Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
102 am CDT Tuesday Sep 1 2015
ceilings have already lowered to MVFR at Sat/ssf...and expect the same
to occur at aus and drt between 9-10z. Ceilings should recover to VFR
by 16z at all sites...but confidence is low due to convection that
is developing along the Gulf Coast near crp. None of the hi-res
models accurately depicted this early onset of thunderstorms and rain...with only
the rap showing some semblance of it. Further...it appears the
midlevel low is a bit further west than most global models are
predicting. Thus...there may be a chance of rain showers at Sat/ssf just
after sunrise...but confidence is too low to include at this time.
The evolution of thunderstorms and rain overnight may have some effect on the
strength of any sea breeze and associated convection that develops
tomorrow. Assuming that ongoing thunderstorms and rain do not expand and disrupt the
development of a sea breeze tomorrow...expect it to pass through
Sat/ssf around 20z and aus around 21z with isolated 20-25 knots wind
gusts for a few hours. Rain showers and thunderstorms and rain coverage should remain below
20-30 percent...particularly at aus...so only included vcsh for
Sat/ssf at this time. Will reevaluate this for the 12z taf package
after seeing how convection tonight along the Gulf Coast evolves.
Previous discussion... /issued 817 PM CDT Monday Aug 31 2015/
convection has dissipated with the loss of daytime heating and
updated the forecast to take the mention of rain out for most of
the County Warning Area...excluding the coastal plains where some additional
activity may be possible overnight east of the upper low. Updated
products have been sent.
Previous discussion... /issued 646 PM CDT Monday Aug 31 2015/
isolated rain showers/thunderstorms and rain currently crossing I-35 corridor will dissipate by
01/01z. Earlier thunderstorms and rain at kssf and rain showers at kaus have dissipated and
impacts are no longer expected for tonight. Isolated/scattered rain showers/thunderstorms and rain
will develop over the coastal plains by morning...spread to the
west on Tuesday to the I-35 corridor...and then dissipate while
moving into the eastern Hill Country early Tuesday evening. For
now...mentioned vcsh at kaus/ksat/kssf middle afternoon into early
evening and will monitor radar and model trends for updates to
VFR skies prevail this evening. Stratus with MVFR ceilings will
develop overnight along the Escarpment and spread to near the Rio
Grande by morning. Have only sct020 at kdrt as ceilings should stay
just east of the site. Clouds will lift to VFR skies by midday.
Except local MVFR ceilings/visibilities possible in shra/tsra.
S to southeast winds 10 to 15 kts this evening in the wake of the
seabreeze...decrease to 7 kts or less overnight. Winds increase
to 7 to 10 kts Tuesday morning and then back with passage of the
seabreeze while increasing to 10 to 18 kts. Wind gusts up to 35
kts are possible in/near rain showers/thunderstorms and rain and wind gusts up to 25 kts are
possible for an hour or two after the passage of the seabreeze.
Previous discussion... /issued 308 PM CDT Monday Aug 31 2015/
Short term (tonight through Tuesday night)...
No significant highlights this period as near average temperatures
persist with only 20-30% rain chances for the coastal plains. Heat
index values will maximum out in the upper 90s with a few sporadic 100f
A few isolated showers are ongoing along an outflow boundary moving
northwest across Gonzales...Fayette and push into Bastrop/Caldwell
and Guadalupe over the next hour. These showers should dissipate
over the next few hours and not likely make it into the metroplexes.
A quiet overnight is expected through 4am for all of the region but
a new moisture surge looks to make its way north along the coast
with some shower activity infiltrating the coastal plains possibly
by 6am. This activity will spread north through the morning and
afternoon hours per hi-res and global models. This activity should
slowly dissipate through the evening hours as the far east locations
may have showers linger through the early morning hours Wednesday.
However...the probability of showers overnight into Wednesday will
be 20% at best.
Long term (wednesday through monday)...
No significant highlights during the long term period as well with
rain chances decreasing through the end of the week and over the
weekend. It appears 20-30% rain/tstorm chances will be the best we
can muster through this period.
By middle to late week...global models diverge in the middle and upper
levels with the evolution of the current closed low over US. Both
models initially take the system farther east over the lower
Mississippi Valley with the ec keeping it there while the GFS
retrogrades it back towards US by Friday. Looking at the ensemble
perturbations...more support seems to be noted for the retrograding
solution of at least a inverted trough to shift back towards the
Texas coast. Following this solution however still seems to be 20-
30% pop Worth given the 700-300mb divergence area south towards
Brownsville. Overall signals will need to be monitored for this
evolution and if this divergence area shifts north. By late weekend
to early next week...better ridging across North Texas should
further the dry and warm trend with no large areas of significant
Preliminary point temps/pops...
Austin Camp Mabry 93 74 94 74 94 / 20 20 20 - 10
Austin Bergstrom international Airport 92 71 93 71 92 / 20 20 20 - 10
New Braunfels Muni Airport 93 73 94 73 94 / 20 20 20 - 10
Burnet Muni Airport 92 72 92 72 92 / 10 10 10 - 10
del Rio International Airport 96 75 96 76 96 / 10 10 - - -
Georgetown Muni Airport 92 73 92 73 92 / 20 20 20 - 10
Hondo Muni Airport 94 72 94 72 94 / 10 10 10 - 10
San Marcos Muni Airport 92 72 92 73 92 / 20 20 20 - 10
La Grange - Fayette regional 92 73 93 73 92 / 40 40 30 10 20
San Antonio International Airport 93 75 94 75 93 / 20 20 20 - 10
Stinson Muni Airport 94 74 94 74 95 / 20 20 20 - 10