Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 181128
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
628 AM CDT Wed Oct 18 2017

.DISCUSSION...
18/12Z TAf Issuance.

&&

.AVIATION...
Sfc high pres continues to ridge swwd over the area, providing
light east to northeast winds. The dry airmass in place will
result in VFR/SKC conditions at TAF sites through tonight, while winds
will veer slightly east to southeast around 5 KT during the day
before bcmg lt/vrbl tonight.

24

&&

.PREV DISCUSSION... /issued 335 AM CDT Wed Oct 18 2017/

SYNOPSIS...
A surface high is centered over the Mid-Atlantic states ridging
down into the forecast area helping to cut off the Gulf moisture
and keep a drier continental air mass in place. This is resulting
in cool conditions this early morning with temperatures in the
upper 40s to mid 50s away from the coast. Temperatures are in the
lower 60s right along the coast modified by the Gulf waters.

Rua

DISCUSSION...
The surface high will remain generally over the Mid-Atlantic
states for the next couple of days. This combined with a ridge
aloft will keep fair conditions in place. Air mass will gradually
modify as wind flow in the low levels becomes more easterly and
southeasterly.

By the end of the week the surface high will be centered further
to the northeast, allowing a more southerly fetch off the Gulf of
Mexico and thus increasing low level moisture and humidity. The
upper level ridge will also move further to the east over the
eastern Gulf of Mexico, and allow a short wave to approach the
forecast area. Therefore, with more lift and moisture, showers and
a few storms will be back in the forecast for this day and
continue into Saturday as the upper level trough feature hangs
around to combine with moisture and daytime heating.

Guidance begins to diverge some on Sunday into the Monday time
period. The general theme is a cold front will enter the forecast
area on Sunday Afternoon. Decent moisture return is seen ahead of
the front with Precipitable Water values increasing to over 1.80
inches. Therefore, a good bet for showers and storms on Sunday as
the frontal lift interacts with increasing Gulf moisture.

ECMWF members are more progressive and moving the front through
by Sunday Night. Whereas the GFS members only slowly move the
front through the forecast area with it lingering into Monday as a
cut-off upper level low feature develops over the region.

Instability parameters and shear values are also better on the GFS
with the development of the upper level low, which could mean some
strong storms ahead of and along the frontal system, and with a
slower movement, the possibility of locally heavy rainfall.

Therefore, a lower confidence in the forecast is noted for the
Sunday-Monday time period as to when the rain will end and if any
heavy rainfall or strong storms will occur. At this point, will
have likely pops on Sunday gradually lowering on Sunday Night. Have
put slightly more weight on the ECMWF for Monday. Therefore, will
only go with only a slight chance for showers on that day.

Drier conditions with cooler temperatures will move in behind the
front early next week for the end of the forecast period.

Rua

MARINE...
Easterly winds will gradually increase later today into Thursday
as gradient between high pressure over the Mid-Atlantic states and
trough over the extreme southern Gulf tightens. Possibility for
Small Craft Exercise Caution conditions for tonight into Thursday,
especially over the outer waters beyond 20 nm.

A cold front will move into the coastal waters either Sunday Night
or Monday Morning. Increasing north winds will occur behind the
front.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  82  52  82  55 /   0   0   0   0
LCH  83  59  84  64 /   0   0   0   0
LFT  83  58  84  63 /   0   0   0   0
BPT  82  63  83  66 /   0   0   0  10

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...None.
&&

$$

PUBLIC/MARINE...07
AVIATION...24


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