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Nowcast

• 

• Now as of 8:50 PM CDT on May 25, 2013

  Flash Flood Watch in effect until 8 am CDT Sunday... Through 11 PM...only isolated showers are expected...moving slowly northward at 20 mph across south central Texas and the eastern Hill Country. Spotty rainfall amounts will be one tenth inch or less. Redevelopment of showers and thunderstorms is still possible toward midnight into the early morning hours with locally heavy rainfall of 2 to 4 inches...isolated 6 inches.

Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Sunday
• 
• High: 86 °
• Low: 70 °
• Chance of T-Storms

• Monday
• 
• High: 82 °
• Low: 72 °
• Partly Cloudy

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

• Wednesday
• 
• High: 90 °
• Low: 66 °
• Chance of Rain

• Thursday
• 
• High: 88 °
• Low: 72 °
• Chance of a Thunderstorm

Area forecast discussion 
National Weather Service Austin/San Antonio Texas 
902 PM CDT Sat may 25 2013 


Update... 
no significant changes made to ongoing forecast. The threat for 
additional rainfall...locally heavy...will continue overnight. 


&& 


Discussion... 
a lull in activity will continue this evening...but another round 
of showers and thunderstorms is expected overnight as a middle/upper 
level short-wave moves across the area. Storm development overnight 
will be less widespread than we have had the last 24-36 hours. 
However...the combination of rich moisture through the lower 
levels (00z area soundings indicate precipitable water values of 1.5 to near 2 
inches)...and a weak stalled front suggest the potential for 
efficient rain-producing thunderstorms which will also move slowly 
and/or train over the same area. Therefore...locally heavy 
rainfall remains a concern. New rainfall totals for midnight 
through Sunday morning will average one to two inches...with 
spotty amounts of two to four inches...and isolated totals as high 
as six inches possible. The potential for the highest rainfall 
totals will generally be across the eastern Hill Country...greater 
Austin metropolitan area...and the plains east of Austin. However...due 
to the recent heavy rains over the last 24-36 hours...any additional 
rainfall will likely be problematic and will therefore keep the 
Flash Flood Watch in effect for the eastern half of the region. 


The only changes made to the ongoing forecast package were to 
reduce probability of precipitation and quantitative precipitation forecast for 00-06z as well as remove wording of heavy 
rainfall before midnight. New zones will be out shortly. 


&& 


Previous discussion... /issued 630 PM CDT Sat may 25 2013/ 


Aviation... 
slow eastward moving upper air trough over south Texas will keep 
a moist southerly low level flow into S Texas over the next 24 hours. 
Generally VFR conditions...except for isolated rain showers/thunderstorms and rain 04z will 
give way to MVFR ceilings after 04z and MVFR-IFR ceilings 08z-14z. 
Ceilings/visibilities lower after 05z more organized rain showers/thunderstorms and rain could develop 
along the i35 corridor and continue through about 12z before lifting 
northeastward out of the area. Otherwise S-southeasterly winds of 5-15 knots prevailing. 
MVFR ceilings after 15z Sunday becoming VFR most areas by 18z...with 
isolated rain showers/thunderstorms and rain mainly due to afternoon heating behind the 
upper trough. 


Previous discussion... /issued 347 PM CDT Sat may 25 2013/ 


Short term (tonight through Sunday night)... 
flood potential has temporarily abated for most areas for late 
this afternoon as the majority of the middle to upper level 
disturbance has shifted east. However...an additional shortwave 
will lift northeast into south central Texas by late this evening. A 
few strong thunderstorm cells will possible take advantage of 
outflow boundaries...pooled moisture and heating to produce 
locally heavy rainfall across areas SW of San Antonio. We 
currently think this could be a brief late afternoon round of rain 
that should be separate from the shortwave induced activity that 
develops later tonight. The effects of this more progressive 
shortwave seems poorly handled by most of the models given the 
very high precipitable water values close to 2 inches...so will factor in some 
slower departure from our counties as the convection taps into a 
broader middle-level shear axis. Thus there remains an isolated 
potential for another outbreak of warm core rains...but the more 
progressive upper level pattern should shift the heavier rainfall 
totals slightly east of I-35. Still...with a potential for heavy 
slow moving thunderstorms capable of producing a 4 inch rain in 
one hour...will continue the existing watch area through 8 am 
Sunday to account for the extra sensitive soils and swollen 
streams. This forecast may appear to be a bit of an outlier to 
what is forecast by most models...but recollections of how models 
handled earlier warm season shear axis-based pattern such as the 
July 2002 patterns...would suggest the models are too quick to 
improve stability. 


Long term (monday through saturday)... 
the large amount of water stored in soils should also continue to 
linger into daytime hours Sunday and possibly have a slight 
influence on weather...particularly temperatures...for the next 
week or so. Thus have trended on the moist side of probability of precipitation for the 
next 5 days...as a possible disturbance that could enhance rain 
and storm chances by middle-week should still benefit from locally 
higher precipitable water values. Model consensus shows a flat ridging pattern 
that should eventually establish hotter and drier days by next 
weekend. 


&& 


Preliminary point temps/pops... 
Austin Camp Mabry 69 90 69 91 71 / 70 30 10 10 - 
Austin Bergstrom international Airport 69 88 68 90 71 / 70 30 10 10 - 
New Braunfels Muni Airport 68 90 67 90 70 / 70 30 10 10 - 
Burnet Muni Airport 67 87 66 89 69 / 50 20 10 10 - 
del Rio International Airport 73 91 72 95 74 / 20 10 10 10 - 
Georgetown Muni Airport 68 87 67 88 70 / 70 30 10 10 - 
Hondo Muni Airport 70 90 69 93 71 / 50 20 10 10 - 
San Marcos Muni Airport 69 89 69 90 71 / 70 30 10 10 - 
La Grange - Fayette regional 73 88 72 89 74 / 60 30 10 10 10 
San Antonio International Airport 70 89 70 91 72 / 60 30 10 10 - 
Stinson Muni Airport 70 89 69 91 71 / 60 30 10 10 - 


&& 


Ewx watches/warnings/advisories... 
Flash Flood Watch until 8 am CDT Sunday for the following counties: 
Atascosa...Bastrop...Bexar...blanco...Burnet...Caldwell...Comal... 
Delaware Witt...Fayette...Gillespie...Gonzales...Guadalupe...Hays... 
Karnes...Kendall...Lavaca...Lee...Llano...Travis...Williamson... 
Wilson. 


&& 


$$ 


Mesoscale/aviation...01 
synoptic/grids...25 
public service/data collection...31