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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Tuesday
• 
• High: 91 °
• Low: 68 °
• Chance of a Thunderstorm

• Wednesday
• 
• High: 90 °
• Low: 70 °
• Partly Cloudy

• Thursday
• 
• High: 93 °
• Low: 72 °
• Partly Cloudy

• Friday
• 
• High: 90 °
• Low: 66 °
• Mostly Cloudy

• Saturday
• 
• High: 90 °
• Low: 68 °
• Mostly Cloudy

Area forecast discussion...updated 
National Weather Service Austin/San Antonio Texas 
632 am CDT Tuesday may 21 2013 


Discussion... 
see aviation for the 12z taf discussion. 


&& 


Aviation... 
main forecast challenge for this issuance is the timing of convection 
at the taf sites. Thunderstorm impacts at the taf sites will be based on a 
blend of the 00z hi-res arw and nmm along with the 00z 3km ttu WRF. 
All of the I-35 terminals are also in the Storm Prediction Center slight risk area for 
this afternoon and evening. At this time will go with a tempo group at kaus 
with prob30 groups at ksat and kssf. Will not mention thunderstorms in the 
kdrt taf due to low confidence of occurrence. MVFR ceilings this morning 
will improve to VFR by 17z with thunderstorms most likely on the increase 
after 22z. Timing of the return of MVFR ceilings late tonight into 
Wednesday morning will be directly dependent of the strength of 
the convective outflow boundaries. At this time will delay return of MVFR 
ceilings by a couple of hours compared to persistence. 


&& 


Previous discussion... /issued 316 am CDT Tuesday may 21 2013/ 


Short term (today through wednesday)... 
deep vortex over the Pacific northwest will dig southward and eject 
the downstream trough pushing over northwest Texas today. Extremely 
unstable air-mass in place over south central Texas with widespread 
3000-4000 j/kg MLCAPES expected this afternoon into tonight. The 
upper trough will push into central Texas this afternoon with an 
attendant cold front sliding into far western portions by early 
afternoon and slowly into The Hill Country by early evening. 
Initially...a strong cap may inhibit storms from forming along the 
front over far western portions this afternoon however as the upper 
trough digs a little further south across The Hill Country and 
northeast corridor towards evening...storms will be expected to 
back-build across central Texas into our area. An increasing low 
level jet over the eastern half of the region impinging the front 
will only worsen the severity. The main threats will be from large 
hail (and in some cases very large hail) and damaging thunderstorm 
winds from late afternoon to the early morning hours Wednesday. 


The main threat area per Storm Prediction Center will be generally across the eastern 
half of the region...but our analysis would give heightened 
concern from the eastern Hill Country through the northeast 
corridor...including the cities of Burnet...Georgetown...Austin 
and Giddings. This is because of the upper level cap...which 
according to sounding forecasts this evening...will have sufficiently 
eroded by the slight dig of the upper trough by the time of 
frontal passage. With the extreme amount of instability present... 
isolated tornadoes cannot be ruled out from developing super-cells 
across the eastern Hill Country through the northeast corridor 
late this afternoon through this evening. Rainfall of 1 to 3 
inches is possible as well across eastern portions of south 
central Texas this evening where the low level jet meets the 
front. 


Today though...morning clouds will decrease to partly cloudy this 
afternoon with a slight chance of showers and isolated thunderstorms 
Hill Country to the northeast corridor in a capped atmosphere. Highs 
today ranging from the upper 80s hills to the upper 90s Rio Grande 
plains. Tonight...as mentioned earlier...severe storms will 
back-build or develop across The Hill Country and spread 
southeastward over the remainder of south central Texas late this 
afternoon and during the evening...exiting the area during the early 
morning hours. Lows tonight low to middle 60s hills to middle 70s southern 
and eastern portions. On Wednesday west northwest flow aloft will 
bring in drier air while a subtropical ridge begins developing 
north over the area. Decreasing cloudiness becoming partly cloudy 
Wednesday afternoon with highs near 90 or low 90s over much of the 
region except middle to upper 90s over south central portions and the 
Rio Grande plains. 


Long term (wednesday night through monday)... 
the subtropical ridge will continue building across south and 
central Texas Wednesday night and Thursday but with a continued 
southeast flow off the Gulf...morning clouds are expected becoming 
partly cloudy by Thursday afternoon. This will likely remain the 
overall weather pattern Friday through the early part of next week 
as the subtropical ridge remains dominant. As the ridge builds 
aloft...weaker southeast winds may allow for temperatures to cool 
more overnight (to near seasonal) while highs will remain a few 
degrees above normal each day Friday through Monday. A few weak 
waves on the backside of the ridge may help develop Burro Mountain 
development over northern Mexico Friday through Sunday but 
uncertainties whether or not they will reach our area will result 
in silent 10 probability of precipitation each day. 


&& 


Preliminary point temps/pops... 
Austin Camp Mabry 92 70 92 71 94 / 20 40 - - - 
Austin Bergstrom international Airport 91 69 91 69 92 / 20 40 - - - 
New Braunfels Muni Airport 92 70 92 69 93 / 10 40 - - - 
Burnet Muni Airport 88 66 90 68 91 / 20 30 0 - - 
del Rio International Airport 99 72 98 75 98 / 10 20 - - - 
Georgetown Muni Airport 88 68 88 69 91 / 20 40 - - - 
Hondo Muni Airport 95 70 95 71 96 / 10 30 - - - 
San Marcos Muni Airport 90 71 90 70 91 / 20 40 - - - 
La Grange - Fayette regional 91 75 92 73 92 / 10 40 10 - - 
San Antonio International Airport 92 71 93 72 93 / 10 30 - - - 
Stinson Muni Airport 92 71 92 71 93 / 10 30 - - - 


&& 


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


$$ 


Mesoscale/aviation...13 
synoptic/grids...02