Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 271735
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
1235 PM CDT Mon Mar 27 2017

.AVIATION...
/18Z TAFS/

Main concern for this TAF package is MVFR/IFR ceilings moving in
from south to north after midnight. VFR continues from now until
around 6-8Z, then a low level jet will bring increased winds and
low clouds into the area. May also see a bit of drizzle across the
SOA and JCT TAF locations by morning. Clouds will be slow to
clear. Expecting thunderstorms to develop tomorrow
afternoon/evening, but initiation of storms is just outside the
current TAF package, so will not mention in the forecast quite
yet.


&&

.PREV DISCUSSION... /issued 658 AM CDT Mon Mar 27 2017/

AVIATION...
/12Z TAFS/

Expect mainly VFR conditions at the terminals today and this
evening. Stratus will return north across much of West Central
Texas late tonight and going with MVFR ceilings at most of the
terminals after 06Z. Keeping KABI VFR for now.

PREV DISCUSSION... /issued 404 AM CDT Mon Mar 27 2017/

SHORT TERM...
(Today and Tonight)

Looks a dry forecast for the next 24 hours across West Central
Texas. A cool front will move south across much of the area today,
with north winds of 10 to 15 mph behind the front. Also, there
will be little CAA across the area. Highs will be in the upper 70s
across the Big Country to the 80s elsewhere. For tonight, strong
upper level trough(currently over central California) will move
east- southeast into the Southern Rockies by Tuesday morning. As a
result, surface pressure falls will develop across the Southern
Plains, and a warm front will move north to the I-20 corridor by
12Z. Low level gulf moisture will advect north across West Central
Texas as dewpoints will be in the mid 50s to lower 60s by Tuesday
morning, along with low clouds across the southern 1/2 of the
area. Lows will be in the 50s to lower 60s.

21

LONG TERM...
(Tuesday through next Sunday)

.Conditions for severe weather potential Tuesday into Tuesday
night still look favorable...

By Tuesday, models are in good agreement with the placement of the
digging upper level low in western New Mexico. The low is then
expected to move into west Texas Tuesday night, then turn to the
northeast and into the Southern Plains Wednesday into Wednesday
night. At the surface, moisture will have been drawn northwestward
ahead of the low Monday night into Tuesday morning.

Model calculated CAPE values suggest instability will be readily
available all day Tuesday into Tuesday night. Although, for the
afternoon hours, this may be dependent on the extent of morning
convection. However, GFS shows surface based CAPEs of 1500-2500
J/kg, and MLCAPEs in the 1500-2000+ J/kg range. This instability
will persist into the evening hours as well, ahead of the main
upper level low and cold front as it moves into west Texas. As
stronger winds move in aloft with the low, 0-6km bulk shear values
will increase to greater than 50 knots by the evening hours, and
low level shear will also be enhanced as surface winds back just
ahead of the cold front. Height falls and cooling aloft will also
overspread the area, especially during the evening and overnight
hours.

A dryline is expected to become established near our western
border as a result of low level moisture increase. Weak upper
level shortwave energy in southwest flow ahead of the upper level
low may help trigger elevated morning showers and thunderstorms
near the dryline. While these storms aren`t expected to be the
main severe weather concern, some of these could become strong as
well. Coverage of thunderstorms from the morning through the
afternoon is uncertain at this time, but the environment will be
conducive for any storms that develop to quickly intensify,
especially during the afternoon.

After 00Z, as the low moves in and upper level support increases,
a cold front will move east into the area, likely triggering a
line of thunderstorms developing near our western border shortly
after sunset. These storms will then move east/northeast across
our area during the evening into overnight hours. Large hail,
damaging winds, and a few tornadoes will be possible with these
storms. Storms will move out of the area Wednesday.

Quieter weather will finish out the work week. As the upper level
low moves off to the northeast Wednesday night, a cold front will
drop into the area, bringing briefly cooler temperatures for
Thursday.

Another upper level low moves into the AZ/NM area next weekend,
which will bring another chance for showers and thunderstorms to
the area.

20

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  79  56  79  55 /   0   0  50  60
San Angelo  86  60  83  55 /   0   5  50  70
Junction  88  60  81  56 /   5  10  40  70
Brownwood  78  58  78  56 /   0  10  50  70
Sweetwater  80  55  81  54 /   0   0  60  60
Ozona       86  60  81  54 /   0   5  40  70

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
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