Dangerous Heat, Humidity Returns to the Northeast

Tom Moore
Published: August 11,2016
Another spell of extreme discomfort is in store for those who live around the major metro areas of the Northeast through the upcoming weekend, when hot temperatures and elevated humidity levels will combine to send the heat index into the danger zone.
High temperatures will generally range from 5 to 15 degrees warmer than average for this time in August from New England down through the mid-Atlantic region. In addition, a surge of moisture, on the heels of a southwesterly wind flow, will increase humidity levels and make it feel even hotter.
The National Weather Service has already issued various heat alerts, including heat advisories and excessive heat watches, for parts of the Northeast, including Boston, New York City, Philadelphia and the Baltimore-Washington, D.C. area.

Heat Alerts issued by the National Weather Service

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Heat and Humidity Envelop The Northeast

Washington D.C. and Philadelphia will see high temperatures in the mid-90s from Friday through Sunday.
An excessive heat warning is in effect for the metro Philadelphia area, where the heat index (how hot it feels) could approach 105 degrees in the afternoon hours through Saturday. Baltimore and Washington D.C. are also likely to see the heat index climb above 100 degrees and a heat advisory is in effect for these metro areas.
That advisory is likely to be extended later.
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A heat advisory is in effect for the New York City metro area through Saturday evening. A heat advisory is also in effect for Boston and Hartford, Connecticut on Friday afternoon.
High temperatures in New York City are expected to reach the low 90s, and the heat index will be between 95 and 100 degrees. Hartford will see highs in the mid-90s with heat indices above 100 degrees.
For the Boston metro area, Friday's high temperature will also reach the mid 90s before cooling off a bit on Saturday.
The high temperature in New York City could approach or break daily records on Friday and Saturday. Daily records will also be threatened Saturday in Hartford and Atlantic City, New Jersey.
Also, with so much moisture in the air, the heat of the day is trapped by clouds and moisture, so low temperatures in the New York City to Richmond, Virginia, corridor will only fall to around 80 degrees.
These conditions are particularly dangerous to those who are most vulnerable, such as the sick or elderly, especially if they are without air conditioning.

Forecast Highs

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Setup For Dangerous Heat and Humidity

A ridge of high pressure aloft (bulge in the jet stream) will slowly build up the Eastern Seaboard into the weekend. Meanwhile, winds from the Southwest will transport moisture into the region, increasing humidity levels. There will be some rain and thunderstorms to the west of the major East Coast cities, but these storms are likely to weaken as they move into the ridge.
As a result, any potential cooling thunderstorms will be widely scattered .
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Weekend Jet Stream Forecast (Ridge Indicated In Red)

The National Weather Service has published some heat safety tips.

• Job Sites: Stay hydrated and take breaks in the shade as much as possible.
• Indoors: Check up on the elderly, sick and those without air conditioning.
• Outdoors: Limit strenuous outdoor activities, find shade and stay hydrated.
• Vehicles: Never leave kids or pets unattended - "look before you lock."

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