Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
645 FXUS62 KKEY 190207 AFDKEY Area Forecast Discussion National Weather Service Key West FL 1007 PM EDT Sat Jul 18 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Moderate southerly breezes are expected across Florida Keys coastal waters. - 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 1000 PM EDT Sat Jul 18 2026 All eyes have been on Invest 91L over the eastern Gulf waters, because we are very much nerds when it comes to the atmosphere. Current nighttime satellite imagery shows the sloppy low slowly spinning over the eastern Gulf waters with associated showers and thunderstorms widely scattered across the Southeast. Mean layer wind analysis suggests the low may have lost some of its "stacked" feature, but the low is still present at the surface with troughing in place across are region. While most of the island chain has remained dry this evening, the Dry Tortugas area saw an impressive line of showers and thunderstorms along a boundary earlier. Unfortunately, there were no surface observations available in the area, but our best educated guess is that this line was producing gusty winds around 20 to 25 knots with heavy downpours. Similar observations occurred along the SWFL coastline when comparable bands went through today. GOES-19 was able to detect some lightning activity in isolated, stronger cells within the band. Along the island chain, temperatures are sitting in the mid 80s. A very narrow band of high level clouds associated with Invest 91L is currently passing across our skies, but low to mid level cloud debris noted on GOES-19 CLoud Top will linger across the area, so tonight would be a bad night for stargazing. Our KBYX radar isn`t currently detecting showers within our forecast area, but there are a few thunderstorms firing over Cuba. In theory, outflow boundaries from these thunderstorms could migrate over our waters, and we could see some activity trigger during the overnight hours. Hi res guidance favors some activity showing up over the waters to the west and north of the Keys, so we are keeping that in the back of our mind. The 00Z sounding from our balloon launch this evening doesn`t show an environment too impressive. Winds in the lowest levels of the profile are backing with height, and even though there is some moisture noted, the calculated PWAT was only 1.51", between the tenth and twenty-fifth percentile. Opting to maintain the inherited slight chance (20%) of showers and thunderstorms. No changes are needed with this evening update. && .MARINE... Issued at 1000 PM EDT Sat Jul 18 2026 A broad area of low pressure over the eastern Gulf of America will shift northward through Monday, with prevailing gentle to moderate south to southeasterly breezes across Florida Keys coastal waters. An Atlantic high pressure ridge will extend to the Florida Peninsula for the next several days. Gentle southeasterly breezes are expected to prevail across Keys coastal waters Monday night through Thursday, with overnight surges and afternoon lulls. && .AVIATION... (00Z TAFS) Issued at 1000 PM EDT Sat Jul 18 2026 VFR conditions will prevail through the TAF period with FEW to occasionally SCT skies near FL025. If shower activity can increase during the overnight hours, occasional MVFR CIGs may occur at either terminal, but the chances of this are very low, around 10 to 20 percent, and will be short lived. There is not enough confidence with regards to timing and prevalence to include in the current TAFs. Southeast surface winds will remain near 10 knots. && .PRELIMINARY POINT TEMPS/POPS... Key West 83 90 83 90 / 20 20 20 10 Marathon 82 91 82 92 / 20 20 20 10 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...DP Aviation/Nowcasts....DP Data Acquisition.....11 Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest