FXUS64 KEWX 101127

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
627 AM CDT Fri Apr 10 2020

IFR ceilings have developed at AUS with VFR elsewhere. MVFR will
likely develop and persist for much of the day at the remaining TAF
sites. IFR is then expected tonight with some possible visibility
restrictions as well. While a shower or storm cannot be completely
ruled out for DRT this afternoon, chances were too low to mention in
the TAF. The better chances for convection will be tonight after
06z. Most high-res models show a complex coming out of Mexico and
possibly impacting DRT around the end of the valid TAF period and
moving near SAT at the end of their extended 30 hour TAF. Will handle
this with a PROB30 for DRT as the bulk of the activity could be
south of that terminal. Will prevail -SHRA VCTS for the San Antonio
sites and just

-SHRA for AUS late tonight.


.PREV DISCUSSION... /ISSUED 257 AM CDT Fri Apr 10 2020/

SHORT TERM (Today through Saturday)...
Mostly cloudy skies prevail across the area overnight with light
northerly winds left in the wake of the afternoon and evening
convection. The remainder of the overnight period through the
morning hours should remain fairly quiet. Temperatures are in the
60s across the area and highs this afternoon should warm into the
70s for the region. By the late afternoon and evening hours, some
convection will be possible initially developing near the Rio
Grande. This development will be aided by a subtle disturbance aloft
embedded into the westerly flow ahead of a deeper low still near
southern California. High res-model guidance is in fairly good
agreement that this convection will be able to move eastward late
this evening and overnight as the weak forcing spreads east. Should
see a cluster of storms moving near San Antonio after midnight
before weakening and eventually moving east of the forecast area.

Instability amounts will initially be highest in closer proximity to
the Rio Grande where development is expected this evening. However,
CAPE values are expected to remain less than 1500 J/kg as forecast
soundings show poor lapse rates in the mid-levels of the atmosphere.
With decent shear and straight hodographs, storm mode will likely be
splitting multi-cellular clusters and therefore can't rule out a
marginally severe storm this evening. The new Day 1 outlook from The
Storm Prediction Center has areas along and west of Highway 281 in a
marginal risk for severe storms and this seems very reasonable.
Otherwise, low temperatures tonight will bottom out in the upper 50s
to middle 60s.

As this activity shifts east by Saturday morning, surface winds will
become more southerly once again as a warm front lifts to the north
which will help increase the amounts of low-level moisture once
again. This should allow for some showers and possible thunderstorms
to develop during the day on Saturday. However, our thermodynamic
environment will likely remained capped during the afternoon
Saturday and am not expecting organized convection until Saturday
evening and overnight when forcing erodes the CAP. If the CAP erodes
a bit quicker than anticipated, then the threat for severe weather
could begin in the late afternoon hours in the west. The coverage of
the shower activity will be highest in the morning as the best lift
is expected to occur with the initial surge of the return to
southerly flow behind the warm front. High temperatures on Saturday
will be in the 70s to 80s with the higher values in the western and
southern counties.

LONG TERM (Saturday Night through Thursday)...
Active weather pattern will be in place to begin the long term
period. The upper level low moving out of the southwestern US will
pass over the region as an open wave. Latest guidance brings the
feature further south and slows the progression a bit with most of
the forcing passing over Saturday evening and night. Moisture return
will be well under way by then with a warm front surging northward
into central TX. Storm development will initially be focused along
the moisture axis as the forcing is ejected over the region Saturday
night. Explosive surface based CAPE of upwards of 4000 J/kg,
impressive mid level lapse rates of +8 C/km, and healthy deep layer
shear around 60-70 kts will all be in place by Saturday evening. The
major question in previous packages was would there be enough
moisture and forcing at the surface to get surface based convection.
Now that all these ingredients are coming together, chances for
severe weather is looking more likely.

Initially convection looks to be elevated for our western areas but
storms will track eastward into more moisture rich environment at
the surface. Texas Tech WRF shows convection initiation around 23Z
out in Val Verde County along the dryline. Will need to monitor
future high resolution model runs as they become available. Large
hail will be the primary threat along with damaging winds especially
under heaviest precip loaded storms and where any upscale growth
occurs. There will be a non- zero chance of tornadoes. As surface
based convection becomes more prevalent, tornado threat slightly

After the passage of this system a strong cold front will push into
the area and a cooler airmass settles into the region. Temperatures
will be 15 to 18 degrees below normal for most of the area, lows on
Sunday night will dip into the upper 30s for parts of the Hill
Country. These cooler temperatures hang around into early next week
as a gradual warming trend takes hold throughout the week. Fairly
benign weather pattern next week with little to no chance for rain
through the period.


Austin Camp Mabry 73 60 75 66 80 / - 20 60 80 20
Austin Bergstrom Intl Airport 74 60 76 66 80 / - 20 60 80 20
New Braunfels Muni Airport 74 61 77 65 79 / - 50 60 80 10
Burnet Muni Airport 71 58 72 61 76 / - 20 70 80 10
Del Rio Intl Airport 78 65 86 61 85 / 20 60 20 40 0
Georgetown Muni Airport 72 58 73 64 78 / - 20 60 80 20
Hondo Muni Airport 76 62 82 63 81 / - 60 60 70 0
San Marcos Muni Airport 74 60 77 65 79 / - 40 60 80 10
La Grange - Fayette Regional 75 59 78 68 80 / - 10 50 80 30
San Antonio Intl Airport 76 62 79 66 79 / - 50 60 80 -
Stinson Muni Airport 76 63 80 66 80 / - 50 60 70 -




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