Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
197 FXUS62 KKEY 210842 AFDKEY Area Forecast Discussion National Weather Service Key West FL 442 AM EDT Tue Jul 21 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Tropical Storm Bertha is located across the northeastern Gulf, and the National Hurricane Center continues to issue advisories. This system poses no threat to the Florida Keys. - Heat indices may approach 108 to 110 degrees each afternoon for some Florida Keys island communities. - Saharan Air Layer plumes will transit the area through at least mid week, limiting rain and thunder chances. && .DISCUSSION... Issued at 442 AM EDT Tue Jul 21 2026 CIMSS products shows Tropical Storm Bertha continues to slowly churn northwestward across the northeastern Gulf while two ridges remain in play on either side of it. Also, broad troughing remains in place across the Northeast and the Mid-Atlantic. This is leaving Bertha in a very weak steering flow environment. At the surface, the western flank of the ridge over the Atlantic continues to hold on just enough to influence our winds. Marine observation platforms surrounding the Island Chain are recording southeast to south breezes of 10 to 15 knots. KBYX radar has not detected any shower activity for the last few hours. GOES 19 Nighttime Microphysics imagery shows partly cloudy skies throughout the Keys with some high level clouds along with low level cumulus. Temperatures along the Island Chain are in the mid 80s and dew points are in the mid to upper 70s. .FORECAST... Tropical Storm Bertha will continue to run the headlines for the next few days as it only slowly traverses across the North Gulf Coast. However, this system poses no risk to the Florida Keys. With that said, the western periphery of an Atlantic ridge will continue to be the dominant feature for the Keys sensible weather. Overall, slight chance of showers and thunderstorms will continue through much of the week as moisture undulations move through the region, except for today where we have removed rain chances. Latest indications are for dry air to remain dominant today along with some residual Sahara dust still over the region. Outside of the slight rain chances, seasonably to slightly above normal temperatures are expected to continue through the week. Daytime highs will be near 90 degrees and overnight lows in the lower to mid 80s. Dew points will continue to be tropical and steamy resulting in heat index values of 105 to 110 degrees. Make sure to continue to take breaks and stay hydrated! Peaking and lulling gentle to moderate southeast to south breezes are expected through mid week before shifting more to the east to southeast for late week and into the weekend. Occasionally, breezes may decrease to light to gentle. Guidance continues to show signs of another Tropical Upper Tropospheric Trough (TUTT) cell moving swiftly westward to west- southwestward for mid to late week. It continues to look like it will cross the Bahamas sometime Wednesday night and then Cuba around Thursday before continuing to move towards the Yucatan by the weekend. Latest guidance has shown a slight nudge northward with this TUTT, therefore, we have increased the forecast to represent chances of showers and thunderstorms for Thursday night and Friday. && .MARINE... Issued at 442 AM EDT Tue Jul 21 2026 There are currently no watches, warnings, or advisories across the Florida Keys coastal waters. From synopsis, as of 5 AM EDT, Tropical Storm Bertha was centered over the northeastern Gulf waters. Bertha is expected to continue moving slowly to the northwest or west-northwest today, followed by a turn to the west by the middle part of the week. On the forecast track, TS Bertha will move near or along the northern Gulf coast during the next several days. Closer to home, an Atlantic ridge of high pressure will extend to the Florida Peninsula for the next several days. Moderate breezes will slacken to mainly gentle this afternoon. Thereafter, breezes will continue to peak overnight and lull during the day through Friday. && .AVIATION... (06Z TAFS) Issued at 442 AM EDT Tue Jul 21 2026 VFR conditions are expected to persist at both EYW and MTH terminals through the TAF period. Near surface winds are expected to remain southeast to south this morning before shifting to east to southeast this afternoon and evening. Dry weather is expected to prevail throughout much of the Keys today. && .CLIMATE... On this day in 2017, the daily record warm low temperature of 85F was recorded in Key West. Temperature records for Key West date back to 1872. On this day in 2023, the daily record warm low temperature of 85F was recorded in Marathon. Temperature records for Marathon date back to 1951. && .PRELIMINARY POINT TEMPS/POPS... Key West 90 84 90 84 / 0 10 10 10 Marathon 90 82 90 82 / 0 10 10 10 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...MJV Aviation/Nowcasts....MJV Data Acquisition.....MJV Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest