Special Weather Statement, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1044 PM CST Tue Mar 3 2020

.AVIATION...
Convection is beginning to increase near DRT as large scale forcing
begins to arrive. To the east there are some scattered areas of light
rain with minimal impacts. Will begin the I35 sites with a mention of
VCSH and DRT with -SHRA VCTS to cover the increasing convection.
Activity should be east of the DRT terminal around 11-12z with
improving flying conditions. For the I35 sites, AUS will have the
best chances of prolonged impacts and will prevail -SHRA with a
TEMPO group for -TSRA. from 13-17z. For the San Antonio sites, will
just mention -SHRA with a VCTS for now. Otherwise, MVFR/IFR ceilings
will continue tonight before lifting to VFR tomorrow morning for all
but AUS who should see prolonged restrictions as low-level moisture
remains there in closer proximity to the low.

&&

.PREV DISCUSSION... /ISSUED 828 PM CST Tue Mar 3 2020/

UPDATE...
Things have been slow going thus far on area radars as of 815 pm with
only some elevated returns beginning to stream into our western
counties from the southwest. Latest mesoanalysis shows little to no
CAPE at the present time which is why we aren't seeing any sustained
convection at this time. However, the upper low remains southwest of
the area and as the low continues to move east, deeper forcing will
arrive which will introduce more instability to the area. The latest
run of the HRRR shows some better convection by 06z but the overall
trends of the latest runs show somewhat less of a trend of a linear
system with more of scattered thunderstorms within an area of rain.
Given the shear, some of these could still be strong to severe with
possible hail and damaging winds being the main threats. The best
chances for severe weather remain in the slight risk closer to the
path of the expected surface low.

PREV DISCUSSION... /ISSUED 528 PM CST Tue Mar 3 2020/

AVIATION...
Large scale forcing for ascent should approach the region over the
next 12-18 hours and bring periods of showers and storms to the area
terminals. This should begin at DRT around 2-3z lasting into the 11z
hour and at the I35 sites between 4z and 16z. Some of these storms
could be strong at times. In addition to the threat of storms,
MVFR/IFR conditions can be expected with both ceilings lowering
throughout the night and periods of visibility restrictions within
the heavier thunderstorm activity. Conditions should improve to VFR
at DRT around 14z and SSF/SAT around 16z with drying conditions. AUS
will likely remain MVFR throughout tomorrow, as wrap around moisture
lingers there on the backside of the upper low.

PREV DISCUSSION... /ISSUED 213 PM CST Tue Mar 3 2020/

SHORT TERM (Tonight through Wednesday Night)... The main forecast
issue in the short term is the prospect for severe convection and
heavy rainfall. The 12Z regional/global models are in good agreement
with the synoptic morphology of moving the shortwave trough now over
northwestern Mexico across Texas over the next 36 hours. This trough
is fairly high amplitude and slow moving, so we expect a little bit
longer than average period of sustained lift. Therefore, high PoPs
(especially Wednesday morning) are a given.

Despite the synoptic-scale agreement, the mesoscale details differ,
especially in regards to convective timing and intensity. There seem
to be two camps, with the Texas Tech WRF, HRW ARW, and other
typically "Dry Plains Environment" models keeping cellular
convection confined to the Rio Grande Plains, and generally only
bringing a weak line of storms across the rest of the area. In
contrast, the HRRR and HRW NSSL have a more coverage and stronger
cellular convection over the Rio Grande Plains, and carry an short-
line MCS through the eastern Hill Country and northern half of the I-
35 corridor. This is one of those cases where splitting the
difference is not an appropriate solution -- it will either be one
morphology or the other.

Given the release of CAPE earlier this morning over northern Mexico,
it seems a phase-shift to the east would be a preferred outcome for
tonight. This would also line up with the diurnal strengthening of
the LLJ. The result should be close to the TTech WRF and ARW
solutions of lesser activity, both in coverage and intensity. That
said, there could still be isolated hail and wind damage reports
with some of the stronger storms, especially on the Rio Grande
Plains, but the I-35 corridor, including Austin and San Antonio,
should see sub-severe storms.

Rainfall amounts through Wednesday night will vary widely, from 1/10
to 1/4 inch in the southeast coastal plains, to 1-2 inches in the
Edwards Plateau and Hill Country. One or two spots in Llano, Burnet,
or Gillespie counties may see up to four inches of rain. While there
main be some minor flooding of the low water crossings and other
typical spots, we do not foresee significant flooding.

The moderate to heavy rain should end by noon Wednesday, but
moisture wrapping around the low will maintain scattered showers
along and north I-10 until sunset Wednesday.

FIRE WEATHER...
Strong gusty winds and low humidity in the southwestern corner of our
CWA, including Eagle Pass, will lead to Near Critical Fire Weather
conditions on Wednesday afternoon. Severity will be dependent on
rainfall amounts in the area. This area will need to be watched for
further actions.

LONG TERM (Thursday through Tuesday)...
With the system moving out of the area to the northeast, ridging
builds in behind it. Thursday, cooler and drier air will take a few
degrees off of the high temperatures bringing back down to near
normal of upper 60s and low 70s. We maintain a dry forecast through
the weekend with winds switching back out of the southeast on
Saturday. This will kick off a warming trend into the beginning of
next week. Next chances for rain are Sunday through Monday with
abundant moisture in place as multiple disturbances in the southwest
flow.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              61  66  47  68  46 /  60  90  10   0   0
Austin Bergstrom Intl Airport  61  68  46  69  45 /  60  90  10   0   0
New Braunfels Muni Airport     62  71  46  69  45 /  60  70  -    0   0
Burnet Muni Airport            55  59  43  67  43 /  80 100  10   0   0
Del Rio Intl Airport           56  67  45  73  46 /  90  20   0   0   0
Georgetown Muni Airport        58  62  45  68  44 /  70  90  10   0   0
Hondo Muni Airport             60  71  44  73  43 /  80  50   0   0   0
San Marcos Muni Airport        62  70  46  69  45 /  60  80  10   0   0
La Grange - Fayette Regional   64  75  48  68  45 /  50  80  10   0   0
San Antonio Intl Airport       63  75  47  71  47 /  70  60  -    0   0
Stinson Muni Airport           65  76  48  71  47 /  60  60  -    0   0

&&

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

Short-Term/Aviation...Hampshire
Long-Term...BMW

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
249 PM CST Tue Mar 3 2020

TXZ171>173-183>194-202>209-217>225-228-042100-
Llano-Burnet-Williamson-Val Verde-Edwards-Real-Kerr-Bandera-
Gillespie-Kendall-Blanco-Hays-Travis-Bastrop-Lee-Kinney-Uvalde-
Medina-Bexar-Comal-Guadalupe-Caldwell-Fayette-Maverick-Zavala-
Frio-Atascosa-Wilson-Karnes-Gonzales-De Witt-Lavaca-Dimmit-
249 PM CST Tue Mar 3 2020

This Hazardous Weather Outlook is for South-Central Texas..

.DAY ONE...This Afternoon And Tonight.

Showers and thunderstorms are forecast to develop across western
areas of the Hill Country and Rio Grande Tuesday late this evening
then move east overnight, reaching areas along and east of the
I-35 corridor late overnight into Wednesday morning.

There is a Slight Risk some of these storms could become severe.
The main hazards will be large hail and damaging wind gusts. A
isolated tornado is possible, but chances remain low.

In addition, some pockets of heavy rainfall will be possible
across the Edwards Plateau and Hill Country. This could produce
some localized flash flooding in these areas.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

A few strong to severe storms could linger into Wednesday morning
across northern areas like Williamson, Travis, and Lee counties.
The primary threat will be strong gusty winds. A few heavy
downpours are also still possible through Wednesday morning across
these same northern areas of the I-35 corridor.

Gusty northwest winds and low relative humidity values will
contribute to Near Critical fire weather conditions Wednesday
afternoon across portions of the Rio Grande and Winter Garden
regions.

No other hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed Tuesday evening through mid day
Wednesday.

Special Weather Statement
National Weather Service Austin/San Antonio TX
1204 AM CST Wed Mar 4 2020

TXZ183-040645-
Val Verde TX-
1204 AM CST Wed Mar 4 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN VAL VERDE COUNTY
UNTIL 1245 AM CST...

At 1203 AM CST, Doppler radar was tracking a strong thunderstorm 13
miles northeast of Comstock, moving northeast at 35 mph.

Half inch hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Loma Alta, Juno, Bakers Crossing, Vinegarone, Devils River State Nat
Area Del Norte and Devils River State Nat Area Big Satan.

LAT...LON 3029 10101 3029 10070 2988 10070 2969 10101
      2981 10119 3001 10127
TIME...MOT...LOC 0603Z 230DEG 29KT 2982 10101

HAMPSHIRE