785 
fxus64 klch 210558 
afdlch 


Area forecast discussion 
National Weather Service Lake Charles la 
1158 PM CST Friday Nov 20 2009 


Aviation... 
surface low now appears to be centered off the Texas coast...about 60 nm 
southeast of Matagorda Bay...in the vicinity of stronger 
convection in the western Gulf. Low is still expected to track 
across the northwest Gulf...toward southern or southeastern la...remaining 
south of our taf sites. Radar currently shows just patchy light 
rain over la and southeast Texas with an area of heavier rain offshore. 
Expect rainfall to increase in area tonight over southern taf 
sites as the low moves closer to the coast...with heaviest 
rainfall to remain offshore. Ceilings and visbys also expected to 
lower to MVFR tonight as rain area increases. In 
addition...northeast winds are expected to strengthen to between 
10-15 knots tonight...gradually shifting to the north by midday 
Saturday at kbpt and klch...and middle afternoon at kaex...klft and 
kara. Conditions should begin to improve late Saturday as the low 
system moves northeast of the area. 24 


&& 


Previous discussion... /issued 921 PM CST Friday Nov 20 2009/ 


Discussion... 
latest surface analysis shows a broad area of low pressure off the 
middle Texas coast while water vapor imagery shows shortwave trough 
crossing cntl Texas. Weak vorts rounding the shortwave evident in 
clusters of rain...one currently moving out of S-cntl la and into 
southeastern la with another larger area moving along the Upper Texas coast 
toward southeastern Texas. Yet another round of rain showing up over cntl 
Texas near the main shortwave trough. Some convection noted within the 
rain shield over the northwestern Gulf in vicinity of the surface low. 


Main change to the forecast tonight is to remove mention of 
thunder over most of the forecast area as conditions look too 
stable. However left mention of isolated thunder over the southeastern 
zones as storms offshore could move ashore into this region later 
tonight given current and forecast trajectories. Otherwise going 
forecasts look good with rain a good bet overnight. Temperatures/winds 
look fine as is and no changes planned there. 


Update out shortly. 


25 


Previous discussion... /issued 553 PM CST Friday Nov 20 2009/ 


Aviation... 
an area of light rain was moving east across southern la...mainly 
affecting southeastern taf sites. Will see a break early this evening with 
the next round of light rain expected to move into the northwest Gulf and 
across southern areas late this evening into the overnight hours. This 
rainfall is the result of an upper level trough and associated surface 
low near the Texas coast that will lift NE across the area tonight into 
early Saturday. Expect periods of mainly light rain beginning 
around 02z at kbpt...with rainfall progressing east across klch and 
into klft and kara from 03z-06z. VFR ceilings and visbys expected at 
kaex. VFR also expected at klft and kara through late 
tonight...becoming MVFR between 10z-12z...while generally MVFR 
conditions to prevail throughout the period at klch and kbpt. 


In addition...as the surface low develops and moves toward the area 
tonight...a tightening gradient will produce breezy northeasterly 
winds with possible gusts between 20 and 25 kts overnight into 
early Saturday mainly for southern taf sites. 24 


Previous discussion... /issued 435 PM CST Friday Nov 20 2009/ 


Discussion...rather challenging forecast and hence running a 
little late. Was hoping for better continuity between models...particularly 
the emcwf and GFS...but this did not occur. Have trended toward 
the GFS solution which was offered some support by the local WRF 
model as well as HPC. Thus a more progressive and shorter-lived event 
than advertised by the European model. 


Radar showing light to moderate rains over south Louisiana 
advancing east. Expecting secondary batch of rains to advance 
across the area overnight so carrying categorical probability of precipitation 
south...likely north. Primarily looking at over-running rains and 
any lightning activity to be be minimal at most. Rains amounts of 
1 to 2 inches expected along the Interstate 10 corridor south...and 
lesser amounts further north. 


Rains taper off Saturday with system advancing east. Remainder of 
weekend looking dry and cool with a northerly flow remaining in 
place. Next potential frontal passage and rain-maker coming Tuesday. 


Marine...low pressure deepening and moving across the northwest Gulf will 
bring strengthening winds and building seas tonight. Widespread 
rain will accompany the system. Winds and rains will diminish 
Saturday as the system exits east. 


&& 


Preliminary point temps/pops... 
klch 50 63 46 71 / 80 40 10 10 
kbpt 51 65 46 71 / 60 30 10 10 
kaex 50 62 43 68 / 60 40 10 10 
klft 52 60 47 67 / 80 50 10 10 


&& 


Lch watches/warnings/advisories... 
la...none. 
Texas...none. 
GM...Small Craft Advisory from 6 am to 6 PM CST Saturday for 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-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. 


Gale Warning until 6 am CST Saturday for 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-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. 


Small Craft Advisory until 6 am CST Saturday for Calcasieu Lake- 
Sabine Lake-Vermilion Bay. 




&& 


$$