Area Forecast Discussion
Issued by NWS Lake Charles, LA
FXUS64 KLCH 220535
Area Forecast Discussion
National Weather Service Lake Charles LA
1135 PM CST Tue Feb 21 2017
For the 02/22/17 0600 UTC TAF package.
Numerical guidance has trended away from the earlier advertised
lower CIGS/VSBYS at KLCH and KBPT. While backing off a bit, it
remains insistent on at least IFR CIGS/VSBYS developing at KAEX
and the Acadiana terminals. Observational and satellite trends are
thus far giving more credence to raw model output, which suggests
no worse than MVFR. Shifted the forecast toward the latter in
portraying lowering CIGS with light VSBY restrictions, yielding a
period of prevailing MVFR at these latter 3 sites with just TEMP
MVFR at KLCH and no restriction at KBPT.
.PREV DISCUSSION... /issued 831 PM CST Tue Feb 21 2017/
Pesky light to moderate showers continue to stream across parts of
central and south central Louisiana this evening as they wrap around
the back side of a slowly departing upper level low. Went ahead
and increased pops until midnight for these areas and inserted
20% pops from midnight to 600 AM as it looks like this activity
will linger a bit longer.
The showers and cloud cover may serve to keep temperatures a
degree or two above forecast, but as the cloud cover was expected
to linger anyway and temperatures aren`t expected to fall
much from where they are now, any differences should be minimal
so left overnight lows unchanged.
Fog appears less likely overnight with the proximity of the upper
low and ongoing showers. However, some patchy fog could still
develop during the predawn hours Wednesday morning once the
showers abate. Greatest probability of this happening will be
across the areas that have seen showers this evening. More
specifically, central and south central Louisiana.
PREV DISCUSSION... /issued 606 PM CST Tue Feb 21 2017/
For the 02/22/17 0000 UTC TAF package.
Isolated/scattered shower activity moving SE thru Central LA at
this time within flow around upper low centered over AR. Saw no
reason to significantly alter the inherited TAF package, with a
decided split between deterministic/probabilistic model data and
numerical MOS regarding lower CIG/VSBY development tonight. Will
monitor OB trends through the evening and incoming 00Z model
suite, but for now the prevailing MVFR/TEMPO IFR appears
reasonable given multi-model time heights/FCST soundings,
especially at KAEX and the Acadiana terminals.
PREV DISCUSSION... /issued 450 PM CST Tue Feb 21 2017/
Quick update this afternoon to increase POPS along and ahead of a
broken line of activity extending from near Alexandria southwest
to just east of Lake Charles. The line is associated with the
upper level low centered over southeastern Arkansas and moving
into central Mississippi. Expect the showers to continue pushing
to the east and out of the area as the evening progresses.
PREV DISCUSSION... /issued 325 PM CST Tue Feb 21 2017/
Water vapor imagery shows mid/upper-level low crossing cntl/nrn LA
this afternoon...and combo of this feature with lingering low-
level moisture continue to produce scattered mainly light showers
over nrn LA/srn AR, with a few drifting drifting into the nern
zones. Meanwhile convection associated with sfc low just offshore
of Vermilion Bay is pushing through lower Acadiana and the
adjacent coastal zones...should be clear of the sern zones by 00z.
Drier air moving in behind the low aloft has led to some clearing
over the forecast area, although the lingering low-level moisture
has led to cu formation with heating this afternoon. Main weather
story tonight could be some fog formation mainly over the ern
zones where boundary layer moisture is progged to be best...and
patchy fog has been included in these areas.
Our encroaching drier airmass behind the low/front is progged to
linger through mid-week while weak sfc high pressure builds over
from the Atlantic Sea Board. Another low aloft will help dig a
mid/upper-level trof through the Rockies late in the week...
associated sfc low crossing the Plains will pull another front
across the region during the late Friday/early Saturday time
frame. Forecast soundings currently show moisture lacking and very
limited POPs (all sern zones where best moisture is progged) are
being carried with this system for now. Coolest temps during the
forecast period are expected at this time with highs Saturday and
Sunday likely not reaching 70 most locations...and wake up temps
Sunday morning in the 40s all but coastal swrn zones.
Next significant chance of rain comes late in the period as the
next storm system crossing the wrn CONUS approaches and begins
picking up Gulf moisture...unfortunately this includes Mardi Gras
Caution-criteria...and possibly sneaking into SCA range...winds
look likely for the early part of the weekend, behind this next
strong front...otherwise no flags are anticipated on the coastal
waters through the period.
.PRELIMINARY POINT TEMPS/POPS...
AEX 55 73 53 80 / 40 0 0 0
LCH 56 75 56 76 / 10 0 0 0
LFT 56 74 55 78 / 30 0 0 0
BPT 56 78 57 77 / 10 0 0 0