textproduct: Key West

KEY MESSAGES

- Windy conditions will ensue Friday, continuing through at least early next week. Small Craft Advisory conditions expected for all Keys waters, with near-gale conditions possible.

- Frequent fast-moving showers with possible thunderstorms will push through the Keys at times, mainly Friday night through Monday.

- Seasonal king tides combined with northeasterly winds will lead to coastal flooding through early next week, with the greatest impacts in the Upper Keys.

DISCUSSION

Issued at 204 PM EDT Wed Oct 21 2026

A highly amplified synoptic pattern is in place across the CONUS with strong ridging across the Plains and longwave troughing across the eastern US and western Atlantic. This troughing across the eastern CONUS and western Atlantic is supporting a vertically stacked nor'easter situated offshore of the Mid-Atlantic states. An exceptionally deep northerly flow on the backside of this system in tandem with an expansive area of high pressure in the Great Lakes has brought the humidity levels to a comfortable range for late October standards in the Florida Keys with dewpoints area-wide generally in the mid 60s. Additionally, impressively dry PWAT readings were observed on the 21/12Z KEY RAOB with values at 0.80 inches and for climatological context, this value essentially falls within the daily minimum for late October. Another item of note from this particular sounding was the robust stable layer sampled between the 800-750 mb this stable layer combined with the moisture- starved air mass will essentially maintain near-nil rain chances through tonight and most of Thursday.

The aforementioned nor'easter will start to gain latitude and shift to the northeast through through the end of the week as a potent shortwave digs out of eastern Canada. The base of the upper trough then pinches off and closes into a mid to upper level low that will meander for an extended period around the Florida Keys and Cuba. This feature will help to draw deep tropical moisture and at the same time, an extended fetch of low-level northeasterlies will develop across the Florida Keys. As such, rain chances will be on the increase late week and especially by the weekend as this pattern evolves. While there will be sufficient forcing in place associated with the upper low, there remains uncertainty in where the deepest moisture axis sets up as a surface low/trough emerges into the southwest Atlantic. Regardless, PoPs will still be well above climatological values with likely and even occasional categorical PoPs in the forecast for the weekend as model forecast sounding show increasingly saturated columns. Depending on how the rainfall materializes, it could be rather problematic as we enter the peak of King Tide season with coastal flood headlines of some sort almost all but a guarantee. Thus, rainfall totals each day will need to be monitored closely, especially during periods of high tides given the backflow of saltwater through the drainage system. The one positive at this point is that any shower activity that does develop should have quick storm motions and this will limit residence time over any particular area but either way, we will be monitoring trends closely in the coming days.

There will be a notable drop in PoPs by early next week as the upper low that will meander in the region this weekend will finally depart to the east as an upper trough shifts offshore of the Eastern Seaboard. A quasi-zonal flow pattern should then develop towards the middle of the week in the wake of this departing feature but a moist low-level northeasterly flow may still keep at least Slight/Chance PoPs to be a possibility through the end of the forecast period. In addition, despite the lowering rain chances, astronomical tide levels will still remain extremely elevated with the continued northeasterly flow and full moon early next week supporting a high likelihood of a prolonged period of coastal flood headlines.

MARINE

Issued at 204 PM EDT Wed Oct 21 2026

Northeasterly winds continue across the Florida Keys coastal waters as a nor'easter remains in place across the western Atlantic and high pressure builds in from the north. Wind speeds through Thursday should mostly be in the 10-15 kt range, though small craft exercise cautionary conditions could briefly occur at times through Thursday evening. Winds are then expected to freshen late week and into the weekend as the pressure gradient increases as a secondary high pressure system builds into the Northeast US. Thus, there will be an extended period of fresh to strong northeasterly breezes this weekend with a return of small craft advisory headlines expected. In addition, seas will build to as high as 8 to 12 feet by Sunday with hazardous marine conditions expected across the coastal waters surrounding the Florida Keys. The northeasterly flow will also bring quick moving shower and thunderstorm activity to the region as well as deeper moisture returns to the area by the weekend.

AVIATION

(18Z TAFS) Issued at 204 PM EDT Wed Oct 21 2026

Very dry air across the region will yield VFR conditions through Thursday evening. Surface winds will remain out of the NE around 5-10 kts and occasional gusts of 15 kts at times.

KEY WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Advisory until 5 AM EDT Thursday for FLZ076.

GM...None.