Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 160754

Area Forecast Discussion
National Weather Service Miami FL
354 AM EDT Tue Jul 16 2019

Short term (Today through Thursday): subtropical high pressure
extending from the western Atlantic across Florida and into the
eastern Gulf of Mexico will be the main synoptic weather feature
over our region this week. Small, low-amplitude features embedded in
the deep E/SE wind flow will play the primary role in coverage of
showers and thunderstorms through Thursday.

Today: one of these small features is a low level trough which is
moving through South Florida early this morning, which is combining
with a pocket of higher moisture to produce scattered showers and a
few thunderstorms from the near-shore Atlantic waters to across
metro Miami-Dade and Broward counties. This feature will translate
west today and help to spread the morning precipitation into Palm
Beach County (as well as the rest of SE Florida) after daybreak,
then gradually transition to the interior and Gulf coast by
afternoon and continue into the early evening hours. The mean low
level wind will be SE today compared to the E wind flow of the past
couple of days, which will lead to higher coverage of showers and
thunderstorms over the Lake Okeechobee area as well as over
western sections of Glades and Hendry counties in the area of
maximized low level convergence between the west coast seabreeze
and the prevailing SE flow. Mid- level lapse rates are expected to
be in the 6.5 C/km range this afternoon, which should support a
few stronger storms with gusty winds and frequent lightning.

The SE wind today should allow the west coast seabreeze to move
inland a little earlier than past days. This along with a bit more
cloudiness and precip should cut high temperatures down a couple of
degrees from yesterday, but still leaning on the higher end of the
model guidance with lower to mid 90s most locations. Heat index
values will once again be in the 100-105 range most areas, and as
high as 107 over portions of Collier County.

Tonight and Wednesday: as the low level trough moves west of the
area, moisture levels decrease slightly so do not expect as much
night/morning showers and thunderstorms along the east coast as this
morning, with models showing a possible focus in Palm Beach County
which makes sense based on the SE wind flow which typically favors
that area for nocturnal and early day precipitation. The slightly
lower moisture levels should reduce the coverage of afternoon and
evening storms over the interior and Gulf coast, but scattered
storms, a few strong, can still be expected. Warm and muggy
nighttime conditions will continue and lows will likely stay at or
above 80F over the east coast metro, with highs again reaching the
lower to mid 90s on Wednesday and heat index values in the 100-105
range once again.

Wednesday Night and Thursday: another low-amplitude trough, this one
extending into the mid-levels/500 mb, is forecast by the global
models to move west across the Florida peninsula on the southern
side of the subtropical high pressure area, possibly enhancing
nighttime and morning showers and a few thunderstorms over the
east coast metro areas, and eventually interior and Gulf coast
areas by Thursday afternoon. Little change in temperatures,
perhaps a degree or two cooler, due to the slight increase in
clouds and precip.

Long Term (Thursday Night through the upcoming weekend): global
models point towards a strengthening mid/upper level high pressure
area covering most of the eastern half of the U.S., with a general
E/SE wind flow continuing across South Florida and little change in
the diurnal precipitation pattern (night/morning east coast metro
and afternoon/evening interior and Gulf coast). Little corresponding
change in temperatures which are forecast to be near to slightly
above seasonal norms.


Thunderstorms will be the main marine hazard over the next several
days as wind and seas stay well below cautionary thresholds. The
Gulf of Mexico waters will have the greatest threat of periods of
thunderstorms with gusty winds and locally rough seas, and the
Atlantic waters will have a higher chance of storms Wednesday
night and early Thursday.


Onshore wind at 10-12 knots will lead to a slight risk of rip
currents at the Atlantic beaches for most of the week.


West Palm Beach  91  80  91  80 /  20  30  20  20
Fort Lauderdale  89  81  89  81 /  20  10  20  20
Miami            92  81  91  80 /  10  10  20  20
Naples           93  77  93  77 /  60  30  40  20



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