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afdewx 


Area forecast discussion 
National Weather Service Austin/San Antonio Texas 
735 PM CDT Thursday Jul 24 2008 


Update... 
have let the Tornado Watch expire. A cell passed just to the 
southwest of the office showed some rotation, however never 
dropped a funnel. There were a couple of funnel cloud reports 
earlier. Due to some training of cells due to continued banding of 
showers and thunderstorms, have mentioned locally heavy rainfall 
for all of south central Texas this evening. Expect bands to 
contract closer to the center of Tropical Depression Dolly as it 
moves west into the mountains of Mexico. Have maintained Flash 
Flood Watch for the far southwestern counties due to a potential 
for very heavy core rains. Otherwise, ongoing forecast on track 
with trends to the sensible weather grids updated. 


&& 


Previous discussion... /issued 630 PM CDT Thursday Jul 24 2008/ 


Aviation...scattered showers and thunderstorms will continue to 
develop and affect south central Texas this evening. Intermittent 
showers and thunderstorms are expected to occur over the I-35 
terminals at least through 02z...and at kdrt overnight. Conditions 
will vary from VFR to MVFR. Overnight...ceilings will generally become 
MVFR around 07z...and return to VFR by 17z Friday. Winds will 
continue to be breezy out of the east through Friday. 


Previous discussion... /issued 626 PM CDT Thursday Jul 24 2008/ 


Update... 
have extended Tornado Watch until 7 PM as some cells continue to 
show some rotation. Have let wind expire as Tropical Depression 
Dolly continues to move west northwest away from south central 
Texas with winds decreasing to around 15 miles per hour. 
Previous discussion... /issued 354 PM CDT Thursday Jul 24 2008/ 


Discussion... 
wind shear over the NE quadrant of circulation around Dolly is 
breaking down with more unidirectional flow occurring where 
strongest convective cells are occurring. Closer to the center of 
Dolly daytime heating and gradually decreasing high clouds could 
mean new cells developing west of San Antonio where shear is still 
sufficiently high for rotation. Will hold off cancelling the 
eastern portions on this shift since individual cells are becoming 
stronger during daytime heating, making brief boundary 
intersection vortices possible. The Wind Advisory for SW counties 
earlier also looks on track to expire at 23z. 


The flash flood potential looked impressive early in the day with 
excellent rainfall coverage of 1-3 inches over central counties. 
However...convection failed to increase under the cirrus canopy to 
threaten the counties in the flash flood advisory area up to this point. The center 
of Dolly has also accelerated far enough east to lower the risk of 
dangerous warm core flash flooding along the Rio Grande. However, 
the outskirts of warm-core activity remains possible, and an 
increase in early evening rainfall is expected over the watch 
area; therefore will continue the watch into the evening hours and 
let the evening shift cancel if necessary. Rain projections for 
the next watch product will remain at "locally 5 inches"; meanwhile 
rainfall potentials for the western counties adjacent to the watch 
will be more in the 1-3 inch range while the eastern two-thirds of 
south central Texas after 00z should drop to around 1/2 inch or 
less. 


Chances should decrease from east to west during the day Friday 
with hot and dry weather resuming for the rest of the forecast 
package. A few slight chance probability of precipitation are added in the extended in the 
southeast counties as the past few model runs show a weak TUTT low 
moving into Texas. 


&& 


Preliminary point temps/pops... 
Austin Camp Mabry 75 95 76 98 75 / 40 20 - - - 
Austin Bergstrom international Airport 75 95 73 97 73 / 40 20 - - - 
del Rio International Airport 74 92 74 96 76 / 70 50 20 - - 
San Antonio International Airport 74 92 75 95 75 / 50 20 - - - 


&& 


Ewx watches/warnings/advisories... 
Flash Flood Watch until 7 am CDT Friday for the following counties: 
Dimmit...Maverick...Zavala. 


&& 


$$ 


04/03