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

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FXUS64 KEWX 180554
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1254 AM CDT Thu May 18 2017

.AVIATION...
ISOLD --SHRA linger overnight into Thursday morning. ISOLD/SCT SHRA
will develop by midday with ISOLD/SCT TSRA during the afternoon into
evening. Left mention out for the TAF sites as the best chances will
be in the Hill Country along with some uncertainty in timing. A mix
of IFR/MVFR CIGs prevail overnight into morning. Patchy IFR/MVFR
VSBYs in BR are possible over the higher elevations. CIGs/VSBYs will
lift to VFR by midday into early afternoon. However, brief IFR/MVFR
CIGs/VSBYs are expected in SHRA/TSRA. IFR/MVFR CIGs return Thursday
evening. S to SE winds 5 to 12 KTs increase to 12 to 20 KTs with
gusts to 30 KTs on Thursday. ISOLD wind gusts to 50 KTs are possible
in/near the stronger TSRA.

&&

.PREV DISCUSSION... /ISSUED 629 PM CDT Wed May 17 2017/

AVIATION.../00Z Update/
VFR conditions were present at all terminals, except KAUS where MVFR
cigs were developing. Expect the quick return of MVFR cigs at the
I-35 terminals 02Z-03Z and then falling to IFR after 05Z. With the
moisture pushing back west overnight could see light showers, but no
clear time frame so have not included in the forecast at this time.
KDRT will see MVFR cigs develop around 09Z. Winds overnight E/SE 8-12
knots. Cigs will begin to improve after 15z and VFR conditions are
expected after 18z. After 16Z winds will be S/SE at 10-15 knots with
gusts to near 20 knots after 19Z. For KSAT/KAUS will see a return of
low clouds and MVFR cigs around 03z Friday. There will be a chance
for showers and thunderstorms on Thursday, mainly afternoon into the
evening. Since there is still a question on timing did not include
any mention of thunderstorms.

PREV DISCUSSION... /ISSUED 239 PM CDT Wed May 17 2017/

SHORT TERM (Tonight through Thursday Night)...
Upper air analysis this morning showed a trough rotating through the
southern plains with southwesterly flow over TX. At the surface, a
boundary depicted as a cold front was stretched from Forth Worth to
Brackettville. The contrast across the boundary was more a moisture
difference than temperature difference. Dewpoint temperatures ahead
of the boundary were in the 60s and 70s while behind it they were in
the 30s and 40s. During this period an upper level low will move out
of the central Rockies keeping southwesterly flow over TX. The dry
air will retreat to the west overnight as a dryline spreading moist
air back over our northern and western area. There could be
sufficient lift for isolated showers in this moist flow. The dryline
will move back to the east Thursday and generate thunderstorms. These
storms will move and propagate to the east. Convective parameters are
forecast to be at levels that will allow for strong to severe storms
as they move across the western half of our CWA. The most likely
threat will be large hail and damaging wind gusts with a non-zero
tornado. As usual we are at the southern end of storm development
and the most active area may be farther north. Storm chances will
decrease Thursday night.

LONG TERM (Friday through Wednesday)...
The upper low will move slowly through the central plains Friday and
Saturday. The dryline will be active again Friday with thunderstorms
developing during the afternoon and moving east. The best convective
parameters will be over our northwestern area and this looks the area
with the best chance for strong to severe storms Friday afternoon and
evening. Saturday a cold front will move into the region and move
slowly to the south through our CWA. With strong moist flow ahead of
the front there will be copious amounts of moisture in the boundary
layer for the front to work with. This will lead to a locally heavy
rain threat for Saturday and Saturday night. The front will stall
south of the our area and keep rain chances in the forecast Monday
through Wednesday. However, chances will decrease each day.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              73  89  73  87  68 /  30  30  30  60  60
Austin Bergstrom Intl Airport  73  88  72  87  67 /  30  20  30  50  60
New Braunfels Muni Airport     73  89  73  87  68 /  30  30  30  50  60
Burnet Muni Airport            71  85  70  83  63 /  40  30  40  60  60
Del Rio Intl Airport           75  91  72  86  69 /  20  40  30  50  60
Georgetown Muni Airport        73  87  72  85  65 /  30  30  30  60  60
Hondo Muni Airport             73  90  73  87  69 /  30  30  40  50  60
San Marcos Muni Airport        73  88  72  87  67 /  30  30  30  50  60
La Grange - Fayette Regional   74  89  74  88  70 /  20  10  20  50  60
San Antonio Intl Airport       74  90  73  87  70 /  30  30  30  50  60
Stinson Muni Airport           74  90  74  88  70 /  40  20  30  40  60

&&

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

$$

Mesoscale/Aviation...04
Synoptic/Grids...TB3



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