Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 182338

Area Forecast Discussion
National Weather Service Lake Charles LA
538 PM CST Sun Feb 18 2018

Ceilings cont to bounce around this eve as the old frontal
boundary lifts back to the north and washes out. This will
finally allow the gulf moisture to become established and race
northward into Arkansas and Oklahoma thru the early mrng hours.
There is a stronger front expected to push into northern Oklahoma
around sunrise. But we will remain under the influence of the gulf
moisture surging northward.

Ceilings and vsby dropping thru the late eve into the overnight
hours. IFR/LIFR twrds sr conts improving drg the late mrng hrs.


.PREV DISCUSSION... /issued 337 PM CST Sun Feb 18 2018/

A warm front has been moving north across the forecast area today
in response to deepening southerly flow over the region and as of
3 pm or 18/21Z has pushed out of Southeast Texas and just about
out of Central Louisiana. Temperatures are mainly in the mid 70s
with the exception of two areas, Central Louisiana, where low
level frontal inversion has kept overcast skies and temperatures
in the mid 60s, and near the coast, where sea fog is hanging
around and keeping temperatures there also in the mid 60s.


The battle for this week will be between the upper level sub-
tropical ridge extending from the western Atlantic into the Gulf
of Mexico, and a deepening broad upper level trough over the
middle and western US. This pattern will keep the forecast area in
a deep southerly flow for a majority of the week that will bring
unseasonable warmth and moisture to the forecast area.

In the near term, the issue is fog. Sea fog has persisted along
the near shore waters west of Freshwater Lock, with visibility at
Cameron (KCVW) less than 1/4 of a mile at 18/2120Z or 3:20 pm
local. As the upper level energy ejects out from the upper level
trough out west and across the Rockies, a surface low and frontal
trough is expected to form across the Southern Plains. This will
increase the pressure gradient across the region, and thus
increase wind speeds. This may help lift in any advancing sea fog
into a low stratus deck toward the I-10 corridor and areas to
north after midnight tonight.

The breezy and gusty southerly winds are expected for Monday into
Tuesday, with very warm temperatures during the daytime, away from
the coast, as mixing will help erode any morning stratus and bring
about broken sunshine by afternoon. Again, the wind speeds should
keep any significant fog from forming inland from the coast on
Monday night into Tuesday morning.

By mid-week, the frontal system in the Plains, will near the
forecast area in form of a cold front. Still some differences as
to when and where the cold front will eventually stall out
sometime from Wednesday night into early Thursday. Deep southerly
fetch will bring copious amounts of Gulf moisture ahead of the
front, with Precipitable Water Values progged to be near 1.75

Ascending air ahead of the surface front and upper level trough
should get showers and a few storms going by Wednesday afternoon
becoming more numerous through the night into early Thursday. With
very high moisture values ahead of a slow moving frontal boundary
and low level flow becoming parallel to the front and low level
theta-e ridge, there could be some heavy rainfall for the region,
but too early to pinpoint exactly where and if it will be in the
forecast area.

The front will begin moving back north late Thursday or Friday,
with the cycle beginning all over again with another front progged
for late next weekend.


Satellite pictures, web cam views, and surface observations show
the sea fog has stayed around for the near shore waters west of
Freshwater Lock. Therefore, the dense fog advisory for that area
was extended through Monday morning. Southerly flow will persist
through the night, and this will allow sea fog to reform, or push
into the near shore waters between Marsh Island and the lower
Atchafalaya River, and into the coastal lakes and bays. Therefore,
have gone ahead and issued a dense fog advisory for those areas
starting later this evening and continuing into Monday morning.

A surface low pressure and frontal system will form over the
Plains later tonight into Monday. This will tighten the pressure
gradient over the Northwest Gulf with south winds becoming
moderate and gusty through Tuesday. Small craft exercise caution
may be needed for portions of the outer waters on Monday night
into Tuesday. The increase in winds may also keep sea fog more
patchy in nature from Monday afternoon into Tuesday.

The frontal system will near the coastal waters on late Wednesday
into early Thursday before stalling. The south winds will decrease
as the front nears, along with an increase in showers and



AEX  60  82  63  81 /  10  10  10  30
LCH  62  80  65  80 /  10  10  10  30
LFT  63  81  67  81 /  10  10  10  20
BPT  63  80  66  78 /  10  10  10  40


GM...Dense Fog Advisory from 9 PM this evening to 9 AM CST Monday for

     Dense Fog Advisory until 9 AM CST Monday for GMZ450-452.



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