883
FXUS62 KKEY 250820
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
420 AM EDT Tue Jun 25 2024

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

.DISCUSSION...
Issued at 420 AM EDT Tue Jun 25 2024

After several hours with no shower activity across the area,
widely scattered showers have recently developed around the Upper
Keys. Temperatures along the island chain are mostly in the upper
70s to lower 80s, with dewpoints in the mid 70s, and winds on
land light/variable or from the SSW at 5 mph or less. Surface
analysis indicates that the Atlantic ridge axis has settled
southward into the Straits during the night, with a front
extending from the western Atlantic into the Southeastern states.
Aloft, the weak mid/upper trough which has lingered near Florida
for the past few days has shifted eastward into the Bahamas, with
satellite imagery showing the associated cloudiness and convection
extending from the Bahamas eastward across the Atlantic for
several hundred miles. Some mid-level weakness still lingers
across our region, to the south and southwest of a mid latitude
trough moving offshore from the Eastern Seaboard. A very moist
airmass remains in place across the Keys, as shown by the 00Z Key
West sounding which measured PW of 2.35 inches. Recent MIMIC-TPW
satellite imagery shows the Keys remaining embedded within a large
area of 2+ inch PWs extending from the Caribbean and Greater
Antilles WNW through the southern and central Gulf of Mexico.

Weak WSW low level flow, ample moisture in place, and the lack of
a dominant ridge aloft all should favor island cloud line
development during the day, with above average potential for
waterspouts. Accordingly, have maintained somewhat above climo 40
percent PoPs. Outside of cloud line activity, we generally expect
less convective coverage compared to the past few days. Also have
reduced thunder to slight chance, as there has been very little
lightning activity across our area during the past 36 hours or so.
Otherwise, expect high temps to reach the upper 80s to near 90,
with sticky dewpoints in the mid 70s and light breezes making for
a typically oppressive June day.

The ridge axis will remain just to our south through Thursday,
with continued weak WSW flow favoring daytime island cloud lines.
Some mid level dry air is forecast to move into our area on
Thursday, thus nudge PoPs down from 40 percent on Wednesday to 30
percent on Thursday. Nighttime typically sees less activity in
this pattern, although there is always the potential for late
night reactivation of lingering old cloud line boundaries.

Late this week and into the weekend, the subtropical low level
ridge should shift back northward, allowing for more typical
midsummer gentle ESE surface flow to resume. The latest
operational GFS as well as the GEFS ensemble guidance show a mid
level trough developing over Florida during this time, which
combined with ample moisture may encourage somewhat above climo
PoPs. Convection will be possible anytime but perhaps favoring
the night and morning hours in the expected easterly flow
pattern. Have nudged PoPs up to 40 percent from Friday through
Monday.

&&

.MARINE...
Issued at 420 AM EDT Tue Jun 25 2024

Limited overnight observations show S/SW breezes around 5 knots
off the Upper Keys, with light/variable flow likely prevailing
around the Lower Keys, and seas at Satan Shoal running below 1
foot. Conditions will be favorable for cloud lines and waterspouts
across the nearshore waters around the Keys island chain today.
From the synopsis, a weak ridge axis will extend westward from the
western Atlantic across the Straits of Florida today through
Thursday evening, with light to gentle southwest to west breezes
prevailing over the Keys waters. Breezes may become variable at
times during this period. The ridge will shift back northward late
this week into the weekend, allowing gentle east to southeast
breezes to resume.

&&

.AVIATION...
(06Z TAFS)
Issued at 420 AM EDT Tue Jun 25 2024

VFR conditions will prevail for the upcoming TAF period. Near-
surface winds will become persistent southwesterlies by sunrise,
between 4 to 8 knots, which means cloud lines are possible during
the day. VCSH was added to the TAF with slightly lower ceilings to
account for potential nearby showers and associated possible sub-VFR
conditions.

&&

.CLIMATE...
On this day in 1976, a record rainfall of 1.67" was measured in
Key West. Rainfall records for Key West date back to 1873.

&&

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

$$

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

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