textproduct: Key West

KEY MESSAGES

- One final day of light and variable winds before gentle to moderate southeast winds develop through the end of the week.

- Elevated rain and thunder chances expected through the end of the work week.

- Rain chances return to near normal for the weekend and early next week.

AVIATION

(18Z TAFS) Issued at 115 PM EDT Tue Aug 4 2026 VFR conditions will mostly prevail through the remainder of the day but occasional SHRA/TSRA activity may occur at times and this could result in brief flight restrictions. A brief lull in activity is then expected overnight before rain chances increase again Wednesday morning into the afternoon with additional restrictions possible, especially during periods of heavier precipitation. Otherwise, surface winds will remain near 5 kts and VRB through this evening before shifting to the SE tonight into Wednesday with wind speeds around 7-10 kts.

DISCUSSION

Issued at 1057 AM EDT Tue Aug 4 2026 The 12Z KEY RAOB shows a rather moist atmospheric profile with a PWAT of 2.16 inches and low to mid RH values of 79% and 74%, respectively. Moderate instability values were calculated with SBCAPE around 2700 J/kg with minimal inhibition noted as well, though recent KBYX radar imagery is only detecting a few light echoes in the offshore zones in both the Gulf and Atlantic waters. As the day progresses, precipitation coverage should be on the increase around the Island Chain and nearshore coastal waters as the expectation is for a cloud line to develop later this afternoon and evening given the light and variable flow pattern that will be in place through at least early to mid evening before the arrival of a stronger synoptic southeasterly flow regime. However, one potential limiting factor in cloud line formation will be the rather thick mid/upper level cloud cover that is across the region but this should slowly erode throughout the day. That said, there should be enough ingredients for at least some cloud line formation with slow moving downpours, occasional lightning strikes, gusty winds, and a non-zero waterspout risk being the main hazards so this will be monitored closely. In addition, convective activity across both the mainland and northwestern Cuba could provide additional convective triggers in the form of outflow boundaries, which then interact with the boundary associated with the cloud line, similar to what occurred last evening. However, the contribution from Cuba this evening compared to yesterday is more in question since the mean layer flow within the 1000-700 mb layer is a bit weaker, which was calculated around 6 kts out of the SE. Despite some of the limiting factors discussed, it shouldn't take much for shower and thunderstorm activity to develop given the moisture in place, so PoPs were adjusted slightly upwards in the morning update. now ranging from around 30-50% with highest values in the Bay/Gulf waters generally north of the Island Chain.

By tonight, as mentioned previously, the synoptic flow will transition into a southeasterly flow regime as an upper low across the Southeast US drifts northward and Atlantic ridging both at the surface and aloft build westward. Thus, the focus for precipitation development going forward will be more a result of speed convergence and moisture undulations with scattered shower and thunderstorm activity developing nearly anywhere late overnight into Wednesday and storm motions to the WNW.

MARINE

Issued at 115 PM EDT Tue Aug 4 2026 No watches, warnings, or advisories are currently in effect for the Floria Keys waters. From synopsis, light to gentle breezes will continue through this evening before wind speeds increase to the gentle to moderate range tonight through late week as a southeasterly flow pattern develops. In addition, rain chances will remain elevated through the end of the week as pockets of deep moisture push through the region at times within the southeasterly flow regime. Higher winds and seas should be expected in the vicinity of thunderstorm activity.

PREV DISCUSSION

Issued at 444 AM EDT Tue Aug 4 2026 An active night has turned into a peaceful morning for the Florida Keys! KBYX radar is now shower-free though Nighttime Microphysics is displaying upper level clouds still over a majority of our CWA. Even though showers have diminished in comparison to earlier, the air still remains very moist. MIMIC PWAT reveals around 2 inches of precipitable water in our area. Temperatures are a little lower this morning than previous morning's likely cooling from last nights shower activity. Temperatures across the island chain are in the lower 80s. Along the Reef, marine locations are recording southerly winds at near 5 knots. For today, there is a chance of showers and thunderstorms later in the afternoon after the atmosphere has time to recharge from last nights events.

As winds become southeasterly and freshen starting tonight into Wednesday rain chances will start to become higher due to the influx of tropical moisture. As a ridge starts to try to build in over South Florida we will see a slight lull in convection activity before it ramping back up to higher chances to end out the week. By Saturday rain chances will return to near normal for this time of year.

KEY WATCHES/WARNINGS/ADVISORIES

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