Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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000
FXUS64 KEWX 142356
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
656 PM CDT Sat Oct 14 2017

.UPDATE...
See below for the 00z aviation discussion...

&&

.AVIATION...
Currently VFR at all terminals. VFR conditions are expected to
prevail for the rest of the evening and into the early overnight
period. Low clouds should develop in the 10-11z time period dropping
flight categories to MVFR at DRT and IFR at AUS/SAT/SSF. The cold
front should move through the terminals in the 12z-15z time period.
Models suggest a thin line of showers along the front with isolated
showers behind it, so have -SHRA in the TAFs at AUS/SAT/SSF for a few
hours to account for this. Behind the front, winds shift to
northerly with sustained winds of 15 knots and gusts up to 25 knots.
CIGs improve to MVFR by around 15z and then to VFR by 18z-19z.

&&

.PREV DISCUSSION... /ISSUED 255 PM CDT Sat Oct 14 2017/

SHORT TERM (Tonight through Sunday Night)...
An upper level trough moving through the Rockies and surface low
over the Central high Plains will maintain a moist southerly lower
level flow over South Central Texas tonight. Well above normal low
temperatures and another round of stratus and patchy to areas of fog
are expected during the overnight into early morning. The trough and
low move out across the Plains on Sunday bringing a cold front across
our area. Current projections have it entering the Hill Country just
before sunrise, moving off the I-35/Highway 90 Escarpment, including
the Austin and San Antonio metro areas, by mid morning, and then
exiting to our south and east by midday. Upper level dynamics pass
well north of our area as an upper level ridge axis remains over our
area making the front the only forcing mechanism. A moist airmass
with PWS up to 1.7 inches is forecast ahead of the front. Moisture
convergence should be sufficient for a line of showers and
thunderstorms to enter the Hill Country. Then, moisture convergence
weakens during the morning as slightly drier north winds bridge the
front causing the line to break apart. However, some brief isentropic
lift keeps showers and thunderstorms going over southern portions of
the Rio Grande Plains late morning into the early afternoon. In the
wake of the front, breezy to windy conditions are expected due to a
tight surface pressure gradient and moderate to strong cold
advection. Wind speeds may reach advisory levels across western Val
Verde County in the morning. Expect an abrupt drop in temperatures
with the front, then a slow rise during the afternoon as sunshine
reappears. Clearing skies and cold advection enable temperatures to
drop below normal Sunday night, though mixing keeps them up somewhat.

LONG TERM (Monday through Saturday)...
Dry surface ridging holds on early into middle of next week. The
pressure gradient weakens on Monday with decreasing winds in the
afternoon. Nearly efficient radiational cooling is expected at night
as winds become mostly calm with mostly clear skies. The coldest
periods are Tuesday and Wednesday mornings when the coldest
temperatures of the season thus far are expected with lows in the
40s most areas, except near 50 in the urban areas. Cannot rule out a
few upper 30s in low lying spots. A weakness in the upper ridging
develops late week into next weekend. Southerly winds return bringing
a warming and moistening trend. Moisture may deepen sufficiently for
some streamer showers on Friday and Saturday across eastern areas.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              70  76  53  76  49 /  10  40   0   0   0
Austin Bergstrom Intl Airport  69  77  53  76  48 /  10  40   0   0   0
New Braunfels Muni Airport     70  78  55  76  48 /  -   30   0   0   0
Burnet Muni Airport            66  71  50  73  46 /  30  50   0   0   0
Del Rio Intl Airport           69  76  56  76  51 /  10  40   0   0   0
Georgetown Muni Airport        68  74  51  73  47 /  20  50   0   0   0
Hondo Muni Airport             70  80  55  77  48 /  -   40   0   0   0
San Marcos Muni Airport        70  78  54  76  48 /  10  30   0   0   0
La Grange - Fayette Regional   70  81  56  76  48 /  -   20   0   0   0
San Antonio Intl Airport       71  79  56  77  50 /  -   30   0   0   0
Stinson Muni Airport           71  80  59  77  52 /  -   30   0   0   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Mesoscale/Aviation...Williams
Synoptic/Grids...24



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