July 15, 2012: Hot, Stormy, Then Colder

Forecast Highlights:

– Tuesday peak of heat; widespread mid-upper 90s, possibly 100
– Scattered storms, possibly strong, on Wednesday
– Much cooler, less humid ending to week


Saturday, July 14 Observations:

Little changes were observed in the area compared to the previous day, with widespread cloud cover although the storm activity stayed to the south of the area. Temperatures reached the upper 80s across most of the area, with lower 90s in parts of Long Island. This was different than the previous days, when Long Island had the coolest temperatures in the area. Less cloud cover was observed further north/NE, with more widespread 90s observed in New England.

Sunday, July 15 Observations:

Mainly cloudy skies were observed today as widespread showers and storms, some of them heavy, affected the region, fueled by widespread moisture in the region with precipitable water values over 2 inches. Flash flooding was observed in parts of Orange, Rockland and Westchester counties in SE NY as well as Fairfield county in CT, where amounts were locally as high as 3 inches. Some of the storms were strong with strong winds and hail. Heavy storms were observed in southern parts of NYC, central NJ, and central Long Island, with northern NJ missing out on the storm activity with less than 1/4 inch for most places. Temperatures reached the lower 90s from NYC and further west which were not affected by the mid afternoon storms, and the mid to upper 80s across the rest of the area due to more widespread afternoon storms.

Monday – Wednesday: Another Heat Wave, Ends With Storms

The warmer than average pattern which started around June 20 with occasional periods of near-slightly below average temperatures is still in place, as the 3rd heat wave of the year will affect the area during the first half of this week. Temperatures will be a bit slow to warm up on Monday as the core of the warm air mass will still be organizing over the north central US, with highs reaching the lower 90s for most places from NYC and further north/west, with upper 80s to lower 90s across most of Long Island/S CT as well due to a WNW wind. Immediate coastal areas especially further east should be a bit cooler, closer to 85 degrees.

The peak of the warm air mass will move into the area on Tuesday, with 850 mb temperatures near 20C along with mostly sunny skies and west/WSW winds, supportive of upper 90s in parts of the area. The NAM is showing low 100s in NE NJ, the 5th time it has shown 100+ degree heat in the area this year; the first 3 times failed to verify with upper 90s instead, although the previous time the NAM modeled 100 degrees, it failed to verify further north due to more widespread cloud cover from unexpected morning showers, although Newark and surrounding areas still reached 100 degrees. In this case, I am going with temperatures slightly cooler than those of the NAM, with mid to upper 90s from NYC and further north/west, with the hottest temperatures near NE NJ, and lower to mid 90s across Long Island/S CT with areas closer to NYC near/possibly a bit above 95 degrees. More sea breeze influence is expected in Long Island/S CT with SW/SSW winds.

Temperatures will be slow to cool down overnight, staying in the 70s for most of the area, failing to drop much below 80 degrees in NYC. As a result, temperatures will be quick to rise on Wednesday morning, already reaching the lower to mid 90s in the immediate NYC area by 11 AM. The cold front will already be approaching by then, however, with temperatures failing to warm up much afterwards. Scattered thunderstorms are expected during the afternoon and evening, some of which could be strong or possibly severe, although depending on the exact timing of the front, it is possible that the best risk of severe weather may stay to the north of NYC.

Thursday – Next Weekend: Cooler, Then Warming Up

Following the cold front on Wednesday, a cooler air mass will return into the region for the late week into the early weekend. Mostly sunny skies are expected with highs on Thursday in the mid to upper 80s for most of the area, dropping into the lower to mid 80s for Friday and Saturday. Overnight lows will be in the 50s inland and in parts of Long Island with 60s elsewhere.

By later in the weekend into the start of the following week, with the Canadian high pressure shifting south of the area, a building warm air mass in the north central US will move east into the region. At this time, this appears to be more of a stretch of upper 80s and some 90s as opposed to a widespread heat wave, although there is still some time for changes with the set up given the time range. Stay tuned for more information on the longer range outlook.

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