Weather Wednesday: Why pop-up summer thunderstorms are among the hardest weather to predict
We all want to know if it’s going to rain on any given day.
When you check your local forecast from Rowan County Weather, you notice there’s a 50 percent chance of thunderstorms this afternoon. A few questions will probably cross your mind.
What does this chance of thunderstorms really mean? Is it going to rain? Should you cancel your round of golf or tee off as planned?
Most meteorologists would agree summer is the most challenging time of year to forecast the chance of rain. There is typically plenty of moisture and instability to help fuel the development of scattered showers and thunderstorms, particularly in the South.
Summer thunderstorms sometimes flare up on subtle outflow boundaries from previous thunderstorms in our area. For this reason, it’s difficult for forecasters to provide a yes or no answer as to whether or not you’ll see rain today at your exact location.
Understanding the chances for rain may help you know if you will see rain in your area.
If there’s a 30 percent chance of rain, that means there’s a 70 percent chance of dry weather during your outdoor activities. You probably think to yourself, “Those odds sound favorable; there’s no reason to cancel my plans.”
Then, when the event begins, so does the rain. Everyone is wet, not happy, and your plans are ruined.
Occasionally, storms may be so isolated that only a small part of the county gets drenched while the rest of the county stays dry. As a result, summer thunderstorm forecasts are often broad, making use of terms like “isolated” and “scattered.”
According to the National Weather Service, isolated corresponds with a 10 percent chance of measurable precipitation (0.01 inches or more) at a given location. Scattered indicates there will be a 30 percent to 50 percent coverage of convective weather, such as thunderstorms in the forecast zone.
“Widely scattered” is used for a forecast of 20 percent coverage.
Over the past few weeks, you have likely noticed that it may rain at your house one day and not the next. You may have also noticed your neighbor’s home getting rain while you are experiencing dry conditions.
Mark Wilson of China Grove photographed his front porch in August 2016 and shared it with Rowan County Weather.
The next time you think your neighbor’s yard gets all the rain, while your yard stays dry, you may just be right.
This week has certainly not been as dry with spotty pop-up storms and shower activity. We have been blessed with 1 to 4 inches of rainfall around Rowan County since Sunday. Most of the rain came Tuesday with almost an inch of rain at the weather center.
My forecast for the remainder of the week has rain chances at 60 percent today.
When you are making outdoor plans, be sure to check Rowan County Weather for the latest forecast and radar to help you know if you should keep the rain gear handy.
Steve Monday is chief forecaster for Rowan County Weather.
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