773 
fxus64 klch 231217 
afdlch 


Area forecast discussion 
National Weather Service Lake Charles la 
617 am CST Monday Nov 23 2009 


Discussion... 
12z taf issuance discussion. 


&& 


Aviation... 
satellite imagery and surface observation indicate persistent low clouds 
hovering over the forecast area this morning with ceilings ranging 
from 500 feet at kaex to almost 3000 feet at klft/kara. 
Visibilities haven't been the problem previously thought with 
readings basically bouncing around anywhere from 1/2sm to 10sm. 
Forecast soundings indicate that the low clouds should gradually 
mix out this morning leaving behind just scattered clouds through 
the afternoon hours. However model time-height sections indicate 
increasing low-level moisture while MOS guidance shows higher 
dewpoints by 12z Tuesday so have included some restrictions to 
visibility for late in the forecast. 


25 


&& 


Previous discussion... /issued 448 am CST Monday Nov 23 2009/ 


Synopsis... 
water vapor imagery and upper air analysis shows upper low lifting 
off to the NE with the area under primarily zonal flow aloft. 
Another upper level low located upstream is moving over the northern 
rockies. 


At the surface...high pressure ridging over the area is providing light 
variable winds. A large swath of stratus persists over the lower MS 
Valley West into the Sabine valley under a subsidence inversion. 
These clouds have developed westward during the night with the 
westernmost edge extending from roughly lfk to bpt. Mostly clear 
skies were noted earlier tonight over southeast Texas and western la which allowed 
for the development of some patchy dense fog. Visbys have improved 
some early this morning...but remain highly variable in time and 
space ranging from less than one mile to five miles. A dense fog 
advisory remains in effect through middle morning...mainly west of a 
Marksville to Cameron line. 


Furthermore...in areas where skies were mostly clear...enough 
cooling has taken place to lower temperatures into the lower 
50s...while across the eastern zones where skies have remained 
overcast...temperatures have been steady in the upper 50s. 


Discussion... 
expect the persistent low cloud layer to begin mixing out today...with 
skies gradually clearing from west to east. Surface high pressure will 
continue to shift east of the area with light southerly winds 
developing. Will begin to see a modest return of low level 
moisture as well. Expect temperature to warm into the upper 60s or 
near 70 by this afternoon. However...this is dependent upon how quickly 
the clouds dissipate with high temperatures possibly a bit cooler 
than forecast over the eastern zones with overcast anticipated to linger 
here a bit longer. 


The upper low currently over The Rockies will move into the Central 
Plains the next couple of days...bringing a cold front through 
the area Tuesday. Have gone with scattered probability of precipitation for Tuesday...a 
compromise between the higher met and the lower mav pop guidance. 
This may be a bit high however...with rather meager moisture 
return and limited instability. 


The initial low will lift NE through the remainder of the 
week...with another low dropping out of Canada into the central 
Continental U.S. Trough by Thursday. This will push a reinforcement of cool 
dry air across the area. High pressure at the surface and dry nwrly flow 
aloft will bring an extended period of dry cool weather for the 
Thanksgiving Holiday into the weekend. Temperatures will be near 
or a bit below seasonal norms. 


Another system will be taking shape over the western US late next 
weekend with a chance for showers returning Sunday afternoon ahead of 
the next frontal passage on Monday. 


Marine... 
light winds and low seas will persist through late Tuesday. 
Southeast winds will gradually shift to a northerly direction by 
Tuesday night as a cold front moves across the coastal waters. 
Behind the front...offshore winds will strengthen by Wednesday 
morning to 15 to 20 knots...with seas building to 5 to 6 feet. 
Moderate to strong offshore flow will continue through Friday. 
High pressure will move east of the area Saturday with onshore 
flow resuming. 


&& 


Preliminary point temps/pops... 
klch 70 53 73 50 67 / 0 10 40 20 10 
kbpt 72 56 74 48 67 / 0 10 40 10 10 
kaex 69 48 71 45 65 / 0 10 40 10 10 
klft 70 53 74 51 68 / 0 10 40 20 10 


&& 


Lch watches/warnings/advisories... 
la...dense fog advisory until 9 am CST this morning for the following 
zones: Allen...Avoyelles...Beauregard...Calcasieu... 
Cameron...Evangeline...Jefferson Davis...Rapides...Vernon. 


Texas...dense fog advisory until 9 am CST this morning for the following 
zones: Hardin...Jasper...Jefferson...Newton...Orange... 
Tyler. 


GM...none. 
&& 


$$