Key West, Florida

New SHORT TERM, MARINE, AVIATION

• Coastal flooding will continue to gradually decrease over the weekend, but receding rates will be slow, especially in the Upper Keys.
• Gentle to moderate breezes will continue today with strongest breezes just offshore to the southeast of the Upper Keys.
• A wet, stormy period is expected to continue through tomorrow. Locally heavy rainfall, if timed with high tides, may exacerbate coastal flooding hazards.

The most notable change to the forecast package with this very early morning update is that we have replaced the Coastal Flood Warning in the Upper Keys with a Coastal Flood Statement. Peak high tides are still trending downward, but we still have a ways to go before high tide is below critical values. Therefore, the entire island chain will remain under a Coastal Flood Advisory.

Most of our weather conditions overnight were fairly benign as residual shower activity from last night had tapered off. We can`t say the same now as our KBYX radar has been busy detecting an increase in showers across the forecast area once again. The most active thunderstorms have stayed well offshore, particularly over the distant Florida Straits. MRMS rainfall estimates indicate that most of our island communities may have seen a few very light sprinkles over the past few hours, but a few isolated showers may have brought rainfall amounts closer to a tenth of an inch to some communities in the Lower and Upper Keys. The 00Z balloon was launched in the vicinity of showers last night, and since those showers have been long gone, the sounding associated with that launch is probably not representative of the environment anymore. However, satellite-derived precipitable water values highlight a swath of moist air up to 500 mb across the region. CIMSS vorticity analysis highlights a swath of low to mid level vorticity coming together coinciding with this moisture, so showers and thunderstorms should have a healthy environment to thrive in today. Opting to keep the 70% rain chances along the Keys today with the disclaimer that CAM guidance has had trouble honing in on where the heaviest showers will pass through. The widespread cloud cover should keep high temperatures closer to the lower 80s, but a few mid 80s will be possible if any sunshine can peak through.

Ensemble guidance suggests that the most reasonable rainfall amounts along the island chain will be somewhere around an inch over the course of today and tonight. While that would usually be easy to handle, there will be embedded heavier showers in this setup that are virtually impossible to forecast the location of before these bands develop. If any of these heavier showers pass over the Keys around the time of high tide, localized flooding will be exacerbated.

Small Craft Should Exercise Caution across the portions of Hawk Channel and the Florida Straits adjacent to the Upper Keys due to freshening breezes. Otherwise, there are no watches, warnings, or advisories in effect for the local waters. However, an increase in shower and thunderstorms activity throughout today and tonight will result in localized hazardous marine conditions including gusty and erratic strong winds, confused seas, and occasional lightning strikes. Conditions will improve over the course of Monday and Tuesday as relatively drier air will filter in.

While VFR conditions will prevail at both island terminals, occasional observations of MVFR CIGs will occur as shower and thunderstorm coverage will increase through the TAF period today There is still some uncertainty related to timing. Will opt for a broadbrushed VCSH becoming VCTS for now, and can narrow timing for more impactful conditions once activity increases. Surface winds will generally be out of the east near 10 knots, but any shower or thunderstorm will be capable of producing stronger, variable winds.

On this day in Keys Weather History, in 2005, 4.14" of rain fell in Key West in the early morning hours. With streets and storm drains clogged with debris only a week after Hurricane Wilma, the heavy rain caused significant flooding throughout the city. Precipitation records for Key West date back to 1871.

Key West  83  75  83  76 /  80  70  50  30
Marathon  84  76  83  77 /  70  70  50  30

FL

Coastal Flood Advisory until 5 AM EST Monday for FLZ076>078.

GM

None.