Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 191547
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
1047 AM EST Sun Nov 19 2017

.UPDATE...
No significant changes to the forecast with this late morning
update. A cold front continues to approach South Florida. Its
current position is over Central Florida. However, models continue
to indicate it will be mainly a dry passage, with a few showers
possible along the coast. For the rest of the of day, mainly clear
skies through early afternoon. As the cold front approaches,
cloud cover will begin to increase from north to south.

&&

.PREV DISCUSSION... /issued 629 AM EST Sun Nov 19 2017/

AVIATION...
Quiet weather once again across the area, keeping VFR conditions
in the forecast for all sites through the period. However, a weak
cold front will move across the area tonight, causing mainly a
wind shift to the northwest, and a bump up in speed to around 10
kts. There may be a few offshore showers, of which some may come
close to being onshore at times tonight and tomorrow. However, the
uncertainty is too low at this time to include in the TAFs.

PREV DISCUSSION... /issued 354 AM EST Sun Nov 19 2017/

DISCUSSION...

SHORT TERM (Today through Tuesday)
Quiet weather has prevailed overnight, with clear skies and nearly
calm/light drainage flow creating conditions favorable for some
patchy fog to form before sunrise. Temperatures are seasonably
mild, with 50s interior and 60s elsewhere. High pressure will
slide to the south and east today, allowing westerly winds to
develop. Low relative humidity values will persist, and
temperatures should rise a few degrees warmer in most locations,
reach low 80s most areas. A weak cold front will cross the region
tonight, bringing on slightly cooler temperatures, and rain
chances confined to marine areas as well as east coast, due to
lack of moisture. Better rain chances will develop Monday, as the
front stalls over the Florida Straits and northeast winds bring
increasing moisture from the Atlantic to the east coast. Flow
aloft will transition southwesterly as an upper-level shortwave
trough behinds to deepen over the northern Gulf of Mexico
beginning Monday night. Rain chances will continue to increase,
and spread from only the east coast Monday and Monday night to the
entire region Tuesday. Models aren`t in great agreement as to how
numerous showers and possibly thunderstorms will be Tuesday, but
as deeper layer moisture surges north, the front to the south
begins to lift north, and upper-level diffluence to the east of
the upper-level trough, POPs have been raised Tuesday. At the
point, cloud-to-ground lightning looks to be primary hazard from
any thunderstorms Tuesday. Temperatures will take a quite tiny
version of a roller coaster in the short term, with slightly
cooler temperatures tonight and Monday (minima 60s with 50s
northwest, maxima in upper 70s) followed by warmer temperatures
Monday night and Tuesday (60s/low 70s to low 80s).

LONG TERM (Tuesday night through Saturday)
At least with 0z global model runs, solutions have come in better
alignment for progression of shortwave trough over northern Gulf
and subsequent low pressure/cold front impacts on South Florida.
Will wait for temporal consistency to develop before much increase
in confidence occurs, however. As it appears now, the H5 trough
will continue to deepen Wednesday and potentially close off as it
approaches north Florida on Thanksgiving Day. At the surface, the
remnant boundary/front will move north into northern Florida by
Wednesday, taking the best support for convection with it. It will
leave our region in a warm and humid airmass, so some scattered
showers are possible, but coverage will likely be less than
Tuesday, and with little focus for convection. As the upper level
feature crosses to the north, a surface trough will move through
South Florida on Thanksgiving Day, likely bringing showers and at
least a few thunderstorms. Behind the surface trough, the upper-
level trough axis will remain to the west, perhaps keeping some
showers in the region Friday, before drier air filters in
Saturday. Although latest ECMWF calls for faster departure of the
system and subsequent arrival of dry air, neither it nor GFS
suggest significant cooler air in its wake. Thus, even behind the
system, expect highs to remain in upper 70s to low 80s, with lows
in the mid to upper 50s interior, 60s both coasts and urban areas.

MARINE...
A cold front will cross the region tonight, bringing gusty north
winds and increasing seas. Therefore, a Small Craft Advisory has
been issued for outer Gulf waters from 2z-16z Monday and one is
warranted for Atlantic waters, excluding Biscayne Bay, from 4z-0z
Tuesday. Hazardous marine conditions may persist on Atlantic
waters Monday night. A few showers may accompany the front, but
rain chances will steadily increase behind it, especially on
Atlantic waters, into Tuesday, with thunderstorms are possible.
Winds Monday and Tuesday will be northeast to east. Another cold
front and enhanced chance for showers and thunderstorms is
forecast Thanksgiving.

BEACH FORECAST...
A cold front will pass through tonight, and winds behind it will
turn northeast to east early this week, and be breezy. This
onshore flow will increase the risk for rip currents on Atlantic
beaches.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  84  65  78  72 /   0  20  30  40
Fort Lauderdale  84  66  79  72 /   0  20  40  50
Miami            85  67  79  71 /   0  20  40  50
Naples           80  65  80  68 /   0  10  10  20

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 11 PM this evening to 7 PM EST Monday
     for AMZ650-651-670-671.

GM...Small Craft Advisory from 9 PM this evening to 11 AM EST Monday
     for GMZ676.

&&

UPDATE...13
DISCUSSION...23/SK
MARINE...23/SK
AVIATION...13
BEACH FORECAST...23/SK



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