Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 272046
AFDSJT

Area Forecast Discussion
National Weather Service SAN ANGELO TX
346 PM CDT FRI MAY 27 2016

.SHORT TERM...
(Tonight and Saturday)

A complex surface pattern across West Central Texas this
afternoon. An outflow boundary was located from east of Junction
to near Ballinger and intersects a dryline near Abilene. The
dryline extends north to just west of Throckmorton. The dewpoints
have crashed across the Northern Edwards Plateau, much of the
Concho Valley, western Big Country and much of the Northwest Hill
Country, with mainly 30s and 40s. Across the rest of the area, low
level moisture remains in place, with dewpoints in the 60s.
However, a lot of mid and upper level subsidence noted on WV
imagery, is hurting possible thunderstorm development along
outflow boundary/dryline. However, a few storms are possible
through 7 PM mainly along and east of a Brownwood to Junction
line. Otherwise, a quiet night is in store, with some low clouds
developing late along the I-10 corridor and Heartland.

For Saturday, there is a chance of thunderstorms during the
afternoon hours across much of the area. Low level moisture will
be advected back northwest across much of West Central Texas. A
dryline will be located near our western border by mid afternoon.
A few high res models are indicating scattered thunderstorms
developing, like the experimental HRRRX. If storms develop, the
combination of strong instability and good vertical wind shear may
result in a few storms becoming severe. the main hazards will be
large hail and damaging winds. Highs will be mainly in the lower
90s.

21

.LONG TERM...
(Saturday night through Friday)

An upper-level trough to our west will be the primary feature of
interest over the next week. This trough will dig over the
southwest CONUS through the weekend, inching ever so slowly to the
east through midweek. The prevailing southwesterly flow aloft will
provide a nice path for shortwave troughs approaching West TX.
Low-level moisture will remain in place through this time,
resulting in a moist, unstable air mass across the region. In
addition, the dryline will move into West TX most afternoons and
provide at least a weak forcing mechanism for convective
initiation. There will be at least a nominal threat for severe
weather during the long-term period given the strong instability,
enhanced by the steep lapse rates aloft resulting from the
elevated mixed layer.

The negating factors for convective development are the capping
aloft resulting from the advection of the EML over the region and
the lack of strong surface convergence. These factors may be
overcome by well-time shortwave troughs during the afternoon and
evening hours, but timing these features beyond a few days is
quite difficult. Thus, PoPs are generally in the 30-50% range
through much of the period. One of the more likely periods for
rainfall will be late Wednesday as the southwest trough begins to
lift northeast across the Plains. This is expected to bring a weak
cold front south into the CWA, enhancing low-level forcing.

Beyond Wednesday, model guidance begins to diverge. The 12z run of
the ECMWF indicates a more progressive pattern, phasing the
aforementioned trough with a northern stream wave traversing the
Great Lakes. On the other hand, the GFS produces a cut-off cyclone
to our northeast, meandering the circulation over the Southern
Plains all the way into the weekend. This could prolong rain
chances depending on its exact location. Given the uncertainty, we
have maintained rain chances through Friday. When all is said and
done, most of West Central TX is expected to receive 1-3 inches of
rain, with localized higher amounts.

Temperatures will be slightly below normal for much of the period.
Overnight low temperatures will be in the mid/upper 60s and
afternoon highs will typically be in the mid 80s.

Johnson

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  62  91  69  85 /   5  10  20  30
San Angelo  60  92  67  87 /   5  20  30  30
Junction  65  92  69  85 /  10  30  30  30

&&

.SJT Watches/Warnings/Advisories...
None.

&&

$$

21/25


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