Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 202343
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
643 PM CDT Sun Jun 20 2021


.AVIATION...

A few showers and thunderstorms will continue to move across the
area through the next few hours, with the inland convection
expected to die off around 02Z. Most areas will waffle between VFR
and MVFR conditions between now and then, with all terminals
expected to hold VFR conditions overnight. Gusty winds will also
continue through this period, relaxing as convection dies off and
remaining south around 07-10kt overnight. Tomorrow, a similar
weather pattern to today is expected with isolated to scattered
showers beginning in the mid to late morning along the coast,
spreading inland through the day, and dying off after sunset.
Like today, any showers that move across the airports will be
capable of producing periods of gusty winds, reduced visibility,
and low ceilings. Away from thunderstorms, conditions will be
mainly VFR.

17


&&

.PREV DISCUSSION... /issued 345 PM CDT Sun Jun 20 2021/

SYNOPSIS...
Sfc high pres building back acrs the Gulf of Mexico in the wake of
TC Claudette is resulting in southerly low level flow acrs the
region. This has allowed for higher dewpoints and deeper moisture
to advect northward. Recent WV imagery and UA analysis shows a
weakness aloft between the departing TC and ridging over the
Desert SW. The end result of all of this has been an increase in
showers and tstms acrs the area this aftn, although the bulk of
the convection has remained over the NW Gulf. The region is
expected to remain in an active pattern the next few days as a
trough over the northern states digs southeastward over the MS
Valley.

24

SHORT TERM (Tonight through Tuesday night)...

Aftn showers and tstms will linger into early evening before
dissipating with the loss of daytime heating. Some isolated to
widely sctd convection could persist through the overnight hours,
especially near the coast. Elevated dewpoints acrs the area will
limit cooling overnight, with low temps only expected to fall into
the middle to upper 70s (about 5 degrees, give or take, above
normal).

Showers and storms are expected to develop and increase along and
south of I-10 Monday morning, especially as convective temps are
expected to be reached early in the day. In the meantime,
shortwave energy translating through the base of a mid-upper
level trough over the N/Cntl CONUS will dig southeastward acrs the
mid/lower MS Valley, merging with the weak trough already in
place over the region. This will help to enhance the potential for
daytime convection acrs the area Monday, resulting in more
widespread storms with low level forcing provided by seabreeze and
mesoscale boundary interactions.

The deepening trough will also help to usher a frontal boundary
into the region by Monday night into Tuesday, providing additional
support for widespread showers/tstms to continue. Precip water
values will approach 2 inches during the day Monday, and, as
moisture deepens and pools ahead of the weak frontal boundary,
could reach 2.2 inches Monday night (just a little below the max
moving avg for this time of year per SPC climatology). These
anomalously high PWATs will support heavy rainfall and fairly
efficient rainfall rates within some of the storms. Given the
reprieve in rainfall over the past few weeks, do not anticipate
any widespread or significant flooding problems acrs the area, but
localized minor flooding in urban and low lying areas will be
possible. The Weather Prediction Center has outlined much of sw and
southern LA in a SLGT risk for excessive rainfall from Monday
into Tuesday, and this coincides with area rainfall totals between
2 and 4 inches. Elsewhere acrs the area, the Excessive Rainfall
Outlook is MRGL, with rainfall totals up to 2 inches possible.

One "good" aspect of the increase in showers is that daytime
temperatures will be held in check for the most part. High
temperatures both Monday and Tuesday are expected to be below
normal, especially on Tuesday as thicker and more widespread cloud
cover will likely hold temperatures in the lower 80s acrs our
northern tier of Parishes and Counties.

24

LONG TERM (Wednesday through Sunday)...

The decaying remnants of a stalled frontal boundary will provide a
weak focus for convection over the coastal waters Wednesday morning
that will gradually work inland through the afternoon.

The persistent upper level ridge baking the southwestern U.S. in
a record breaking heatwave is progged to build eastward Thursday
into Friday which will limit diurnally driven convection across
southeast Texas. This will allow afternoon temperatures to climb
into the mid and perhaps even upper 90s in some locations with
heat indices flirting with or perhaps exceeding heat advisory
criteria. Guidance still shows scattered to widespread afternoon
convection across southwest and south central Louisiana where
deeper moisture will exist and the ridge`s influence will be more
limited.

While there is some notable discrepancies between models, the
general pattern heading into next weekend depicts the ridge being
shunted back to the west as another somewhat unseasonable trof digs
south across the central and eastern U.S. The associated frontal
boundary is unlikely to bring any materially cooler air this far
south, but will likely provide another focus for enhanced
precipitation next weekend.

Jones

MARINE...
A relative tight pres gradient between high pres over the Gulf and
lower pres acrs the southern plains will maintain elevated
onshore flow through early this week. Exercise caution flags will
remain for the coastal waters zones through at least Monday. Sctd
to nmrs showers and tstms can be expected as the region remains
beneath a weak trough aloft. Onshore flow will diminish by Tuesday
into Wednesday as a weak front settles over the region and
gradually washes out. Rain chcs will taper off through the latter
part of the week as an upper ridge builds into the region from the
west.

24

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  76  89  73  84 /  20  70  90  70
LCH  78  89  76  88 /  40  70  90  90
LFT  77  86  76  86 /  40  70  90  90
BPT  78  89  76  89 /  50  70  90  80

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Exercise Caution through Monday afternoon for GMZ450-
     452-455-470-472-475.

&&

$$


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