Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 271323

Area Forecast Discussion
National Weather Service Miami FL
923 AM EDT Tue Jun 27 2017

A few showers were moving northward across Broward and Palm Beach
counties during the late morning hours with only light rain
associated with them. Modified KMFL sounding suggest potential
CAPE values near 4K and good microburst index values this
afternoon. Best chances for thunderstorms remain over interior
areas, but a few strong storms could affect coastal metro areas at
times. Inherited forecast package remains on track and no
significant changes are required for the morning update.


.PREV DISCUSSION... /issued 802 AM EDT Tue Jun 27 2017/

VFR prevails this morning at all sites, except MIA with a TEMPO
for periods of MVFR cigs through 14Z. Then showers and
thunderstorms could bring periods of MVFR after 18Z as sea
breezes push inland. TEMPOS may be included in the update package
for the Atlantic terminals as convection develops in the
afternoon. Winds will remain generally light with 5-10KT through
the evening hours.

PREV DISCUSSION... /issued 306 AM EDT Tue Jun 27 2017/



As of 305 AM EDT...A weak frontal boundary continues to remain
draped across north/central Florida, with broad longwave troughing
across much of the eastern third of the CONUS. A ridge of high
pressure extends southwestward from Bermuda across South Florida
helping to keep a light east/southeasterly flow in place. Earlier
overnight thunderstorms over the Gulf waters and portions of the
Gulf Coast continue to dwindle, with isolated to widely scattered
showers over the Atlantic waters and portions of the east coast.
This trend will continue through daybreak, with areas primarily
west of the Florida Turnpike trending dry, with the best chances
for showers/storms east and over the Atlantic waters.

For today, the aforementioned frontal boundary to the north will
move little, with the longwave trough and a secondary upper-level
low gradually breaking down the Bermuda ridging across the region.
This pattern will keep South Florida relatively void of any major
synoptic features and allow for local mesoscale sea breeze effects
to drive the day`s weather. With light flow in place, expect both
the Atlantic and Gulf sea breezes to fully develop and be the
primary foci for scattered showers and thunderstorms beginning in
the late morning hours and persisting through much of the afternoon.

Latest mesoscale and CAM guidance depicts two areas of convective
initiation, one across the far southern interior and the second
along the leading edge of the Gulf sea breeze. While initiation may
not necessarily occur in these areas, much of the convective
activity will be focused across the interior, with a trend towards
portions of the east coast metro with a light southwesterly steering
flow. Mid-level temps will be around normal for this time of year,
so expecting most of the activity to be general thunder, although
some storms may briefly be strong along enhanced boundary
collisions. The main threats will be frequent lightning and locally
heavy rain, with brief gusty winds also possible with the stronger

High temperatures will reach 90 for most areas, with lower to mid
90s in the interior. The summer heat will be on with heat indices
likely reaching into the lower 100s across many areas as well,
especially south.


The short term period will continue to see the frontal boundary to
the north gradually wash out with time, as upper-level energy across
the Northeast helps keep the Bermuda high suppressed and a weak flow
pattern dominated by sea breezes in place across South Florida.
Other than some minor surges in moisture through the period, the
pattern will generally remain stagnant across the immediate region,
with scattered to locally numerous showers and thunderstorms
primarily focused in interior areas during the afternoon and evening
hours. By Thursday, the Bermuda high will begin to restrengthen and
mark a transition to a more moderate easterly flow regime.

Temperatures will be near to slightly above normal with highs in the
upper 80s/near 90 along the coasts to lower and mid 90s in the
interior. Low temperatures will generally be in the 70s.


The long term period will continue to see the reestablishment of the
Bermuda high, along with a predominately summertime easterly flow
regime. This pattern will feature typical sea breeze development
during the afternoon hours, with scattered showers and thunderstorms
favored over the interior and Gulf Coast, with nighttime activity
favored over the Atlantic waters and east coast. With the Bermuda
high becoming well established, subsidence in the mid-levels will
lead to near of slightly below normal PWATs for this time of year,
helping to keep rain chances towards seasonal norms. Temperatures
will be near normal during the long term period.

Generally good boating conditions will prevail across the local
waters for the next several days with light southeasterly flow.
Local sea breezes may briefly enhance winds near the coast to 10-15
knots during the afternoon, from the southeast along the Atlantic
coast and west/southwest along the Gulf coast. Additionally, locally
erratic winds along with lightning will be possible in and around
thunderstorms which are expected to be isolated to widely scattered
in coverage. Seas will be 3 feet or less heading into the

Decaying convection should lead to -RA at Naples until 630-8z,
otherwise only isolated showers /not worthy of TAF mention/
expected through noon. Thereafter, expect scattered showers and
some thunderstorms through sunset. Risk of thunder isn`t
exceptionally high, so considered converting VCTS to VCSH at
east-coast terminals. At KAPF, where rain chances are lowest, did
maintain only VCSH for now. Dont think there will be entire 6-10
hour period of VCTS, but right now, timing uncertainties preclude
a narrower window.

Light winds /possibly drainage AOB 5 KT/ through sunrise, then
generally SE at 8-12 KT. Wind will calm again by midnight.

West Palm Beach  92  76  91  79 /  50  50  50  40
Fort Lauderdale  92  78  91  80 /  50  50  40  30
Miami            93  78  92  79 /  60  40  50  30
Naples           91  76  91  76 /  30  20  40  20



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