textproduct: Miami - South Florida

KEY MESSAGES

Updated at 148 PM EDT Fri Sep 4 2026

- An active weather pattern remains in place through the upcoming holiday weekend as scattered to numerous showers and thunderstorms will develop each day. The strongest storms could contain heavy downpours and frequent lightning. - Heavy downpours with high rainfall rates combined with slow moving storms will increase the risk for localized flooding especially over the urban and poor drainage areas. - High temperatures will generally rise into the lower 90s across most of South Florida through the holiday weekend, creating widespread Moderate HeatRisk.

SHORT TERM

(Rest of today through Saturday) Issued at 148 PM EDT Fri Sep 4 2026

We remain in a typical early September rainy pattern across South Florida. Satellite and mesoanalysis data this morning confirm the presence of a large and distinguishable cyclonic rotation over the central Gulf, associated with an upper level low that has slowly retrograded to the west since yesterday. A sprawling, widespread low- level cumulus field combined with isolated towering cumuli across the rest of our region is a testament to the type of superficial instability (4000-5000 J/Kg) we will be contending with today. At the surface, high pressure over the southwest Atlantic is helping induce a relatively light south-southeasterly flow across our region, which will eventually be counteracted by a penetrating Gulf breeze as daytime heating continues to kick in. Model guidance, which is being verified this morning by ACARS sounding data and RAP analyses, continues to have above average regional PWATs of 2.0-2.2" (representing the 80th-95th percentiles for the date). There is nothing really in the way of upper-level support when it comes to atmospheric forcing, so much of the convective activity we see today will be both diurnally and sea breeze driven.

Shower and thunderstorm activity that is already ongoing across both of our coastal metro areas will continue to grow upscale and primarily overspread the interior sections of South Florida through the remainder of the afternoon, waning in coverage during the early evening hours tonight. Exceptionally warm mid-level temperatures of - 6 degrees Celsius (which are roughly around the 75th percentile for the date), a fairly moist atmosphere with limited amounts of dry air, meager low-level lapse rates (6-7 degrees Celsius), and light bulk shear below 10 kts should all keep chances of strong storms low. As with the past few days, heavy downpours could lead to isolated instances of urban flooding due to the overall slow motion of storms. Frequent to excessive lightning strikes, and gusty winds of 20-30 mph will also be hazards with any storm. Nonetheless, this should continue to provide beneficial rain for the interior where severe D2 drought conditions now prevail, having just recently improved from what were extreme D3 conditions.

A fairly similar setup as we go into our Saturday, with a slight southeastward shift in our subtropical ridge still inducing a gentle southeasterly flow across South Florida through the early part of the day before the Gulf sea breeze kicks in past noon. Moisture levels (PWATs of 2.0-2.3") will remain elevated enough to prompt the development of scattered showers and thunderstorms, mainly favoring the interior during the afternoon hours and gradually tapering off around sunset. Dangerous cloud-to-ground lightning, heavy rainfall, and gusty/erratic wind shifts will be the main hazards in and around thunderstorms.

Seasonably hot conditions will remain one of our other top storylines, with highs expected to reach the low to mid 90s both today and tomorrow and heat indices maxing out each afternoon in the 100-105 F degree range. Areas that are liberated from morning convection should be able to easily attain these values earlier in the day, before temporary reprieves are eventually provided by developing showers and thunderstorms.

LONG TERM

(Saturday night through next Thursday) Issued at 148 PM EDT Fri Sep 4 2026

A pretty classic looking Omega blocking pattern will set up across the continental United States for the back half of the Labor Day weekend. An anomalously strong upper level low pressure system over the Pacific Northwest will finally begin to push into the Intermountain West by Sunday. This will begin to flatten and shift the influence of the Great Plains ridge further to the east and closer to Florida. Meanwhile, deep mid level troughing will extend south across the eastern seaboard as the main trough axis pushes pushes offshore into the mid-Atlantic. The passage of this trough will help push a surface cold front south into North Florida by Monday. This trough looks to stop just short of South Florida and stall over the northern part of the peninsula through the middle of the week. However, some guidance is hinting at a few shortwave vorticity impulses digging further south into the Peninsula behind the main trough axis, which would likely invigorate storm activity and increase coverage of precipitation throughout the region. The overall wind pattern will remain pretty weak, but the surface high over the Atlantic will keep winds more southerly. As a result, deep moisture will continue to advect into the region through the middle of the week. Guidance continues to hint at PWATs remaining above 2 inches, which is above the 75th percentile for this time of year. There is an indication that some coastal convergence may develop closer to the stalled front, as winds aloft shift more westerly and southeasterly winds at the surface keep storms pinned to the coast. But with relatively weak steering flow, most convection will generally focus along sea breeze and outflow boundary interactions during the afternoons. Under a moisture rich atmosphere, locally heavy rainfall will be the main threat each afternoon, bringing nuisance urban flooding concerns to low lying and poor drainage areas.

By the middle of the week, the ridge over the central CONUS will expand eastward into Florida. The surface boundary over north Florida will wash out and surface high pressure over the Atlantic will once again exert greater influence over the peninsula and shift winds easterly again. Moisture content looks to be on the downtrend by the end of the week, which will lower chances of precipitation across the region. Scattered storm coverage will likely favor interior and southwest Florida, along sea breeze boundary interactions. Storms will be more run-of-the-mill, with typical locally heavy rainfall, frequent lighting, and gusty winds being the main threats. Temperatures through the period will remain near normal for this time of year, with highs in the upper 80s to low 90s. Widespread Moderate HeatRisk will continue to impact all urban areas, affecting sensitive individuals without proper hydration and cooling.

AVIATION

(18Z TAFS) Issued at 148 PM EDT Fri Sep 4 2026

VFR conditions will prevail across the region this afternoon. However, have included brief TEMPOs for all eastern terminals early in the afternoon for scattered thunderstorms developing along the Atlantic sea breeze. Storm activity will then shift towards interior South Florida, with most storms then dissipating after sunset. Winds will generally be out of the southeast for all eastern sites, while a Gulf Breeze will shift winds west at KAPF. Winds become more light and variable overnight.

MARINE

Issued at 223 AM EDT Fri Sep 4 2026

A gentle to moderate southeasterly breeze will continue across most of the local waters through the first half of the weekend. The exception to this will be across the Gulf waters, where they will become south southwesterly each afternoon during this time frame. Winds shift and become south southwesterly across all local waters heading into the second half of the weekend and into early next week. Seas across the Atlantic and Gulf waters will remain at 2 feet or less through the upcoming weekend. Scattered to numerous showers and thunderstorms will be possible each day through the weekend and into early next week.

PRELIMINARY POINT TEMPS/POPS

Miami 80 90 78 91 / 20 60 20 80 West Kendall 78 89 76 90 / 20 70 20 90 Opa-Locka 80 90 77 91 / 20 70 20 80 Homestead 79 90 77 91 / 30 60 20 80 Fort Lauderdale 80 89 79 90 / 30 60 20 80 N Ft Lauderdale 80 90 79 91 / 20 60 10 80 Pembroke Pines 79 90 78 91 / 20 60 20 80 West Palm Beach 79 91 77 92 / 20 70 10 80 Boca Raton 80 89 78 90 / 20 60 10 80 Naples 77 90 77 90 / 30 70 40 60

MFL WATCHES/WARNINGS/ADVISORIES

FL...None. AM...None. GM...None.