Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 200322

Area Forecast Discussion
National Weather Service Lake Charles LA
922 PM CST Sun Feb 19 2017

.UPDATE...Dense fog is present over the nearshore coastal waters,
however with the wind elevated the fog does not penetrate much
inland. Will keep the dense fog advisory for the coastal waters
only. The remainder of the forecast remains on target as well.


.PREV DISCUSSION... /issued 543 PM CST Sun Feb 19 2017/

For the 20/00Z TAF issuance.

Modest southerly flow in the boundary layer will continue tonight
as low pressure system to the west over the eastern Rockies gains
strength and moves to the east. The south winds will continue to
increase moisture with the result an increase in low cloud cover,
that will likely see a majority of the terminals have IFR/LIFR
conditions. With the winds staying up enough, expect more in the
way of low stratus then dense fog.

Only slow improvement in the IFR conditions expected on Monday
morning as the developing storm system to the west approaches the
area. A few showers will begin the develop over Southeast Texas in
the morning hours, then spread east during the afternoon. The more
intense shower activity and rainfall does not look to affect the
KBPT terminal until after 20/20Z, and other terminals right at the
end or after the current TAF package.


PREV DISCUSSION... /issued 345 PM CST Sun Feb 19 2017/

Mid-afternoon sfc analysis shows an area of low pressure
developing over the Rockies with a trailing cold front situated
over the Front Range into far wrn TX. Closer to home high pressure
was noted over the Ohio Valley...with a serly low-level flow
providing for moist serly breezes over the forecast area as
dewpoints continue rising well into the 60s today. Water vapor
imagery shows deep troffing over the Rockies/nrn Mexico pushing
ewd. Visible imagery shows our low overcast finally mixing out
with partly cloudy skies prevailing over much of the region
now...although another round of sea fog has been developing over
the near shore waters. Temps have responded nicely with readings
in the upper 70s to near 80 most locations.

No huge changes this forecast package with a significant rainfall
event still setting up for much of Monday and on well into
Tuesday. In the short-term, will have to watch the sea fog to see
how far inland it may encroach later...for now have just inserted
patchy fog wording for early evening coastal zones, then gradually
spreading inland through the night with a little stronger wording
later for the coast. Will let the evening shift re-evaluate the
need for any advisories tonight.

Rockies trof is still progged to advance ewd into Monday, with
deepening srly flow increasing moisture through the column
significantly (MRH values progged to exceed 80 percent and PWAT
values running to near 1.80 inches/260 percent of normal). High-
res models are pinging on widespread showers developing west of
the forecast area tonight, pushing ewd to a point where activity
will be moving into the far wrn zones toward daybreak Monday...
with showers and storms then spreading into the remainder of our
TX zones and the border parishes through the day. Mid/upper-
level low is progged to cut off over sern TX by late Monday/early
Tuesday which will help slow the ewd progression of the
system...with the most widespread activity not expected to reach
the Atchafalaya Basin til after midnight tomorrow night. As of
this time, forecast average QPFs are running 1.5 to 2.5 inches,
with isolated higher amounts of course possible. This is well
within the range of current flash flood guidance...running
generally 4-5 inches in a 6-hour although certainly
flooding cannot be absolutely ruled out, the threat appears low
enough at this time to not require a Flash Flood Watch at the
moment. Severe weather is also not expected as forecast soundings
indicate weak lapse rates and minimal shear...maybe a storm or two
producing damaging wind gusts at most looks likely.

Sfc reflection moves through the forecast area early Tuesday but
slim rain chances linger as system aloft slowly plods by. A drier
wrly flow is progged through mid-week while weak sfc high pressure
builds over...thus no rain chances are included in the forecast
through Thursday. Next shortwave/sfc front looks to pass late
Friday, although best moisture is progged across the nern zones so
only slim POPs are included there. Most of the weekend looks dry
before the next storm system developing to our west begins to
push ewd toward the region for late Sunday.

Dense Fog Advisory has been issued for the near shore waters,
valid til 15z Monday. Also caution headlines have been introduced
for the outer waters beginning at 00z for increasing srly flow.


AEX  64  76  61  73 /  10  60  90  50
LCH  67  75  62  72 /  30  80  80  50
LFT  67  77  63  72 /  10  50  90  60
BPT  67  77  60  73 /  40  90  70  40



     Dense Fog Advisory until 9 AM CST Monday for GMZ450-452-455.



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