Rounds of heavy rain, strong thunderstorms possible this week in Florida
Rounds of heavy rain and thunderstorms will make for a soggy end to April across the Sunshine State.
Surface observations Monday morning shows a tale of two tales across the state of Florida. Dew points behind a cold front in the Panhandle have fallen into the 40s while dew points across South Florida are in the lower 70s. The slow-moving cold front was located between Gainesville and Lake City. As this cold front pushes south towards the I-4 corridor through Monday afternoon, instability ahead of the front could prompt the development of strong and severe thunderstorms across Central and South Florida. A "marginal" risk of strong thunderstorms is present on the Storm Prediction Center's Day 1 Outlook for Monday, with areas from Orlando to Miami, to Fort Myers under the risk for damaging winds, hail, and a brief spin-up tornado.
SEVERE STORM OUTLOOK: Scattered to numerous t-storms will likely develop across S FL this afternoon. Hazards may include: lightning, strong wind gusts, small/severe hail, and a brief tornado. Storms will generally develop in the afternoon, but may continue into the evening. #FLwx pic.twitter.com/j3SBwoagMx— NWS Miami (@NWSMiami) April 24, 2023
This risk designation means that severe storms will likely be more isolated in nature and are not likely to be numerous. High-resolution model guidance suggests storms initiate along the Gulf sea breeze during the heating of the day before becoming more numerous across the interior of the state. The strongest cells will be able to tap into moderate amounts of instability, with daytime heating and a nearby front providing an extra boost to the atmosphere through Monday evening. Aside from Monday's risk of severe weather, heavy rains could lead to flash flooding from Port St. Lucie to Miami. Storms are expected to push offshore Monday evening after sunset, with a few showers or storms lingering through the early overnight hours along the I-95 corridor.
Tuesday will feature a renewed round of shower and thunderstorm activity across the Peninsula, as an upper-level disturbance is forecast to pivot overhead during the afternoon and evening. As of publishing, model guidance suggests much of Tuesday's activity will be focused along and south of I-4. Another round of potentially strong storms could develop from the Space Coast to South Florida, with wind, hail, and a brief spin-up tornado possible. Slow-moving storms on Tuesday could lead to localized instances of flash flooding, especially in recently hard-hit Broward and Miami-Dade Counties.
Uncertainty exists regarding exact placement of a stalled frontal boundary on Wednesday, with recent model trends generally keeping the stalled front along the I-4 corridor. Another upper-level disturbance is forecast to ripple along the stalled frontal boundary on Wednesday, keeping rain and thunderstorm chances present across much of the Peninsula. The Storm Prediction Center's Day 3 Outlook for severe storms Wednesday depicts a "marginal" risk along and south of a line from Daytona Beach to Cedar Key, including areas like Orlando, Tampa, and Miami. The maximum threat area will likely change over the next 24 to 36 hours as new forecast data comes in, but it appears that hail will be a risk factor in the strongest cells that develop. Heavy rain could lead to more flash flooding in areas of Central and South Florida through Wednesday evening.
As the forecast period advances, forecast uncertainty does grow. Where exactly frontal boundaries stall and other small-scale boundaries lie will ultimately lead to forecast changes over the course of this week. Current forecast guidance suggests an area of low pressure will be anchored offshore of the Carolinas, with an associated cold front bisecting the state Thursday. Meanwhile, a low pressure area will be moving into the Gulf of Mexico. These two features will work in tandem to provide ample moisture across the state, with continued rain and thunderstorm chances in the Peninsula. The Gulf low will push into the Southeast through the day Friday, with a cold front expected to move into the Panhandle. The cold front is forecast to gradually wash out over Central Florida by Saturday before another cold front arrives Sunday into Monday. Following this frontal passage, it does appear that drier and slightly cooler conditions will return to most of the Sunshine State for the first week of May.
This week could provide much-needed rainfall for much of the state, with a swath of between 1 and 3 inches of rain forecast over the next seven days. Areas of extreme drought have developed from Tampa to the Nature Coast, where widespread year-to-date deficits of 5 to 10 inches exist. Locations in South Florida, particularly near Fort Lauderdale, could see an addition 2 to 4 inches of rain through Sunday. This will likely contribute further to the ongoing rainfall surplus in this area, where year-to-date rainfall is nearly 300 to 400 percent above average. The first week of May is likely to continue the unsettled pattern, with the Climate Prediction Center depicting the entire state with above-average rainfall.