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

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FXUS64 KEWX 211146
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
646 AM CDT Tue Aug 21 2018

.AVIATION...
VFR flying conditions prevail. FEW-SCT MVFR level stratus expected
at KAUS/KSAT/KSSF this morning and again late tonight into Wednesday
morning as SW flow above the surface keeps BKN MVFR CIGs east of the
sites. ISOLD-SCT SHRA/TSRA are expected this afternoon into early
evening mainly NE of KSOA to KHYI to KVCT line. Only KAUS has decent
PROBs of impacts. However, have only gone with VCSH as TSRA PROBs are
less. Will monitor model and radar trends for updates for any site.
Brief MVFR CIGs/VSBYs and wind gusts to 40 KTs are potential impacts.
At KAUS/KSAT/KSSF, S-SW winds 7 KTs or less become SE this afternoon
increasing to 10 to 18 KTs as the seabreeze moves across this
evening, then S-SW 5 KTs or less tonight. At KDRT, E winds less than
10 KTs become SE around 10 KTs by midday, then E tonight.

&&

.PREV DISCUSSION... /ISSUED 359 AM CDT Tue Aug 21 2018/

SHORT TERM (Today through Wednesday)...
A diffuse frontal boundary is draped from near Dryden in Terrell
County east towards Burnet per 3 AM CDT surface analysis. A dry but
humid start this morning across much of South Central Texas will give
way to another round of scattered shower and thunderstorm
development along this boundary mid to late afternoon as daytime
heating allows for convective temperatures around 97-99 degrees F to
be reached.

Upper ridging building over South Central Texas from New Mexico
will do little to move the frontal boundary today and expect showers
and thunderstorms to again develop across the northern and eastern
counties, roughly north and east of a Sonora to San Marcos to Cuero
line. Limited environmental shear (less than 10 knots) will keep
thunderstorms fairly short-lived. However, gusty downburst winds will
once again be possible given inverted-V forecast sounding profiles
for areas along the frontal boundary and a very dry sub-cloud layer
with dew point depressions this afternoon in excess of 30 degrees F.
Similar to yesterday, brief heavy rain will also be possible in
stronger thunderstorms as GOES total precipitable water vapor
satellite imagery early this morning shows 1.8-1.9 inch PWATs pooled
along and south of the boundary.

Highs today are forecast to reach or exceed 100 degrees F in many
locations along and east of the Interstate 35 corridor and this,
combined with ample humidity this afternoon, will result in heat
indices again climbing into the 102 to 107 degree range this
afternoon and evening. Showers and thunderstorms along the remnant
frontal boundary may linger into the early afternoon hours, but loss
of heating will allow for this activity to dissipate by mid-evening.

Lows Wednesday morning are expected to fall into the 70s. Increasing
subsidence across the region from the building upper ridge is
expected to suppress rain chances along the lingering frontal
boundary on Wednesday as it washes out somewhere across the eastern
counties. Expect highs in the mid 90s to lower 100s Wednesday
afternoon and heat index values again in the 102-107 degree range for
many locations along and east of Interstate 35.

LONG TERM (Wednesday Night through Monday)...
Upper ridging remains centered over the state Wednesday night and
Thursday, shifting towards the ArkLaTex this weekend as a series of
shortwave troughs dive across the northern United States from Canada.
Hot and dry conditions will persist through the end of the work week
with highs in the mid 90s to lower 100s, but the shifting of the
upper ridge will result in highs dropping a few degrees into the 90s
this weekend. A stray shower or two may even be able to make it into
the coastal plains along the sea breeze on Sunday or Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry             102  77 102  76 101 /  30  20  -   -    0
Austin Bergstrom Intl Airport 101  75 102  74 101 /  20  20  -   -    0
New Braunfels Muni Airport    100  74 101  74 100 /  10  20  -   -    0
Burnet Muni Airport            99  74 100  73  99 /  30  20  -   -    0
Del Rio Intl Airport          100  77 102  77 101 /  10  -   -   -    0
Georgetown Muni Airport        99  75 101  74 102 /  30  20  -   -    0
Hondo Muni Airport            100  74 103  73 102 /  10  -   -   -    0
San Marcos Muni Airport       100  75 102  74 100 /  20  20  10  -    0
La Grange - Fayette Regional  101  76 102  75 101 /  20  20  10  -    0
San Antonio Intl Airport       99  76 101  76 100 /  10  10  -   -    0
Stinson Muni Airport          100  77 102  76 100 /  10  10  -   -    0

&&

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

$$

Mesoscale/Aviation...04
Synoptic/Grids...Huffman


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