Weather

July 4th forecast not as perfect anymore, but don’t panic — it’s not a washout either

There are some changes to the 5-day forecast and they unfortunately affect Independence Day. Now, before you run and cancel plans or start worrying about a washout, that is not what’s currently predicted. The overall change is because nearly all of the computer models have now predicted a shift north in a storm’s cloud and precipitation shield that was expected to remain too far south to impact southern New England.

The chart below, based on computer models, shows the chance of rain increasing tomorrow evening.

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This is a similar situation to several we see during winter months, when the storm track shifts one way or another and you hear about a major change to a snowfall forecast. The cut-off to the cloud and shower shield will be rather sharp from this system.

You might ask if the forecast could change further, and the answer is absolutely. The shift could be an anomaly and we go back to the previous thinking of dry weather, or it could be a trend and the showers and clouds push further north and impact the forecast more. We will need to wait until later this afternoon and evening to have a firm handle on this.

The National Weather Service in Taunton tweeted the following this morning which summarized the situation quite well:

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The chance of precipitation increases dramatically towards New York where the rain is likely and they could have to cancel some events tomorrow if the rain is steady and heavy enough. Notice the chances of rainfall decrease rapidly the further north you live.

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I am not looking at a large amount of precipitation. The two maps below show how much rain is forecast. The first map is more of a model average and the second map is a wider look from one of the models. Notice there is quite a lot of rain with the system, but the heaviest is well offshore.

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The chart below gives another look at the forecast on an hourly basis. This is for Boston. Notice the brief increase in both cloud cover and chance of showers late in the afternoon and early in the evening tomorrow.

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I’ll be tweeting about changes to the forecast on Twitter @growingwisdom, especially after I digest the new information later today.

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Sunshine and warm weather returns for Sunday and much of next week. I think later in the week there will be more clouds and rain chances may increase again, but this is way too far away to make any definitive forecast.

Have a safe and happy 4th of July. It’s America’s birthday, have fun celebrating.

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