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

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000
FXUS64 KEWX 240541
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1241 AM CDT TUE MAY 24 2016

.AVIATION...
No significant changes to ongoing TAFs. MVFR cigs will lower
further through the night to LIFR in Austin and San Antonio. DRT
will stay MVFR. There is a slight chance for light rain or drizzle
around sunrise, but probability is low and any light precip will
not change category. Improvement Wednesday will be slow and CIGs
will not rise to VFR until mid-afternoon.

&&

.PREV DISCUSSION... /ISSUED 1025 PM CDT MON MAY 23 2016/

UPDATE...
Tornado Watch 199 has been allowed to expire as convection has
dissipated over the Rio Grande Plains and the impressive supercell
complex (with -82 deg C cloud tops and echoes to 68 kft) southwest
of Eagle Pass in Mexico should stay out of our CWA. A strong cap
evident on the 00Z DRT sounding and recent aircraft soundings at
AUS and SAT suggest that only shallow convective shower activity
would be possible tonight. Hi-res models show very little
coverage overnight, so have removed POPs everywhere except for the
western Hill Country, Rio Grande Plains, and Edwards Plateau. Kept
a slight chance of thunderstorms along the border just in case
another cell tries to pop up in any remnant outflow, but the cap
should prevent this. Very isolated light showers are still
expected along the I-35 corridor tomorrow morning after sunrise,
though probably lower in coverage than the last two mornings.

PREV DISCUSSION... /ISSUED 334 PM CDT MON MAY 23 2016/

SHORT TERM (Tonight through Tuesday Night)...

Main highlight for the next 36 hours will the the slight to
marginal risk of strong and severe storms across the Rio Grande
Plains and portions of the southern Edwards Plateau late this
afternoon and evening. Main risks will be large hail, straight-
line damaging winds and a brief tornado can not be ruled out. Storm
coverage and strength is expected to decrease through late evening.

Scattered light to moderate showers are ongoing across central and
eastern areas as weak isentropic lift occurs underneath embedded
mid-level impulses in the SW flow aloft. Luckily a capping
inversion is in place and limiting vertical extent of this
activity. Farther west however, warmer low-levels resulting in
higher mixed-layer instability of 4000-5000 J/KG will be able to
ignite strong and severe storms across the Big Bend of Texas and
along the Burros Mountains. KDRT model soundings and SPC
mesoanalysis still suggest a capping inversion in place albeit
weaker. Storms should initiate farther NW of the area and on the
higher terrain where the capping is weaker and then move towards
Val Verde/Edwards late afternoon/early evening. Very large hail
could be possible given the CAPE values and lapse rates in place.
Downdraft CAPE is over 1000 J/KG that could result in pockets of
damaging straight-line winds. Low-level 0-1 km SRH is only 50-100
m2/s2 but 0-3 km SRH is upwards of 150 m2/s2 that could support
the possibility of a brief tornado in this area.

Storms are expected to weaken into the late evening and overnight
as they slowly push east/southeast towards the southern Edwards
Plateau and along the Rio Grande Plains.

Tuesday will feature slightly stronger H5 ridging as the dryline
retreats farther westward. With ridging and capping in place,
rain and thunder storm chances will be lower. However, if a storm
were to break through the capping inversion, it could become
strong. Capping will be slightly weaker over the Hill County and
the Burros again and this area will need to be monitored.

LONG TERM (Wednesday through Monday)...

Potential heavy rain event could take form late week into the
beginning of Memorial Weekend. Multiple model guidance suggests
an increasing probability of several rounds of heavy rain Thursday
and then again Friday. Please stay tuned as we approach this time
frame given the already saturated soil across the area.

Wednesday will feature additional H5 ridging while a deeper
trough develops across the desert SW of the US. A implied stronger
shortwave trough will should shift across the Rio Grande Plains
ahead of the parent low pressure system late Wednesday night to
help usher the first round of showers and storms across the
region. Greater synoptic lift coupled with PWATS increasing to
near 1.8" to 2" could lead to very efficient rainfall through the
day Thursday. A brief break may occur late Thursday night into
Friday morning but then the greatest synoptic lift will shift
across south-central Texas Friday afternoon and evening as the
base of the parent trough shift over the southern Plains. Again,
with the ongoing, and by this time likely very saturated soil,
high amounts of run off are becoming an increasing concern. A
flash flood watch may be needed for this time period. Please stay
tuned as details and rain amounts become more clear going into the
holiday weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              87  74  88  74  83 /  20  10  10  20  60
Austin Bergstrom Intl Airport  87  74  88  74  83 /  20  10  10  20  60
New Braunfels Muni Airport     87  73  88  74  83 /  20  10  10  20  60
Burnet Muni Airport            86  72  87  73  82 /  20  10  10  20  60
Del Rio Intl Airport           91  76  91  75  89 /  20  10  20  50  30
Georgetown Muni Airport        85  73  87  74  82 /  20  10  10  20  60
Hondo Muni Airport             88  74  89  75  84 /  20  10  10  40  60
San Marcos Muni Airport        86  73  88  74  82 /  20  10  10  20  60
La Grange - Fayette Regional   87  75  88  75  83 /  10  10  10  20  50
San Antonio Intl Airport       87  74  88  74  82 /  20  10  10  30  60
Stinson Muni Airport           89  75  90  75  85 /  20  10  10  30  60

&&

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

$$

Mesoscale/Aviation...05
Synoptic/Grids...Hampshire


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