Scientific Forecaster Discussion
fxus64 klch 241205
Area forecast discussion
National Weather Service Lake Charles la
605 am CST Sat Feb 24 2018
low ceilings have been bouncing around this am but vsby has
managed to remain abv 3sm all taf lctns. Radar is indcg a few
streamer showers in se TX lifting to the north. Conds for br have
been creeping in from the east and lft and Ara seems to have the
best potential for vsby to drop due to br thru 14z to 15z. Winds
will pick up later this am as a frontal sys that has been stalled
to our northwest gets a kick that will push it off to the east
later tdy... look for this development drg the aftn hrs. Ceilings
will improve somewhat late mrng early aftn hrs. But shwrs will
mov in late this aftn and thru the eve hours. Shwrs and tstms will
incr in area coverage and strength into the early morning hrs on
Sunday W/ frontal passage is xpcd around sr at lch.
Previous discussion... /issued 415 am CST Sat Feb 24 2018/
a few areas of patchy light fog being observed inland this morning
mainly across Acadiana. Meanwhile areas of dense sea fog continue
to plague the near shore coastal waters and the immediate
coastline. Guidance is not particularly enthusiastic about
widespread development of inland fog this morning and the lack of
significant development thus far seems to corroborate this
analysis. That said, other than some slightly elevated winds,
there really isn't much to inhibit fog development so I did opt
to keep patchy fog wording in the forecast area wide until 15z to
account for the possibility of fog development in areas where
winds are a bit lighter.
A frontal boundary extends from just east of Dallas southwest to
Waco Texas this morning. As this front slowly progresses east
today, the tightening pressure gradient will result in increasing
winds which should serve to help erode the marine fog along the
coast and offshore. Further inland, sustained winds of 15 to 20
knots with gusts to 30 can be expected with the strongest winds
occurring this afternoon.
The front will move into the area late this evening before
stalling resulting in a potentially long duration heavy rain
event with low end severe potential on top. On the rainfall side
of things, the official forecast will indicate quantitative precipitation forecast totals of
around 1.5 inches, but some guidance is going as high as 3 inches
and this will certainly be possible in some areas. Given that the
front will be stalled over the area for around 24 hours, it is
reasonable to assume that a precip training situation could set up
resulting in totals considerably higher.
On the severe side of things, the overall severe potential across
our area remains low as the best thermodynamics will remain to the
north across north Louisiana and southern Arkansas. Anemic lapse
rates will be the big inhibiting factor locally. However,
forecast soundings do indicate favorable low level directional and
speed shear so a few strong to severe storms cannot be ruled out
with the highest probability of occurrence being this evening
through early Sunday morning. The Storm Prediction Center has the
area highlighted in a slight risk for severe weather.
The severe weather threat decreases Sunday although the shower and
thunderstorm activity will not. The front will finally be shunted
off to the east by a second upper trough swinging through the
region Sunday night into early Monday. This second boundary will
be accompanied by some drier and cooler air which will filter into
the area Monday providing a brief, but welcome reprieve from the
"may is the new february" pattern we've been in the last couple
of weeks. Even with the relatively cooler air, both high and low
temperatures will still be about 10 degrees above normals for this
time of year.
Surface high pressure slides to the east by early Tuesday turning
winds back out of the south ahead of the next frontal boundary
progged to move through the area Thursday. This front, if the long
range guidance is to be believed, will usher in an airmass that
will provide US with the first dry weekend we've seen in several
a long fetch of south to southeast winds will continue to drive
warm and moist air over the relatively cooler shelf waters of the
northwest Gulf. This will maintain sea fog over the nearshore
coastal waters and coastal lakes and bays through at least midday
Saturday. South winds will increase and become gusty Saturday
ahead of an approaching cold front. A shortwave trof advancing
through the plains will push this cold front into the area late
Saturday night into Sunday morning where it is expected to stall.
Showers and thunderstorms will accompany the front and continue
into Sunday before coming to an end early Monday as a second
shortwave trof advances through. A brief period of light to modest
offshore flow will prevail Monday with winds turning east and
then southeast on Tuesday through the end of the week.
Preliminary point temps/pops...
aex 79 57 62 49 / 30 80 80 80
lch 79 65 69 57 / 30 90 80 80
lft 80 67 72 61 / 20 70 80 90
bpt 79 64 69 55 / 30 90 80 70
GM...small craft exercise caution through this evening for gmz450-452-
Dense fog advisory until noon CST today for gmz430-432-450-452.
Small craft exercise caution from noon CST today through this
afternoon for gmz430-432-435.