Area Forecast Discussion
Issued by NWS San Angelo, TX

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580
FXUS64 KSJT 232311
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
611 PM CDT Tue Apr 23 2019

.AVIATION...
/00Z TAFS/

Widespread thunderstorms will continue to be the main concern
across West Central Texas terminals through the period. KABI has
already seen one round of storms, with more this evening. AS a
cold front sag south, additional storms will develop late this
evening across the central and southern terminals. Once the storms
reach the area, the storms will continue off and on through much
of the day on Wednesday.

&&

.PREV DISCUSSION... /issued 255 PM CDT Tue Apr 23 2019/

SHORT TERM...
(Tonight and Wednesday)

..Heavy rain/flooding and potentially severe weather this
afternoon into tonight...

As of mid afternoon, a weak cold front extended from Wichita Falls
to near Abilene and then southwest into the Trans Pecos region.
Scattered showers and a few embedded thunderstorms were occurring
along and just north of the frontal boundary, with an isolated
supercell producing large hail located over Shackelford county. The
airmass south of the frontal boundary is starting to destabilize as
some breaks in the cloud cover is occurring, with surface based
CAPES around 1500 J/Kg per SPC mesoanalysis. Additional thunderstorm
development is expected along and south of the boundary across
portions of the Concho Valley, heartland and southwest into the
Northwest Hill Country later this afternoon into early this evening.
Given steep lapse rates, moderate instability, and adequate deep
layer shear, large hail will be the main concern with any storms
that develop into the evening hours.

The severe threat will diminish by mid to late evening, with a
transition to a heavy rainfall and flooding threat overnight into
Wednesday. The surface front is expected to shift south across
southern portions of the Concho Valley and Heartland by late tonight
and early Wednesday morning. An approaching upper level low to our
southwest will aid in large-scale ascent overtop of the frontal
boundary, with periods of showers and thunderstorms expected. Winds
aloft favor training of showers and thunderstorms across the frontal
boundary, which will contribute to heavy rainfall and the potential
for flooding. At this time, it appears the heaviest rainfall will
occur between 1-20 and 1-10, where storm total rainfall amounts
between 2 ans 4 inches are expected, with locally higher amounts
near 5 inches possible. After coordinating with other offices, a
Flash Flood Watch will be issued generally south of Interstate 20
from late this afternoon through Wednesday evening when
precipitation is expected to gradually diminish.

24

LONG TERM...
(Wednesday Night through next Tuesday)

The upper-level low will continue to move eastward through central
Texas tomorrow evening. A fair amount of moisture is expected to
wrap around the upper low and will increase chances for
additional rainfall for most areas. However, thunderstorm chances
will be minimal as the main instability will have shifted eastward
by this time. This system should exit the region by Thursday
morning, allowing conditions to dry out. A surface high will
settle across west Texas by Friday night, allowing overnight lows
to fall into the 50s. Otherwise, southerly return flow should set
up for Friday, bringing high temperatures back into the upper 80s
to near 90. Along with these warm temperatures, moisture amounts
will remain high, with otherwise sunny to partly cloudy skies
through the weekend.

By early to middle next week, models are hinting at another
system passing through the Central Plains. This might drag a weak
cold front into the Big Country and generate some additional
thunderstorms. However, timing, intensity and system track are
highly uncertain at this time. As a result, we have gone with just
low chance PoPs for Tuesday and Wednesday.

SK

AVIATION...
/18Z TAFS/

MVFR ceilings will prevail across the southern terminals this
afternoon, while ceilings will remain mostly VFR at KSJT and
KABI. Scattered showers and a few thunderstorms will be possible
primarily at KABI this afternoon, then scattered to numerous
showers and a few thunderstorms will develop overnight into
Wednesday due to a stalled frontal boundary and an approaching
upper level low. Ceilings will lower to MVFR across the northern
terminals this evening and overnight, with IFR ceilings developing
across the southern terminals after 24/09Z. A few of the storms
may be severe this afternoon and evening, with a transition to
heavy rainfall overnight into Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  56  64  52  78 / 100  80  50  10
San Angelo  57  67  50  81 / 100 100  30   5
Junction  61  72  52  81 /  80 100  40   5
Brownwood  59  66  52  76 / 100 100  60  20
Sweetwater  54  62  52  78 /  90  80  50  10
Ozona       57  68  50  81 /  90 100  30   0

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Wednesday evening for Brown-Callahan-
Coke-Coleman-Concho-Crockett-Irion-Kimble-Mason-McCulloch-Menard-
Nolan-Runnels-San Saba-Schleicher-Shackelford-Sterling-Sutton-
Taylor-Tom Green.

&&

$$

07



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