July 17, 2013: Severe Storms To End Heat On Saturday

Forecast Highlights:

Another day of hot temperatures is expected across the region, with the 4th consecutive 90+ degree day for most of the area since the current heat wave started on Sunday. As with yesterday, humidity will not be significant yet, but will gradually increase with warming temperatures as the peak of the heat wave takes place from Wednesday through Friday. A cold front on Saturday will end the heat wave but is also expected to produce widespread strong to severe thunderstorms.

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Tuesday, July 16 Observations:

A high pressure remained parked in place over the region on Tuesday, with temperatures similar to those on Monday, peaking in the 90s across the area. Northern NJ was slightly cooler than Monday, peaking in the low to mid 90s, while southern CT and most of Long Island reached the mid to upper 90s, along with north/NW winds and mostly sunny skies. The hottest temperature was 97 degrees in New Haven, CT.


Record highs on Tuesday, July 16, 2013:

Islip, NY
94 degrees (previous record: 93 degrees - 1999)
Bridgeport, CT
95 degrees (previous record: 94 degrees - 1983)

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Today - Friday: Still Hot, Humid

Heat continues across the region for another day as ridging persists overhead, with 500mb heights approaching 600dm. Humidity yesterday was lower compared to Monday with a northwest wind, although ridging will slowly flatten over the next few days with a westerly flow developing, advecting a warmer and more humid air mass into the region for Thursday and Friday. 850mb temperatures are expected to warm up to the 18-22C range, along with dew points in the upper 60s-low 70s and mostly-partly sunny skies to result in hotter temperatures for the late week time frame.

Humidity today is still not expected to be significant, slightly higher than yesterday with high temperatures reaching the low to mid 90s across most of the area, peaking near/above 95 degrees in NE NJ and NYC. The hottest temperatures are expected for Thursday and Friday, with partly sunny skies, light west/WSW winds, and highs in the mid to upper 90s except for the coast, where highs are expected to reach the low to mid 90s. Isolated afternoon storms may be possible especially inland. With more humid conditions, heat index values are expected to reach the upper 90s to mid 100s across the area.


Weekend - Next Week: Storms, Possibly Severe, Then Colder

A cold front will move through the region on Saturday, removing the hot and humid air mass while also producing thunderstorms and a potential severe weather outbreak. The highest instability on Saturday is likely to focus on an axis just north of the area, from northern Pennsylvania to southern New York state and southern New England, where the highest risk of severe weather exists in the afternoon and evening hours. The setup for the area is a bit more marginal, however, with bulk shear modeled to be around 30 knots with the higher shear located north of the highest instability, and mid level lapse rates are moderately favorable for storms, around 6 to 6.5 C/km. Widespread thunderstorms are still expected in the region, reaching the area later in the afternoon into the evening, with the highest risk of severe storms of at least 30% to the north of the area near the aforementioned axis, although at least some strong to severe storms are still possible in the area. Stay tuned for more information on the potential storms over the next few days.

Behind the cold front, drier conditions are expected to return for Sunday into early-mid next week with a trough setting up over the region, leading to slightly below average temperatures reaching the upper 50s-60s for lows and the upper 70s-mid 80s for highs. A slight warm up in temperatures is likely later into next week with rain probabilities modeled to increase towards mid-late next week.