July 18, 2012: Heat Wave Over, Cooler Temps Return

Forecast Highlights:


- Cloudy, chilly, rainy on Friday; highs to struggle passing 70-75°
- Drier, warmer weather returns by weekend


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Records set/tied today:

LaGuardia, NY
101 degrees (previous record: 100 degrees - 2006)
JFK Airport, NY
96 degrees (previous record: 95 degrees - 2010)
Bridgeport, CT
95 degrees (tied record: 95 degrees - 2006)
Newark, NJ
104 degrees (previous record: 100 degrees - 1982)

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Today's Observations:

The hot pattern observed since June 20 with only a few occasional breaks ended today with the peak of the entire heat wave, with both the hottest day of the year as well as one of the stormiest days of the year. Temperatures quickly warmed up in the morning, but the warming continued faster and longer than expected straight through 2 PM in some areas, allowing for warmer than expected temperatures peaking in the upper 90s inland, lower to mid 100s in the immediate NYC area, and lower to mid 90s in southern CT and Long Island. Humid conditions were observed as well with dew points in the 70s, resulting in heat index values as high as 108 degrees.

The heat was not the only highlight today, as widespread thunderstorms affected the area, some of them severe. Activity started today with a line of training storms over the NY/NJ line moving into SW CT, followed by more widespread storm development over western NJ focusing over Sussex county, where strong winds, heavy rain and hail were observed with some of the storms. While that was taking place, widespread strong storm development took place over NYC with the storms training in place, resulting in frequent cells moving through including heavy rain and hail, even reported in parts of Manhattan, with localized rain amounts above 2 inches resulting in flash flooding. Storms also trained over parts of Nassau county, especially further north, with strong winds and flash flooding due to heavy rainfall. Power outages and tree damage were observed in the harder hit areas as a result of the storms, mainly in the areas previously mentioned as well as other areas in New Jersey, SE NY and Connecticut. Other parts of the area, such as parts of northeastern NJ, eastern Long Island and coastal CT, missed out on the storms and generally had close to a tenth of an inch of rain.

Temperatures will return to normal behind the cold front as the pattern becomes colder than it has been so far this month; Friday will even end up much cooler than normal, with highs only in the 70s and even the upper 60s for some places. Temperatures will warm up back to normal or slightly above afterwards, although a cooler pattern will develop which will prevent widespread 90s across the region through the foreseeable range.


Thursday - Friday Outlook: Much Cooler, Rainy


Following the cold front, mostly cloudy skies are expected on Thursday with scattered showers and highs reaching the lower to mid 80s across most of the area, with upper 80s in parts of the immediate NYC area and cooler temperatures further east. Friday will be much cooler, however, as there is a growing consensus for a wave of low pressure to form along the stalled front and move east with the actual low pressure staying south of the area, resulting in widespread periods of rain with cloudy skies and chilly temperatures, only in the upper 60s to lower 70s north and west of NYC and in the lower to mid 70s from NYC and further east. There is still some uncertainty on exactly where the heavy rain axis sets up, although at this time it appears to be west and south of NYC. In this axis of heavy rain, amounts above 1 inch of rain may be possible. The exact axis of rain is still subject to some changes, however, thus resulting in some slight uncertainty with the temperature outlook as well. Any changes in the forecast will be mentioned with Thursday's update.


Longer Range: Warming Up, But Not As Hot


Temperatures will slowly warm up by the weekend, reaching the upper 70s to lower 80s across most of the area on Saturday and the lower to mid 80s by Sunday. Dry conditions are expected for both days as the wave of low pressure moves offshore. Temperatures are likely to continue warming through Monday and Tuesday, with more widespread highs in the mid to upper 80s, perhaps reaching 90 degrees on Tuesday, ahead of a cold front expected to move through sometime around the middle of next week with a risk of showers and thunderstorms. This will prevent another heat wave from developing, with temperatures expected to remain generally close to average. Stay tuned for more information on the outlook for next week.