Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Austin/San Antonio Texas
1018 PM CDT Tue Mar 28 2017
a Severe Thunderstorm Watch is in effect for areas along and west of
I-35 corridor through 4 am CDT.
Latest radar images showing a line of strong to severe storms
pushing across Val Verde County. The line will continue to fill as it
moves to the east and encounter favorable atmospheric conditions.
Hires models have a good handle on current radar trends and bring the
squall-line along the I-35 corridor around 3/4 am time frame. Main
weather threats tonight into the overnight hours will be damaging
winds and large hail. An isolated tornado is possible but the chances
of occurring are low. Heavy downpours associated with stronger
storms could lead to localized minor flooding across area roadways
and underpasses as well as poor drainage locations.
Previous discussion... /issued 636 PM CDT Tue Mar 28 2017/
isolated +tsra will pass just north of kdrt in the next hour and have
gone thunderstorms in the vicinity there. Otherwise, rain showers/thunderstorms and rain will develop over the lower
Pecos Valley into the Edwards Plateau later this evening and then
gradually form into a line by midnight and then move across the
remainder of south central Texas overnight into Wednesday morning to
midday. Have timing of 03z-05z at kdrt, and 08z-11z kaus/ksat/kssf.
VFR skies start the forecast, then MVFR cigs develop this evening.
Clouds lift to VFR after passage of the line of rain showers/tsra, then
become few-scattered a few hours later. S to southeast winds 10 to 20 kts with
gusts to 30 to 35 kts ahead of the line will become S to SW 5 to 15
kts with its passage, except west to northwest across the Rio Grande into the
Edwards Plateau. Wind gusts up to 50 kts are possible with any thunderstorms and rain.
Previous discussion... /issued 341 PM CDT Tue Mar 28 2017/
Short term (tonight through Wednesday night)...
for the next few hours, the main area of concern will remain out west
along the Rio Grande and southern Edwards Plateau. Currently, we are
beginning to see the low clouds erode across the Rio Grande plains.
Several hi-res models suggest development is possible along this
differential heating zone and this area will need to be monitored
carefully through this afternoon. For the early evening hours, the
Pacific cold front will overtake the dryline across west central
Texas, including the Edwards Plateau. As this occurs, convection
should quickly develop, then progress eastward into the Rio Grande
plains, southern Edwards Plateau and western Hill Country between 9
and 11 PM. For the overnight hours, this line will move eastward and
impact the remainder of The Hill Country and I-35 corridor between
midnight and 6 am. We continue to expect damaging winds and large
hail to be the main severe weather concern for tonight as this line
of storms moves through the area. However, we can't rule out an
isolated tornado as well. As the line shifts east of the I-35
corridor after 6 am, most models indicate a weakening trend as this
line of convection moves east of the strongest upper level lift.
However, we will still need to monitor this line of storms carefully
as it will be moving into favorable moisture and low-level wind
shear. Given the speed of this system, the risk for heavy rainfall
appears rather low at this time. Storm total amounts will likely be
lowest (1/4 inch or less) along the Rio Grande, with amounts
increasing to 1/2 - 1 inch for areas north of a Kerrville to Cuero
line. Some spots could pick up around 1.5 inches north of this line,
but these amounts should be isolated. Areas east of I-35 can expect a
low chance of rain Wednesday afternoon, with the remainder of the
area remaining dry.
Long term (thursday through tuesday)...
a relatively quiet weather pattern is in store Thursday and Friday
and this will lead to a dry forecast along with above normal
temperatures. The pattern is expected to once again become
increasingly active for the upcoming weekend into early next week as
another upper level storm system takes aim at the region. The medium
range models are starting to show a little better agreement with
regards to the mid-level flow pattern. This system should come across
Texas at a lower latitude and this should Bode well for a good chance
of rainfall and active weather across south central Texas, especially
Saturday night and Sunday. This upper system moves to our east by
late Monday, temporarily leaving a dry forecast into Tuesday.
Preliminary point temps/pops...
Austin Camp Mabry 66 87 55 78 55 / 90 50 10 0 0
Austin Bergstrom Intl Airport 65 86 54 78 52 / 90 60 10 0 0
New Braunfels Muni Airport 64 86 53 79 53 / 90 50 10 0 0
Burnet Muni Airport 60 82 51 74 52 / 90 20 10 0 0
del Rio Intl Airport 58 85 54 82 56 / 60 0 0 0 0
Georgetown Muni Airport 63 85 52 76 52 / 90 50 10 0 0
Hondo Muni Airport 60 86 52 81 53 / 90 10 10 0 0
San Marcos Muni Airport 66 87 53 78 52 / 90 50 10 0 0
La Grange - Fayette regional 69 85 56 76 53 / 80 80 20 - 0
San Antonio Intl Airport 64 86 54 80 55 / 90 30 10 0 0
Stinson Muni Airport 66 86 54 80 55 / 90 30 10 0 0