726
FXUS62 KKEY 070829
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
429 AM EDT Sun Jul 7 2024

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

.DISCUSSION...
Issued at 429 AM EDT Sun Jul 7 2024

Relict island cloud lines activated around midnight along parts
of the Upper Keys and just north of the Lower Keys, but that
activity was pushed WNW into the Bay and Gulf waters by
developing weak ESE low level flow, and radars currently detect
only isolated showers dotting the region. Temperatures along the
island chain are hovering in the mid 80s, with dewpoints in the
mid to upper 70s, and winds on land generally from the east to
southeast at 5 to 10 mph. Surface analysis depicts a weak pressure
gradient across our area, between high pressure over the western
Atlantic, a tropical wave over the western Caribbean Sea, and
Tropical Storm Beryl over the western Gulf of Mexico. Aloft, mid
level ridging prevails over Florida, between Beryl to the west and
a well-defined Tropical Upper Tropospheric Trough (TUTT) cell
northeast of the Bahamas. The 00Z Key West sounding measured PW of
2.20 inches (over the 90th percentile for the date). More recent
GOES-TPW satellite imagery shows a slightly drier airmass, with
estimated PWs between 1.8 and 1.9 inches, moving across the
Florida Straits toward the Keys.

For today, there are conflicting signals as to rain chances, with
the slightly drier airmass expected for at least this morning,
along with the current weak ESE low level flow, appearing not
especially favorable for rainfall. The CAM guidance is also
rather dry through much of the day. On the other hand, we do
expect a surge of moisture along with increasing SSE flow later in
the day as the tropical wave over the western Caribbean passes to
our south, and the MOS/NBM guidance has fairly high rain chances.
Have opted to maintain the existing 40 percent PoPs for today.
The best rain chances may occur from later in the afternoon
through the evening hours when the deepest moisture along the
northern edge of the tropical wave passes through our area.
Otherwise, expect typical summertime temps and dewpoints for
today, with highs near 90 at most locations.

Monday through Tuesday, a much drier airmass associated with a
Saharan Air Layer (SAL) moves across the Keys, with PWs plummeting
to below 1.5 inches. Rain chances will be minimal during this
time, with the main concern being heat as high temps climb into
the lower 90s. Heat advisories may be needed both days.

By Wednesday, the TUTT cell currently located northeast of
the Bahamas is forecast to be centered nearby, although not as
well-defined as it is currently. With ample moisture returning to
our area behind the departing SAL, have maintained above climo 40
percent PoPs. Thereafter, we should remain in a typical midsummer
pattern, with gentle easterly flow pattern to the south of the
Atlantic ridge. Daily rain chances will be modulated by subtle
changes in moisture, stability and steering flow, along with any
passing weak tropical waves. For now, have maintained 30 percent
PoPs, which is slightly above climo, but slightly below the MOS
consensus. Temps will remain near normal, with highs around 90,
and lows in the lower to mid 80s outside of any brief downpours.

&&

.MARINE...
Issued at 429 AM EDT Sun Jul 7 2024

After remaining light and variable through much of the night, 4 AM
obs show the expected SE breezes of of 5 to 10 knots kicking in
along the reef and at Long Key C-MAN. No marine headlines are
currently in effect, and none are expected through the next
several days. From the synopsis, gentle southeast to south
breezes will continue across the Keys coastal waters through
Monday, between high pressure over the western Atlantic and
Tropical Storm Beryl over the western Gulf of Mexico. High
pressure will build westward across the Florida peninsula and into
the Gulf beginning Tuesday, bringing gentle to occasionally
moderate easterly breezes to the Keys waters.

&&

.AVIATION...
(06Z TAFS)
Issued at 429 AM EDT Sun Jul 7 2024

VFR conditions will prevail through the TAF period at both EYW and
MTH with southeasterly near-surface winds of 5 to 10 knots. There is
a possibility of scattered showers and isolated thunderstorms later
today, but confidence is low with respect to timing, so opting to
keep VCSH out of the TAFs for now.

&&

.CLIMATE...
On this day in 2023, both the daily record warm low temperature of
84F and the daily record high temperature of 96F were recorded in
Marathon. Temperature records for Marathon date back to 1950.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&

$$

Public/Marine/Fire...Jacobson
Aviation/Nowcasts....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