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

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FXUS64 KEWX 191720 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
1120 AM CST Sun Feb 19 2017

.UPDATE...
Latest SPC Day 1 Convective Outlook has included much of South
Central Texas in a slight risk of severe thunderstorms with the
exception of the extreme northwest and far east. Primary threats are
expected to be damaging wind gusts up to 60 mph and large hail up to
one inch in diameter. One or two tornadoes can`t be ruled out.
Also, heavy rain is expected with these strong to severe storms and
minor flooding is anticipated across small streams/rivers and canals.
Rainfall amounts of 1 to 2 inches are expect along and east of
highway 281 with isolated pockets of 4 to 5 inches. These rainfall
amounts will prompt closures of low water crossings and area
roadways.

Moderate to heavy showers and strong to severe storms are expected to
begin early this evening into late tonight across the southern
Edwards Plateau and then transitioning into the highway 281 area.
The potential for severe weather diminishes late tonight into Monday
morning transitioning into a heavy rain event as upper level support
shifts to eastern Texas.

We are holding off on a Flash Flood Watch due to the progressive
nature of the upper level system, the archived 14 days rainfall map
and locations where the maximum rainfall amounts are expected to
occur. However, will be monitoring closely the situation as the event
unfolds later today.

&&

.PREV DISCUSSION... /ISSUED 552 AM CST Sun Feb 19 2017/

AVIATION.../12Z TAF CYCLE/

IFR to MVFR conditions are ongoing across the region as ample
moisture streams in from the southeast. -DZ will also be possible
across KAUS/KSAT/KSSF sites through the mid morning to late morning
hours. Visibilities may also reduce to 3-4SM at times through 15Z but
will return to P6SM thereafter. IFR conditions should improve
through 15-17Z but MVFR ceilings should stick around through much of
the morning and into early afternoon. Some cloud breaks will be
possible by mid to late afternoon across the far south but may be
tough to come by at TAF sites themselves. VCSH will be possible
towards KAUS through the mid afternoon and this trend for TAF
inclusion will need to be watched.

By early to mid-evening, widespread SHRA and TSRA should develop
near KSAT/KSSF/KAUS and persist through the overnight and into Monday
morning. Depending on heavy rain placement, IFR to LIFR conditions
will be possible at times as visibilities sporadically jump up and
down along with ceilings. SHRA and TSRA will slowly clear to the east
after 12-15Z Monday morning.

PREV DISCUSSION... /ISSUED 437 AM CST Sun Feb 19 2017/

SHORT TERM (Today through Monday)...
Very active weather expected today into Washington`s Birthday
(Monday). An upper level trough over Arizona into Sonora state of
Mexico is moving to the east with a moist lower to mid level flow
over South Central Texas. Isentropic lift will produce isolated to
widely scattered showers this morning into early afternoon.

The upper level trough moves into New Mexico to Chihuahua state of
Mexico this afternoon encouraging larger scale lift to develop.
Forecast soundings for late this afternoon into evening show MUCAPEs
of 1K to 2.4K J/KG and 0-6 KM shear of near 50 KTs across much of
our area with the highest values along the I-35 corridor. Some mixing
of the airmass is expected, especially southwest of San Antonio
allowing for some breaks in the clouds in that area to realize some
of that instability. Isolated thunderstorms will develop in that area
and race to the northeast along to just east of I-35. Some of these
could become strong to marginally severe with large hail and strong
winds the main threats.

Stronger lift occurs tonight as the trough moves into Western Texas
to south of the Big Bend. Showers and thunderstorms become more
numerous across our area tonight with the greatest coverage along and
east of Highway 281. Storms may organize into line segments with
damaging winds and isolated large hail the main threats. An airmass
with PWs near seasonal maximums at 1.6 inches and flow allowing for
training indicates at least a marginal risk of locally heavy rains
along and east of Highway 281 with the greatest threat from near the
Coastal Plains to along the Highway 77 corridor.

The upper level trough slows down on Monday as it loses contact with
a northern stream upper trough. Expect some showers and thunderstorms
on Monday morning with possibly some locally heavy rains lingering
near the Coastal Plains to the Highway 77 corridor. Drier air will
filter into our area during the afternoon with some showers and
thunderstorms east of I-35.

Rainfall totals along and east of Highway 281 will average 1 to 2
inches with isolated amounts of 5 inches possible where training
occurs. This may cause some flooding. West of Highway 281, less than
an inch is expected.

Clouds and rain will keep high temperatures lower today and Monday,
but, still well above normal.

LONG TERM (Monday Night through Saturday)...
The upper level trough moves east of our area by Tuesday with upper
level ridging building from northwestern Mexico into Texas late
Tuesday into Wednesday. An upper level trough moving through the
Central Rockies will allow for lower level flow from off the Mexican
Plateau increasing high temperatures again midweek. The trough moves
out into the Central Plains by early Friday pushing a weak cold front
across the area. Due a much drier airmass from a couple of days of
upper level ridging and flow off the Plateau, no rains are expected.
Temperatures will fall a little, but remain above normal for Friday
into Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              77  61  74  54  78 /  30  90  50  -   -
Austin Bergstrom Intl Airport  78  62  74  53  78 /  30  90  50  -   -
New Braunfels Muni Airport     79  62  75  53  80 /  30  90  50  -   -
Burnet Muni Airport            74  57  73  49  77 /  30  70  40  -   -
Del Rio Intl Airport           78  55  79  49  81 /  20  50  10   0   0
Georgetown Muni Airport        76  60  73  52  77 /  30  90  40  -   -
Hondo Muni Airport             82  60  78  49  81 /  30  70  40  -    0
San Marcos Muni Airport        77  62  74  53  78 /  30  90  50  -   -
La Grange - Fayette Regional   79  63  72  56  76 /  30 100  60  10  10
San Antonio Intl Airport       80  62  76  53  79 /  30  90  40  -   -
Stinson Muni Airport           81  62  77  54  81 /  30  90  40  -   -

&&

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

$$

Mesoscale/Aviation...24
Synoptic/Grids...17
Public Service/Data Collection...Treadway



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