textproduct: Key West

KEY MESSAGES

- A 20 to 30% chance for showers will persist through this afternoon due to the possibility of cloud line activity and lingering boundary collisions. - While highs will be seasonably warm in the upper 80s through at least mid week, lows will remain warmer than normal, providing little relief from the heat in the overnight hours.

- The next opportunity for an uptick in active weather looks to be the middle of the week.

DISCUSSION

Issued at 140 PM EDT Mon Jun 1 2026 Daytime heating initiated a potent cloud line across the Middle and Upper Keys this morning. Multiple waterspouts were observed from south of the Seven mile Bridge to Lower Matecumbe Key over the course of two hours. A radar derived estimate for storm total rainfall over portions of Long Key was 2.6 inches. Estimates place at least an inch of rainfall over the northeastern half of Marathon and Duck Key.

Hazards for the rest of the afternoon and evening are likely to be in the Lower and Upper Keys. The environment over the Lower Keys was not tapped as heavily for convection, and outflow boundaries moving south from the Everglades would provide a source of lift for showers. Keep watching the radar, wet season is nowhere near over.

MARINE

Issued at 530 AM EDT Mon Jun 1 2026 There are no watches, warnings, or advisories in effect for the Florida Keys local waters. From synopsis, weak high pressure across the area will support light to gentle breezes going back and forth between southwest to northwest over the next couple of days. Near normal rain and thunder chances also expected. A weak frontal boundary may stall near the Keys coastal waters by mid week, supporting an uptick in breezes as well as rain chances.

AVIATION

(18Z TAFS) Issued at 140 PM EDT Mon Jun 1 2026 Afternoon cloud line development will be the primary weather concern for EYW and MTH. Periods of MVFR to IFR conditions are possible near or during SHRA. TSRA are more likely near MTH. Additional TS are possible in the general airspace along another morning cloud line or lingering boundaries south of the mainland. Expect patches of MVFR to IFR CIGs near the terminals. Winds outside of showers will remain light and variable.

PREV DISCUSSION

Issued at 530 AM EDT Mon Jun 1 2026 As the day goes on, a few factors are at play as to whether or not there are more showers. Similar to the past few days, winds along the island chain may assume a southwesterly direction due to daytime heating. If this southwesterly wind is sustained just long enough, a reverse cloudline could develop. The skinny forecast soundings suggest that any individual shower could become an efficient rain-producer, and this goes for cloudlines too. Another factor will be colliding residual boundaries that have been noted on radar. Any boundary collision could trigger new shower activity. All of this is to say that someone is going to see rain today, it's just a matter of who? Since the Middle and Upper Keys currently have a few outflow boundaries at play, as well as the potential for afternoon showers from mainland convection in the afternoon, we'll advertise a chance of showers (around 30%) for these communities. For the Lower Keys, we're betting on the lingering activity from this morning, and once this fizzles out we may be done for the day, so we'll advertise a 20% chance for these communities.

How the middle of the week plays out will depend on the evolution of troughing down the east coast. The most recent model runs have the frontal boundary associated with this trough stalling around the middle of the peninsula. The closer that front can get, the better lift we will see in the environment, so this will impact rain and thunder chances. Either way, the best chances for showers and thunderstorms look to be on Wednesday and Thursday. This front doesn't look like it will be able to get close enough to bring drastically drier air, but knocking off a few degrees from our dew point will make the air feel just a little bit less muggy. After the parent trough had the opportunity to lift away from the area, closer to normal conditions will be able to settle in.

PRELIMINARY POINT TEMPS/POPS

Key West 81 91 80 90 / 10 20 30 50 Marathon 81 88 80 87 / 10 20 30 50

KEY WATCHES/WARNINGS/ADVISORIES

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