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

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000
FXUS64 KEWX 150545
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1245 AM CDT Tue Oct 15 2019

.AVIATION...
Currently all airports have VFR conditions. MVFR ceilings should
develop in the Austin and San Antonio areas over the next few hours
and then prevail through the morning. These ceilings will spread to
DRT by around sunrise. A cold front will move into the region this
evening bringing northerly winds and a chance for showers and
thunderstorms. The wind shift will arrive at DRT around 03Z, AUS 05Z,
and San Antonio 06Z. Convection chances will begin around 00Z at AUS
and 03Z in San Antonio and Del Rio.


&&

.PREV DISCUSSION... /ISSUED 333 PM CDT Mon Oct 14 2019/

SHORT TERM (Tonight through Tuesday Night)...
Subsidence drying associated with a weak mid-level wave has allowed
for clearing skies across much of the Rio Grande Plains this
afternoon, with temperatures rising into the upper 80s to lower 90s
across the southern half of the region. Earlier showers have
generally shifted north and east of the region and dry conditions are
expected to persist through the remainder of the overnight hours.
With moist, southerly flow in place, return of nocturnal stratus will
keep overnight lows in the upper 60s to low 70s.

A surface cyclone over the Northern Plains associated with a
northern stream shortwave trough will drag a strong cold front
towards the region during the day Tuesday. An attendant pre-frontal
trough sliding across West Central Texas ahead of the front is
expected to reach the Edwards Plateau and Hill Country by late
Tuesday afternoon. Veered low level flow ahead of this feature will
result in temperatures climbing further into the low to mid 90s
across much of the region on Tuesday. Forecast soundings near Del Rio
show this daytime heating contributing to modest destabilization
along and ahead of the surface trough with CAPE values ranging from
1000-1500 J/kg. Additionally, afternoon water vapor imagery shows an
embedded southern stream shortwave trough has pinched off over
southern California and Nevada within broad troughing across the
western United States. The approach of this shortwave during the day
Tuesday will result in 0-6 km bulk shear values exceeding 35 knots.
Higher resolution guidance continues to indicate the potential for a
few discrete thunderstorms to develop somewhere across the lower
Trans Pecos, Edwards Plateau or Hill Country along this pre-frontal
trough and the aforementioned environmental parameters may result in
a strong or possibly severe thunderstorm developing during the late
afternoon or evening hours. Large dewpoint depressions indicate that
gusty winds will be the primary threat with any thunderstorm that is
able to develop, but some small hail also cannot be ruled out with
steep mid-level lapse rates in excess of 6.5 C/km.

West to southwest flow ahead of the California shortwave trough will
also ensure that the region maintains its mid/upper level Pacific
moisture tap from the area of disorganized thunderstorms near Baja
California. This will keep atmospheric moisture values near or over
200 percent of normal for this time of year, which will raise
concerns for at least brief heavy rainfall. Cold pool interactions
may allow for early evening thunderstorm activity to grow upscale and
propagate south and east towards Interstate 35, but the cold front
is ultimately expected to overtake this activity Tuesday night as it
sweeps south across the region. Scattered to numerous thunderstorms
expanding across the front may produce as much as 1 to 2 inches of
rain along and south of Highway 90/Interstate 10, but locally higher
amounts will be possible across the entire region given the very
moist environment. SPC HREF members have remained consistent in
advertising isolated 2 to 4 inch pockets of rainfall. While most of
the area is only expected to receive beneficial drought relief, high
rain rates could result in some localized minor or nuisance flooding
issues in urban areas or areas with poor drainage Tuesday night.
Otherwise, expect some cooler air to filter in behind the front with
lows in the mid 50s to upper 60s.

LONG TERM (Wednesday through Monday)...
Rain chances will linger through the day Wednesday as the California
shortwave closes off somewhere across eastern New Mexico or West
Texas as warm, moist flow overrides the shallow post-frontal layer.
The deterministic GFS is currently the fastest and deepest with this
closed low, but is faster than all of its ensemble members... which
are more closely aligned with the European. Analysis of model trends
over the past few runs have shown the deterministic GFS has offered a
rather erratic trend with the solutions for this wave and have
trended rain chances for Wednesday, Wednesday night, and Thursday
closer to the slower European as a result. This would keep isolated
to scattered showers and isolated thunderstorms possible across the
entire region through this time with coverage likely increasing as
the base of the closed low slides west to east across the region on
Thursday.

Drier and warmer conditions are expected behind the front by Friday,
but return flow may allow for a few showers and storms to creep into
the Coastal Plains over the weekend. The next cold front, and
potential for areawide rain chances, looks to reach the region by
Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              92  62  69  54  76 /  30  60  30  20  20
Austin Bergstrom Intl Airport  92  62  68  53  75 /  30  70  40  20  20
New Braunfels Muni Airport     93  63  68  54  76 /  20  70  50  20  30
Burnet Muni Airport            89  59  69  51  74 /  40  60  20  20  20
Del Rio Intl Airport           94  65  71  58  78 /  10  60  60  30  30
Georgetown Muni Airport        90  60  69  52  74 /  40  60  20  20  20
Hondo Muni Airport             96  64  71  56  77 /  10  70  70  30  30
San Marcos Muni Airport        93  62  68  54  75 /  20  70  50  20  20
La Grange - Fayette Regional   92  65  70  56  76 /  30  70  50  20  10
San Antonio Intl Airport       94  64  69  57  76 /  10  70  60  20  30
Stinson Muni Airport           94  65  70  58  76 /  10  70  60  30  30

&&

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

$$

Aviation...05
Short-Term/Long-Term...Runyen


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