Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 250234 AAC
AFDSJT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN ANGELO TX
934 PM CDT Fri Apr 24 2015

.UPDATE...

The remaining portion of the Tornado Watch was cancelled, with
the showers and thunderstorms having exited our area. No
additional development is expected for the rest of tonight.
Have updated the forecast to remove rain chances. High cloud
coverage will decrease from west to east overnight.

&&

.PREV DISCUSSION... /ISSUED 657 PM CDT Fri Apr 24 2015/

AVIATION...
/00Z TAFS/

Aside from thunderstorms, which will move through the Junction
and Brady area within an hour, expect VFR conditions to dominate
for the next 24 hours. Surface winds tomorrow will be mainly from
the west.

PREV DISCUSSION... /ISSUED 637 PM CDT Fri Apr 24 2015/

UPDATE...
The Tornado Watch has been cancelled for the area along/northwest
of an Baird to Ballinger to San Angelo to Mertzon line. The Watch
continues along/ahead of a band of showers and thunderstorms
extending frm southern Brown County to northern Sutton County.
PoPs and sky condition were also updated. No additional showers/
thunderstorms are expected tonight after the aforementioned band
of convection moves out of our area.

19

PREV DISCUSSION... /ISSUED 310 PM CDT Fri Apr 24 2015/

SHORT TERM...
(Tonight and Saturday)

A Tornado Watch is in effect through 10 PM this evening...

Currently, an upper level trough located over New Mexico is moving
east toward the southern plains with a 120+ knot jet at 250mb, and
60+ knots at 500mb, creating a highly sheared environment over west
central Texas. This has resulted in 0-6 km shear values around 60
knots. In the low levels, CAPE values were exceeding 1500 J/kg over
the southern 2/3 of the CWA, with SRH values from surface to 1 km of
greater than 200 m2/s2 downstream of the currently developing
storms. Storm motions are expected to range from 40 to 50 mph so in
addition to large hail, severe strength winds will also be a
considerable threat. Thunderstorms that have already begun
developing are rapidly intensifying to severe levels within this
environment. This trend is expected to continue through the evening
hours as the entire scattered line of storms moves to the east.
These storms will continue to rapidly intensify with the potential
of producing tornadoes the farther east they move. As the event
continues to develop, a line of embedded severe storms may develop
during the evening hours, before the entire line moves east of the
CWA.

For Saturday, clear and dry conditions are expected behind the
upper level trough moving through the area tonight. We will have
breezy west winds across the area, and warm temperatures with
highs in the mid 80s to near 90 degrees.

20

LONG TERM...
(Saturday night through Friday)

The next upper level low/trough is forecast to be across the Desert
Southwest on Sunday, then eventually track across the South Plains
late Monday into Tuesday. As this upper level system approaches,
showers and thunderstorms will increase across West Central Texas,
especially across our northern/eastern counties. The overall
synoptic pattern between models is very similar. The main difference
is that the GFS continues to be more aggressive in moving the
dryline into our eastern counties, while the ECMWF is farther west
with the position of the dryline during the afternoon/evening. The
GFS solution would favor keeping the bulk of the precipitation
Sunday and Sunday night to the east of West Central Texas, while the
ECMWF solution would result in showers and thunderstorms across a
large part of the area. For now, very little change was made to the
forecast, which is a conservative middle ground between the drier
GFS and more optimistic ECMWF. Strong to severe thunderstorms will
be possible, given an unstable atmosphere and 0-6km bulk shear
values of 35 to 50 knots. Highs on Sunday will be in the mid to
upper 80s.

As the upper level low moves across the South Plains, the best
chance of showers and thunderstorms will be across the Big Country
and Heartland. In the meantime, a strong cold front will drop south
through the area Monday night. Isolated to scattered showers and
thunderstorms will be possible along and behind the front, mainly
across the northern two thirds of the region. Temperatures on
Tuesday will be well below seasonal normals, with highs in the mid
to upper 60s, and overnight lows in the mid to upper 40s. A slow
warm up will ensue through the end of the work week.

Daniels

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  58  86  58  87  57 /   5   0   0  20  30
San Angelo  54  88  56  88  58 /   5   0   0  10  20
Junction  55  89  58  89  57 /   5   0   5  20  20

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$






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