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98L is struggling with high shear while east of Bermuda
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Show Area Forecast Discussion - Key West, FL (Florida Keys) Selection: |
| #1279129 (Received by flhurricane at: 1:51 PM 17.Sep.2026) AFDKEY Area Forecast Discussion National Weather Service Key West FL 140 PM EDT Thu Sep 17 2026 ...New AVIATION... .KEY MESSAGES... - Well above normal rain chances (around 60-70%) will persist across the Florida Keys through the weekend and possibly into early next week. - Heavy rainfall is becoming increasingly likely. Most locations in the Keys can generally expect an additional 2 to 4 inches of rainfall through Sunday, with locally higher amounts possible. - Gentle to moderate (10 to 15 mph) breezes will relax by Friday. While breezes will then be light to gentle (5 to 10 mph) through the weekend, gusty winds will be possible with any thunderstorm. && .AVIATION... (18Z TAFS) Issued at 140 PM EDT Thu Sep 17 2026 Scattered showers and thunderstorms will remain in the vicinity of the terminals throughout the TAF period. The greatest coverage in sub-VFR ceilings and visbilities will be through 00z this evening, with a low confidence in wind direction for gusts associated with any thunderstorm outflow. Coverage is expected to wane in the evening hours, before redevelopment may occur in the late overnight and Friday morning hours. Have included just a mention of VCSH in that extended period for now due to lack of confidence in the extended TAF forecast evolution. && .PREV DISCUSSION... Issued at 308 AM EDT Thu Sep 17 2026 Models are in good agreement that the center of the upper low will move across central Florida later this week and into the start of the weekend, promoting broad cyclonic flow aloft. As to be expected with the proximity of this feature, this will keep rain chances elevated over the coming days. At the same time the upper low continues to make its approach towards central FL, the surface flow locally across the Keys lessens to generally less than 10 knots, which could favor a messy scenario where daily convective activity could be driven by boundary collisions and make for slow-moving erratic storm motions at times. The core of the colder air aloft with temps as low as -8C to -9C looks to stay just north of our area closer to the center of the upper low but 500 mb temps are still projected to lower to around -7C and this should help to steepen mid-level lapse rates at times. Thus, the end result of this pattern with persistent forcing for ascent in the form of the upper low, cooling mid level temperatures, and PWATs in excess of 2 inches, an unsettled stretch of weather is expected with daily PoPs in the high chance to likely range. By late weekend and early next week, the upper low shifts into the east-central Gulf but models differ with when this feature ultimately departs as the ECMWF opens this feature into a trough and lifts out of the region by Monday but the GFS lingers the closed circulation into Tuesday. Regardless, its influence across the region will lessen by early next week but PoPS may remain elevated well through the end of the long term period as attention might start to turn to the south of the Keys by the middle of next week. Several ensemble members on a variety of global models show deep tropical moisture from the Caribbean potentially streaming into the area, which could be related to the Central American Gyre and this would make sense from a climatological perspective as this feature tends to become more established in the early fall time frame. While there remains considerable uncertainty in exact forecast details at this time, trends will need to be monitored closely in the subsequent forecast issuances as the synoptic picture becomes more clear. && .MARINE... Issued at 945 AM EDT Thu Sep 17 2026 Scattered showers and thunderstorms will grow in coverage and intensity through the afternoon and evening hours. Any stronger thunderstorm will be capable of producing gusty winds, as well as suddenly building and confused seas. From synopsis, high pressure across the North Atlantic will maintain gentle to moderate northeast to east breezes through tonight. Winds will then slacken for Friday through the start of the weekend, becoming light to gentle out of the east and southeast, as the high north of the Keys marine zones weakens. An increasingly wet pattern will develop across the Florida Keys coastal waters through at least Sunday, as an upper- level low retrogrades westward towards South Florida and then eventually the Gulf. Confidence is low in the marine forecast for early next week, largely determined by where the upper-level low resides for that time frame. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ |
| #1279120 (Received by flhurricane at: 10:45 AM 17.Sep.2026) AFDKEY Area Forecast Discussion National Weather Service Key West FL 1033 AM EDT Thu Sep 17 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Well above normal rain chances (around 60-70%) will persist across the Florida Keys through the weekend and possibly into early next week. - Heavy rainfall is becoming increasingly likely. Most locations in the Keys can generally expect an additional 2 to 4 inches of rainfall through Sunday, with locally higher amounts possible. - Gentle to moderate (10 to 15 mph) breezes will relax by Friday. While breezes will then be light to gentle (5 to 10 mph) through the weekend, gusty winds will be possible with any thunderstorm. && .DISCUSSION... Issued at 945 AM EDT Thu Sep 17 2026 The 12z sounding at KEY sampled deep tropical moisture, limited inhibition, and a weakly veered low-level wind profile. Surface analysis continues to highlight two features of interest: a decaying stationary front extending from South Florida northeastward towards the Bahamas and into the western North Atlantic, and a continental high pressure system immediately to its north across the Mid-Atlantic states. Further aloft, GOES-19 infrared satellite imagery is highlighting a well-developed upper- level low centered northeast of the Bahamas slowly retrograding southwestward. This upper-level low will be the main feature of interest for the Florida Keys for the next seven days, providing bouts of heavy rainfall from slow-moving showers and thunderstorms. For today, weakly confluent flow, decent steering flow, and the lack of any large-scale climatologically-favored ridging will support showers and thunderstorms to proliferate as we move into the afternoon and evening. The primary threats will continue to be high rainfall rates owed to the copious tropospheric moisture, as well as gusty winds from any stronger thunderstorm. With little variance in the pattern over the last 24 hours, a persistence forecast is prudent, with no changes to the inherited forecast proposed. && .MARINE... Issued at 945 AM EDT Thu Sep 17 2026 Scattered showers and thunderstorms will grow in coverage and intensity through the afternoon and evening hours. Any stronger thunderstorm will be capable of producing gusty winds, as well as suddenly building and confused seas. From synopsis, high pressure across the North Atlantic will maintain gentle to moderate northeast to east breezes through tonight. Winds will then slacken for Friday through the start of the weekend, becoming light to gentle out of the east and southeast, as the high north of the Keys marine zones weakens. An increasingly wet pattern will develop across the Florida Keys coastal waters through at least Sunday, as an upper- level low retrogrades westward towards South Florida and then eventually the Gulf. Confidence is low in the marine forecast for early next week, largely determined by where the upper-level low resides for that time frame. && .AVIATION... (12Z TAFS) Issued at 945 AM EDT Thu Sep 17 2026 Although the Florida Keys are currently experiencing a lull in convective activity, expect showers and thunderstorms to have increasing coverage in the vicinity of the terminals through the TAF period. Due to a lack of certainty in timing, have included a general mention of VCSH through 12z Friday morning for now, and this will be reevaluated for the 18z TAF issuance. Divergence from the advertised northeast to east winds at near 10 knots will be possible with any thunderstorm, including variable wind directions and gusts 20 to 25 knots. && .PRELIMINARY POINT TEMPS/POPS... Key West 91 81 91 79 / 60 60 60 60 Marathon 89 81 89 80 / 60 60 60 60 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ |
| #1279101 (Received by flhurricane at: 5:00 AM 17.Sep.2026) AFDKEY Area Forecast Discussion National Weather Service Key West FL 444 AM EDT Thu Sep 17 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Well above normal rain chances (around 60-70%) will persist across the Florida Keys through the weekend and possibly into early next week. - Heavy rainfall is becoming increasingly likely. Most locations in the Keys can generally expect 2 to 4 inches of rainfall through Sunday, with locally higher amounts possible. - Gentle to moderate (10 to 15 mph) breezes will relax by Friday. While breezes will then be light to gentle (5 to 10 mph) through the weekend, gusty winds will be possible with any thunderstorm. && .DISCUSSION... Issued at 308 AM EDT Thu Sep 17 2026 The Florida Keys remain in a deep easterly flow regime as an elongated surface high stretches from offshore of the Northeast US southwestward across the remainder of the Eastern Seaboard. Meanwhile, an anomalously strong upper ridge is centered across the lower MS valley. On the southern flank of the surface high, a quasi-stationary frontal boundary is in place across south FL and extends eastward into the northern Bahamas. While the frontal boundary is rather diffuse at this point, it does delineate the drier air mass across northern and central FL where dewpoints are in the 60s to low 70s versus the muggy mid/upper 70s in place across south FL and the Florida Keys. Those hoping for a taste of an autumnal air mass in our region will need to be remain patient as this drier air just to the north will not advect further southward this time around. The deep moisture south of the boundary combined with the easterly flow could potentially favor cloud line formation today with storm motions around 10 knots mostly in a WSW direction. Precipitation activity will then become more synoptically-driven by tonight through the remainder of the week and into the weekend as an upper level low in the SW Atlantic gradually advances towards Florida. Models are in good agreement that the center of the upper low will move across central Florida later this week and into the start of the weekend, promoting broad cyclonic flow aloft. As to be expected with the proximity of this feature, this will keep rain chances elevated over the coming days. At the same time the upper low continues to make its approach towards central FL, the surface flow locally across the Keys lessens to generally less than 10 knots, which could favor a messy scenario where daily convective activity could be driven by boundary collisions and make for slow-moving erratic storm motions at times. The core of the colder air aloft with temps as low as -8C to -9C looks to stay just north of our area closer to the center of the upper low but 500 mb temps are still projected to lower to around -7C and this should help to steepen mid-level lapse rates at times. Thus, the end result of this pattern with persistent forcing for ascent in the form of the upper low, cooling mid level temperatures, and PWATs in excess of 2 inches, an unsettled stretch of weather is expected with daily PoPs in the high chance to likely range. By late weekend and early next week, the upper low shifts into the east-central Gulf but models differ with when this feature ultimately departs as the ECMWF opens this feature into a trough and lifts out of the region by Monday but the GFS lingers the closed circulation into Tuesday. Regardless, its influence across the region will lessen by early next week but PoPS may remain elevated well through the end of the long term period as attention might start to turn to the south of the Keys by the middle of next week. Several ensemble members on a variety of global models show deep tropical moisture from the Caribbean potentially streaming into the area, which could be related to the Central American Gyre and this would make sense from a climatological perspective as this feature tends to become more established in the early fall time frame. While there remains considerable uncertainty in exact forecast details at this time, trends will need to be monitored closely in the subsequent forecast issuances as the synoptic picture becomes more clear. && .MARINE... Issued at 308 AM EDT Thu Sep 17 2026 High pressure across the north Atlantic will maintain gentle to moderate east to northeast breezes through tonight. Winds will then lessen on Friday and into the start of the weekend into light to gentle range out of the east and southeast as high pressure weakens north of the area weakens. In addition, a wet pattern will develop across the Florida Keys coastal waters through Sunday as an upper-level low retrogrades westward towards the region. The upper-level low will move out of the area by early next week but deep moisture lingering across the region will maintain daily rain chances into next week with winds remaining 10 kts or less throughout this time. && .AVIATION... (06Z TAFS) Issued at 308 AM EDT Thu Sep 17 2026 Scattered SHRA and isolated TSRA will move westward across the area throughout the day, which could result in periods of MVFR/IFR restrictions at times. Outside of the occasional shower and thunderstorm activity, VFR conditions will prevail with surface winds out of the ENE at around 5-10 knots. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ |
