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4th Of July Forecast: Daytime Thunderstorms

By Terry Eliasen, Meteorologist, WBZ-TV Exec. Weather Producer
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BOSTON (CBS) – There will be fireworks Wednesday evening.  But will they be man-made or the work of Mother Nature?

Check: Current Conditions | Weather Maps | Interactive Radar

It seems just about every 4th of July there is a thunderstorm threat.  It is that time of year after all.

Some of our hottest temperatures come in early July, along with some of our more humid days, fueling the atmosphere with the stuff it needs to produce severe weather.

In fact, our hottest day on record came on July 4th, 1911 when Boston hit 104 degrees!

We certainly won’t have to worry about any record heat this 4th, but the thunderstorm threat is very real and will come in two separate waves.

The best chance of getting wet, oddly enough, will come in the early morning hours tomorrow.

A warm front ushering in hotter and more humid air will arrive after midnight tonight and pass through Boston just after dawn.

This will almost certainly be accompanied by a 2-to-3 hour period of showers and thunderstorms from about 4-to-7 a.m. on Wednesday.

Some of these showers could briefly be heavy and while the timing is not indicative of producing any severe weather, it cannot be ruled out.

This first wave of showers will play a crucial role in determining what, if anything, happens later in the day.

There is a chance that Wednesday morning’s wet weather could linger a bit longer and zap the energy from the atmosphere, thus preventing a second round of storms.  This would be a good thing for those with outdoor afternoon and evening activities planned.

However, there is an equal chance that the morning’s showers could slide mainly south of our region allowing the sunshine and heat to build quickly, spawning a second and more potent round of showers and storms later on Wednesday.

At this point, we believe that the morning is likely to produce the most widespread rainfall and round two will be more scattered in nature, but perhaps more severe.

The sun will emerge during the mid-to-late morning and go to work, heating areas inland well into the 80’s.  There will be a gentle seabreeze along the immediate coastline, keeping temperatures about 5-to-10 degrees cooler there.

The humidity will also be a factor on Wednesday, dew points will climb between 65-70 degrees, making it feel like it is in the 90’s.

By early to mid-afternoon you will notice the clouds building into towers and then eventually those puffy towers becoming more numerous and darker at their base.

Some of these rising cumulus castles will become showers and thunderstorms, predicting exactly where they will occur is nearly impossible, but all of southern New England should be alert and keep an eye to the sky and on Doppler Radar between 3 and 8 p.m.

As the sun begins to set, the fuel for these showers and storms will be cut off and many of those cloud towers will begin to melt away, clearing the skies for some man-made fireworks.

You can follow Terry on Twitter at @TerryWBZ.

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