FXUS62 KKEY 041601 AFDKEY Area Forecast Discussion National Weather Service Key West FL 1201 PM EDT Tue Aug 4 2026 ...New DISCUSSION, AVIATION... .KEY MESSAGES... - One final day of light and variable winds before gentle to moderate southeast winds develop through the end of the week. - Elevated rain and thunder chances expected through the end of the work week. - Rain chances return to near normal for the weekend and early next week. && .DISCUSSION... Issued at 1057 AM EDT Tue Aug 4 2026 The 12Z KEY RAOB shows a rather moist atmospheric profile with a PWAT of 2.16 inches and low to mid RH values of 79% and 74%, respectively. Moderate instability values were calculated with SBCAPE around 2700 J/kg with minimal inhibition noted as well, though recent KBYX radar imagery is only detecting a few light echoes in the offshore zones in both the Gulf and Atlantic waters. As the day progresses, precipitation coverage should be on the increase around the Island Chain and nearshore coastal waters as the expectation is for a cloud line to develop later this afternoon and evening given the light and variable flow pattern that will be in place through at least early to mid evening before the arrival of a stronger synoptic southeasterly flow regime. However, one potential limiting factor in cloud line formation will be the rather thick mid/upper level cloud cover that is across the region but this should slowly erode throughout the day. That said, this will be something that will be monitored closely as the moist atmospheric environment would certainly favor some potential for slow moving downpours. In addition, convective activity across both the mainland and northwestern Cuba could provide additional convective triggers in the form of outflow boundaries, which then interact with the boundary associated with the cloud line, similar to what occurred last evening. However, the contribution from Cuba this evening compared to yesterday is more in question since the mean layer flow within the 1000-700 mb layer is a bit weaker, which was calculated around 6 kts. Despite some of the limiting factors discussed, it shouldn't take much for shower and thunderstorm activity to develop given the moisture in place, so PoPs were adjusted slightly upwards in the morning update. now ranging from around 30-50%. By tonight, as mentioned previously, the synoptic flow will transition into a southeasterly flow regime as an upper low across the Southeast US drifts northward and Atlantic ridging both at the surface and aloft build westward. Thus, the focus for precipitation development going forward will be more a result of speed convergence and moisture undulations with scattered shower and thunderstorm activity developing nearly anywhere late overnight into Wednesday and storm motions to the WNW. && .MARINE... Issued at 444 AM EDT Tue Aug 4 2026 No watches, warnings, or advisories are currently in effect for the Floria Keys waters. From synopsis, light to gentle breezes will return by this afternoon before wind speeds increase to the gentle to moderate range for mid to late week as a southeasterly flow pattern develops. In addition, rain chances will also be increasing by tonight as deeper moisture spreads into the region ahead of a frontal boundary approaching northern Florida. As chances for showers and thunderstorms increase, mariners can expect higher winds and seas near this activity. && .AVIATION... (15Z TAFS) Issued at 1057 AM EDT Tue Aug 4 2026 VFR conditions will mostly prevail through the remainder of the day, though brief MVFR restrictions may occur at times if any shower and thunderstorm activity associated with cloud line formation impacts the Island Chain terminals. Light/VRB winds are generally expected throughout the day before southeasterly winds prevail tonight into Wednesday around 5-10 kts. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...RG Aviation/Nowcasts....RG Data Acquisition.....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