Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 260007 AAA

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
807 PM EDT Tue Jul 25 2017

.AVIATION...The winds will remain light and variable tonight over
all of the taf sites before swinging to an easterly direction
around 10 knots on Tuesday. The only exception is at KAPF taf site
where the winds will be from the westerly direction after 18Z
Tuesday. The weather will remain dry over the east coast taf sites
tonight into Tuesday, as the shower and thunderstorm activity
will be over the interior and west coast metro areas on Tuesday.
Therefore, VCTS will be in place after 18Z Tuesday for KAPF taf
site. The ceiling and vis will also remain in the VFR conditions
through Tuesday for all of the taf sites.


.UPDATE...Active afternoon across South Florida with numerous
boundary collisions, including the collision of the seabreezes
across the interior. After a few strong storms, the majority of
activity has diminished, leaving on a few storms across Collier
and Hendry counties. Based on radar trends, have trended pops
downward this evening, keeping only isolated chances across the
interior where a few more boundary collisions have yet to play
out. Most activity will end in the next few hours leaving
generally dry conditions overnight. A few Atlantic showers may
brush the east coast overnight.


.PREV DISCUSSION... /issued 402 PM EDT Tue Jul 25 2017/

THIS AFTERNOON AND TONIGHT: Strong ridge remains stretched across
the FL peninsula this afternoon, with it`s axis just to the north of
the region. Morning sounding had 500mb heights above normal around
595dm, and temperatures have responded topping out a few degrees
above normal in the low-mid 90s. This in combination with dewpoints
still in the 70s has led to heat indices of 100-105F across most of
South Florida, with inland Collier and Miami-Dade County climbing
into the 105-110F range. A Heat Advisory remains in effect for these
areas until 6pm this evening.

With light winds, both seabreezes have been able to develop and are
moving slowly inland this afternoon with active convection along
both. With a little more moisture and steeper lapse rates, coverage
is already higher than yesterday and expect this trend to continue
through this afternoon and evening hours. The best coverage will
shift into the interior over the next few hours with the seabreeze
collision later today. A few strong storms will be possible, mainly
with any boundary collisions.

Showers and storms will wane after sunset with generally dry
conditions overnight beyond the occasional Atlantic shower.

WEDNESDAY AND THURSDAY: There will be a slow erosion of the mid
level western Atlantic ridge through mid week as troughing across
the Deep South-Gulf Coast swings a little more east. Diffuse low
level ridge axis will also extended across the Florida peninsula at
around Lake Okeechobee. These features will keep steering flow
relatively light, allowing both seabreezes to develop and move
inland during the afternoon hours.

Another Saharan Airmass is expected to push through the Caribbean
during this timeframe, though models show the bulk of the dust
remaining to our south. However, we will likely see a reinforcement
of the current dry mid level airmass in place across the area.
Overall rain chances will be a little lower, though still expect
scattered showers and storms, becoming locally numerous over the
interior, as the lift with the seabreezes will overcome quite a bit
of convective inhibition.

High temperatures both days will remain above normal, with highs
expected to be in the low 90s along the immediate coasts, and mid-
upper 90s for the metro areas and interior South Florida. With
dewpoints near climo in the mid-upper 70s, heat indices both days
will climb back into the 100-110 range. Another heat advisory looks
likely for Wednesday for at least a portion of South Florida, and
potentially on Thursday as well.

FRIDAY INTO NEXT WEEK: Upper level shortwave sliding through the
Great Lakes on Friday will help deepen the east coast trough,
further suppressing the western Atlantic ridge off to the south and
east. Both the GFS and ECMWF show the trough digging as far south as
the FL peninsula this weekend, potentially driving an unseasonably
robust surface front into the state early next week. Significantly
deeper mid-level moisture doesn`t arrive until the trough digs down
early next week. However, expect to see a steady uptick in shower
and thunderstorm chances through the extended as increasing south-
southwesterly flow taps into deeper low level moisture. The change
in wind flow will also limit the inland penetration of the east
coast seabreeze, with storm chances expected to be a little more
uniform across South Florida.

MARINE...Ridge axis extending across the Florida peninsula will
keep prevailing winds southeasterly around 10 knots into Thursday,
veering more southerly late week and southwesterly by late this
weekend. Overall speeds will remain light enough for both the Gulf
and Atlantic seabreezes to develop each afternoon, with locally
higher speeds behind the seabreezes.

Afternoon showers and storms will generally remain over the
interior, with more isolated activity over the open waters during
the nights and morning. Coverage of showers and storms expected to
increase as we head into the weekend.


West Palm Beach  80  92  79  90 /  10  20  20  10
Fort Lauderdale  81  91  81  90 /  10  20  20  20
Miami            80  91  80  90 /  10  20  20  20
Naples           78  91  78  90 /  10  40  30  20



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