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

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FXUS64 KEWX 170454 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
1054 PM CST Mon Jan 16 2017

.AVIATION.../06Z TAF CYCLE/

MVFR conditions have developed across KAUS/KSAT/KSSF with KDRT
remaining VFR as of 0450Z. -DZ and -SHRA is ongoing as well across
the Texas coastal plains and this activity is beginning to move into
the KAUS terminal area over the past half hour. This slow west trend
of the -DZ/-SHRA activity will continue through the overnight hours.
Have added -DZ and -RA to KAUS/KSAT/KSSF TAFs through the overnight
as this activity expands. Ceilings will also fall through the night
to at least IFR. KDRT will be delayed in the MVFR and IFR conditions
until 10-11Z. All sites will likely remain IFR and MVFR through the
all of Tuesday morning with gradual improvement to higher-end MVFR by
Tuesday afternoon. There could be some sporadic VFR pockets but it
will not be widespread as scattered -RA continues over the most of
the region. Greater coverage in some elevated thunderstorms could
occur late Tuesday night into Wednesday morning. This, plus further
saturated conditions, will contribute to lower visibilities in the
2-5SM range. Poor flying conditions will persist through the next
24-30 hours. Surface winds will initially be north overnight and then
become more NE through the day Tuesday.

&&

.PREV DISCUSSION... /ISSUED 938 PM CST Mon Jan 16 2017/

UPDATE...
Made few minor changes to the first period. Removed mentioning of
isolated thunderstorms across the eastern part of South Central Texas
through at least midnight tonight. The new NAM12 and HRRR model
solutions keep light showery activity across the eastern half of the
area through the overnight hours. Later tonight, the warm front is
expected to push back to the north and to the east of the I-35
corridor. Area forecast soundings suggest a light chance for elevated
convection and decided to go with isolated thunderstorms across the
far east after 06Z Tuesday. Showers and thunderstorms are expected to
increase late Tuesday morning into the afternoon as the warm frontal
boundary interacts with the upper level forcing of an upper level
disturbance over the four corners region moves into Southern Plains.
A few isolated strong to severe storms are possible Tuesday afternoon
across the far southeast where instability values and forcing are
best.

PREV DISCUSSION... /ISSUED 556 PM CST Mon Jan 16 2017/

AVIATION.../00Z TAF CYCLE/

VFR conditions are ongoing as of 2355Z at terminals but decreasing
ceilings through the next 1-2 hours will create MVFR conditions
through the early to mid-evening hours for KAUS/KSAT/KSSF. Further
reduction to IFR is expected after 06Z for those respective sites as
a cold front shifts back west towards the I-35 corridor. In addition
to the low ceilings, -SHRA is on going across the Texas Coastal
Plains and this activity will shift west into the KAUS/KSAT/KSSF
terminals overnight and remain through a good portion of Tuesday.
Have placed VCSH and -DZ. -RA may need to be added based on trends
overnight. Visibilities will also likely drop overnight as the front
backs up as a weak warm front. Visibilities could drop down to 3-5SM
and could be lower at times through the day Tuesday with saturated
and -SHRA conditions. KDRT will be delayed in MVFR and IFR until
09-11Z Tuesday morning but will eventually follow suit as other TAF
sites. Little recovery is expected Tuesday as the stalled front
remains over the area. IFR then MVFR by the afternoon will hold on
most of the day.

PREV DISCUSSION... /ISSUED 311 PM CST Mon Jan 16 2017/

SHORT TERM (Tonight through Tuesday Night)...
Late afternoon surface observations show a weak cold front in place
from just north of Giddings to just north of Pleasanton. East of this
boundary, isolated to scattered showers continue to move from south
to north across the coastal plains and Highway 77 corridor. Most
hourly rainfall totals are around one quarter inch or less. However,
a few spots have picked up close to three quarters of an inch in an
hour with repeated showers moving over the same area.

For tonight, the frontal boundary will gradually slide southward as a
reinforcing surge of surface high pressure moves in from the north.
This should keep the higher rain chances east of the I-35/I-37
corridors tonight. We do expect an increase in warm air advection
just above the surface front to take shape tonight. This will lead to
low clouds spreading north and westward across south central Texas,
with cloudy skies across all areas by Tuesday morning. The warm air
advection pattern strengthens on Tuesday as an upper level low
pressure system approaches from the west. This will lead to
widespread showers along with a few thunderstorms on Tuesday. Highs
will also be cooler with lower 50s in the Hill Country to lower 60s
in the coastal plains. For late Tuesday afternoon and evening, we
can`t completely rule out a strong storm or two across the coastal
plains with a lingering frontal boundary and some lift associated
with the upper level trough. Areas of concern include Karnes, DeWitt
and Lavaca counties. In addition, we could see some locally heavy
rainfall given into Tuesday night given training of cells within a
moist (precipitable water values ~ 1.5") environment. At this time,
we will not mention heavy rain in the forecast or Hazardous Weather
Outlook as the above mentioned areas have not seen any significant
rains recently.

LONG TERM (Wednesday through Monday)...
Rain chances continue to remain high across most of south central
Texas on Wednesday as an upper level trough axis continues to
organize to our west. This trough does begin to move east across
Texas Wednesday night and Thursday and we will show decreasing rain
chances from west to east. A much drier weather pattern will take
shape for the end of the work week into the upcoming weekend as the
quality low-level moisture should remain east of the region. We do
expect another upper level trough to move through on Sunday, but
given the lack of moisture, we will only keep a low chance of
rainfall across the coastal plains and Highway 77 corridor on Friday
and Saturday. Sunday is shaping up to be quite windy across the
region as a band of stronger mid-level winds is forecast to move
across central Texas. We have increased wind speeds and will need to
monitor in subsequent forecasts.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              62  56  48  61  49 /  30  60  70  60  20
Austin Bergstrom Intl Airport  60  57  48  61  49 /  30  60  70  70  20
New Braunfels Muni Airport     64  57  49  62  50 /  30  60  70  60  20
Burnet Muni Airport            61  53  45  58  46 /  20  60  70  50  10
Del Rio Intl Airport           63  59  49  65  47 /  -   60  50  10  10
Georgetown Muni Airport        64  54  46  59  47 /  20  60  70  60  20
Hondo Muni Airport             66  60  50  65  49 /  20  60  70  50  10
San Marcos Muni Airport        61  57  49  62  50 /  30  60  70  60  20
La Grange - Fayette Regional   60  61  52  63  53 /  50  60  80  70  50
San Antonio Intl Airport       64  59  50  63  51 /  30  60  70  60  20
Stinson Muni Airport           66  60  51  63  51 /  30  60  70  60  20

&&

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

$$

Mesoscale/Aviation...Allen
Synoptic/Grids...17
Public Service/Data Collection...30



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