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FXUS62 KMFL 182016
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
416 PM EDT Mon Mar 18 2019

.DISCUSSION...

SHORT TERM (Tonight through Wednesday night)
With the cold front having stalled south of the region and the
much advertised shortwave trough remaining over the Central Gulf
today, an overcast yet dry day has ensued, with temperatures
getting a bit warmer than anticipated with the lack of rainfall.
Temperatures have peaked in the mid 70s to low 80s across the
region, despite being on the cool side of the boundary. Overall
synoptic setup remains unchanged from previous forecasts. Potent
shortwave trough and subtropical jet max will approach the region
tonight and cross South Florida on Tuesday. This alone will
provide plenty of isentropic lift to support widespread moderate
showers across the region from late tonight through Tuesday
afternoon. Some heavy rain is possible with the aforementioned
features, but the most likely culprits for heavy rain will likely
come from two additional features. The first of these features
will be mesoscale in nature, thus there is inherent uncertainty in
timing and location of the heavy rain potential. Coastal
convergence may set up overnight in the vicinity of the the
Atlantic coast, as marine flow turns more northeasterly and
enhances, while land flow continues with a cool advection/north-
northwest regime. With PWATs approaching 2 inches, this zone of
convergence could support locally quite heavy rainfall, and
various models have 4-6 inch bullseyes of precipitation forecast
overnight along the east coast, or adjacent waters. This should
mainly occur after 6z, and if this zone sets up over the waters,
significant rainfall could remain over the Atlantic and not impact
the region. Still, WPC has highlight the east coast urban areas in
a Marginal Risk for excessive rainfall/flooding. Mesoscale trends
will be closely monitored overnight.

The second feature that could lead to heavy rainfall is the
surface low that is expected to form along the nearly stationary
boundary over the Keys in response to the shortwave trough. The
low track is forecast to remain south of the region, but if it
comes close enough, more widespread heavier showers may impact
southeastern parts of the area. This possible scenario could lead
to a few elevated thunderstorms as well.

Regardless of whether or not either heavy rain scenario holds
true, the widespread isentropic lift induced rainfall should
produce 1 to 3 inches across the region by Tuesday night.
Temperatures Tuesday will be cool due to the widespread rainfall,
with some areas likely not reaching 70 degrees. Upper level
support and moisture scour away on Wednesday, but low-level
moisture and northeast flow will prevail, potentially keeping
scattered to numerous showers ongoing along the Atlantic coast.
Temperatures will rebound somewhat, but still be a bit below
normal for Wednesday and Wednesday night. Maxima will mainly be in
the 70s with minima in the 50s interior, low to mid 60s across the
east coast urban areas.

LONG TERM (Thursday through Sunday)
Rain chances decrease on Thursday and for the remainder of the
forecast period as a another weak, dry frontal passage helps to
clear out the deeper moisture well to our south. Rainfall will
remain mostly along the Atlantic and east coast until the front
clears. Thereafter, high pressure returns, allowing cooler and
drier air to filter in across the peninsula.
&&

.MARINE...
Hazardous boating conditions are developing this afternoon across
Gulf and Atlantic waters, as northerly wind will increase to 20 to
30 knots overnight and remain at similar speeds Tuesday and
Tuesday night (while veering northeasterly). Seas in Gulf waters
will build to 6 to 8 feet, with Atlantic seas increasing to 8 to
10 feet, higher in the Gulf Stream. A Small Craft Advisory is in
effect for Gulf waters into Tuesday night and for Atlantic waters
through Wednesday, as high seas may continue in the Atlantic
through at least Wednesday. Widespread rain is expected into
Tuesday night, with isolated thunderstorms along with waterspouts
possible in Atlantic waters during this time.

&&

.AVIATION...
Scattered showers will become more numerous tonight into Tuesday
morning. Ceilings will favor MVFR through much of the TAF period,
with IFR possible, especially late tonight into Tuesday morning.
N-NNW winds early this afternoon should transition towards NNE-NE
over the next few hours, and prevail in that direction into this
evening. Speeds will increase overnight, with gusts up to 25 kt
possible on Tuesday. Ceilings should gradually improve to MVFR/VFR
late tomorrow afternoon into tomorrow evening.

&&

.BEACH FORECAST...

Due to forecast northeast wind of 20 to 30 mph, there is a High
Risk of Rip Currents on Atlantic beaches for Tuesday and Tuesday
night. This high risk will likely continue through at least
Thursday.

&&

.HYDROLOGY...
Widespread rainfall amounts from late tonight through Tuesday
night should average 1 to 2 inches across South Florida, with 2 to
4 inches likely across the east coast metropolitan areas. Amounts
of this magnitude spread over 6 or more hours should not cause
significant flooding issues beyond urban/street ponding, as
antecedent conditions are quite dry. However, localized much
higher amounts are possible, especially near the Atlantic coast,
are possible, and these amounts, if they occur within a few hours,
may cause flooding. WPC has placed the east coast urban areas in
a marginal risk of excessive rainfall/flooding for tonight and
Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 65 70 63 77 / 80 90 60 40
Fort Lauderdale 64 71 65 78 / 80 90 60 40
Miami 65 72 65 79 / 70 80 60 40
Naples 61 70 60 79 / 80 80 50 10

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk from Tuesday morning through Wednesday
morning for FLZ168-172-173.

AM...Small Craft Advisory until 8 PM EDT Wednesday for AMZ650-651-670-
671.

GM...Small Craft Advisory until 2 AM EDT Wednesday for GMZ656-657-676.

&&

DISCUSSION...23/SBK
MARINE...23/SBK
AVIATION...34/SPM
BEACH FORECAST...23/SBK
HYDROLOGY...23/SBK
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