Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
757 FXUS62 KKEY 170920 AFDKEY Area Forecast Discussion National Weather Service Key West FL 520 AM EDT Tue Sep 17 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 515 AM EDT Tue Sep 17 2024 The stillness of yesterday evening following the dissipation of a few cloud lines has been broken this morning. Outflow boundaries ejected from late evening Cuba convection drifted north through the Straits of Florida with very little fanfare. That changed as it crossed the island chain and exploded with a handful of thunderstorms arranged in a broken line. As of writing this discussion, these storms are currently ongoing with more bubbling further down the boundary in the northern waters of the Keys. Despite the spark of unsettled weather, most island communities have yet to see precipitation this morning (with the exception of portions of the Upper Keys at this moment). Temperatures are floating around the mid 80s with near 80s over areas with ongoing rain. Light to gentle breezes are stubbornly out of the south along the Reef and likely aiding in convergence with more stagnant air north of the island chain. This morning is just a preview of conditions expected in the short term forecast. As the low pressure that was Potential Tropical Cyclone 8 continues to sync with the upper level trough over the southeast CONUS, deep layer troughing will establish itself over Florida. This will not only allow deep tropical moisture to advect into our area but provide decent synoptic upper level support to prospective thunderstorms. On the other hand, background flow will remain light with no organized lift sources in sight. Clearly this is somewhat of a non-issue as storms have initiated just fine with the left over boundaries from yesterday resulting in what could be described as a mesoscale feast. Surprisingly, several CAMs runs have done a decent job capturing the mode and location of ongoing convection, even if it was an hour late or so. We expect storms to percolate throughout the short term only finding some lulls in activity to recharge the atmosphere and find its next source of lift. Likely PoPs are held into tomorrow as a result, but may need to be adjusted with the timing of the previously mentioned lulls overnight. By the end of this week PoPs will stabilize back near normal as the deep layer troughing slides northeast up the Eastern Seaboard. Left with no strong synoptic influence of sensible weather, conditions will return to a normal late wet season regime. Light and at times variable breezes will persist through the weekend. Some guidance suggests a slight dip in dewpoints around the start of the weekend due to the passage of the stationary front currently parked over Central Florida, but its certainly not going to bring any early fall weather with it. PoPs will remain near normal, if not a touch higher, for the remainder of the extended period. && .MARINE... Issued at 515 AM EDT Tue Sep 17 2024 From synopsis, light and generally variable breezes will continue through Saturday across the Florida Keys coastal waters. Winds and seas will be elevated in and around thunderstorms, particularly on Tuesday and Wednesday, though background winds will remain light and variable. Northerly swell generated by the low pressure on the Eastern Seaboard will linger through Tuesday and Wednesday. This disturbance will deepen into an upper level trough and slowly slide south towards the Florida Peninsula through Saturday. Unpredictability in the movement of this trough means confidence in the extended forecast is very low. A Coastal Flood Advisory remains in effect for the Upper Keys, and a Coastal Flood Statement remains in effect for the Middle and Lower Keys. Boaters can expect less clearance under fixed bridges. && .AVIATION... (06Z TAFS) Issued at 515 AM EDT Tue Sep 17 2024 A mix of showers and thunderstorms will persist across the area this morning and afternoon, so VCSH will be maintained in the TAFs for both island terminals. The timing related to individual stronger cells moving over either site is still in question though, so amendments will be issued as warranted. In general, VFR conditions should prevail into the early morning, but once these showers and thunderstorms become more widespread in coverage, MVFR CIGs will likely prevail with intermittent periods of IFR and LIFR CIGs and VIS from stronger cells. Prevailing winds will remain southeasterly at 5 to 10 knots, but occasional erratic gusts may stem from any given cell. && .CLIMATE... On this day in Keys weather history in 1985, the daily record low temperature of 69F was recorded at Key West International Airport. This also tied for the coldest temperature ever recorded in September. && .PRELIMINARY POINT TEMPS/POPS... Key West 90 81 90 81 / 60 60 60 40 Marathon 90 81 90 81 / 60 60 60 40 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 5 PM EDT this afternoon for FLZ076. GM...None. && $$ Public/Marine/Fire...JAM Aviation/Nowcasts....DP Data Acquisition.....DP Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest