A Pop-Up Thunderstorm Next Few AfternoonsAugust 3rd, 2012 at 11:16 am by Michelle Muscatello under General Talk, Tony's Pinpoint Weather Blog
Heat and humidity will be plentiful the next few days, and a pesky cold front will be near-by through Sunday. Those three ingredients will combine to give us a risk of brief, isolated showers and thunderstorms over the next few afternoons. If you’re trying to plan outdoor activities, it’s the kind of forecast that can be irritating.
We love to “Pinpoint” time, location, impact in our futurecasts, but it can be particularly difficult to do with summertime convection. “Convective precipitation” forms when there is moisture, instability and lift… thunderstorms fire up because of the very warm air near the ground rising rapidly through the atmosphere. These strong updrafts tend to cause random showers and storms that bring brief heavy rain, thunder and lightning. It can be difficult to predict why one towering cumulus cloud will continue to develop into a strong thunderstorm while a neighboring cloud remains harmless. So we do the best we can to give you the most detailed forecast… while trying to emphasize that these storms will be “hit or miss”.
Here’s what we’re thinking for the next few afternoons:
TIMING: Afternoon through early evening… typically 2pm to 6pm.
LOCATION: While a thunderstorm or brief shower could pop-up anywhere in our area… they are going to be more prone to develop in our inland areas, away from the stabilizing effect of the ocean air along the coast and closer to the location of the cold front. I’d give the areas northwest of I-295 a 40% chance of a thunderstorm, while the Providence metro area will have about a 30% chance of seeing thunder and at the coast that drops to a 15% chance.
IMPACTS: One step outside and you can just feel all the heaviness in the air… that high moisture content will give us the risk of heavy downpours in any storms that develop. Lightning is always dangerous and the thunderstorms could contain brief gusty winds. Look for localized (but short-lived) street and poor drainage flooding.