Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
1245 PM CDT Wednesday Jul 27 2016
one more day of isolated shower and thunderstorms that could
impact the terminals through the afternoon. Aus is experiencing a
break in shower and thunderstorm activity that impacted the
terminal through the morning hours. More isolated storms are
currently moving north from baz and hyi that could impact the
terminal from 19z to 22z. For this reason have included a tempo at
aus with prevailing thunderstorms in the vicinity at all other sites. Precipitation should
end around sunset so mention of precipitation has been taken out
Another round of MVFR cigs is expected along I-35 through the
morning hours tomorrow, with some high MVFR cigs are possible at
drt as well. Winds will remain light out of the southeast but
could be gusty around any storms that impact the terminals.
Storms should be more isolated today compared to yesterday and
Monday evening. Amendments will be made as needed through the
afternoon if thunderstorms approach terminals.
Previous discussion... /issued 1025 am CDT Wednesday Jul 27 2016/
persistent small area of thunderstorms on the east side of Austin.
High resolution models show this area dissipating over the next
few hours. Regional radar showing a boundary extending to the east
from this cluster through Bastrop and Lee counties. We will
continue to watch this region for further development. For now,
our ongoing forecast looks to be in pretty good shape. My only
concern is our quantitative precipitation forecast will be too low if storms form along this
boundary. Will keep an eye on it.
Previous discussion... /issued 249 am CDT Wednesday Jul 27 2016/
Short term (today through thursday)...
Mid/upper level cyclonic flow has become broad and elongated with
a shear axis from nern Mexico across the coastal Bend to nrn
Mississippi. A secondary shear axis at 700 mb extends nwd across
our forecast area and into ern OK, and model consensus shows this
feature sharpening today and possibly acting as a increased
convective focus this afternoon. Another and possibly more
significant area expected to destabilize is along a mid-level
moisture gradient over S TX, and models show fair to good
agreement on the convective focus on this focus expanding
northward with time later this morning. Thus locally higher pops
are distributed generally along an an east-west axis 50 miles either
side of US Hwy 90, but scattered convection remains a possibility
over all of the forecast area today into early this evening.
Pwat values will again be in the 1.8 to 2.3 range over much of
the area, and slow expected storm motions could lead to more
isolated pockets of 2-3 inch rains. Should this happen over
certain areas, localized flooding is possible, but most areas
have not seen amounts over half an inch of rain since the rain
chances increased Monday afternoon. The severe weather potential statement will likely look
similar to that of yesterday, with marginal threats for heavy
downpours and wind gusts, with decreasing threats afterwards.
Weak shear over south central Texas should limit overnight rain
chances, and the mid-level shear feature that tightens over
north-cntrl Texas continues to show better focus for rain chances while
pwat values suggest better rain chances east of I-35. Thus for
Thursday, pops are still forecast to be isolated from the San
Antonio area and points west while low end sct convection remains
possible over the nrn Hill Country and east of I-35.
Given the abundance of clouds/convection over the area the next
couple days, will not stray off the blended guidance which remains
below normal today and returns to normals for Thursday.
Long term (thursday night through tuesday)...
Rain chances continue to shrink ewrd Friday into Saturday as the
mid/upper level cyclonic shear pattern continues to weaken and is
replaced with ridging from the west. The 700 mb ridge remains more
anchored over the sern US and Atlantic, which maintains deeper
onshore flow and moisture levels into next week. Thus daily
isolated pops will continue well into the extended over the
coastal prairies as inland areas continue to bake under the broad
upper ridging pattern. Another weakness in the mid-upper levels is
forecast move onshore from the Gulf into Texas by the 00z runs of
the GFS/ecm for late next week.
Preliminary point temps/pops...
Austin Camp Mabry 93 76 97 76 98 / 40 30 30 10 20
Austin Bergstrom Intl Airport 92 76 96 75 96 / 50 30 30 10 20
New Braunfels Muni Airport 92 75 95 75 97 / 50 20 20 10 10
Burnet Muni Airport 92 75 94 74 95 / 40 30 30 20 10
del Rio Intl Airport 95 77 98 78 98 / 40 30 20 20 10
Georgetown Muni Airport 92 76 95 76 96 / 40 30 30 20 20
Hondo Muni Airport 91 75 95 74 96 / 50 20 20 10 -
San Marcos Muni Airport 92 75 95 75 96 / 50 20 30 10 20
La Grange - Fayette regional 92 77 95 76 96 / 50 20 30 10 30
San Antonio Intl Airport 91 76 95 77 96 / 50 20 20 10 10
Stinson Muni Airport 93 77 97 76 97 / 50 20 20 10 10
public service/data collection...Williams