Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
1244 PM CDT Thursday Jul 24 2014
Update...18z aviation below.
Aviation...a middle level disturbance is contributing to chances for
rain showers and thunderstorms today across south-central Texas. Coverage has
diminished over the past 2 hours along and east of the I-35
corridor...with now just a lone thunderstorm north of aus moving SW into
The Hill Country. Latest hi resolution runs of hrrr and ttech seem
to have slightly better handle on trends...although not perfect...
and show isolated convection developing middle afternoon through sunset
along and south of I-10...with best chances to mention vcsh in
taf at drt. Rain showers/thunderstorms should end after sunset. Outside of
precipitation...VFR conditions will prevail across the region this
afternoon and evening.
Previous discussion... /issued 919 am CDT Thursday Jul 24 2014/
just sent a major update to the forecast for the remainder of the
day through 02z this evening. In short...the mesoscale convective system that developed
over Oklahoma/Arkansas yesterday held together enough to bring
showers to locations along and north of Interstate 10 this
morning. A second area of stronger storms has developed in the
Brenham area. This latter area of storms matches well with the
ttech and csu WRF runs...and to a lesser extent with the hrrr.
Thus...we expect this area to grow in size and begin moving nearly
due west along with the general motion of the remnant from a TUTT
low over Louisiana in previous days. The highest probability of precipitation and best
chances for rain are in the extreme eastern areas of the coastal
plains...with chances and quantitative precipitation forecast decreasing to the west. Temperatures
will be 3-5f cooler than the previous forecast...due to the
extensive cloudcover...which will last through early afternoon
before scattering out due to mixing and ingesting of boundary
layer moist air in to developing thunderstorms.
Previous discussion... /issued 647 am CDT Thursday Jul 24 2014/
today's first round of showers are affecting the Austin area
terminals with VFR conditions prevailing at all sites. A second round
of showers and thunderstorms are anticipated later in the
afternoon as an upper level disturbance moves across south central
Texas. Opted to leave out mentioning rain showers/thunderstorms and rain from the 12z tafs
package as anticipated showers or storms will be isolated and
difficult to pinpoint at this time. Winds will be light and
variable through about noon today and becoming southeasterly at 5
to 10 knots in the afternoon. Otherwise...VFR conditions to
dominate the area sites for the forecast period.
Previous discussion... /issued 352 am CDT Thursday Jul 24 2014/
Short term (today through friday)...
northeasterly flow aloft is well entrenched across south central
Texas per area 24/00z radiosonde observation data. This pattern usually does not
Bode well for precipitation. However...the latest radar data does
show some weak echoes developing across portions of central Texas.
This activity is likely enhanced by a middle-level shortwave trough
moving through the central portion of the state early this
morning. In addition...a surface trough located roughly along an
Austin to Rocksprings line as of 06z could aid in the development
of convection today. The hi-res RUC...3km Texas tech WRF and sref
are in good agreement in showing additional convection this
afternoon across a good portion of south central Texas. Based on
the above...we have included a 20% chance for showers and
thunderstorms across most areas today. A decrease in activity is
expected with the loss of daytime heating and with subsidence
moving in behind the middle-level shortwave trough. On Friday... a
few showers and storms remain possible across the coastal
plains... with the remainder of the region expected to remain dry.
Otherwise...hot and humid conditions will persist through Friday
with highs in the middle 90s to near 100 and lows in the 70s.
Long term (friday night through wednesday)...
the flow aloft slowly begins to change from northeast to east this
weekend as the dominant subtropical ridge axis expands across the
region. With this pattern intact...we expect dry weather along with
continued hot and humid conditions through the weekend. For the
early and middle portion of the upcoming work week...the medium
range models continue to remain consistent with the large scale
flow pattern across the Continental U.S.. the subtropical ridge will
retrograde into the Desert Southwest...while a deep trough
develops over the eastern half of the lower 48. This will bring
northwest flow aloft to south central Texas beginning Tuesday and
continuing through next week. A cold front is expected to
gradually work southward into Texas next week...with the timing of
this front likely controlled by the amount of convection that
develops near the boundary. MOS guidance probability of precipitation are rather low...but
given the pattern...would not be surprised if later data began to
show an increase in precipitation chances. For now...we will keep
probability of precipitation low (20%) for Tuesday and Wednesday...with locations
generally north of I-10 remaining favored for precipitation.
Temperatures should also begin a slow downward trend next
week...but current data suggests that will not happen until
Preliminary point temps/pops...
Austin Camp Mabry 97 76 100 76 99 / 30 30 - - -
Austin Bergstrom international Airport 96 73 99 73 98 / 30 30 - - -
New Braunfels Muni Airport 96 73 99 73 99 / 40 40 - - -
Burnet Muni Airport 95 74 97 74 97 / 40 30 - - 0
del Rio International Airport 98 77 100 77 101 / 20 20 - - 0
Georgetown Muni Airport 95 75 98 75 98 / 30 30 - - 0
Hondo Muni Airport 95 73 98 74 99 / 30 30 - - 0
San Marcos Muni Airport 95 73 98 74 98 / 40 40 - - -
La Grange - Fayette regional 95 75 98 76 97 / 70 50 20 10 10
San Antonio International Airport 95 76 98 76 98 / 30 30 - - -
Stinson Muni Airport 96 75 98 75 99 / 30 30 10 - -
public service/data collection...33