Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
FXUS64 KEWX 250530
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1230 AM CDT Tue Apr 25 2017
.AVIATION DISCUSSION...FOR 06Z TAF PERIOD...
Models continue to indicate at least IFR CIG development by around
daybreak for I-35 terminals. Moisture profiles even indicate a period
of LIFR after dawn for KSAT/KSSF this morning. Included this in the
TAF based off these trends. Winds should stay up enough to prevent
much in the way of BR. Expecting improvement to VFR by around 16Z.
Breezy conditions will be the main story for the afternoon, mostly
for the KAUS terminal.
PREV DISCUSSION... /ISSUED 256 PM CDT Mon Apr 24 2017/
SHORT TERM (Tonight through Tuesday Night)...
A compact mid level impulse crossing the Mexican mountains will
generate isolated showers and thunderstorms there this afternoon.
Only the HRRR shows any of this moving across the Rio Grande into our
area this evening. Also, previous runs of TTU-WRF showed some moving
into our far western counties. Have a 5 POP for Maverick and Dimmit
Counties where steering flow would take them.
As an upper level trough moves across the Rockies and out into the
High Plains, a surface low drifts to the northeast across the
Southern Plains. South to southwest lower level flow will result.
This increases moisture for stratus formation later tonight into
Tuesday morning, then it mixes out by midday. The main impact of
this will be a rapid strong warmup as 850 MB temperatures warm to
21C-27C and 925 MB to 27C-33C on Tuesday. High temperatures Tuesday
will be about 10 degrees above normal, with some approaching 100
along the Rio Grande. A dryline moves into western areas late Tuesday
night. There may deep enough moisture below a strong cap for patchy
drizzle along and east of Highway 281 by Wednesday morning. Have
silent 10 POPs for this.
LONG TERM (Wednesday through Monday)...
The upper level trough moves out across the Plains on Wednesday with
the dryline moving across the remainder of our area by midday. In
spite of a right entrance region of an upper level jet passing
overhead, moisture will be confined to below a strong cap with only
patchy drizzle for only silent 10 POPs east of I-35. Should moisture
become deeper and linger longer, then isolated showers and perhaps a
thunderstorm are possible along the Highway 77 corridor around
midday. Downslope flow will keep temperatures above normal Wednesday.
Strong mixing and a tight pressure gradient will result in breezy
conditions. Some guidance shows speeds near advisory levels. Low
humidities combined with the winds mentioned above will create
elevated to near critical fire weather conditions with best chances
for these conditions west of San Antonio along and southwest of the
Escarpment to the Rio Grande. A cold front moves across our area late
in the afternoon into evening after peak heating. No rain is
expected with the front as moisture will have been scoured out by the
dryline. Cool surface high pressure settles into our area Wednesday
night for a return to below normal low temperatures. Cool down will
be short lived as south to southwest lower level flow quickly returns
on Thursday with high temperatures back above normal. The surface
high moves off to the east as surface pressures lower in the Plains
as an upper level trough takes shape over the western states. Another
strong warming trend is expected for late week into next weekend as
850MB and 925MB temperatures rise again. There are good chances for
100 degree high temperatures along parts of the Rio Grande on Friday
and Saturday as 925MB temperatures near 35C.
The western states upper level trough moves across the Plains next
weekend with a dryline/pre-frontal trough and a cold front moving
across South Central Texas. Timing and consistency issues have been
noted in the models and run to run. The 12Z runs show slightly better
agreement and for now, have gone with a Saturday night frontal
passage and a Sunday upper trough passage. Expect isolated showers
and thunderstorms on Saturday to become more numerous Saturday night
and then end on Sunday. There is a potential of strong to severe
storms as forecast soundings indicate high CAPE and shear.
Temperatures fall below normal in the wake of the front and remain
below normal into next Monday due to cool surface high pressure.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 72 89 55 85 69 / 10 10 - 0 0
Austin Bergstrom Intl Airport 72 88 52 84 68 / 10 10 - 0 0
New Braunfels Muni Airport 71 90 53 85 68 / 10 10 - 0 0
Burnet Muni Airport 68 84 51 83 67 / 10 - - 0 0
Del Rio Intl Airport 67 91 58 91 69 / 0 0 0 0 0
Georgetown Muni Airport 71 86 52 83 68 / 10 10 - 0 0
Hondo Muni Airport 66 91 53 88 67 / 0 - 0 0 0
San Marcos Muni Airport 71 89 53 85 68 / 10 10 - 0 0
La Grange - Fayette Regional 72 89 54 84 68 / 10 10 - 0 0
San Antonio Intl Airport 72 90 55 87 69 / 10 - 0 0 0
Stinson Muni Airport 71 91 56 87 68 / - - 0 0 0