638
FXUS62 KKEY 191905
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
305 PM EDT Thu Sep 19 2024

...New DISCUSSION, MARINE, AVIATION...

.DISCUSSION...
Issued at 300 PM EDT Thu Sep 19 2024

Currently - Weak mostly northwesterly breezes prevail across the
Keys this afternoon. This is due to a weak pressure field brought
about by weak troughing along the Atlantic Coast and day time
heating sitting between a high over the southeastern United States
and a bubble high east of the Bahamas. Amplifying troughing
remains aligned along the Atlantic Coast and into the Gulf of
Mexico. This along with continued copious lower to mid level
moisture is keeping a wetter than normal weather pattern in place
across our broader area. Activity along the Keys has been somewhat
muted this afternoon. This is not to say there has been no
activity, and portions of our forecast area has and continue to be
affected by healthy clusters of showers and thunderstorms.
Considerable cloud cover from mid and upper decks arriving from
gulf convection has kept temperatures muted for much of the day.
However, it is early and a number of observation have been able to
climb high into the upper 80s to near 90. Dew points remain
broadly in the mid 70s.

Forecast - The deep layered troughing over the Atlantic Coast will
continue to amplify over the next couple of days. However, much
of the trough will pivot out to the northeast as robust ridging
builds northeastward through the heartland. In response, surface
ridging centered over the Mississippi Valley will strengthen and
expand while the mid to upper trough near our area breaks off and
eventually balls up near the Yucatan. As a result, after another
night and day of faint and variable breezes, a light broadly
easterly flow will begin to take shape. The still present trough
will remain a player through this period. However, lower level
moisture is expected dip some. Above normal rain chances tonight
will slip back to near normal by tomorrow night. Expect near
normal temperatures and dew points through this period.

Forecast uncertainty ramps up for early to mid next week. All
guidance has been very consistent with the development of a low
pressure system that gets its start in the Northwestern Caribbean
Sea. Meanwhile, the previously mentioned surface high will have
expanded, strengthened, and built eastward through the Atlantic
states. This combination should result in an inexorable tightening
of the local pressure gradient and accompanying freshening east to
southeasterly breezes. In addition, all sensible weather elements
will be highly dependent on how not just the low, but the overall
pattern, unfolds. Stay tuned.

&&

.MARINE...
Issued at 300 PM EDT Thu Sep 19 2024

A nebulous pressure field across the Keys will maintain a light
and variable wind regime through tomorrow. High pressure will
gradually take hold of the southeast heading into this weekend
resulting in winds becoming a prevailing broadly easterly flow.
Uncertainty ramps up early next week due to the expected
development of a low starting out in the northwestern Caribbean
Sea. Expect east to southeasterly breezes to freshen considerably
early to mid next week. Stay tuned.

&&

.AVIATION...
(18Z TAFS)
Issued at 300 PM EDT Thu Sep 19 2024

Shower and thunderstorm activity has diminished for the time being
at both terminals leaving VFR conditions prevailing. VCSH is
reintroduced tonight as shower activity may return but confidence is
not very high and it is possible will not see any further impacts
tonight. Near surface winds will be light and mostly variable.

&&

.CLIMATE...

On this day in 1917, the daily record cold high temperature of 79F
was recorded in Key West. Temperature records for Key West date back
to 1872.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory for FLZ076.
GM...None.

&&

$$

Public/Marine/Fire...11
Aviation/Nowcasts....AP
Data Acquisition.....AP

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