A cold front is expected to crash into the heat July 19-20, starting in Chicago and then sweeping east to New York and New England, said Rob Carolan, founder of Hometown Forecast Services Inc. in Nashua, New Hampshire.
“Chicago and Detroit are going to get clipped in the afternoon so they are going to have some severe weather,” Carolan said by telephone. “New York City potentially Saturday afternoon, Philadelphia and Pittsburgh as well.”
About 87.1 million people live in the path of the two-day event, according to the U.S. Storm Prediction Center in Norman, Oklahoma. There is more than a 30 percent chance of severe storms from Madison, Wisconsin, to Buffalo, New York, July 19 and then from Cleveland to New England the next day.
Severe thunderstorms caused $15 billion in insured losses in 2012 and $25 billion in 2011, according to the Insurance Information Institute in New York.
From 1992 to 2011, thunderstorms and tornadoes accounted for the second-highest amount of catastrophic losses in the U.S., $130.2 billion, topped only by hurricanes and tropical storms with $161.3 billion, the institute said.
Carolan said the timing of when the cold front moves into the area will determine how severe the storms are. If it hits in the afternoon when the temperature is above 90 degrees Fahrenheit (32 Celsius), high winds and thunder can be expected.
If the front passes through at night when temperatures are in the 70s, then it won’t be as severe, which is what Carolan said he believes will happen in New England. In New York, it is harder to say right now.
Yesterday’s high in New York’s Central Park was 94, 10 degrees greater than normal, though lower than the daily record of 102 set in 1995, according to the National Weather Service.
In Boston the high was 92; Chicago, 89; Washington, 96; and in Philadelphia, 95, weather service records show.
Utilities have urged customers to conserve energy and have placed crews on standby to deal with outages.
New York power demand peaked yesterday at a record for the year of 32,703 megawatts, enough for 26.2 million homes on an average day, according to the New York Independent System Operator Inc., which runs the state power grid. Demand will be 33,300 today, the ISO said in a statement.
Natural gas will be used to fuel about 32 percent of power plants this year, according to the Energy Information Administration.
“We are forecasting most of the East Coast cities to come in a degree or two hotter than yesterday’s high temperatures,” Rogers said in an e-mail interview. “At first glance that would suggest higher demand, but we are noticing that dew points are drier than yesterday too, meaning slightly lower humidity and lower heat index.”
New York may reach 97 today and stay at or above the 90-degree mark into this weekend, according to the weather service. Chicago may reach 92 today; Washington, 98; Boston, 92; and Toronto 90. Those high temperatures are expected to linger until this weekend.
The lower humidity and heat index scores have caused the weather service to scale back on some of its heat warnings and advisories along coastal New Jersey and Massachusetts. They still are in place in New York, Washington, Baltimore and Philadelphia.
“Along the immediate coast from New England to New Jersey, a light sea breeze may set up that will push temperatures into the 80s,” Carolan said.
These onshore winds may also push down energy demand in those areas, Rogers said.
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