Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 192334
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
534 PM CST Mon Feb 19 2018

.AVIATION...
Southerly winds are brisk this afternoon but will taper off after
sunset with clouds expected to fill into the region with height
fall drg the overnight hours. The next front looks to move down
into Texas and northern Louisiana and this will add showers to
the mix of weather issues.

&&

.PREV DISCUSSION... /issued 357 PM CST Mon Feb 19 2018/

SYNOPSIS...
With a surface high ridging across from off the Atlantic coast and
lower pressure over the Plains, pressure gradient has tightened
over the region today producing elevated and breezy southerly
winds. Vad wind profiles showing wind speeds 25 to 30 knots off
the surface and these speeds have occasionally mixed down to the
surface in gusts. These winds have helped mix out most low clouds
and fog. With decent sunshine and flow off the Gulf, unseasonably
warm and humid conditions are occurring this afternoon with
readings in the upper 70s to lower 80s feeling more like a spring
day.

Upper level analysis and water vapor imagery shows a sub-tropical
ridge extending from the western Atlantic across Florida and
across the Gulf of Mexico. Meanwhile, a broad trough is noted from
the Mountain West down into the East Pacific with subtropical jet
running across Old Mexico to the Great Lakes.

Rua

DISCUSSION...
In the short term, looks like pressure gradient will remain tight
for the night into Tuesday. Although winds at the surface will
likely decrease with no real significant gusts after sunset,
overall boundary layer winds look to remain elevated, and this
will likely preclude any significant fog development tonight.

For the remainder of the week, it still looks to be a battle
between the Sub-tropical ridge from the Western Atlantic, and
broad upper level trough out west. Upper level energy emanating
out from the base of the trough will try to push a cold front into
the region on Wednesday. However, looks like sub-tropical ridge
will hold enough to have front stall before moving through. Still
some settle differences in guidance as to when and where this will
happen. However, most like scenario is front stalls late Wednesday
just north of the forecast area, then pushing back north during
Thursday, keeping a warm and humid air mass in place for the
remainder of the week.

Robust and deep southerly flow developing across the region will
transport and converge both East Pac and Bay of Campeche along the
frontal boundary, that will provide very high anomaly moisture
into the region. Precipitable water values will near 1.75 inches
just ahead and behind the frontal boundary. Ascending air ahead of
the trough will allow the moisture to form into widespread showers
and a few thunderstorms. Best chance for heaviest rainfall will be
right along and behind the frontal boundary, as flow becomes
parallel to the slow moving frontal boundary. Therefore, the
positioning of the frontal boundary will be critical to the heavy
rainfall potential. At this time, the heavy rainfall will be just
north of the forecast area, although a marginal risk of excessive
rainfall has been outlined for portions of upper Southeast Texas
and Central Louisiana. Rainfall amounts for these areas will on
average range from 1 to 1.5 inches, with isolated higher amounts,
and the isolated higher amounts may reach flash flood guidance,
thus the marginal risk. Remainder of the area will see rainfall
amounts average between 0.5 and 1 inch.

The next cold front is progged to come down into the forecast area
over the weekend. Still some differences as to if the front will
move through the forecast area. Latest GFS and ECMWF now have the
front reaching the coast. However, both seem to be a little off
from the ensemble means that keep the front over the forecast area
or north. Therefore, will not make too many changes for the
weekend and near the Superblend output.

Rua

MARINE...
Elevated southerly flow is occurring over the coastal waters this
afternoon as gradient over the region tightens between high
pressure off the Atlantic coast and low pressure over the Plains.
The elevated winds have mixed out any sea fog with surface
observations and web cam views showing good visibility.

The elevated and sometimes gusty southerly flow will continue into
Tuesday. Wind speeds in the outer waters will be 15 to 20 knots
with seas building to 3 to 6 feet. Therefore, Small Craft Exercise
Caution will be headlined. The elevated winds are also expected to
keep any sea fog development patchy in nature.

A cold front will stall well north of the coastal waters on late
Wednesday into Thursday. Southerly winds will decrease somewhat as
the pressure gradient relaxes. Therefore, could be a better chance
of sea fog formation for Wednesday night. Should also be a good
chance for showers and a few thunderstorms as abundant moisture
will pool ahead of the front.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  66  83  66  77 /  10  30  30  80
LCH  66  80  68  78 /  10  40  30  80
LFT  67  82  70  80 /  10  20  20  70
BPT  66  79  67  78 /  10  40  50  80

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Exercise Caution through Tuesday afternoon for
     GMZ470-472-475.

     Small Craft Exercise Caution through late tonight for GMZ450.

&&

$$


AVIATION...19



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