Royal Plm Beach, Florida Weather Forecast Discussion

658
FXUS62 KMFL 171105
AFDMFL
Area Forecast Discussion
National Weather Service Miami FL
705 AM EDT Wed Sep 17 2025
...New AVIATION...
.SHORT TERM...
(Today through Thursday)
Issued at 1258 AM EDT Wed Sep 17 2025
The dawn of a more active pattern begins across South Florida as the
combination of deep layer moisture, a transient mid-level vort max,
and the strengthening of a nearby upper level jet-streak set the
stage for enhanced showers and thunderstorm activity across South
Florida today and tonight. 05z Mesoanalysis highlights this well as
precipitable water values continues to trend up on ACARS (aircraft
data) from our local SoFlo airports with KAMX and KBYX radars
picking up an increasing amount of activity over the nearshore
waters. However before we take a deep dive into all of the
ingredients and impacts, it`s important to mention that there still
remains some uncertainty on exactly how today will play out.
Overnight mesoscale models indicate that convection will continue to
fire up over the Florida Keys and our nearshore waters over the next
several hours with a large amount of upper level cloud cover being
lofted northwards into South Florida via the sub-tropical jet-
stream. At the same time, forecast model soundings still show some
residual dry air aloft during the morning hours of today. This may
result in an initial delay in widespread heaviest rain occurring
across South Florida, with an onset of the heaviest rainfall during
the second half of the day continuing into tonight. However even
with abundant cloud cover aloft, diurnal heating should result in
the eventual beginning of widespread land-based shower and storm
activity during the afternoon hours. Outside of the heavy rainfall
threat we will discuss in great detail below, storms today could
also produce gusty winds and excessive lightning. Now let`s get back
to the deep dive on today`s setup and then segway into what may
transpire on Thursday.
The cut-off low that has remained stationary across the southeastern
United States will begin a slow acceleration to the northeast today,
with the development and strengthening of an upper level jet streak
across the Gulf, north and central Florida, and the western Atlantic
waters. Our placement in the right entrance region of this jet
streak will facilitate divergence aloft and low level convergence at
the surface. However that is just one piece of the bigger picture as
a lobe of mid-level vorticity (vort max) lifts northward from the
Caribbean later today. However, our most important ingredient will
be the continued progression of deeper layer moisture into the
region associated with a frontal boundary making a return to the
region. Forecast precipitable water values increase to the 2.1 to
2.3 range today (which is now over the 90th percentile for the
date). The combination of aided ascent, deep layer moisture, and a
stalled frontal boundary will set the stage for a more active
pattern both during the day and overnight. A saturated atmosphere
brings an increased threat of heavy rainfall that could result in
accumulations adding up over a short period of time. Although there
still remains uncertainty on exact onset timing as well as where the
greatest rainfall totals will fall today (just offshore or directly
over the east coast metro), the atmosphere is definitely primed for
bursts of heavy rainfall in a very short time. The Weather
Prediction Center (WPC) has maintained a Marginal Risk (level 1 of
4) of excessive flooding for the east coast metro of South Florida
today. This means that there is a 5-15% chance of excessive rainfall
that may lead to flash flooding within a 25 mile radius of a
location. High temperatures will trend lower lower today due to
abundant cloud cover and the cooling influences of showers and
storms, forecasted highs area-wide will be in the middle to upper 80s.
With the background environment increasingly conducive for heavy
rainfall, the main driving force behind rainfall accumulations will
continue to be the coverage and storm motion of showers and storms
across the region Wednesday night into Thursday. Overnight model
guidance continues to hone in on this time period being the day with
the greatest potential of seeing higher end QPF values as the
aforementioned jet-streak nearby and the stalled boundary directly
overhead act to provide favorable conditions for numerous showers
and storms. The deterministic GFS and Euro continue to hint at a
lobe of mid-level vorticity pivoting across South Florida late
today into Thursday with forecasted precipitable water values
potentially increasing to the 2.2 to 2.4 range which would be very
close to the daily max value for the date. Forecast model
soundings during this time frame continue to depict a classic
skinny CAPE profile that points to the potential of efficient
rainfall rates that could lead to localized flooding concerns over
urban metro areas. Coastal convergence along the coast may
maximize rainfall totals along a corridor confined to the
immediate east coast overnight. The Weather Prediction Center also
maintains a marginal risk of excessive rainfall for the east
coast of South Florida on Thursday. With the abundance of
convective activity and resultant cloud debris, high temperatures
may be held in check once again on Thursday with forecast highs in
the mid to upper 80s.
&&
.LONG TERM...
(Thursday night through Tuesday)
Issued at 1258 AM EDT Wed Sep 17 2025
As the mid-level vort max and deepest atmospheric moisture pivot
northeast away from South Florida in tandem with the departing cut-
off low, residual moisture is forecast to remain draped across the
eastern half of our region on Friday. While precipitable water
values will begin to trend down, enough moisture will remain to
support the potential of scattered to numerous afternoon showers and
storms across the region. The Weather Prediction Center maintains a
Marginal Risk (level 1 of 4) of excessive rainfall for the east
coast metro of South Florida on Friday. With cloud cover lessening
across the region, high temperatures will trend back to
climatological norms, with forecasted high temps in the upper 80s to
low 90s.
Models have come into better agreement showing surface cyclogenesis
occurring in the western Atlantic waters along the stalled frontal
boundary during the day on Saturday. Cyclonic flow around this
developing feature may result in the potential of drier air moving
southward across the peninsula which may limit rain chances during
the weekend as opposed to the mid to late work week. Uncertainty
remains regarding this solution however, and forecast rainfall
chances on Saturday and Sunday currently remain near climatological
norms in the 50-60% range. The lessening of mid-level flow aloft
will once again result in sea-breeze circulations remaining the main
foci of diurnal convection each afternoon and evening which will
likely focus the greatest convective chances across interior areas
each afternoon during the weekend. High temperatures over the
weekend will remain near climatological norms in the upper 80s to
low 90s.
After persistent troughing across the region for what has felt like
weeks, model guidance hints of the potential of brief mid-level
ridging occurring during the early portion of next week. If this
indeed pans out, this could result in lower rain chances across
South Florida coupled with high temperatures slightly above
climatological norms.
&&
.AVIATION...
(12Z TAFS)
Issued at 703 AM EDT Wed Sep 17 2025
ENE winds 5-10 kts today with Scattered to broken MVFR ceilings
prevailing. Scattered thunderstorms increasing in coverage this
afternoon into early evening which may result in brief flight
restrictions and erratic winds.
&&
.MARINE...
Issued at 1258 AM EDT Wed Sep 17 2025
A moderate east-northeasterly breeze will enhance later today and
continue into the late week period. Seas across the Atlantic
waters will generally remain between 2 to 5 feet through Thursday
morning while seas across the Gulf waters remain at 1 to 2 feet.
Periods of rough seas and gusty winds will be possible each day
near the most robust shower and thunderstorm activity.
&&
.BEACHES...
Issued at 1258 AM EDT Wed Sep 17 2025
A high risk of rip currents will continue along the Palm Beach County
beaches today as onshore flow enhances this afternoon and a
northeasterly swell in the Atlantic waters lingers. A moderate
risk of rip currents will continue at Broward and Miami-Dade
County beaches. As east-northeasterly winds continue through late
this week, the elevated risk of rip currents is forecast to remain
along the east coast.
&&
.HYDROLOGY...
Issued at 1258 AM EDT Wed Sep 17 2025
The Weather Prediction Center`s latest 5 Day Quantitative
Precipitation Forecast (QPF) has trended slightly lower in overall
rainfall totals over the last 24 hours. Widespread amounts of 1-3
inches are now forecast for the immediate east coast of South
Florida through Sunday night. However, an important point to make
is that these forecasted values are indeed widespread values.
Similar to the pattern last week, sharp rainfall gradients may
materialize with problematic pockets of higher rainfall totals
resulting in the potential of localized urban flooding along the
east coast metro. While the overall forecasted rainfall totals may
continue to shift over the next several days, the main takeaway
is that saturated soils over the east coast could result in a
heightened urban flood threat across the east coast metro
particularly today through Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Miami            86  76  85  77 /  80  80  80  50
West Kendall     86  75  86  75 /  80  70  80  50
Opa-Locka        87  76  87  76 /  80  70  80  50
Homestead        86  75  85  75 /  80  80  80  50
Fort Lauderdale  86  76  85  76 /  80  80  80  50
N Ft Lauderdale  86  76  85  77 /  80  70  80  50
Pembroke Pines   88  76  88  76 /  80  70  80  50
West Palm Beach  85  75  85  75 /  70  70  70  50
Boca Raton       87  75  87  75 /  70  70  80  50
Naples           87  75  90  74 /  70  50  70  30
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Thursday evening for FLZ168.
AM...None.
GM...None.
&&
$$
SHORT TERM...Hadi
LONG TERM....Hadi
AVIATION...CMF

NWS MFL Office Area Forecast Discussion