textproduct: Miami - South Florida

KEY MESSAGES

Updated at 739 AM EDT Tue Sep 8 2026

- Numerous showers and thunderstorms will develop today, primarily across inland areas between 2-8 PM. Gusty winds and dangerous cloud to ground lightning is possible with any storm. - Slow moving storms will increase the risk for localized flooding especially if rainfall occurs in a short period of time over an urban area. - High temperatures will generally rise into the lower 90s across most of South Florida through this week, creating widespread Moderate HeatRisk each day.

SHORT TERM

(Today through Wednesday) Issued at 125 AM EDT Tue Sep 8 2026

05z Mesoanalysis depicts quite the saturated boundary layer across South Florida early this morning, as the combination of decaying cold pools and a land breeze has resulted in a classic peninsular drainage flow pattern. The 00z MFL RAOB (Rawinsonde Observation/ Upper Air Sounding) in tandem with recent ACARS data from SoFlo airports depicts ample convective inhibition within much of the vertical column (500-1000mb) and a stout near surface inversion. For the remainder of the overnight hours through daybreak this pattern will act to focus shower and thunderstorm activity offshore (nearshore Atlantic & Gulf waters) where instability is maximized and aided by the diurnal cycle of atmospheric convection (oceanic convection peaks in intensity and coverage during the early morning hours). Some of this shower and thunderstorm activity may make it close to the coast (especially along the east coast of South Florida) prior to or around daybreak but should remain maximized where instability is greatest. Back onshore, ample moisture trapped underneath the near surface inversion may set the stage for pockets of localized dense fog across inland areas where winds decouple under clearing skies. HREF probabilities for visibility values below a half a mile remain low in the 10-20% range with a maxima in these values near Lake Okeechobee. Even with low confidence on more significant fog impacts, patchy fog could still prove to be impactful along Alligator Alley, SR-80, and US-27. Any isolated fog that does develop will gradually mix out and dissipate as sunshine erodes the near surface inversion and diurnal atmospheric mixing begins. Wakeup temperatures will range from the low 70s near Lake Okeechobee to temperatures in the mid to upper 70s along the coast.

South Florida will remain to the south of a frontolytic frontal boundary currently draped across the northern half of the Florida peninsula today. As is such the case this time of year (for better or worse), no discernible temperature gradient exists across the aforementioned frontal boundary. What does exist however is a notable moisture gradient from north to south and that will continue to have direct implications on our weather regime and convective coverage here in South Florida. While the use of precipitable water values (averaged out for the entire vertical column) has it's caveats, 05z RTMA analysis as well as forecast soundings (RAP, HRRR, etc) for this afternoon depict precipitable water values across South Florida remaining in the 2.0 to 2.1 inch range. According to SPC's Sounding Climatology interface, these values will be between the 75th to 90th percentile for today's date, a factoid that highlights that the atmosphere remains moist and with enough diurnal heating, unstable. Aloft, orphaned lobes of mid-level vorticity remain just to the north of our region as the waning influence of "parent" mid level troughing has long departed and 500mb heights and temperatures have begun to increase across most of the southern United States as a developing mid level ridge slides eastward.

The nearby boundary and the onset of a strengthening mid-level ridge across the southern United States will also result in light winds (below 5-10 knots) throughout much of the atmospheric column today. As is standard fare and a common occurrence in this type of flow regime, each mesoscale model this morning has a different evolution for what may transpire across South Florida this afternoon and evening. The 00z HRRR depicts convection initiating on the Gulf sea- breeze and advecting to the northwest as the day progresses whereas the 00z RRFS and HiResW show an inverse convective evolution playing out. Rather than just guessing which model solution is correct (lukewarm odds for verifying), we can use forecast analysis and climatology to get a better idea of how things will play out. NWS Tampa Bay produced a comprehensive study a few years back on thunderstorm climatology for the Florida Peninsula that takes into account average mean flow between the 1000mb, 925mb, 850mb, and 700mb layers. When mean flow across these various layers is below 5 knots, convection can propagate (albeit slowly) in any direction. With the onset of diurnal heating, winds will veer onshore along both coasts during the late morning/early afternoon hours as differential heating gets the diurnal sea-breeze circulation going. It'll take some time to fully erode any residual convection inhibition, that stout near surface inversion, and stratified atmosphere at daybreak. Hence inland areas will be the foci for the bulk of convective activity today as both the Atlantic and Gulf sea- breezes gradually push inland and away from the coast as the afternoon progresses.

As convection evolves from initial discrete cores into congealing multicellular clusters, outflow dominant cold pools may result in decaying convection pushing back towards the coast during the late afternoon and early evening hours. 500mb temperatures will remain quite warm today between the 75th and 90th percentile at -5C to -6C with consequently equally meager mid-level lapse rates. While ample instability (forecasted CAPE of 3000-4000+ J/kg) and moisture will lead to numerous shower and thunderstorms this afternoon, the threat of severe convection remains minimal. Frequent lightning, gusty sub- severe winds, and heavy rainfall remains the primary hazard with showers and thunderstorms today. With a saturated environment and variable flow (Corfidi upshear and downshear vectors below 10 knots) in the vertical column, pockets of heavy rainfall are once again possible today, especially when convection is pinned along boundary collisions. HREF's LPMM depicts isolated pockets of 2-3" of rainfall across primarily inland locales through 00z (8pm) this evening. Model guidance can be fickle in the exact placement of these higher pockets of QPF, so some potential remains for inland suburbs to see heavy rainfall and localized urban flooding, although the threat will remain fairly marginal in nature. While convective timing can be hard to nail down, model guidance and environment analysis depict the bulk of diurnal convection across South Florida occurring between 2pm to 8pm. High temperatures are forecast to peak in the low 90s this afternoon before overspreading convection (and resultant cloud debris) act to cool temperatures down. Before any relief from the heat, ample humidity and sunshine will result in apparent temperatures in the 100F to 105F degree range across most of the region. NWS's Probabilistic HeatRisk has high probabilities (70-90%) of Moderate HeatRisk for most of South Florida today. Be sure to take necessary heat precautions today if you or your loved ones are sensitive to heat.

As mid-level ridging continues to build across the southeastern United States, a large and expansive area of surface ridging will also begin to build across the western Atlantic waters tonight into Wednesday. Anticyclonic surface flow around this feature will enhance in tandem which will result in background winds shifting to a southeasterly direction by tonight. Although the diffuse boundary to our north is forecast to dissipate during this time frame, deep moisture will remain in place across our region. The confluence of a land breeze from earlier diurnal convection and light southeasterly flow over the nearshore Atlantic waters may set the stage once again for early morning shower and thunderstorm activity across the Gulfstream waters tonight through daybreak on Wednesday. With a southeasterly wind component now in play, early morning showers and thunderstorms may move onshore along the east coast of South Florida before a stable atmosphere results in the waning and dissipation of activity. The subtle shift in surface winds will focus afternoon convection across inland and coastal southwestern Florida on Wednesday afternoon as a pinned Gulf breeze will be prevented from making much headway inland. Convective hazards remain similar to what will transpire today (gusty sub-severe winds, frequent cloud to ground lightning, and heavy rain) with the caveat that heavy rainfall on Wednesday afternoon/evening may fall directly over portions of the Naples metro which could cause isolated urban flooding. High temperatures on Wednesday afternoon are forecast to reach the low to mid 90s before the cooling influence of convection and cloud cover act to reduce temperatures once again.

LONG TERM

(Wednesday night through Monday) Issued at 125 AM EDT Tue Sep 8 2026

Upper-level ridging over the eastern CONUS will gradually push eastward into the Atlantic as it becomes flattened by an upper-level trough during the second half of the week. At the surface, high pressure situated over the western Atlantic is expected to maintain a general easterly flow across South Florida through the weekend. Under this regime, isolated to scattered showers and thunderstorms migrating onshore from the Atlantic waters will be possible along the East Coast each morning. As daytime heating ramps up and sea breezes push inland, the primary focus for convection will shift toward the interior and SW Florida, where activity will be maximized during the afternoon and early evening hours each day.

Current LREF ensemble mean guidance indicates that atmospheric moisture content will remain slightly above normal through the period, with PWATs generally in the 1.9-2.1 inch range. However, global models continue to show a Saharan dust plume approaching the region this weekend into early next week. While the highest dust concentrations should remain well to the south of the peninsula, any mid-level dry air intrusion could potentially enhance mid-level lapse rates and DCAPE, thereby increasing the potential for localized severe winds in robust afternoon convection. Confidence in this scenario remains low at this time, given uncertainty regarding the timing and extent of the dry air intrusion. Otherwise, the potential for severe weather is expected to remain fairly limited, with wind shear staying weak and 500 mb temperatures forecast to remain near to slightly warmer than climatology through the period.

High temperatures will rise into the lower 90s across most areas through early next week, reaching the mid 90s over interior SW Florida. Overnight lows will range from the low 70s across the interior to the low 80s along the coasts. Major HeatRisk probabilities will gradually increase across coastal and metro areas into the weekend as persistent onshore flow keeps heat indices elevated and limits overnight cooling.

AVIATION

(12Z TAFS) Issued at 739 AM EDT Tue Sep 8 2026

Periods of sub-VFR conditions could be possible after 18Z for some of our East Coast sites (KDJT, KFXE) as SHRA/TSRA develops. Across the rest of the area, VCTS will be likely through the afternoon, but much of the activity should remain inland of the terminals. Light and variable winds this morning will give way to light southeasterly flow after 16Z, except at KAPF where a Gulf breeze will develop. Light and variable winds again overnight, with a easterly/southeasterly flow likely again tomorrow.

MARINE

Issued at 125 AM EDT Tue Sep 8 2026

Light to gentle southerly winds will prevail today before shifting southeasterly tonight into Wednesday. Afternoon sea breezes will produce localized wind shifts once again today, turning winds southeasterly over the Atlantic waters and southwesterly over the Gulf waters today. Winds across all waters will veer to a southeasterly direction tonight into Wednesday, with the exception of a brief period of onshore wind flow across the nearshore Gulf waters each afternoon through the remainder of the work week. Scattered to numerous showers and thunderstorms will develop over the local waters each day. Gusty and erratic winds, along with brief periods of rough seas, will be possible in and around thunderstorms. Seas across the Atlantic and Gulf waters will generally remain at 2 feet or less through tonight, before wave heights enhance to 3-4 feet across the Atlantic waters on Wednesday in response to increasing northeasterly swell.

BEACHES

Issued at 125 AM EDT Tue Sep 8 2026

The combination of increasing northeasterly swell and onshore surface winds may result in an elevated rip current risk at Palm Beach County beaches beginning on Wednesday.

PRELIMINARY POINT TEMPS/POPS

Miami 90 80 90 79 / 40 40 50 30 West Kendall 90 78 90 79 / 50 30 50 20 Opa-Locka 91 79 90 80 / 40 40 60 30 Homestead 91 79 90 79 / 40 30 50 30 Fort Lauderdale 90 80 89 80 / 40 40 60 30 N Ft Lauderdale 91 81 90 81 / 40 40 60 30 Pembroke Pines 91 79 90 79 / 40 40 60 30 West Palm Beach 91 79 91 79 / 40 30 60 20 Boca Raton 90 79 90 79 / 40 40 60 30 Naples 91 77 91 77 / 40 30 70 20

MFL WATCHES/WARNINGS/ADVISORIES

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