Weather

Showers in the forecast, but that doesn’t mean it’s going to rain

I know the headline of today’s blog entry is a bit counterintuitive, but hopefully by the end of this it’s clearer.

There are a lot of clouds across the area today, all in conjunction with a frontal system to our west. Eventually, this front will push off the coast leaving us with very warm air for the rest of the work week. As the front moves through, it will bring rain over western New England and a chance of some along the coast.

frontal system map315.gif

Severe weather
The branch of the National Weather Service in charge of severe weather has put parts of New England under a slight risk for severe storms today. This is why you are hearing about showers and thunderstorms as a possibility for this afternoon. The map below shows which areas are most susceptible to thunderstorms today.

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Chance is just a chance.
Risk forecasting is similar to any risk management proposition. There is risk associated with everything we do, but often the risk is so small we don’t think about it. The risk of thunderstorms is often zero in this part of the country, but when it increases to about 20 percent or higher, you start to see it mentioned in the forecast.

A 20 or 30 percent risk of a thunderstorm still means there is a 70 or 80 percent chance you won’t see anything. In spite of being told repeatedly it could rain with thunder, the likelihood of actually being under one of these storms is low.

Most of the probability forecasting revolves around an area seeing a hundredth inch of rainfall or more. In other words, when you see 80 percent chance of rain, this means there’s an 8 in 10 chance your area will see a hundredth of an inch of measurable rain. The map below shows the most likely scenario for rainfall amounts through 8 p.m. this evening.

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On a day like today when the chance of rain is about 50/50, lots of you will miss getting wet. Since it hasn’t rained in a week, and the ground is already dry, you might want to think about watering those newly planted things, including lawns. The images below show how much total rainfall is expected through tomorrow morning. Notice most of the rain is across western New England, not eastern areas.

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Drought continues.
With three days of summer heat on the way, even if you get a shower, it won’t be enough to make much of a difference. Unless you are a gardening enthusiast, you might think the few showers we have around today as well as the rain that started the month is enough for a while. However, after a week or more of no significant showers, the ground becomes dry very fast from June through much of August.

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Weekend forecast
Another front will put thunderstorms back in the forecast for Thursday, but like today, they won’t be widespread. A return to warm and dry air is predicted for Friday.

The weekend begins with another front and a return to showers in the forecast during what will be a mostly to partly sunny day. Highs get back into the 70s.

The conclusion to all of this is to remember during this time of year, in particular, that the mention of showers shouldn’t force you to cancel plans, or think it’s going to rain all day. As a matter of fact, most of time showers are mentioned, most of the day is still dry.

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