Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 230157

Area Forecast Discussion
National Weather Service Miami FL
857 PM EST Mon Jan 22 2018

.UPDATE...Evening sounding shows that the atmosphere has
moistened considerably since this morning, with PWATs now
approaching 1.4" and a fairly moist layer through about 15KFT.
Analysis suggests weak isentropic uplift is helping to generate
the ongoing light showers tracking across the region. While
mesoscale models are picking up on this, a few suggest that this
activity may wane somewhat overnight. However, this is tough to
pinpoint so this evening`s update will include an earlier shower
mention for the remainder of the overnight hours. Fog remains a
concern across the region overnight.


.PREV DISCUSSION... /issued 639 PM EST Mon Jan 22 2018/

The winds will remain southeast around 5 knots tonight before
swinging to a southerly direction around 10 knots on Tuesday at
over all of South Florida taf sites. The weather will remain dry
tonight, but there could be some patchy fog at the taf sites late
tonight. However, the coverage and timing of the fog affecting
the taf sites is not known at this time. Therefore, the taf sites
will remain in VFR conditions for ceiling and vis at this time.


PREV DISCUSSION... /issued 406 PM EST Mon Jan 22 2018/


THIS AFTERNOON THROUGH WEDNESDAY: Satellite imagery this afternoon
shows a large trough moving into the upper midwest with an
associated front/squall line moving through the central Gulf of
Mexico. While the main system will remain well north, the Gulf
front is expected to move into the FL peninsula during the day on

Increasing south-southwesterly flow ahead of the boundary late
tonight into Tuesday morning will continue to moisten the local
atmosphere. A few showers have developed over the local Gulf
waters/Gulf coast this afternoon, with rain chances gradually
increasing overnight with the approach of the front. Models
aren`t as robust with instability across land during the
afternoon, but there looks to be enough to keep the mention of
isolated storms. This will be aided by the interaction of both a
diffuse Gulf breeze in the prevailing SW flow, and an east coast
seabreeze that is expected to develop.

With the parent system well removed north, flow quickly becomes
zonal giving very little southward push to the front. Deeper
moisture lingers into Wednesday, keep a chance for showers across
the region, and a few storms over the local Atlantic.

THURSDAY AND FRIDAY: High pressure builds across the deep south to
end the week, with the frontal boundary stalling just to our south.
Strong pressure gradient will support breezy east-northeast flow to
end of the week. Conditions look dry on Thursday, but increase in
low level moisture may bring a few coastal showers onshore for the
Atlantic coast on Friday and Saturday.

Temperatures on Thursday will be a little cooler behind the boundary
in the low 70s, and a little warmer on Friday though the breezy flow
will hold temperatures along the east coast. Overnight lows will
range from the mid 50 to mid 60s Thursday night and upper 50s to
upper 60s Friday night.

NEXT WEEKEND: Another low latitude shortwave moving across the
northern Gulf late week is expected to lead to weak cyclogenesis
along the remnant boundary into this weekend. This looks to be
connected to the larger system moving into the east coast during the
same time, which is forecast to cross the state on Sunday. There is
agreement on moderate return flow during the period, with enough
moisture and instability for a return of shower chances and the
potential for a few thunderstorms.

MARINE...High pressure slides further east into the Atlantic as
front approaches from the Gulf into Tuesday. East-southeast flow 10-
15kts into this evening, becomes more southerly around 10kts on
Tuesday. However, winds look to become more variable late in the day
as the front itself moves in. North-northeast winds overspread the
local waters as the front starts to stall just to our south. Speeds
look to pick up to 15-20kts, or a solid 20kts into the day on
Thursday. Strong and gusty east winds develop late week as high
pressure builds southeast, with hazardous boating conditions likely
Thursday night into Saturday. Advisories will likely be needed
across the local waters as early as Thursday.

Rain chances increase on Tuesday as the front approaches, with the
potential for a few thunderstorms Tuesday afternoon and Wednesday.
Drier conditions return on Thursday.

AVIATION...Generally VFR with shower chances increasing as a
front approaches. Some sub-VFR low clouds could impact the
terminals, particularly at APF and PBI. Flow will veer from the E
to SSE over the period.

West Palm Beach  69  79  62  72 /  10  60  40  20
Fort Lauderdale  68  78  65  75 /  10  60  40  30
Miami            68  79  64  76 /  10  50  30  30
Naples           67  77  60  74 /  20  40  10  20



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