Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
499 FXUS62 KKEY 281610 AFDKEY Area Forecast Discussion National Weather Service Key West FL 1210 PM EDT Tue Jul 28 2026 ...New DISCUSSION, MARINE, AVIATION, PREV DISCUSSION... .KEY MESSAGES... - Light flow in the lower levels will become southwesterly today, and will favor waterspout development. Boaters are encouraged to keep an eye on the sky if venturing out this afternoon. - However, Small Craft SHould Exercise Caution offshore of the Upper Keys due to a brief freshening of winds this afternoon. Breezes will slacken slightly overnight. - Heat indices may approach 105 to 110 degrees each afternoon for some Florida Keys island communities, especially in the Upper Keys. && .DISCUSSION... Issued at 1102 AM EDT Tue Jul 28 2026 Unsettled weather conditions are still in place across the forecast area this afternoon with sloppily scattered showers and thunderstorms still moving through. The handful of observations available to us show 12-hour rainfall totals in the Middle Keys near a tenth of an inch, but MRMS radar-derived accumulation values show pockets of higher amounts near one inch, particularly along the Upper Keys. MRMS also shows some pockets of higher values over the water, so some of these heftier showers and thunderstorms have made use of the precipitable water in the vertical. The 12Z sounding didn`t show an overly exciting profile, other than a lot of moisture with just over two inches of PWAT. Something of note from the morning sounding is the light and almost variable flow in the lower levels. With southwesterly surface winds expected to hold up through this afternoon as the island chain heats up, the light flow may favor waterspout development, particularly along the Lower and Middle Keys. The locally-calculated waterspout index associated with the morning sounding was 30%, which is no surprise considering the low level moisture and light flow. Waterspouts are not always visible in their entirety, and may only appear as a funnel cloud extending down from the parent storm. Anyone who observes a waterspout is encouraged to report it to our office either by phone or social media. Temperatures along the island chain are currently in the mid to upper 80s with heat index values near 100F. Visible satellite shows a mix of partly cloudy to mostly clear skies, especially as some residual cloud debris from nearby showers diminish. These temperature numbers will likely come up a few more degrees, and everyone out and about, especially those out to spot some waterspouts, are encouraged to stay hydrated and to take breaks in air conditioning if possible. && .DISCUSSION... Issued at 437 AM EDT Tue Jul 28 2026 Surface troughing will remain extended into the Keys for one more day keeping rain chances above normal at 40%. Looking at the global numerical model guidance Total Precipitable Water Normalized anomaly, this makes sense since we still have abundant moisture across the region. A developing low pressure system across the Mid-Atlantic and Northeast combined with high pressure across the North Atlantic will act in tandem with one another creating for a squeeze play across much of Florida. This looks to play out with much of the moisture focused across the central and northern part of the state while the southern part and the Keys get treated to increasingly drier air as it gets funneled in by the high over the Atlantic. This dry air will also get stuck with no where to go and will remain over the Keys for several days. Therefore, starting tonight, rain chances fall to slight chances with some periods late week into the weekend being dried out completely. Since we will have much drier air over us in the coming days, the heat will become the center of the story again. Daytime highs near 90 degrees and in the lower 90s at times and dew points in the mid to upper 70s will create for heat index values of 105 to 110 degrees. As of now, we don`t anticipate Heat Advisory conditions as it should remain just below it. Overnight lows will also not provide for much relief from the daytime heat remaining in the lower to mid 80s in some cases. Developing low pressure off the Northeast and Mid-Atlantic combined with high pressure over the Atlantic will also create for an increased pressure gradient across the area. This will lend to mainly light to gentle southwest to west breezes, occasionally gentle to moderate along the Island Chain, especially the Upper Keys over the next few days. The gradient relaxes for late week into the weekend resulting in a period of light breezes of even variable at times. && .MARINE... Issued at 1102 AM EDT Tue Jul 28 2026 Troughing just off the Eastern Seaboard will continue to reach southwestward across the far southeast for the next day and be reinforced by another shortwave. This will result in a broad confluence zone remaining draped across northern Florida/Georgia for much of this week. Generally light to gentle breezes will continue out of the southwest to west, but may variable at times. Breezes will become gentle to moderate towards mid week before slackening back to light to gentle by late week. && .AVIATION... (15Z TAFS) Issued at 1102 AM EDT Tue Jul 28 2026 VFR conditions will prevail at both island terminals, but lingering lower level clouds from offshore showers and thunderstorms may lead to occasional MVFR observations. If there are lowered categories at either terminal, conditions should improve swiftly. Light and variable winds at the surface will eventually assume a southwesterly direction at 5 to 10 knots. Opting to maintain VCSH due to expected shower development in the middle of the TAF period. && .PRELIMINARY POINT TEMPS/POPS... Key West 89 83 90 83 / 40 10 10 0 Marathon 90 82 90 82 / 40 10 10 0 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...DP Aviation/Nowcasts....DP Data Acquisition.....DP Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest