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

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FXUS64 KEWX 252355
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
655 PM CDT Thu May 25 2017

.AVIATION... /00Z TAFS/
Higher dewpoints in the 65 to 70 degree range moving inland during
the late afternoon hours from the Coastal Bend gives increased
confidence on low cloud timing for tonight. Models all show good
agreement with ovc skies by 06Z or just before. Less certain is the
how low the cigs will get after the gusty winds of this afternoon
relax by a fair amount for tonight into Friday. Will stick with mfvr
categories through the night, but may need to consider a predawn ifr
cig. Mixing out to vfr is expected by around noon Friday.

&&

.PREV DISCUSSION... /ISSUED 339 PM CDT Thu May 25 2017/

SHORT TERM (Tonight through Friday Night)...
An increase in southerly flow in the low-levels will lead to
increased moisture and a return of low clouds across south central
Texas tonight. Overnight low temperatures will be much warmer when
compared to the last couple of nights. Given the increase in moisture
and cloud cover, we expect low temperatures in the 70s tonight. We
could see a few light showers develop east of the I-35 corridor early
tomorrow morning. For now, confidence in measurable precipitation is
low and we will keep the forecast dry. Another warm, humid and breezy
day is on tap for Friday, with highs generally in the 90s. The warm
temperatures along with humid conditions could push afternoon heat
index values to near 103 degrees along the I-35 corridor to near 108
degrees across the Rio Grande plains south of Del Rio. Warm and humid
conditions are in store Friday night, with lows in the 70s.

LONG TERM (Saturday through Thursday)...
Another hot and humid day is in store for Saturday with highs in the
90s and maximum heat index values of 103-105 along I-35, with 105 to
108 degrees along the Rio Grande. Given the strong heating, we can`t
completely rule out some strong to possibly severe thunderstorm
development along and north of a Del Rio to Llano line. Chances of
the cap breaking appear low at this time, so we will keep rain
chances low. Should a few storms manage to develop, the main severe
weather concern will be large hail and damaging winds.

The weather pattern becomes increasingly active on Sunday as a cold
front begins to move into south central Texas during the late
afternoon and early evening hours. Overall instability should be
lower than Saturday, but given the cold front and an increase in
mid-level shortwave troughs, we should see some strong to severe
thunderstorms over the southern Edwards Plateau and western Hill
Country during the late afternoon and evening hours. The front
continues to slowly drop southward Sunday night and with the boundary
intersecting the higher terrain west of the Rio Grande, additional
thunderstorms will develop across the Rio Grande plains. Given the
fairly weak 0-6km winds along with southeast-easterly upslope flow in
the low levels, the pattern appears favorable for some locally heavy
rainfall. The exact location for heavy rainfall is tough to
determine at this time, but would initially favor the Rio Grande
plains and southern Edwards plateau Sunday night. As the front drops
southward late Sunday night into Monday morning, we could also see
some pockets of locally heavy rainfall spread into the Hill country
and I-35 corridor. The frontal boundary becomes increasingly diffuse
by late Monday and this should result in a lower, but continued rain
chances.

The forecast for the middle of the upcoming work week appears wet,
as a series of mid-level shortwave troughs move overhead in the
active southwest flow aloft. The remnant frontal boundary or
convective outflow boundaries will also aid in shower and
thunderstorm development. It will be tough to time the best chance
for activity to develop, so we will keep rain chances generally in
the 30-50% range through the remainder of the forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              74  93  76  95  76 /  10  10  10  10  10
Austin Bergstrom Intl Airport  74  93  77  95  75 /  10  10  10  10  10
New Braunfels Muni Airport     74  93  76  95  76 /  10  10  10  10  10
Burnet Muni Airport            72  94  75  93  74 /  -    0  -   10  20
Del Rio Intl Airport           75  96  78  97  77 /   0  -   -   10  20
Georgetown Muni Airport        74  93  76  94  75 /  -    0  10  10  10
Hondo Muni Airport             74  94  77  96  76 /   0  -   10  10  10
San Marcos Muni Airport        74  93  77  95  76 /  10  10  10  10  10
La Grange - Fayette Regional   74  92  77  94  77 /  10  10  10  10  10
San Antonio Intl Airport       75  94  77  96  77 /  -   10  10  10  10
Stinson Muni Airport           75  95  77  97  77 /  -   -   10  10  10

&&

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

$$

Mesoscale/Aviation...Oaks
Synoptic/Grids...Runyen
Public Service/Data Collection...33



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