Scientific Forecaster Discussion
fxus64 kewx 280046
Area forecast discussion
National Weather Service Austin/San Antonio Texas
746 PM CDT Mon Mar 27 2017
Aviation.../00z taf cycle/
VFR conditions prevail across the region with very isolated thunderstorms and rain
across The Hill Country. This activity will dissipate by 130-02z.
MVFR ceilings will return to kaus/ksat/kssf near 03-04z and then fall
to IFR 07-08z. Ceilings could approach LIFR at times but confidence
in temporal occurrence is low to not include on this issuance. Kdrt
will follow suit but be delayed by 3 hours or so behind the other
sites. Ceilings will improve through mid to late morning hours to
MVFR then VFR by the early afternoon for all locations. Surface
winds will be southeast and then south through the overnight into
Tuesday with some gusts reaching into the 20-25 knot range ahead of
strong storm system. Increased rain showers and thunderstorms and rain activity is expected
late Tuesday night into Wednesday morning across south-central
Texas. Thunderstorms and rain will likely be added to tafs in the next few cycles when
timing can be better assessed.
Previous discussion... /issued 349 PM CDT Mon Mar 27 2017/
Short term (tonight through Tuesday night)...
the main concern in the near term will be monitoring a retreating
frontal boundary for possible convection this afternoon and evening.
Chances are fairly low, but we have included a slight chance for
areas along and north of a Lexington to Burnet to Fredericksburg
line. Any convection that develops is expected to decrease with the
loss of daytime heating. For the overnight hours, south to
southeasterly flow in the low-levels will increase, bringing an
increase in moisture to all areas. Some models show some light
showers developing overnight across the coastal plains and Hill
Country areas. We will leave this out of the forecast for now as
overall confidence is low. Attention will then turn to an upper level
trough set to impact the region beginning Tuesday afternoon. Several
hi-res models show potential for convection to break out during the
late afternoon hours across the Rio Grande plains, southern Edwards
Plateau and Hill Country. If convection does manage to develop,
storms would likely become severe fairly quickly given good cape
values along with adequate vertical wind shear. By early evening,
the dryline located across west central Texas is expected to become
increasingly active. As dryline storms propagate eastward,
thunderstorm chances will be on the increase for areas along and west
of I-35 during the overnight hours. Some of the hi-res models show
the line of storms could weaken as they approach the I-35 corridor.
I'm not completely sold on this solution as we should still have some
good lift across the region with the upper low to our west.
Long term (wednesday through monday)...
early Wednesday morning, we expect showers and thunderstorms to be
ongoing across much of The Hill Country and I-35 corridor. For the
afternoon hours, convection should move east of the I-35 corridor as
the cold front shifts east. We will need to monitor the front during
the afternoon hours on Wednesday as this may provide a focus for
convection. The upper level trough axis moves east of our region
Thursday afternoon as dry, northwest winds spread over the area. Dry
weather continues on Friday, but southerly winds will quickly return
to the area ahead of the next upper level system. There is some
disagreement among the extended models with regards to the timing of
the next upper trough. The European model (ecmwf) remains faster and shows a more open
wave, while the GFS and Canadian show more of a closed upper low. We
will continue to monitor and for now will show rain chances for most
areas Saturday through Monday.
Preliminary point temps/pops...
Austin Camp Mabry 68 86 67 84 57 / 10 30 70 50 10
Austin Bergstrom Intl Airport 68 86 67 83 55 / 10 20 70 60 10
New Braunfels Muni Airport 67 85 67 85 56 / 10 20 70 50 10
Burnet Muni Airport 65 80 62 81 53 / 20 30 80 30 10
del Rio Intl Airport 69 87 60 87 56 / - 30 60 10 0
Georgetown Muni Airport 65 84 65 82 55 / 20 30 70 50 10
Hondo Muni Airport 68 84 64 87 55 / 10 30 70 20 10
San Marcos Muni Airport 68 85 68 84 54 / 10 20 70 60 10
La Grange - Fayette regional 68 86 71 80 59 / 10 10 50 80 20
San Antonio Intl Airport 69 83 67 86 57 / 10 30 70 40 10
Stinson Muni Airport 69 85 67 85 57 / 10 20 70 40 10