Area Forecast Discussion
Issued by NWS Key West, FL

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FXUS62 KKEY 191043
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
643 AM EDT Tue Mar 19 2024

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

.UPDATE...
Issued at 643 AM EDT Tue Mar 19 2024

Northerly peak wind gusts of 35 to 40 knots have been observed in
and around the Lower Keys during the past hour. This is likely
due to a combination of strong northerly flow behind the cold
front and the departing convection over the Straits. These strong
winds will likely last only a couple of hours through mid morning,
but have issued a Wind Advisory for the Lower Keys through 9 AM.
The marine forecast has also been updated to increase winds for
this morning as per the updated marine section below. The
remainder of the discussion is unchanged from the 450 AM issuance.

&&

.DISCUSSION...
Issued at 450 AM EDT Tue Mar 19 2024

We`re off to a surprisingly wet and thundery start this Tuesday
morning across the Florida Keys. Yesterday evening, a broken line
of Cuban thunderstorms meandered into the Straits of Florida
towards the island chain. While most convection dissipated before
reaching land, a lone shower swept through the western Lower Keys
before falling apart. After midnight, northwesterly breezes
started to filter over the island chain and promoted moisture
convergence fueling convective development as originally forecast.
However, instead of being confined to the Straits, showers and
thunderstorms erupted along the Lower and Middle Keys breaking
through the dry air in the middle layers sampled from yesterday
evening`s sounding. In fact, this line developed so quickly that
it`s reminiscent of a cloud line on a summer day. Temperatures
across the island chain have fallen into the lower to mid 70s in
response to the rainfall. Wind observations along the Reef are
generally contaminated by storm outflow, but show a trend of
veering breezes to the northwest as a cold front approaches from
the Gulf.

The cold front on our doorstep will sweep through our area this
morning. Northerly breezes along the island chain, as well as a
southerly shift of the convergence boundary already hint at this
motion. By sunrise, most of the convection will have shifted off
land into the Straits, but another round is pushing through from
the Gulf waters. This line does not look nearly as robust as this
morning`s activity with CAMs generally suggesting it will fall
apart before arriving to the island chain. That being said, slight
chance PoPs are held for the rest of today as the air mass
transitions from moist to dry. Fresh to strong northerly breezes
are imminent across our waters and are expected to persist into
this afternoon before continuing to shift to the northeast and
gradually slackening through tonight.

Cooler and drier weather will follow into the end of the week when
a period of unsettled weather is expected. A trough sliding
through the Great Plains towards the Gulf coast will parent a
surface low in the Gulf of Mexico sometime Thursday evening. As
this low approaches Florida, breezes will freshen out of the east
to southeast Thursday night into Friday over our CWA. While the
exact position of the low will be the final determining factor for
intensity, Small Craft Advisories may be required for this time
period. The low will also pull in a large amount of moisture
resulting in enhanced PoPs from Thursday night through Saturday.
Guidance continues to favor Friday for the highest chances but due
to this event being still a few days away with the major feature
yet to develop will hold at 60% for now. Another round of drier
and cooler weather will be on tap after Saturday night as the low
is expected to drive another cold front through the area for the
start of next week.

&&

.MARINE...
Issued at 643 AM EDT Tue Mar 19 2024

The marine forecast has been updated to increase winds for this
morning. A Small Craft Advisory is in effect for all Florida Keys
coastal waters. From the synopsis, strong northerly breezes this
morning in the wake of a cold front will become northeast and
slacken this afternoon. Breezes will turn easterly and diminish
tonight through Wednesday. Unsettled weather at the end of the
week will result in fresh to strong breezes Thursday night and
Friday, followed by breezes shifting to the southwest then
northwest at the tail-end of the unsettled weather.


&&

.AVIATION...
(06Z TAFS)
Issued at 450 AM EDT Tue Mar 19 2024

Showers and thunderstorms will shift south of the EYW and MTH
terminals before sunrise as a cold front moves through the area, but
periods of MVFR ceilings will remain possible through the morning
hours. VFR conditions should return this afternoon. Gusty north
winds of 12 to 15 knots with frequent gusts over 20 knots will
prevail through midday, then winds will shift to the NE and decrease
to around 10 knots during the afternoon.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory until 9 AM EDT this morning for FLZ078.

GM...Small Craft Advisory until 11 AM EDT this morning for GMZ031>035-
     042>044-052>055-072>075.

&&

$$

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


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