textproduct: Key West

KEY MESSAGES

- A Saharan Air Layer is exiting the Florida Keys this afternoon with slightly better moisture moving back in for the afternoon and evening.

- Heat will be the primary weather concern this week. Heat indices may creep towards 110 before the weekend.

- Shower coverage is expected to increase at the end of the week while a low in the upper atmosphere tracks westward across the Keys. This will be followed by a stronger Saharan Air Layer for the weekend.

DISCUSSION

Issued at 1018 AM EDT Thu Jul 9 2026

The effects of the most recent Saharan Air Layer (SAL) plume was evident this morning with the milky sunrise across the Keys. This plume is on its way out with somewhat better moisture moving in from the Bahamas. This moisture plume is saddled between the exiting SAL plume and a stronger SAL plume that will arrive late Friday. In addition, a Tropical Upper Tropospheric Trough (TUTT) cell will accompany this moisture surge and should lend a hand in bringing relatively large scale lift as it passes through. This hopefully means that our rain chances will spike tonight through Friday. This would be very beneficial as all of the Florida Keys were placed back into the D1 (Moderate Drought) category this week.

Otherwise, we are entering a lull in the winds from last night with generally speeds of around 10 mph across the island chain and 10 to 15 knots at most of our marine platforms. No changes made to the going forecast for the remainder of today. As hinted at above, rain chances will increase tonight along with winds. Expect another period of breezy conditions overnight.

MARINE

Issued at 1018 AM EDT Thu Jul 9 2026

East to southeast breezes have slackened to generally gentle to occasionally moderate this morning and will continue through the early afternoon. By the late afternoon, expect breezes to gradually freshen, starting in the Straits of Florida waters first and then spreading northwest through the evening and overnight. Moderate to fresh breezes expected for most if not all of the coastal waters surrounding the Florida Keys tonight. Expect another cycle of lulls and peaks to persist through Friday and Friday night. In addition, increasing moisture later this afternoon will lead to a greater coverage of showers and thunderstorms this evening through Friday afternoon.

AVIATION

(12Z TAFS) Issued at 1018 AM EDT Thu Jul 9 2026

VFR conditions expected with gentle east to southeast breezes. Will see occasional gusts around 20 knots for the afternoon. This will be followed by a minor surge this evening and overnight with gusts near 25 knots. Lastly, moisture will gradually increase through the forecast period and could see showers and or thunderstorms pop up near the island terminals this afternoon with better coverage overnight.

PREV DISCUSSION

Issued at 1215 AM EDT Thu Jul 9 2026

Quiet weather continues across the Keys this morning. A narrow but healthy surface through lower level Atlantic ridge stretches westward across Central Florida and is driving breezy east to southeasterly flow across the Keys. This flow is holding up temperatures and current readings are in the mid to upper 80s with dew points in the mid to upper 70s. While this evenings sounding indicated a precipitable water not to far from normal at 1.67 inches, there was a robust subsidence inversion based just above 900 mb with a good slug of dry air. This has kept shower activity down to essentially non existent across our forecast area.

A cut off upper low is currently creeping its way westward through the central Bahamas and has produced a weak lower level reflection that is beginning to move across Cuba. While today will remain dry, the weak trough will push through our area beginning tonight. This will wipe out the stable and dry layer holding showers at bay. Expect a slight to low chance for showers and thunderstorms beginning tonight. East to southeasterly breezes will remain moderate to fresh, peaking in the evening and early night hours and lulling slightly during the day. This will continue to drive slightly above normal temperatures with highs near 90, lows in the mid 80s, and dew points holding in the mid to upper 70s.

The previously mentioned upper low will contribute to yet another lower level trough heading into the weekend. This will keep at least a low chance for showers and thunderstorms. Thereafter, much drier and more stable lower levels is expected to sweep in. As a result, rain chances will be slight or less from later in the weekend and well into next week.

PRELIMINARY POINT TEMPS/POPS

Key West 92 83 92 83 / 10 30 40 30 Marathon 90 83 90 83 / 10 30 40 30

KEY WATCHES/WARNINGS/ADVISORIES

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