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

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897
FXUS64 KEWX 182358
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
558 PM CST Thu Jan 18 2018

.AVIATION... /00Z TAFS/
Cigs beneath the center of an upper shortwave have lowered into mvfr
between DRT and SAT, and the edge of this area is not far from DRT.
MOS guidance keeps DRT in the clear, but will suspect dewpoint trends
will favor the 18Z MAV and result in conditions near saturation by
daybreak. Confidence is low so will avoid a prevailing ifr/lifr cig
at this time. Along I-35 terminals, guidances are slow to show an
mvfr cig and will introduce 2500-3000 ft cigs in the evening hours,
given the lowering trends just upstream. Later periods follow closer
to the blend of MOS guidances with precipitation potential expected
to stay mainly east of I-35. With the subsident side of the weak upper
low reaching I-35 Friday evening, a quick drop to lifr or worse
conditions are agreed upon by guidances.

&&

.PREV DISCUSSION... /ISSUED 330 PM CST Thu Jan 18 2018/

SHORT TERM (Tonight through Friday Night)...
Area radars continue to show some light echoes moving from southwest
to northeast across the Rio Grande plains. Observations show cloud
bases have been steadily lowering and we will continue to mention a
few sprinkles through this afternoon. For tonight, a coastal trough
across the southern Texas coast will deepen. The cyclonic flow
associated with this trough will bring an increase in moisture to the
coastal plains tonight. Given the increase in moisture along with
lift from an upper low to our northwest, we will continue to mention
a low chance for rain near the coastal plains tonight. Rainfall
amounts are expected to remain light, with less than 1/10 of an inch
expected. On Friday, the coastal trough should move a little farther
inland as the upper level low moves across southern Texas. This will
result in an increase in rain chances for areas generally along and
east of Highway 281. Increasing cloud cover will also hold down high
temperatures on Friday for all areas, except along the Rio Grande.
Highs should range from near 60 out west along the Rio Grande to the
mid 40s along and east of I-35.

LONG TERM (Saturday through Thursday)...
By early Saturday, the above mentioned upper trough will translate
east of the region. Behind this trough we expect a decrease in rain
chances and we will only mention a low chance for showers along
Highway 77. For Sunday, an increase in southwesterly flow aloft will
begin as an upper low moves into the southern Rockies. Rain chances
will increase across most areas during the daytime hours on Sunday.
We could even see a thunderstorm or two east of the I-35 corridor as
a Pacific cold front moves in during the late afternoon hours. Much
drier air behind the front will quickly bring an end to rain chances
during the very early morning hours on Monday. Much drier air behind
the front moves in Monday, bringing an increased concern for fire
weather conditions. We will continue to mention elevated fire weather
conditions on Monday due to low humidities. Wind speeds will be a
little higher during the early part of Monday and should decrease
during the afternoon as humidities bottom out. Zonal flow aloft will
prevail on Tuesday followed by another trough axis moving in
Wednesday. Southerly flow ahead of this next trough will be rather
meager and for now we will only mention a low chance for rain across
our far southern counties in the coastal plains on Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              34  49  45  70  57 /  -   20  30  -   20
Austin Bergstrom Intl Airport  33  47  44  70  56 /  10  20  30  10  20
New Braunfels Muni Airport     34  48  43  69  56 /  10  30  20  10  20
Burnet Muni Airport            31  55  45  70  53 /   0  -   10   0  20
Del Rio Intl Airport           30  61  39  66  49 /   0   0   0   0  -
Georgetown Muni Airport        31  50  44  68  56 /  -   10  20  -   20
Hondo Muni Airport             34  53  42  70  54 /  -   -   10  10  20
San Marcos Muni Airport        33  47  44  68  56 /  10  30  30  10  20
La Grange - Fayette Regional   34  49  46  68  58 /  10  40  40  20  20
San Antonio Intl Airport       36  50  45  69  56 /  10  20  20  10  20
Stinson Muni Airport           36  49  45  69  56 /  10  30  20  10  20

&&

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

$$

Mesoscale/Aviation...Oaks
Synoptic/Grids...Allen
Public Service/Data Collection...YB



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