Area Forecast Discussion
Issued by NWS Lake Charles, LA

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650
FXUS64 KLCH 232309
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
609 PM CDT Sun Apr 23 2017

.DISCUSSION...
24/00Z TAF Issuance.

&&

.AVIATION...
SCT to OVC stratocu based ~4-5K FT will continue to diminish
through the evening with skies bcmg SKC areawide between 06-08Z.
Gusty northwest winds are beginning to diminish with light winds
expected to prevail overnight into Monday as high pres builds over
the region.

24

&&

.PREV DISCUSSION... /issued 339 PM CDT Sun Apr 23 2017/

SYNOPSIS...
Weather analysis as of 3 PM local or 20Z, shows a surface low over
north Georgia, with surface ridge centered over west central
Texas. Gradient between the two is producing northerly breezes
over the forecast area with unseasonably cool temperatures, and
also some wrap around moisture keeping eastern sections of the
forecast area under cloud cover. Some 10F degree difference
between areas that have seen sunshine (lower 70s) to areas that
have seen mostly cloudy skies (lower 60s.) An upper level trough
is noted on water vapor imagery extending from the Tennessee River
Valley across the southern Ozarks into east central Texas, with
this feature moving off to the east. Further west, Pacific energy
has helped develop an upper low and short wave over the Sierras,
moving eastward into the Rockies.

Rua

DISCUSSION...
Still expect cloudiness to break up over the forecast area this
evening as surface low moves further east lessening wrap around
moisture, and upper level trough passes through providing a deeper
northwest flow and more subsident air. Winds should also decrease
as the surface high moves closer decreasing the gradient. This
should set up a chilly night across the forecast area, as light
winds, clear skies, and a dry air mass look good for radiational
cooling. Overnight lows will be about 10F degrees below seasonal
norms, with mid to upper 40s north of I-10 and low to mid 50s
south of I-10.

Surface and upper level ridging to be in control and across the
forecast area for Monday, setting up a very nice weather day with
plenty of sunshine and mild temperatures.

As the high moves off to the east by Monday Night, southerly winds
will return with the beginning of a warm up and an increase in
humidity values.

The disturbance moving across the Rockies will form a surface low
over the Southern Plains by Tuesday. Southerly winds will increase
setting up a warm and breezy day.

This disturbance looks to have a deeper trough then what has been
seen the past few days in the guidance. Therefore, it is looking
better that as the upper level disturbance pushes the surface low
across Plains into Mississippi River Valley, a cold front trailing
from it will be able to push into the forecast area late Wednesday
into Wednesday Night. Overall front is rather weak from an air
mass point of view. However, good frontal lift is noted and
moisture return should be sufficient (PWAT over 1.25 inches and
Mean RH nearing 60 percent) that some showers and a few
thunderstorms should be able to develop with this system.

Although best dynamics will be north of the forecast area and
Storm Prediction Center has portions of North Louisiana and
Arkansas outlined in a slight risk for Day 4, will have to watch
closely on the timing of this system, as parameters look good on
late Wednesday Afternoon, with most unstable CAPE over 3000 j/kg,
0-6 km wind shear 30-40 knots, and 3-6 km lapse rates above 7.0
c/km, that some strong storms could form for the northern fringes
of the forecast area before sunset.

Front will wash out over the forecast area on Thursday, with
southerly winds quickly forming as upper level trough/low forms
over the Southwest U.S. Timing still needs to be worked out a bit
better with this system. However, at this point looks like an
extended period of warm, humid, and breezy conditions for the end
of the week into next weekend. Consensus of guidance has this
system moving a frontal boundary across the forecast area late
Sunday into Sunday Night. This far out things have a way of
changing as to specific parameters, but could be some heavy
rainfall as the long and strong southerly fetch brings tropical
like moisture across the forecast area ahead of the boundary with
precipitable water values above 2.25 inches and Mean RH over 80
percent.

Rua

MARINE...
Gradient between a surface low over north Georgia and a surface
centered over west central Texas is allowing for moderate
northerly flow over the coastal waters this afternoon. Wind speeds
are between 15 to 20 knots, especially over eastern sections of
the marine area, so will keep small craft exercise caution going
through the evening hours. During the overnight, the winds will
decrease as the surface low continues to move to the east and the
high settles across the region.

The high pressure system will move across the coastal waters on
Monday, and then east of the coastal waters on Monday Night, when
southerly winds will return.

A surface low is expected to form by late Monday over the Southern
Plains. Gradient will increase across the northwest Gulf as the
low deepens, and southerly winds will increase on Tuesday, with
wind speeds nearing 20 knots, and a Small Craft Advisory may be
needed from Tuesday into Wednesday.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  48  79  55  84 /   0   0   0   0
LCH  51  80  60  82 /   0   0   0   0
LFT  52  81  60  84 /   0   0   0   0
BPT  51  81  61  84 /   0   0   0   0

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...Air Quality Alert from 9 AM to 6 PM CDT Monday for TXZ201-215-
     216.

GM...SMALL CRAFT EXERCISE CAUTION until midnight CDT tonight for
     GMZ455-472-475.

&&

$$

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



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