FXUS64 KLCH 151738
Area Forecast Discussion
National Weather Service Lake Charles LA
1138 AM CST Fri Dec 15 2017
VFR conditions are expected to prevail through the afternoon with
BKN/OVC stratus around 10 kft. A few vicinity showers will
continue across Acadiana before ending around sunset. N/NNE winds
around 10 knots will gradually decrease before becoming light and
variable after sunset.
.PREV DISCUSSION... /issued 1106 AM CST Fri Dec 15 2017/
Current forecast is on target with abundant mid/upper level cloud
cover overhead along with CAA helping negate much of a warm up.
In fact, many OBs are still cooler now than they were overnight.
Large swath of rain continues over the coastal waters and into
parts of South Central LA. PoPs for the rest of today were
adjusted only slightly upward along/S of I-10 corridor, with a
larger boost over the Gulf waters. Marine hazards were left as
is, with the expiration of the SCA over the 0-20nm zones at 18Z on
track as winds gradually decrease.
PREV DISCUSSION... /issued 640 AM CST Fri Dec 15 2017/
For 12z TAF issuance.
Sfc observations from around the area continue to show VFR
conditions prevailing with mainly mid/high cloudiness persisting.
Regional 88Ds show a large area of overrunning rains over the
coastal waters extending into extreme srn Acadiana...VCSH has been
initialized at KARA/KLFT just in case some of this activity
manages to spread nwd a bit. Ongoing elevated nrly flow should
linger into the afternoon before diminishing as high pressure
builds over the region.
PREV DISCUSSION... /issued 401 AM CST Fri Dec 15 2017/
A steady stratiform rain shield continues to traverse the coastal
waters at this hour. As expected, the vast majority of this
activity has remained offshore with steady precipitation only
impacting portions of lower acadiana this morning. The cold front
producing the mess offshore is currently analyzed bisecting the
coast across southeast Louisiana and is progged to stall a couple
hundred miles offshore by tonight.
Opted to lower forecast highs for this afternoon as the
combination of overcast skies and cold air advection behind the
front should keep temperatures from rising much from where they
are now with afternoon highs around or just above 50F.
In the wake of the front, high pressure will briefly settle over
the region tonight. While guidance consensus keeps scattered to
broken cloud cover across the area, radiational cooling should be
efficient enough to allow temperatures to fall back into the 30s
across most of the area with a light freeze possible across
portions of central Louisiana.
The high will quickly slide east on Saturday turning winds back
out of the southeast and moistening the atmospheric column in
advance of an upper trough progged to swing northeast out of
Mexico Saturday night into Sunday. With precipitable water values
running in the 1.5 to 1.7 inch range, numerous showers and a few
thunderstorms are expected...some of which could produce heavy
rainfall. The severe weather threat still appears extremely
limited at this point due to a notable lack of instability despite
the presence of robust directional and speed shear. The Storm
Prediction Center has maintained its marginal risk for severe
weather and one or two strong to severe storms cannot be ruled
out, but the overall threat remains very low.
The upper trough bringing the rain Sunday will quickly eject to
the northeast and will be followed by a second upper trough moving
east out of the southwest US. Guidance is in pretty good
agreement that this will result in another round of showers and
thunderstorms Monday into early Tuesday although there may be a
bit of a break between systems Sunday night into early Monday
morning. Beyond that, however, guidance continues to prove
frustrating with considerably different solutions. The
operational GFS swings the trough across northern Louisiana and
southern Arkansas late Tuesday swinging a front through and
ushering in much drier and cooler air for midweek. Meanwhile, the
Euro keeps the second trough much further north, does not move a
front through, but rather develops a third upper trough that
continues to enhance rain chances through early Thursday. Guidance
once again merges late in the period indicating a frontal passage
over the Christmas holiday weekend although the timing of said
front is highly variable. Continued to blend all solutions beyond
Tuesday, but went lower on overall POPs than is being indicated by
the Euro. Forecast beyond Tuesday morning is very low.
Numerous showers will continue to move across the coastal waters
this morning in response to a passing cold front. Behind the
front, increasing offshore flow will develop before diminishing
again this evening as high pressure settles across the area.
An upper trough will approach the area late Saturday into Sunday
resulting in widespread showers and thunderstorms. A second trough
quickly follows Monday keeping rain chances elevated for the early
part of next week.
.PRELIMINARY POINT TEMPS/POPS...
AEX 30 58 49 68 / 0 10 90 70
LCH 39 58 54 70 / 0 10 80 80
LFT 38 58 55 72 / 0 10 50 90
BPT 40 58 53 69 / 0 20 90 50
GM...Small Craft Advisory until 6 PM CST this evening for GMZ470-472-
Small Craft Advisory until noon CST today for GMZ450-452-455.