Scientific Forecaster Discussion
fxus64 kewx 190520
Area forecast discussion
National Weather Service Austin/San Antonio Texas
1220 am CDT Sat Oct 19 2019
VFR conditions currently prevail at the area airports, but should
start to see MVFR ceilings develop within the next few hours near the
i35 sites. Conditions for the San Antonio sites should lower into IFR
categories by sunrise. While ceilings are anticipated to be the main
flight restriction, some visibility restrictions will also be
possible. Conditions will be slow to improve with VFR expected by
17z. Otherwise, winds will remain light through the period and
veering to the northwest by the evening hours.
Previous discussion... /issued 1004 PM CDT Fri Oct 18 2019/
previous forecast package is on track for the rest of the first
period and into the second forecast period. Expect increased low
level moisture to arrive across the area overnight for mostly cloudy
skies. Also, patchy fog is expected to develop later tonight across
the coastal plains and over areas along the I-35 corridor. Clouds
will lift and scattered out during the afternoon hours. A weak and
dry front is forecast to push across The Hill Country early Saturday
afternoon to bring a wind shift from the northwest to north. This
downslope scenario could bring record high temperatures across some
areas on Saturday. Expecting highs in the lower 90s most areas.
Previous discussion... /issued 708 PM CDT Fri Oct 18 2019/
please see the 00z aviation forecast discussion below.
VFR conditions with clear skies and light southeasterly winds will
continue at all taf sites through this evening. We do expect a surge
in low-level moisture overnight and this will result in IFR and MVFR
clouds along with some fog for the I-35 corridor beginning around 08z
Sat and ssf to around 10z at aus. Forecast soundings favor thicker
cloud cover at Sat and ssf, so we will continue IFR here, but leave
out of the forecast for aus. Improvement is expected after 17z as
cloud bases lift and scatter back to VFR. We will also see winds
remain from the southwest along I-35 through the morning hours, then
shift to a more northwesterly direction as a Pacific cold front moves
in from the northwest. At drt, low clouds are not expected to develop
and will keep the forecast VFR.
Previous discussion... /issued 304 PM CDT Fri Oct 18 2019/
Short term (tonight through Saturday night)...
surface ridging sliding east of the region today has allowed for
south to southeast winds to resume. An upper trough extending from
Wyoming to northern Mexico this afternoon will quickly translate
east across Texas tonight, sending a weak cold front and attendant
pre-frontal trough into the region. Higher resolution guidance
members, including the Storm Prediction Center href ensembles, rap, and NAM, generate a
few light showers as the base of the upper trough reaches The Hill
Country after midnight tonight. Overall column moisture appears
fairly marginal (precipitable water values less than 1.5 inches), but
mid-level saturation may allow for a few sprinkles to reach the
ground before dawn. A weakening surface pressure gradient ahead of
the frontal system's arrival and recent rainfall will allow for
patchy fog to develop across much of the eastern two-thirds of the
region by sunrise, but this fog is not expected to last much longer
than mid-morning Saturday. Otherwise, warmer overnight lows are
expected tonight with lows in the low to mid 60s.
The upper trough's quick eastward progression and rapidly modifying
Post-frontal airmass (indicated by decreasing surface pressure
rises) mean this frontal boundary will likely stall or become
diffuse somewhere across the southern half of the region on Saturday.
The front looks to have almost no effect on temperatures, and in
fact may help contribute to some additional warming tomorrow as light
northerly winds aid in some downslope warming. Afternoon highs
tomorrow in the mid 80s to mid 90s may very well tie or set new high
temperature records. Convective temperatures in the mid to upper 80s
may allow for a few showers and possibly a thunderstorm to develop
along the stalled frontal boundary in the coastal plains, with
coverage possibly enhanced by a signal for a sea breeze/stalled front
collision. Visible satellite imagery shows a weak sea breeze
developed this afternoon and, with stronger surface heating tomorrow
combined with nearshore water temperatures in the lower to mid 70s,
expect farther inland penetration of the sea breeze on Saturday.
Showers may persist in the vicinity of this lingering boundary
Saturday night with lows in the mid 50s to mid 60s.
Long term (sunday through friday)...
on Sunday, another trough crossing the Great Plains will result in
surface cyclogenesis and strengthening southerly flow. As the
surface cyclone ejects eastward with the parent trough during the
day, another cold front will surge south into the region Sunday night
and Monday morning with showers and storms developing along the
front. There still remains the potential for a few strong storms
edging into central Texas along the front Sunday night with stronger
jet dynamics over North Texas. Dry and mild conditions are expected
mid- week behind monday's front. Another cold front looks to reach
the region again Thursday night or Friday morning with showers and
thunderstorms along it, sending another round of below normal
temperatures into the region on Friday.
Preliminary point temps/pops...
Austin Camp Mabry 65 91 67 81 55 / 10 10 50 40 -
Austin Bergstrom Intl Airport 60 92 66 81 54 / 10 10 40 40 -
New Braunfels Muni Airport 63 91 65 82 54 / 10 10 30 50 -
Burnet Muni Airport 61 90 62 78 52 / 0 10 50 20 0
del Rio Intl Airport 62 94 65 87 56 / 0 0 10 0 0
Georgetown Muni Airport 60 91 64 80 52 / - 10 50 30 -
Hondo Muni Airport 62 94 67 87 56 / 10 - 30 30 -
San Marcos Muni Airport 63 91 65 82 53 / 10 10 40 50 -
La Grange - Fayette regional 67 92 68 82 55 / 20 10 40 50 10
San Antonio Intl Airport 66 91 68 83 57 / 10 10 30 40 -
Stinson Muni Airport 66 91 68 83 57 / 10 10 30 40 -