Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Austin/San Antonio Texas
633 PM CST Mon Nov 20 2017
please see the 00z aviation forecast discussion below.
VFR conditions are expected at area taf sites through the current
forecast period. Light southerly winds will continue overnight along
the I-35 corridor, while winds back to a more easterly direction at
drt. We will also continue to see plenty of high clouds overnight.
Low cloud development should remain favored east of the I-35 corridor
given south-southwesterly flow in the low levels overnight. We will
continue to mention scattered clouds along I-35, but cigs should still
remain VFR. Winds along I-35 veer to a more westerly direction ahead
of a cold front tomorrow, with the front set to move through in the
00z-02z time frame. Some northerly gusts are expected behind the
boundary, but should remain at or below 20kts. The front should move
through drt a little earlier and we will show a northwest wind shift
around 18z. This could be a little early and would not be too
surprised if we need to delay the wind shift in subsequent forecasts.
Previous discussion... /issued 232 PM CST Mon Nov 20 2017/
Short term (tonight through Tuesday night)...
as one mid level shortwave moves away tonight another approaches on
Tuesday into Tuesday night. Surface ridge drifts off to the east by
Tuesday with southerly lower level flow bringing moisture back into
mainly eastern parts of our area. Will maintain patchy fog across the
far eastern areas for late tonight into early morning. Warmer low
temperatures are expected tonight, though will go slightly below
guidance due to an initially drier airmass across most areas. Warmer,
above normal, high temperatures are expected on Tuesday ahead of a
cold front that moves across our area late afternoon into evening.
Weak isentropic lift briefly develops behind the front and ahead of
the shortwave and right entrance region of an upper level jet streak
and along with sufficient moisture allows for isolated showers near
the coastal plains. Cannot rule out one or two lightning strikes due
to weak instability there. Breezy conditions develop in the wake of
the front due to a tightening surface pressure gradient.
Long term (wednesday through monday)...
the shortwave and jet streak move off to the east ending the weak
lift and showers by early Wednesday morning. Surface high settles
over our area Wednesday into Wednesday night for cool, below normal
temperatures. Breezy conditions Wednesday morning subside as the day
progresses due weakening pressure gradient and less mixing of aloft.
The surface high drifts off to the east with a warming trend to above
normal temperatures for Thanksgiving day through Saturday. An upper
level trough passing by well to our north will drag a weak cold front
into our area late Saturday into night. Not much cool down expected
as cold advection is mostly shunted to our northeast. Front lifts
back north on Sunday with above normal temperatures continuing into
next Monday with lower level moisture returning.
Preliminary point temps/pops...
Austin Camp Mabry 50 75 50 64 41 / 0 0 - 0 0
Austin Bergstrom Intl Airport 47 75 51 64 39 / 0 0 10 0 0
New Braunfels Muni Airport 48 76 51 65 39 / 0 0 - 0 0
Burnet Muni Airport 46 73 44 62 38 / 0 0 - 0 0
del Rio Intl Airport 44 78 47 67 41 / 0 0 0 0 0
Georgetown Muni Airport 49 74 48 63 38 / 0 0 10 0 0
Hondo Muni Airport 45 78 48 68 38 / 0 0 0 0 0
San Marcos Muni Airport 48 76 50 65 39 / 0 0 - 0 0
La Grange - Fayette regional 50 76 53 64 39 / - - 20 0 0
San Antonio Intl Airport 50 76 51 66 41 / 0 0 - 0 0
Stinson Muni Airport 48 77 53 67 42 / 0 0 - 0 0