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Area forecast discussion 
National Weather Service Austin/San Antonio Texas 
120 PM CDT Thursday Aug 21 2008 


Update... 
showers and thunderstorms developing at this time as convective trigger temperatures 
in the upper 80s being reached. We have added isolated probability of precipitation across 
our western counties based on radar trends. 


&& 


Previous discussion... /issued 1248 PM CDT Thursday Aug 21 2008/ 


Aviation... 
4 thousand to 8 thousand scattered with scattered to broken clouds above 10 thousand feet through 
05z. Widely scattered rain showers and thunderstorms and rain are expected along and east of an 
kaqo to kbaz to Cuero line from 18z to 01z. Ceilings are forecast 
to form around 1 thousand to 2 thousand broken after 06z...then becoming 
ceilings 2 thousand to 3 thousand broken by 15z Friday and then VFR with 
3 thousand to 5 thousand scattered around and after 17z Friday. 


Previous discussion... /issued 1122 am CDT Thursday Aug 21 2008/ 


Update... 
latest round of convection is currently located across southeast 
Texas. Airmass across the eastern half of the County warning forecast area is still moist 
and uncapped with the precipitable water at crp at 2.16 inches this morning. 
Afternoon heating will trigger isolated to scattered convection 
mainly along and east of a line from Georgetown to El Indio. With 
precipitable waters  in excess of 2 inches...locally heavy downpours still possible. 
Only minor changes to grids and current forecast. 


Previous discussion... /issued 631 am CDT Thursday Aug 21 2008/ 


Aviation... 
areas IFR/MVFR ceilings with patchy LIFR ceilings and IFR/MVFR visibilities early 
this morning will become VFR with scattered clouds by this late morning. 
Areas IFR/MVFR ceilings with patchy LIFR ceilings and IFR/MVFR visibilities will 
redevelop overnight. Isolated rain showers/thunderstorms and rain can be expected, becoming 
slightly more numerous during the afternoon hours. Brief MVFR ceilings 
are possible in the heavier shra/tsra. S to southeast winds around 5 kts 
will prevail with 7 to 12 kts late morning through early evening. 
Some wind gusts to 30 kts are possible in and near shra/tsra. 


Previous discussion... /issued 329 am CDT Thursday Aug 21 2008/ 


Discussion... 
after several days of some much-needed rain...a slightly drier pattern 
is expected through the rest of the work week. Will see some diurnal 
heating triggered showers and thunderstorms through the next few 
days...but this activity will be limited mainly to the coastal plains 
where residual atmospheric moisture is deepest. However...the NAM 
indicates a weak boundary entering The Hill Country late this afternoon 
and into the evening. Considering that the NAM has been relatively 
trustworthy during these types of near-term scenarios...have thus 
expanded the chance for rain...albeit slight...to include the 
northern half of the County Warning Area. 


An interesting feature enters the picture late Friday and into the 
weekend as models are in fair agreement in developing a middle/upper 
level trough across south Texas and the Rio Grande plains. 
However...there is disagreement on how strong and organized this 
system will be and therefore how much rain can be expected. The 
GFS depicts a better organized system and thus is wetter. Have 
gone with slightly more conservative numbers through the 
weekend...but have kept the best chance for rain across the south 
and southwest portions of the County Warning Area. For the rest of the forecast 
period...have stayed close to climatology probability of precipitation with best chances across 
the coastal plains in response to afternoon sea-breeze activity. 


Higher ground moisture content and evaporation will keep temperatures 
on par with late August normals through the next few days. A 
slight warming trend is expected through the beginning of next 
week...but temperatures will stay comparable to climatology norms. 


&& 


Preliminary point temps/pops... 
Austin Camp Mabry 75 92 73 92 73 / 20 20 20 30 20 
Austin Bergstrom international Airport 73 93 72 92 71 / 20 20 20 30 20 
del Rio International Airport 75 96 74 92 74 / 20 10 30 40 40 
San Antonio International Airport 75 92 74 90 74 / 20 30 20 40 20 


&& 


Ewx watches/warnings/advisories... 
none. 
&& 


$$ 


13/08