159 
fxus64 klch 120247 
afdlch 


Area forecast discussion 
National Weather Service Lake Charles la 
847 PM CST Thursday Mar 11 2010 


Update... 
the dense fog continues to work its way inland tonight across southeast Texas 
and SW la. Observations at korg and klch during the past one to 
two hours indicates visbys lowering from 10 miles to around one 
quarter of a mile or less. Visbys remain up across Acadiana so 
far...but with fog sitting just off the coast...will not rule out 
the potential for some of it to push inland as well this evening. 
At this time...am thinking that the dense fog will stay mainly 
along and south of I-10. With this in mind...have extended the 
dense fog advisory inland to the I-10 corridor from Orange County 
to upper Saint Martin Parish. 


Other concern for this evening's forecast is the potential for 
thunderstorms. A few strong storms popped up just east of Toledo 
Bend Reservoir over northern Vernon Parish and have moved NE...but 
convection further to the south not getting quite as organized. 
Klch 00z sounding shows a slight increase in moisture since this 
morning...but atmospheric column for the most part remains fairly 
dry with precipitable water around 0.7 inch. Despite moderately steep lapse 
rates...atmosphere appears too dry to support significant 
convective development at least across southern zones. Could see a few 
more storms across portions of central la within a zone of enhanced 
lift associated with an upper level shortwave moving out of 
Texas...and this coincides well with the continued slt risk for 
severe weather per latest Storm Prediction Center day 1 convective outlook. 
Thus...kept forecast probability of precipitation as is with a slt chance for southern portions of the 
area...increasing to around 40 pcnt across central la. 


The remainder of the forecast looks on track...with only updates to 
grids and text products to expand the dense fog advisory this 
evening. 24 


&& 


Previous discussion... /issued 639 PM CST Thursday Mar 11 2010/ 


Update... 
latest satellite images show dense sea fog persisting over the 
coastal waters and also beginning to move inland across lower southeast 
Texas and SW la. Reports from southeast Texas regional Airport 
indicate rapidly deteriorating conditions just south and east of 
the Airport with visibilities rapidly lowering to around one 
quarter of a mile. The fog is expected to continue moving 
inland...affecting most locations along and south of I-10 in 
Jefferson County over the next hour or two. Therefore...have 
updated the dense fog advisory to make it effective immediately 
for Jefferson County and Cameron Parish. 


Still expect sea fog to move inland across the southern la parishes 
this evening as well...although at this time the fog still remains 
just offshore. Kept the dense fog advisory confined to the coastal 
parishes and counties for tonight...but will need to monitor 
trends and update to include locations further inland if 
necessary. 


In addition...have also updated the marine dense fog advisory to 
be effective immediately as well as sea fog is currently noted 
over the coastal waters. 


Updated grids and text products sent. 24 


Aviation... 
near term concerns this evening include inland propagation of sea 
fog at coastal terminals...and the potential for convective activity 
across the area. Last few images of visible satellite showed the sea 
fog had reached kbpt and the southern half or so of Cameron Parish. 
Guidance suggests that the fog should not penetrate too much farther 
than it already has...so after amending the kbpt taf...opted to leave 
it out of the remaining terminals. Surface front expected to move 
through the area tonight...with the resulting northwest winds 
spelling the end of the fog. Timed this to occur just before 
midnight at kbpt. As for convective potential...the best support 
will continue to lie primarily across northern parts of the area. 
Inserted a thunderstorms in the vicinity for kaex for middle to late evening since confidence in 
impact is low at this time. VFR expected to prevail tomorrow. 13 


Previous discussion... /issued 424 PM CST Thursday Mar 11 2010/ 


Discussion... 
a few areas of light showers are falling across southeast Texas 
and southern Louisiana. Areas of dense fog in the coastal waters 
this afternoon has been breaking up but will redevelop tonight and 
move into the coastal counties and parishes. 


An upper level shortwave moving through central Texas this afternoon will move 
into eastern Texas and central la tonight but with very limited moisture 
vertically not looking at a whole lot in the way of showers or 
thunderstorms. As the upper level trough finals moves across the 
region...drier and cooler air will make it's way into the region 
around or just after sunrise. 


Tmrw looks to be cooler with temperatures only into the upper 60s which 
will be about 10 degrees cooler than today. But skies will be 
clearing through the morning. 


The weekend is shaping up to be mostly clear but a bit on the 
cool side. 


&& 


Preliminary point temps/pops... 
klch 54 67 45 69 / 20 10 10 10 
kbpt 52 69 45 69 / 20 10 10 10 
kaex 49 66 42 66 / 40 10 10 10 
klft 55 68 46 67 / 20 10 10 10 


&& 


Lch watches/warnings/advisories... 
la...dense fog advisory until 6 am CST Friday for Acadia-Calcasieu- 
Cameron-Iberia-Jefferson Davis-Lafayette-lower St. Martin- 
St. Mary-upper St. Martin-Vermilion. 


Texas...dense fog advisory until 6 am CST Friday for Jefferson-Orange. 


GM...dense fog advisory until 6 am CST Friday for Calcasieu Lake- 
coastal waters from Cameron, la to High Island, Texas out 20 
nm-coastal waters from Intracoastal City to Cameron, la out 
20 nm-coastal waters from lower Atchafalaya River to 
Intracoastal City, la out 20 nm-Sabine Lake-Vermilion Bay- 
waters from Cameron, la to High Island, Texas extending from 
20 nm to 60 nm-waters from Intracoastal City, la to 
Cameron, la extending from 20 nm to 60 nm-waters from lower 
Atchafalaya River to Intracoastal City, la extending from 
20 nm to 60 nm. 




&& 


$$