Area Forecast Discussion
Issued by NWS Lake Charles, LA

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000
FXUS64 KLCH 230537
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
1137 PM CST Fri Feb 22 2019

.DISCUSSION...
For 06Z TAF Issuance

&&

.AVIATION...
Warm front continues to lift northward into central LA this
evening with some scattered showers noted as well. Warm moist air
mass will help keep ceilings low overnight and lead to some fog
potential. That said, winds have remained a bit stronger than
originally expected which has resulted in only minimal visibility
reduction so far. Current expectation is while winds remain
slightly elevated, visibility will continue to slowly reduce at
all terminals as the night progresses, with only BPT/LCH falling
below 1 mile for a time. Winds increase by mid morning
but with moist airmass in place visibilities will still remain
somewhat limited with VCSH and BR ahead of the approaching cold
front. By late morning and into the early afternoon, front pushes
through the area from east to west. Instability may be a limiting
factor, but at least a broken line of -TSRA with gusty winds will
be likely as the front pushes through. Winds remain a bit breezy
for a couple of hours behind the front and shift westerly before
lightening up in the evening. Expect ceilings to begin to
gradually improve behind the front, eventually with only a SCT to
BKN high cloud deck remaining.

&&

.PREV DISCUSSION... /issued 945 PM CST Fri Feb 22 2019/

DISCUSSION...
Grids/zones were updated earlier to introduce a Dense Fog Advisory
for all of sern TX and the coastal zones (plus Calcasieu) of LA.
Sfc obs have shown lowering visibilities off/on through the
evening, primarily across sern TX in vicinity of the stationary
front extending across the forecast area. All of the fog guidance
is in agreement with the likelihood of dense fog developing
through the night in the advisory area...Calcasieu Parish was
added due to the expectation that areas near the Ship Channel will
likely see some dense fog by later overnight. Feel like there
could be some bustability with this forecast, especially if winds
stay up like they did last night...stay tuned.

Otherwise, few changes to the inherited grids zones. KLCH 00z
sounding came in with a ridiculous 1.77 inch PWAT...250 percent of
normal and a new record for the date/flight. The sounding also
showed better instability along with an increasing srly flow off
the sfc although with a more due srly boundary layer flow,
helicity values were down from earlier flights. Meanwhile short-
range high res guidance continues to indicate fairly scattered
mainly shower activity developing through the night in advance of
our expected cold frontal passage later Saturday. Temps are a bit
tricky...look close enough to the ballpark to allow them to pass
through for now.

25

PREV DISCUSSION... /issued 558 PM CST Fri Feb 22 2019/

DISCUSSION...
For 00Z TAF issuance.

AVIATION...
Not any major changes to the overall TAF package outside of
accounting for the cold front at the end of the valid period. Warm
front continuing to slowly lift northward this evening, with all
terminals outside of AEX within the warm and moist southerly
flow... Expectation is at AEX winds will veer to the south over
the next several hours. Otherwise low ceilings and scattered
showers are noted around the area. Most obs showing at worst areas
of BR at the moment, but guidance suggests lowering visibility
through the night, with areas of FG by morning. That said, winds
remaining a bit elevated may cause visibilities to bounce around
for a while after midnight, but overall expectation is that sites
will predominantly be below 1/2 SM. Winds increase by mid morning
but with moist airmass in place visibilities will still remain
somewhat limited with VCSH and BR ahead of the approaching cold
front. By late morning and into the early afternoon, front pushes
through the area from east to west. Instability may be a limiting
factor, but at least a broken line of -TSRA with gusty winds will
be likely as the front pushes through. A few strong to severe
storms cannot be ruled out.

PREV DISCUSSION... /issued 246 PM CST Fri Feb 22 2019/

DISCUSSION...
Wx map shows warm front finally move northward across inland SE
TX and C LA. This has quickly warmed temperatures into the mid and
upper 70s this afternoon along the I-10 corridor. Elsewhere, mid
to upper 60s across C LA. The immediate coastal areas still
experiencing mid 60s and areas of dense sea fog, as noted in
Cameron holding at 1/4-1/2 miles visibility. Some improvement
possible for the remainder of the afternoon, but likely to fog
back in this evening after sunset. Guidance mixed on how far the
sea fog will move inland, as the pressure gradient is expected to
increase slightly overnight, limiting the fog potential inland.
Offshore, will take a while to mix this marine layer out, as
explained in the marine discussion.

For the next order of business is the next cold front and severe
thunderstorm potential for Saturday. SPC continues the slight
risk of severe thunderstorms along and north of I-10. The main
concern will be a band of thunderstorms along and just ahead of
the cold front by late morning into the afternoon. A strong mid-
level jet, coupled with the strengthening 50+ kt low-level jet,
will promote very favorable wind profiles for severe storms. Large
0-2 km hodographs and 50+ kt effective bulk shear will support
supercells with low-level mesocyclones and bowing structures
capable of tornadoes and damaging wind, with peak period during
the afternoon for our region. Marginal risk continues south of
I-10 into the coastal waters. Because of the cooler shelf waters,
will take a little more effort for severe weather potential, which
will likely be along the immediate frontal passage to generate
enough lift to break the marine layer.

By Saturday evening, the front will be exiting lower Acadiana,
with lingering showers offshore for a few hours. Otherwise, the
return to cooler and dry conditions expected overnight Saturday
into Sunday and early Monday.

By Monday afternoon, increasing clouds and a chance of showers
will return through Tuesday as the subtropical jet remains active,
periodically shooting upper level disturbances across the area.
Quite a bit of model discrepancy after Tuesday among the GFS &
ECMWF, so confidence is low for this time period of the extended
forecast.

DML

MARINE...
South to southeast winds will persist tonight, keeping a warm and
moist airmass over relatively cool shelf water. The result has
been, and will be the continuation of dense sea fog through
Saturday morning for the near shore waters and coastal lakes and
bays. Dense Fog Advisory for the 0-20 nautical mile marine zones
and inland lakes/bays will continue through 6 am Saturday. The
onshore winds will increase by daybreak Saturday as low pressure
deepens east of the southern Rockies. The stronger southerly winds
is expected to mix out the dense marine fog after daybreak
Saturday. An advancing cold front will increase the moisture and
lift ahead and along the front, expected to move through late
Saturday morning into the afternoon hours. Modest offshore flow
will develop behind the cold front ending rain chances and sea fog
threat for the remainder of the weekend.

DML

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  64  74  44  63 /  50  80  10   0
LCH  68  74  48  65 /  30  80  10   0
LFT  69  78  51  65 /  30  80  20   0
BPT  67  74  48  65 /  30  80  10   0

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Dense Fog Advisory until 9 AM CST Saturday for LAZ041-052>054-
     073-074.

TX...Dense Fog Advisory until 9 AM CST Saturday for TXZ180-201-215-
     216-259>262.

GM...Dense Fog Advisory until 9 AM CST Saturday for GMZ430-432-435-
     450-452-455.

&&

$$


AVIATION...50


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