Area Forecast Discussion
Issued by NWS Key West, FL

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FXUS62 KKEY 090336

Area Forecast Discussion
National Weather Service Key West FL
1036 PM EST Mon Mar 8 2021

Our analysis this evening reveals a sprawling high pressure cell
covering much of the eastern and southern United States, Gulf of
Mexico, Bahamas, and Greater Antilles. The Florida Keys and
adjacent coastal waters lie at the southeastern flank of this
system, which is supported by ridging aloft. A sharp, north-south
mean sea level pressure gradient is forcing strong ENE breezes.
Modified continental polar air is modifying rapidly under the
influence of healthy upward fluxes of heat and moisture. Data from
the Key West evening radiosonde balloon indicate that the lower
troposphere is well mixed below a strong subsidence inversion
layer, the base of which is between about 5000-6000 feet above
ground. Temperature lapse rates are nearly adiabatic below the
inversion, leading to efficient downward momentum transfer and
strong/gusty winds at the surface. Within the last several hours,
transient, fast-moving stratocumulus cloud decks have thickened,
producing widely scattered patches of drizzle and light rain, as
anticipated by the afternoon shift. However, the precipitation is
not yielding a significant impact on visibility or surface
wetting. Current air temperatures in most Keys island communities
are in the upper 60s to near 70F, with dewpoint temperatures in
the upper 50s to near 60F. Little change in the air mass is
expected overnight, with air temperatures likely to fall only a
few more degrees before daybreak.

Current forecasts and supporting reasoning remain valid, and we
anticipate no adjustments to the digital database or derived
products this evening.

A Small Craft Advisory remains in effect for all Florida Keys
coastal waters zones. A strong dome of high pressure located over
the eastern third of the United States will result in an extended
period of strong northeast to east breezes through Tuesday night.
As the high treks eastward, breezes will slowly slacken late in
the work week into the weekend.

Through 09/24Z, prevailing VFR conditions are expected at both EYW
and MTH. Occasional, but transient VFR stratocumulus ceilings are
likely, with passing patches with light precipitation possible
within the thicker clouds. However, a wet runway remains an
unlikely scenario given the fast movement any light rain. Frequent
wind gusts of 25 knots are expected from 050-070 at both EYW and

On this date in 1989, the daily record cold high temperature of
66 degrees was last recorded in Key West. Temperature records date
back to 1872.

GM...Small Craft Advisory until 5 AM EST Tuesday for GMZ031>035-


Data Acquisition.....JAM

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