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

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FXUS64 KEWX 030000 AAA

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
600 PM CST Fri Dec 2 2016

Please see the 00Z aviation forecast discussion below.


Intermittent showers along with predominantly MVFR cigs will
continue this evening along the I-35 corridor. Some pockets of
heavier showers may temporarily reduce vsbys to IFR, but given
current radar trends, do not have enough confidence to mention
just yet. After 06Z, an increase in rainfall is expected along the
I-35 corridor. This will drop cigs and vsbys into IFR and we will
show this beginning 09Z. Can`t completely rule out a few
thunderstorms as well, but given coverage will likely remain
isolated, we will not mention in the forecast. Rainfall continues
well into tomorrow, but we should see more of a light rain and a
slight increase in vsbys after 19Z.

Out west at DRT, IFR conditions are expected through the period.
We do expect an increase in rainfall after 06Z, with light to
moderate rain continuing through the morning hours. Rainfall
should ease after 18Z, but IFR cigs will continue.


.PREV DISCUSSION... /ISSUED 327 PM CST Fri Dec 2 2016/

SHORT TERM (Tonight through Monday)...

Periods of light to at times heavy rainfall are expected over the
next 48-72 hours that will result in 3-5 inches of rainfall along
and east of the I-35 corridor. Locally higher amounts near 6 inches
could occur in the far SE coastal plains. Rainfall amounts will
decrease east to west from 3 inches central down to 1 inch towards
Rio Grande Plains. Concerns around flash flooding remain low at this
time given modest rainfall rates, dry antecedent conditions, and
overall lack of rainfall concentration in vulnerable areas over a
small timeframe. However, continual monitoring for
training/convective banding, which could be quite possible, will
need to be assessed to determine if this risk increases.

Isentropic upglide and increasing synoptic ascent from the
digging trough over northern Mexico is aiding the increasingly
moisture laden low- and mid-levels to support widespread light to
moderate showers over the region this afternoon. A few deeper
cores could produce some lightning but MUCAPE values remain
limited /<200 J/KG/ through this evening. The warm front will
stall along just south of San Antonio eastward towards Houston.

Late tonight however, multi-global and multi-hi-res solutions
indicate a shortwave trough ejecting across south-central Texas
that will act to increase deeper moisture flux convergence,
coincident with PWATs increasing into the 1.5-1.7" range and a LLJ
near 30-35 knots with increasing MUCAPE to 500 J/KG and Showalters
tipping negative. These conditions should support an enhanced area
of showers and elevated thunderstorms to overspread the region
from the southwest to the northeast near midnight through mid-day
Saturday. With PWATs 2-3 standard deviations above normal along
with 3-4 above normal H850 moisture flux could lead to localized
moderate to heavy rain across the Hill County and I-35 corridor.
Convective banding or training will need to monitored for as
deeper updraft cores evidence exists in the 300mb wind isotach
fields per convective feedback signals.

By Saturday afternoon and evening, rain showers should be more
scattered and intermittent before another potential wave overnight
Saturday into Sunday morning occurs. Hi-res solutions suggest
another wave of moderate to heavy rain shifting over portions of
the region early Sunday morning. A surface low will develop along
the warm front late Saturday into Sunday that will enhance
rainfall along the coastal plains and the coast. While the
greatest amounts are expected to remain farther east and coastal,
the SE coastal plains could experience heavy rainfall Sunday. WPC
has placed a slight to moderate risk of excessive rainfall just
east of south-central Texas. Farther west, rain showers will
likely again become more scattered and lighter in nature Sunday
morning through the afternoon.

Rain showers and thunderstorms coverage will be on the increase
once again Sunday night into Monday morning as the cut-off low
over Mexico opens up as a wave and pivots over the region.
Rainfall could be moderate a times with this final round as it
clears west to east with drier air filtering in by Monday

LONG TERM (Tuesday through Friday)...

Main focus mid to late week will center around low-end rain
chances Wednesday and Thursday along and ahead of a strong cold
front. The cold front will bring well below-normal temperatures
as widespread freezing temperatures could be possible Friday and
Saturday morning.

Moisture will attempt to return by Wednesday into Thursday ahead
of a cold front but remain limited to the coastal plains. There
remains some discrepancies in the GFS/EC on overall rain coverage
and it could be expanded farther west on subsequent forecasts.

Temperatures will plunge behind the front with widespread freezing
temperatures expected Friday and Saturday with readings in the
upper 20s to low 30s across most areas with the exception of the
coastal plains and deep Rio Grande Plains.


Austin Camp Mabry              50  55  48  54  48 / 100 100  80  70  80
Austin Bergstrom Intl Airport  50  55  47  54  49 / 100 100  80  70  80
New Braunfels Muni Airport     52  57  49  54  49 / 100 100  80  70  80
Burnet Muni Airport            47  52  45  51  45 / 100 100  80  70  80
Del Rio Intl Airport           56  60  51  55  47 /  80  70  80  70  80
Georgetown Muni Airport        48  52  46  51  47 / 100 100  80  70  80
Hondo Muni Airport             54  61  50  58  47 / 100  80  80  70  80
San Marcos Muni Airport        51  57  48  55  49 / 100 100  80  70  80
La Grange - Fayette Regional   54  60  50  55  50 / 100 100  90  80  80
San Antonio Intl Airport       53  59  50  55  49 / 100  90  80  70  80
Stinson Muni Airport           55  60  51  56  50 / 100  90  80  70  80




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