By Sarah Wroblewski


BOSTON (CBS) — Some big changes are on the way as tropical moisture approaches, followed by a potential heat wave with dangerously hot and humid conditions.

So let’s start with the remnants of Hurricane Barry. Barry is now just a leftover area of low pressure, but it still contains a lot of moisture and energy. That, combined with an incoming cold front, will aid in enhancing tropical downpours and thunderstorms over New England Wednesday and Thursday in spots.

Isolated to scattered damaging storms are possible Wednesday, and the National Weather Service issued a Severe Thunderstorm Watch for all of Massachusetts, excluding Martha’s Vineyard and Nantucket, until 10 p.m. It’s definitely a day to be weather aware, and be prepared to seek shelter indoors should a storm head your way. Localized flooding and damaging wind gusts are the biggest threats. Any storms that develop could contain frequent lightning. The time frame of highest concern is between 2 and 8 p.m. Wednesday.

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As showers and storms are expected to develop this afternoon and continue through the evening, a Flash Flood Watch has been issued for the area through 11 p.m.

The stronger thunderstorms will be capable of producing torrential rain that could lead to localized flooding, especially in urban areas. Rainfall rates of 1-to-2 inches an hour are possible. Do not drive through a flooded road, it only takes 12 inches of water to move a car and 18-to-24 inches of water to carry away a large SUV. Also, flood waters can damage the road underneath so you don’t know what hazards you’ll encounter.

A flash flood watch means that conditions may develop that may lead to flash flooding. Stay alert to any warnings that develop.

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After the remnants of Barry move through, the attention will then shift to the building heat and humidity through the weekend. Hot conditions will build across the central and eastern U.S. as the jet stream lifts to our north, opening the gate for temperatures to soar well above normal. Average highs in mid-July are typically in the low to mid 80’s. Temperatures will likely reach the 90’s in many spots Friday through Sunday.

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Three days of 90 degree heat or higher marks an official heat wave. While Boston has seen three 90 degree days so far this year (all in July), they have not been consecutive – this weekend could be the first heat wave of the year. The hottest day will be Saturday as the mercury will attempt to near the record high for the date of 99 degrees set back in 1991. Worcester has a good chance to beat the century-old record of 92 degrees set back in 1901.

While it will be very hot and you’ll be looking for ways to cool off, the humidity will make it feel worse.

A very uncomfortable muggy air mass will grip the area, with dew points between 70-to-75 at times. The heat index, or the real feel conditions, will vary from 95 to 110 degrees, with the hottest conditions on Saturday. I wouldn’t be surprised if heat advisories or warnings are issued later this week.

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Heat-related deaths are preventable. Protect yourself and others from the impacts of heat and know the warning signs of either heat exhaustion and heat stroke. No doubt this will be a period when air conditioners will be in overdrive. Make sure to limit your time outside, and avoid strenuous activities. If you have to work outdoors, take multiple breaks in the shade if possible. Also, drink plenty of water and stay hydrated. This is a time when the inside of your car will heat up to deadly conditions quickly. Never leave kids or pets unattended and look before you lock.

Sarah Wroblewski

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