Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
650 PM CDT Thursday Sep 3 2015
Aviation... /00z taf update/
isolated showers near Bastrop could move into the aus vicinity in the
next hour...but with most of this activity lasting only 30 minutes
to 1 hour...will hold off mention in the tafs at this time. Higher
moisture levels noted on 24-hour surface ob trends combined with
the inverted middle-level trough over south central Texas tonight
should lead to more agressive low cloud coverage. Have introduced
small periods or tempos of IFR ceilings along I-35 around
daybreak...as IFR ceilings were noted in a few areas briefly this
morning as well. Some extra taf periods were included mainly to
account for diurnal wind shifts that can occasionally exceed 12
knots in the afternoon and early evening.
Previous discussion... /issued 233 PM CDT Thursday Sep 3 2015/
Short term (tonight through Friday night)...
No significant highlights in the short term with only some
welcomed light to moderate showers this afternoon and expected
coverage again tomorrow. Near normal temperatures will continue
during this time window.
Shallow low-level buoyancy and weak middle-level divergence from the
middle to upper level low over the Gulf is aiding some isolated to
scattered showers across the coastal plains this afternoon.
Mixed layer instability is between 500-1000 j/kg and middle to low-
level lapse rates are poor. This combination of thermodynamics is
not allowing for deeper convection as there is also a warm nose
around 500 mb as suggested by NAM/GFS soundings. All these
factors combined should limit thunder possibilities. Have placed
shower wording as the dominate weather type through 8pm with only
slight chance of thunder in the southeast coastal plains. This activity
will dissipate through the middle to late evening with
For Friday...a similar pattern is expected with slightly steeper
low-level lapse rates and a slightly cooler 500mb layer. This
should allow for isolated/scattered showers and a few thunderstorms to develop
again primarily across the coastal plains but some isolated
showers may develop all way into the Rio Grande Valley and
portions of the southern Edwards Plateau. Again...this activity
will dissipate through the evening hours.
Long term (saturday through thursday)...
Only small to negligible chances of rain during the weekend as
temperatures climb a little higher into the middle and upper 90s with
a ridge building in. Heat index values will reach into the
100-105f degree range for eastern and southern portions of the
Global models are in good agreement that the ridge over North
Texas now will further strengthen Saturday and Sunday while
shifting slightly south towards this area. Other than some sea-
breeze activity in the far southeast...showers will be quite limited and
rain chances are only 10-20% at best. Temperatures will be on the
rise with middle and upper 90f readings with some sporadic low 100s
in the Rio Grande Valley being likely. Heat index values will
climb into the 100-105f range both afternoons.
Ridge positioning continues to slide SW early next week over The
Big Bend as it becomes flatter from stronger middle-latitude flow.
North Texas will likely get some rain relief from some passing
weather systems but they appear to be too far north for this
region to take part. By middle to late next week however... stronger
northwest flow may set up over the region and aid in shower and
thunderstorm chances as ridge center shifts even farther west.
Will need to monitor the evolution of the northwest flow as the ec is a
bit faster than the GFS with the ridge breakdown. Models continue
to fluctuate run-to-run in the longer term with a stronger
longwave trough axis that could bring the first decent front
towards the region sometime late next weekend.
Preliminary point temps/pops...
Austin Camp Mabry 75 95 76 97 76 / 20 20 10 10 -
Austin Bergstrom international Airport 72 93 74 96 74 / 20 20 10 10 -
New Braunfels Muni Airport 74 95 75 97 74 / 20 20 10 10 -
Burnet Muni Airport 73 94 74 95 74 / 10 10 10 10 -
del Rio International Airport 76 97 77 97 77 / 10 20 10 10 -
Georgetown Muni Airport 74 94 75 95 75 / 10 20 10 10 -
Hondo Muni Airport 73 96 75 97 74 / 10 20 10 10 -
San Marcos Muni Airport 73 94 76 96 75 / 20 20 10 10 -
La Grange - Fayette regional 74 93 76 96 76 / 30 20 10 20 -
San Antonio International Airport 76 95 77 96 76 / 20 20 10 10 -
Stinson Muni Airport 75 96 76 97 75 / 20 20 10 10 -
public service/data collection...Treadway