Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 180225
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
825 PM CST Fri Feb 17 2017

.DISCUSSION...
Inflow into approaching surface trof across the NW Gulf off the SE
TX/SW LA coast around 20-25 kts (per platform reports) outside
the thunderstorm area, special marine warning within this line of
thunderstorms. Expecting winds to diminish within the next couple
of hours to 20 knots or below. Not anticipating the need for a 2
hour SCA, but updated forecast to expand Small Craft Exercise
Caution to include 0-20 nm zones. Also, redistributed pops across
the coastal waters for this based on latest HRRR reflectivity
guidance, which still indicates most of this activity diminishing
by 06z or midnight.

DML

&&

.PREV DISCUSSION... /issued 655 PM CST Fri Feb 17 2017/

DISCUSSION...
Wx map shows surface trof and upper level disturbance axis over
East Texas this evening, continuing to move east, with showers
and thunderstorms along and southeast of the axis. Main area of
showers and thunderstorms over lower Acadiana into the eastern
coastal waters, with a secondary cluster of thunderstorms off the
Southeast Texas coast right along the trof axis. Thus, updated
forecast this evening over SE TX/SW LA into the adjacent coastal
waters for higher pops the next few hours, trimming down from NW
to SE towards midnight into the overnight hours.

DML

PREV DISCUSSION... /issued 529 PM CST Fri Feb 17 2017/

AVIATION...Rain will continue to move east across the region for
the next few hours. Lower vis in rain can be expected, however for
the most part the visibility will remain above 3 miles. Lower
ceilings are expected through tonight.

PREV DISCUSSION... /issued 443 PM CST Fri Feb 17 2017/

DISCUSSION...
Upper low over the Red River Valley with a trailing trof quite
evident in water vapor satellite imagery to our west. The trailing
trof axis is TX starting to take on a bit of a negative tilt as
it pivots TWD E TX this afternoon. The upper low is progged to
continue slowly off TWD the ENE tonight, with the with the trof
axis crossing the area this evening. Rain with embedded heavier
convective cells, including isolated thunderstorms, will continue
along/ahead of this axis, ending from west to east during the
evening hours. Low level moisture will linger behind, however,
and there is some potential for patchy fog formation overnight
into SAT morning, but at this time have leaned more toward a very
low cloud deck while maintaining a slight chance of rain.

Deepening westerly flow south of the upper low on SAT will
gradually erode the low level MSTR save for a SFC layer
maintained by southerly onshore winds. Cloud cover will become
more scattered by the afternoon hours, with temperatures climbing
into the upper 70s/near 80. Heights will build SAT night into SUN
as this upper low weakens and accelerates off to the E while a
robust upstream upper trof reaches the Four Corners. Increasing
and deepening moist southerly flow will gradually overspread the
area on SUN as the upper trof slowly moves east of the four
corners, with PWATs climbing to near 2 inches over E TX by early
MON morning, which is plus 2 to 3 standard deviations above the
norm. Fueled by this copious MSTR, despite progged limited
instability, the otherwise broad synoptic lift augmented at times
by a noisy and difluent flow aloft, is expected to yield a
widespread N-S oriented swath of rain and embedded heavier
convective cells/TSTMS developing over E TX late SUN night. There
remains some spread in the global model guidance to contend with
in terms of the timing of the heaviest rain, with the quickest
solution having the onset in my E TX zones after midnight SUN and
the slowest not getting it east of the Atchafalaya until TUE
morning. The overall consensus at this time is for primarily a
Monday event, with the swath of HVY rain entering E TX MON morning
and exiting to the east MON evening. Areawide totals of 1 to 3
inches with locally higher amounts are possible.

Rain chances linger but decrease TUE into WED as the base of the
TROF closes off and tracks SEWD across the GULF. Dry and warm THU
into FRI as a narrow ridge builds in behind the departing upper
low and ahead of another incoming trof.

13

MARINE...
Showers and thunderstorms will continue to affect the Gulf waters
the rest of this afternoon through this evening as an upper trof
over Texas and Oklahoma pivots through the region. This activity
will come to an end after midnight once the trof axis passes,
with the modest southeast winds over the central and eastern Gulf
waters also subsiding. Dry weather and light south winds are
expected on Saturday. Sea fog may become an issued over the
nearshore waters/coastal lakes and bays by Saturday night as very
moist air is transported atop the cooler shelf waters. Winds are
expected to increase Sunday with the approach of another upper
level trof, which is forecast to result in widespread showers and
thunderstorms Monday into Monday night. Rains are expected to
linger but decrease in coverage Tuesday and Wednesday, while winds
become northerly as an area of surface low pressure develops over
the central Gulf.

13

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  54  76  58  81 /  20  10  10  10
LCH  58  76  63  79 /  30  10  10  10
LFT  58  78  62  81 /  40  10  10  10
BPT  60  79  65  79 /  40  10  10  20

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...SMALL CRAFT EXERCISE CAUTION until midnight CST tonight for
     GMZ450-452-455-470-472-475.

&&

$$

PUBLIC...04



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