textproduct: Key West

KEY MESSAGES

- Gentle to moderate southeast to south breezes are expected across Florida Keys coastal waters for the next few days peaking overnight and lulling during the day.

- Heat indices may approach 108 to 110 degrees each afternoon for some Florida Keys island communities.

- Saharan Air Layer plumes will transit the area over the next several days, limiting rain and thunder chances.

DISCUSSION

Issued at 919 AM EDT Sun Jul 19 2026 An upper-level composite analysis this morning reveals newly formed Tropical Depression Two over the northeastern Gulf of America, with deep-layer mean anticyclones positioned to its east and west. The Florida Keys lie within the deep southerly flow between the deep-layer mean cyclonic circulation containing the new depression and the anticyclone centered over the subtropical Atlantic east of the Bahamas. Data from the Key West morning radiosonde balloon indicated a very moist and unstable thermodynamic stratification with near nil convective inhibition. However, at the moment, Key West Doppler radar scans are nearly void of precipitation echoes over the service area. The balloon- derived data likely is more representative of the atmosphere over the Gulf waters just north of the lower Keys as satellite-derived total precipitable water measurements suggest much drier air upstream over the Straits of Florida and Cuba. This factor combined with a lack of mechanisms to initiate deep convection would explain the dearth of cumulus convection observed this morning.

Current air temperatures in most Keys island communities are in the upper 80s, with dewpoint temperatures in the upper 70s yielding heat indices of 100-105F. Steady southerly breezes prevail in most areas.

FORECAST

The big elephant in the room will be Invest 91L for the next few days. The National Hurricane Center (NHC) currently highlights this system across the northern Gulf with a medium (60%) chance of tropical development through 48 hours and 7 days. The system poses no risk to the Florida Keys. Ridging will continue to be the name of the game going forward for the next week or more for the Keys. Moisture undulations will occasionally slide through the Keys resulting in slight chances of showers and thunderstorms. The timing on this appears to be one round this morning with another round this evening. Model guidance seems to be more bullish on the activity this evening, therefore, chances of showers with a slight chance of thunderstorms is in the forecast for tonight. Some guidance is pointing to convection forming either over or just north of Cuba and then racing northward towards the Island Chain, especially the Lower Keys. Any showers and storms this evening will be capable of heavy downpours, gusty winds, and occasional lightning strikes. Outside of that, continued seasonably warm conditions will continue with highs near 90 degrees and overnight lows in the lower to mid 80s. There is the potential for highs to reach the lower 90s this week which will push the heat index values up to 105 to 110 degrees. However, heat Advisories are not being considered at this time.

The Atlantic ridge will continue to dominate the pattern across the Keys resulting in peaking and lulling breezes mainly out of the southeast to south for at least the first half of the week before becoming more east to southeast for mid to late week and beyond.

MARINE

Issued at 919 AM EDT Sun Jul 19 2026 No watches, warnings, or advisories are in effect across Florida Keys coastal waters. At 11:00 a.m. EDT, newly formed Tropical Depression Two was centered over the northeastern Gulf of America, about 280 nautical miles northwest of Key West Harbor, moving north- northwestward at 2 knots. Tropical Depression Two is expected to move slowly northwestward or north-northwestward during the next day or two, followed by a turn toward the west. On the forecast track, the depression will move near or along the northern Gulf coast during the next several days. An Atlantic ridge of high pressure will extend to the Florida Peninsula for the next several days. Gentle to moderate south to southeasterly breezes are expected to prevail across Florida Keys coastal waters from this afternoon through Thursday.

AVIATION

(12Z TAFS) Issued at 919 AM EDT Sun Jul 19 2026 Through 20/12Z, prevailing VFR conditions are expected at both EYW and MTH. Although a sub-VFR episode from a transient rain shower cannot be ruled out completely, the event probability is quite low at both EYW and MTH.

KEY WATCHES/WARNINGS/ADVISORIES

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