the area, which combined with dew points in the low 90s is resulting in heat index values in the upper 90s. Temperatures will continue to warm up, peaking in the mid to upper 90s across the area including most of Long Island and CT as the wind direction is from the northwest, with heat index values reaching the low to mid 100s across the area. The hottest temperatures are expected in northeast NJ and NYC, excluding Central Park which is typically several degrees colder than nearby surroundings in summer heat waves, where widespread upper 90s are expected, approaching 100 degrees especially near Newark. Similar conditions are expected for Tuesday, but with high temperatures a degree or two cooler as well as slightly lower humidity resulting in heat index values mostly in the upper 90s.

For Wednesday through Friday, more of a westerly wind is expected, along with warmer temperatures at 850mb, near to slightly over 20C; a slight increase in cloud cover is expected as well, with high temperatures remaining in the mid to upper 90s away from the coast but slightly cooling down into the upper 80s to mid 90s near coastal areas. At least one of these days may feature near 100 degree weather in parts of northeast New Jersey, and heat index values are expected to reach the upper 90s to mid 100s again.


Next Weekend - Next Week: Storms, Possibly Severe, Then Somewhat Cooler

The next cold front will move through the region on Saturday as a trough slowly sinks southeast through the region. The air mass ahead of the cold front is very unstable, which coupled with relatively high bulk shear, lapse rates and upper level winds, is expected to result in widespread thunderstorms and the potential of a severe weather outbreak. At this time, the greatest risk of these storms affecting the area is on Saturday, although the timing is still subject to some changes. Behind the cold front, by the late weekend into the first half of next week, cooler temperatures are expected, back into the 80s along with noticeably lower humidity and a lower risk of rain.