Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
1234 am CDT Sat may 30 2015
an mesoscale convective system currently from north of kabi to north of kmaf will move to the southeast
overnight into central Texas to Edwards Plateau by Saturday
morning prior to weakening. Outflow boundaries from this mesoscale convective system and a
cold frontal passage will lead to rain showers/thunderstorms and rain later in the day into
Saturday night. Have gone with a blend of more recent hrrr runs
and ttu WRF with prob30s for the taf sites in the afternoon into
evening and vcsh otherwise. VFR flying conditions will turn MVFR
and possibly IFR overnight as stratus and br develop. Conditions
return to VFR late morning to midday. Brief MVFR/IFR ceilings are
possible in shra/tsra. Some MVFR ceilings redevelop Saturday evening.
S to southeast winds 5 to 10 kts will turn to north to NE with the outflow
boundary and frontal passage. Some gusts to 50 kts and gr are
possible in and near thunderstorms and rain.
Previous discussion... /issued 658 PM CDT Friday may 29 2015/
Aviation... /00z taf update/
no convection is expected to impact tafs for the first 9-12 hours.
Saturated soils should interact with moderate surface southerlies
to form low clouds before midnight...with perhaps a slight delay
over the Rio Grande plains and the drt area. Nocturnal boundary
layer wind enhancements look conservative in model time
sections...suggesting an abundance of IFR conditions late tonight.
A weakening storm complex is expected over central Texas by
daybreak...possibly a bit faster if recent runs of the hrrr
verify. Will stick with the more conservative Texas tech WRF and the
coarser scale models for this evening...as the late
afternoon/early evening runs of the hrrr have seemed to be running
too aggressive over the past week.
Previous discussion... /issued 254 PM CDT Friday may 29 2015/
Short term (tonight through Saturday night)...
Locally heavy rainfall possible Saturday across south central
Recovery after last nights mesoscale convective system is slowly taking place west to
east across the County Warning Area. Can not completely rule out an isolated
storm through sunset...but the majority of the County Warning Area will remain
dry through the remainder over the afternoon and evening.
Upstream...models are indicating another organized complex of
storms developing this evening across northwest Texas moving
southeast through west-central Texas overnight. Past few hrrr
runs and 12z tt 4km WRF are indicating this potential line of
storms reaching the northern Hill Country 09z-12z. Unlike last
night...this complex may weaken as it moves into The Hill Country
and central Texas Saturday morning. However...outflow boundaries
left over and an eventual weak cold front...will likely trigger
additional showers and storms Saturday afternoon and evening
across much of south-central Texas. At this time...forecasting
timing and locations of heaviest amounts of precipitation are very
difficult...as larger scale forcing is relatively weak.
However...forecast soundings indicate rather large cape values
across the southern half of the County Warning Area Saturday afternoon...exceeding
3500 j/kg. When combined with slow storm motions across central
and eastern County Warning Area...locally heavy rainfall is a possibility Saturday
into Saturday night. A few strong storms possible out west along
the Rio Grande where better deep layer shear is forecast. Overall
rainfall amounts of around 1 inch are possible...with isolated
amounts of 2-3 inches. Given the saturated conditions across the
area...a quick 1-3 inches will cause flash flooding issues in
several areas. Out of an abundance of caution...have elected to
issue a Flash Flood Watch for Saturday and Saturday night.
Long term (sunday through friday)...upper level trough to the
west deepens Sunday into Monday across Arkansas and la. Better moisture
on Sunday remains pooled across the southern and western County Warning Area...
and farther to the south. Can not rule out scattered showers and
storms in this area Sunday...but forcing appears rather limited.
Finally drier conditions will take place along and west of the
I-35 corridor Monday-Thursday. Can not rule out isolated showers
and storms Monday through Thursday across the coastal prairies
closer to better moisture and lower heights with the trough to
Preliminary point temps/pops...
Austin Camp Mabry 67 82 64 85 66 / 40 20 10 20 -
Austin Bergstrom international Airport 65 81 62 85 63 / 40 30 10 20 -
New Braunfels Muni Airport 66 83 64 86 66 / 50 30 10 20 -
Burnet Muni Airport 64 80 62 83 65 / 40 20 10 10 0
del Rio International Airport 67 86 68 88 69 / 40 30 10 10 -
Georgetown Muni Airport 65 81 62 84 64 / 40 20 10 20 0
Hondo Muni Airport 66 83 65 86 66 / 40 40 10 10 -
San Marcos Muni Airport 66 81 64 84 65 / 50 30 10 20 -
La Grange - Fayette regional 68 82 65 85 66 / 50 40 10 20 10
San Antonio International Airport 68 83 66 85 67 / 50 30 10 20 -
Stinson Muni Airport 68 83 66 86 67 / 50 40 10 20 10
Flash Flood Watch from 7 am CDT this morning through Sunday morning
for the following counties: Atascosa...Bandera...Bastrop...Bexar...