textproduct: Melbourne

KEY MESSAGES

Issued at 242 AM EDT Sat Jun 20 2026

- Not quite as hot as previous days, but temperatures still above normal and very muggy. Peak afternoon heat indices up to 107, and pockets of Major HeatRisk impacts among widespread Moderate. Similar conditions forecast Sunday.

- Showers and lightning storms could start by late morning (20-50% chances), then high (50-70%) chances in the afternoon & evening, especially near the coast along the sea breeze collision. Rain and lightning storm chances back off a bit Sunday.

- Going into the work weak, heat and widespread Major HeatRisk impacts return the first half, then taper off the second half. Offshore flow continues to favor a sea breeze collision over the eastern side of the peninsula, but less moisture brings rain chances closer to normal.

DISCUSSION

Issued at 242 AM EDT Sat Jun 20 2026

Today...The axis of the trough over the eastern US shifts offshore the Atlantic seaboard, while ribbons of energy transiting the pattern slide over Florida. At the surface, a weak front remains stalled well north of Florida, pushing a very weak Atlantic high ridge to the south from near Central Florida to South Florida. Well above normal moisture remains in place over Florida, with PWATs generally 2.0-2.2", except for a slot of drier air across the southern counties where PWATs drop to 1.7". Between the light offshore (SW-WSW) flow around/south of the ridge and high cloud cover, a weak east coast sea breeze is likely to remain pinned near to offshore the coast today. The cloud cover and high/potentially early rain chances also bring high temperatures down a degree or two from previous days to the L-M90s, which combined with humidity, result in peak afternoon heat indices between 102-107, and widespread Moderate HeatRisk impacts with pockets of Major.

Between the modest upper level support and the high moisture, showers and perhaps a lightning storm or two could get started over the interior on a diffuse west coast sea breeze as early as 9 AM. There is some uncertainty where/if this initial convection will develop, with some CAMs calling for activity to start from the Nature Coast and work southeast, others initiating along most of the west coast sea breeze and tracking east, and then the few that are slower/later to start convection. Or in the HRRR's case, any of these three scenarios depending on which run you look at. How convection starts will determine evolution the rest of the afternoon and evening. The official forecast weighs heavily towards the HREF/REFS solutions, which call for the first scenario where showers and storms initially develop along and north of I-4 (PoPs 20-40%), tracking southeast while increasing in coverage, colliding with the pinned east coast sea breeze in the afternoon and evening where PoPs top off at 70%, before moving offshore. Meandering boundaries and additional bands of upper level support could keep showers and storms going into the early overnight. While there is copious instability (MUCAPE and even MLCAPE at times up to 3,000 J/kg), mediocre shear (bulk shear generally 20 kts or less), and warm-ish 500mb temperatures around -7C aren't helping storm organization and strength. Across the northern half of the area, shallow lapse rates (less than 6C/km) and saturated profiles (DCAPE less than 700 J/kg) lend towards high coverage of efficient rain makers capable of wet microbursts. To the south, the drier air aloft results in higher DCAPE at or above 800 J/kg, and low-level lapse rates are forecast to be a bit steeper, which could support slightly stronger storms. All in all, primary storm hazards will be gusty winds 45-55 mph, and can't rule out an isolated damaging gust to 60 mph, locally heavy rainfall 2-3" (very low chance for 4" or more), and frequent cloud to ground lightning. Hail up to 1" is possible, and funnel clouds/ waterspouts can't be ruled out given the high moisture and abundant boundaries.

Sunday-Monday...A persistent pattern begins to lock in as nearly stationary troughing builds over the eastern US in response to a blocking high developing over the desert southwest. Weak high pressure building over the Gulf, Florida, and the Bahamas keeps the trough to the north. The ridge axis of the Atlantic high takes up residence over South Florida to the Straits of Florida as more low pressure systems pass to the north, continuing light to moderate offshore (WSW-SW) surface flow. The next of these low pressure systems is forecast to lift the front stalled over the Southeast north and away, taking some of the higher moisture with and allowing drier air to advect over Florida. Between the drier air and less upper level support, rain chances are knocked back to 40-60% Sunday, and down to only 10-30% Monday. The east coast sea breeze will remain slow/late/pinned, focusing the highest chances near the coast in the late afternoon and evening. Stronger storms remain possible Sunday as instability stays high, and lapse rates and DCAPE improve, with wind gusts up to around 50 mph, locally heavy rainfall, and frequent cloud to ground lightning possible. More typical afternoon thunderstorms are on tap for Monday. Temperatures remain slightly above normal Sunday in the L-M90s, but cloud cover and rain chances undercut HeatRisk, keeping impacts to widespread Moderate with spots of Major, and peak afternoon heat indices 101-106. Heat concerns return Monday as highs push towards the M-U90s, resulting in more mixed Moderate to Major HeatRisk impacts, and peak afternoon heat indices creeping towards 105 or higher again.

Tuesday-Friday...Upper level pattern stagnates as blocking high pressure remains anchored over the desert Southwest, keeping a broad trough over the eastern US. While a weak ridge over the Gulf, Florida, and the Caribbean is expected to keep the trough mostly north of the area, a few impulses of energy transiting the pattern could swing over Florida at times. At the surface, the ridge axis of the Atlantic high remains shunted over South Florida to the Straits of Florida through Thursday by low pressure systems passing to the north, keeping winds light to moderate offshore (SSW-SW) through the week. This flow regime favors slower/later develop of the east coast sea breeze and a collision on the eastern side of the peninsula. Some variability in moisture is forecast, but overall expect below to near normal (20-40%) rain and lightning storm chances. Staying very warm with above normal temperatures in the L-M90s, and peak afternoon heat indices over 100. Widespread Major HeatRisk impacts continue Tuesday. Technically very gradual relief is forecast through the second half of the week, but only shaving a degree or two off heat indices, and HeatRisk remains Moderate to Major.

MARINE

Issued at 242 AM EDT Sat Jun 20 2026

Today-Wednesday...Generally favor boating conditions outside of offshore moving lightning storms. The ridge axis of the Atlantic high is forecast to be shunted over South Florida to the Straits of Florida, where it will remain through the period as low pressure systems pass to the north. Offshore (SW-SSW) winds 5-15 kts shifting onshore (SSE-SE) in the afternoon to early overnight behind the sea breeze will continue through the weekend and most of next week. Seas 1-2 ft, occasionally up to 3 ft in the Gulf Stream. Primary hazard will be offshore moving showers and lightning storms in the afternoons and evenings, especially today and Sunday when scattered to numerous storms capable of gusts over 34 kts and frequent cloud to water lightning are forecast. Rain and storm chances over the Atlantic waters decrease going into the work week.

AVIATION

(18Z TAFs) Issued at 152 PM EDT Sat Jun 20 2026

Scattered convection is off to an early start today with VCTS mentioned at all terminals to start the 18Z TAF. TEMPOs included at all sites but DAB through this afternoon for VIS/CIG impacts in convection. Localized thunderstorm wind gusts 35-45 kts are possible in vicinity of thunderstorm downbursts. Activity will move eastward through the remainder of the day, clearing first across the interior into this evening with lingering VCSH along the coast. Dry overnight. Prevailing westerly flow generally remains 10 kts or less, turning east-southeast along the coast behind the sea breeze. Light and variable winds overnight.

PRELIMINARY POINT TEMPS/POPS

DAB 74 90 75 93 / 50 50 20 30 MCO 75 93 76 95 / 40 50 20 30 MLB 75 90 77 91 / 50 50 30 30 VRB 74 91 76 92 / 50 50 40 30 LEE 76 92 76 95 / 20 50 20 10 SFB 75 94 76 96 / 50 60 30 20 ORL 76 92 77 95 / 40 50 20 20 FPR 74 91 75 92 / 50 50 40 30

MLB WATCHES/WARNINGS/ADVISORIES

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