Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 241130
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
630 AM CDT Tue Apr 24 2018

.DISCUSSION...
24/12Z TAF Issuance.

&&

.AVIATION...
VFR conditions prevail early this morning under clear skies. Some
patchy fog will be possible briefly near the AEX terminal this
morning, but otherwise expect conditions to remain VFR through the
period. Some SCT stratocu is expected during the day, with
northwest winds 5-10 KT. Winds will diminish this evening, with
lower clouds dissipating and a few cirrus streaming over the
region aloft.

24

&&

.PREV DISCUSSION... /issued 338 AM CDT Tue Apr 24 2018/

SYNOPSIS...
Analysis as of 24/08Z, shows an upper level low over the Tennessee
River Valley, moving slowly to the east. This is allowing for a
dry west to northwest flow to occur aloft. Meanwhile, a surface
ridge is building down from the Southern Plains. The light winds,
clear skies, and dry air mass, is again allowing for a cool night,
with air temperatures again roughly 5F degrees below normal. The
water vapor imagery also shows the next weather maker, a short
wave located over the upper Rocky Mountain States, moving
southeast.

Rua

DISCUSSION...
The upper low will continue to slowly move to the east-northeast
reaching the Mid-Atlantic States by tomorrow. As this occurs, a
surface ridge will move across the forecast area today and off to
the east on Wednesday. Therefore, rather benign and pleasant
sensible weather will continue for the forecast area into
Wednesday.

Northwest flow aloft will drop the Rocky Mountain short wave to
the southeast, reaching the region Wednesday night and moving
across the forecast area on the first part of Thursday, pulling a
cold front along with it.

Should be enough time for the Gulf to open up on Wednesday into
Wednesday night, as the high moves off to the east, that decent
moisture will pool ahead of this system. Progs show a band of
Precipitable Water (PWAT) Values between 1.35 and 1.50 inches,
which is between the 75th and 90th percentile for this time of
year, and Mean RH values over 75 percent, for overnight Wednesday
into early Thursday. Decent 1000-850 moisture flux convergence
along the front, and some upper level divergence, provided by
right entrance region of upper level jet, that this moisture should
be lifted into shower activity.

Overall, instability will be very weak, with forecast MUCAPE
values 200 j/kg or less, and this should keep shower activity from
becoming too strong. Bulk shear values from 0-3km of 25-30 knots,
and 0-6km of 30 to 40 knots, along with 3-6km lapse rates nearing
6.5 c/km, could allow for a few elevated thunderstorms, and
therefore will have a slight chance for thunderstorms in the
weather grids. However, the predominate weather mode should be
rain showers. Progressive nature and low intensity of convection
should keep rainfall amounts down, with on average a quarter to
half inch expected, with locally higher amounts in any storm that
can get going.

The northwest flow aloft will continue through the end of the
week, and this will allow for another short wave to drop down and
bring a re-enforcing cold front across the forecast area during
the day on Friday.

Moisture return looks rather meager ahead of this system as no
real southerly flow develops, therefore the Gulf doesn`t open up.
PWAT values are progged to be just over an inch, which is right
around the 50th percentile. Mean RH values vary from near 50
percent for western and southern zones, and up to 70 percent for
the northeast zones. Instability and other parameters look rather
weak again, and therefore, do not expect much with this frontal
passage. Maybe some isolated to widely scattered showers where
moisture is the best and will keep just a 20 pop for the northern
and eastern zones during the day on Friday.

High pressure will the settle in over the region for the weekend,
bringing cool nights and mainly sunny pleasant days, with no
chance of rain in the forecast. Probably the best weather weekend
in a while for this area.

Rua

MARINE...
A light to modest offshore flow is found over the coastal waters
this early morning as weak high pressure builds down from the
Southern Plains. These conditions will continue through tonight.
The high pressure will begin to move off to the east of the region
on Wednesday, and light onshore flow will gradually develop
during Wednesday. The light onshore flow will continue until a
cold front moves across the coastal waters on Thursday morning.
This front will bring a chance for showers and maybe an isolated
thunderstorm. Light to modest offshore flow will then develop
behind the front, and persist through the remainder of the week.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  80  56  80  57 /   0   0  10  50
LCH  80  59  81  60 /   0   0  10  40
LFT  79  59  81  61 /   0   0   0  30
BPT  81  60  82  59 /   0   0  10  40

&&

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

$$


AVIATION...24


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