textproduct: Key West

KEY MESSAGES

- Very warm and humid conditions over the next few days will lead to a generally moderate risk of heat illness with periods of high risk conditions. - High confidence that rain and thunder chances to gradually decrease starting tomorrow.

- Breezes on track to gradually decrease to gentle to moderate during the second half of the week.

DISCUSSION

Issued at 1010 PM EDT Tue May 19 2026 Conditions across the Florida Keys continue to be warm and muggy. Dew points are lingering in the lower to mid 70s with temperatures struggling to drop into the lower 80s. KBYX radar observations this evening are tracking shallow, fast moving showers across the Florida Keys waters. GOES East satellite observations indicate most of the clouds tonight are high altitude cirrus clouds generated by thunderstorms near Tampa. That observation is further corroborated by the 00Z KKEY radiosonde. The balloon highlighted a higher moisture concentration near 35,000 feet amidst 50 knot winds. The rest of the sounding was not as interesting. Winds were nearly uniform from the surface to about 10,000 feet. Sampled PWAT also rose above the 90th percentile value for the day. Overall, the weather pattern tonight does not suggest many necessary changes to the forecast.

There is an interesting feature near the Florida Keys, a mid- latitude cutoff low located north of the Bahamas. Winds circulating around this feature are responsible for the river of cirrus aloft. On satellite, the cirrus gives the appearance of a moist upper atmosphere, but the KKEY sounding suggests otherwise. Dry air aloft continues to stream towards the Keys, as seen in the 500-250 mb layer. These features are likely why showers have been struggling to develop into thunderstorms. In addition, the cutoff low is playing a role in mitigating the ridging across the southeastern US. Breezes slackened earlier this evening as the pressure gradient across the Atlantic weakened. On the plus side, winds are once again below Small Craft Should Exercise Caution thresholds. On the negative side, slackening breezes mean less relief from the heat and humidity. The message to take here is to brace for summer like conditions during the rest of the week.

MARINE

Issued at 1010 PM EDT Tue May 19 2026 No watches, warnings, or advisories are in effect for the Florida Keys nearshore and offshore waters. From synopsis, surface high pressure centered north of Bermuda will continue to support gentle to moderate breezes across the Florida Keys waters. Breezes are on track to slowly decrease during the week with peaks expected during the evenings and lulls during the day. Rain and thunder chances will remain above normal through much of the week.

AVIATION

(00Z TAFS) Issued at 1010 PM EDT Tue May 19 2026 VFR conditions will prevail at EYW and MTH for the upcoming period. Near surface winds are on track to slowly decrease after sunrise with medium confidence gusts will drop out late. Shallow showers are still able to form near the terminals, but models do not suggest enough confidence to include VCSH in the TAFs.

PRELIMINARY POINT TEMPS/POPS

Key West 80 90 81 91 / 30 30 30 20 Marathon 79 86 80 87 / 40 30 30 20

KEY WATCHES/WARNINGS/ADVISORIES

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