Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
783 FXUS62 KKEY 220229 AFDKEY Area Forecast Discussion National Weather Service Key West FL 1029 PM 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... Only a few cumulus out over the Keys as the extensive high altitude cirrus shield from Tropical Storm Berthahas retreated to the west and southwest. Temperatures were in the mid 80s with dewpoints generally in the mid 70s. East to southeast winds were around 10 mph over the islands and running 12 to 14 knots over the Reef and over the nearshore Gulf and Bay waters. Isolated showers well offshore the Upper Keys dissipated well before the reef this afternoon. The evening sounding offered little on its own to support rainfall, with column moisture and mixed CAPE values significantly below the 10th percentile for the date. GOES imagery precipitable water estimates indicated even 0.10 to 0.15 inches lower over the Straits than the Key West measurement of 1.29. High altitude flow around 200 mb was cyclonic with the anticyclonic outflow pattern around Bertha`s southern periphery moving westward, but anticyclonic flow was noted 500 mb and below with the subtropical ridge well to the northeast of the Bahamas. Heights were rising slightly this evening across peninsular Florida in the Keys at 500-200 mb, and only north of the Keys at 700 mb. The ridge should take further control over the lower tropospheric flow with Bertha drifting further away, and a slight uptick in winds could set off a few showers and a thunderstorm or two during the early morning hours with any boundaries, perhaps west of Andros Island, caught in the broad speed convergence. Other than that, the dry air should limit coverage and likely prevent organization. The slight 10 percent chances should suffice for the Keys overnight with the pending slight increase in wind speeds already covered in the public zone forecasts. && .MARINE... Issued at 1012 PM EDT Tue Jul 21 2026 No watches, warnings, or advisories are currently in effect in the Florida Keys waters. From synopsis, as of 8 PM EDT, Tropical Storm Bertha was centered over the northern Gulf waters. Bertha is expected to continue moving slowly to the west-northwest or west tonight through Friday, moving Tropical Storm Berth near or along the northern Gulf coast. Otherwise, an Atlantic ridge of high pressure will extend to the Florida Peninsula for the next several days. Gentle breezes will briefly become moderate overnight through early Thursday, then gradually slacken to light to gentle breezes by Friday, peaking overnight and lull during the day. Light winds are expected this weekend. && .AVIATION... (00Z TAFS) Issued at 1012 PM EDT Tue Jul 21 2026 VFR conditions are expected to previal at KEYW and KMTH overnight, with east to southeast breezes generally 8 to 12 knots veering more southeast before sunrise Wednesday and increasing to 10 to 14 knots. Isolated showers and thunderstorms may develop during the early morning hours Wednesday over the Straits, but current thinking is to hold off on any VCSH/VCTS mention in the TAFs, although the slight chances may be a bit higher for KMTH and the upper Keys during the hours surrounding sunrise. VFR is expected to continue Wednesday with winds decreasing slightly while backing to east-southeast. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...JR Aviation/Nowcasts....JR/RG Data Acquisition.....11/RG Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest