Area Forecast Discussion
Issued by NWS San Angelo, TX

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000
FXUS64 KSJT 210442
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
1142 PM CDT Wed Sep 20 2017

.AVIATION...
/06Z TAFS/

MVFR CIGs expected at both KJCT and KSOA between 10Z and 12Z.
Some patchy mist is also possible at KJCT. MVFR CIGs possible at
KBBD, but have low confidence at this time so will not mention.
VFR conditions and breezy southerly winds will continue through
tomorrow.

&&

.PREV DISCUSSION... /issued 700 PM CDT Wed Sep 20 2017/

AVIATION...
/00Z TAFS/

Scattered showers and thunderstorms continue across the area this
evening...closest to the KSJT and KABI terminals. Have included
VCTS at these two terminals through 02Z. Gusty winds and MVFR
conditions are possible with any thunderstorm that drifts over
the airfield. Otherwise, expect VFR conditions at all terminals
overnight. MVFR ceilings and patchy mist are possible at KJCT in
the early morning hours. VFR conditions and breezy southerly winds
will prevail at the terminals tomorrow afternoon.

PREV DISCUSSION... /issued 456 PM CDT Wed Sep 20 2017/

DISCUSSION...
Sent out a quick update to add in PoPs for much of the western
half of the forecast area. Isolated showers and thunderstorms are
developing along a weak dryline late this afternoon. CAPE values
across the area are in the 1000-3000 J/KG range along with
temperatures in the mid 90s to near 100 degrees. An isolated
strong to severe thunderstorm is possible, with strong winds being
the main concern. Otherwise, no other changes area needed at this
time.

PREV DISCUSSION... /issued 405 PM CDT Wed Sep 20 2017/

SHORT TERM...
(Tonight and Thursday)

(Rest of the afternoon)

Record high temperatures...

A 850mb thermal ridge has slowly shift east into our area. 850mb
temperatures have climbed up to 25-26 degrees Celsius. This
translates to surface temperatures climbing into the upper 90s to
around 101. With dewpoints in the low 60s we can expect index
values to climb between 101-103 which will be just below heat
advisory levels.

(Tonight)

Isolated showers and thunderstorms are possible across
the Big Country and Concho valley this evening. The storm prediction
center has these areas under a marginal risk for severe weather.
Convection will be isolated in coverage and will only have a brief
window for development. A 500mb ridge will suppress the convection
from becoming too widespread and keep it confined to just a small
area. After sunset most of the convection will begin to weaken as
it continues to move off to the east. The main threat with the
strong storms will be small hail, damaging winds and locally minor
street flooding. Overnight lows will be warm with temperatures in
the mid 70s.

(Thursday)

The weather will begin to slowly change across the area starting
tomorrow afternoon. A deep upper level trough will begin to move out
of California and into the four corners region allowing for the weak
ridge to begin to erode. With this erosion of the ridge and
increasing divergence aloft, shower and thunderstorm activity could
be more widespread tomorrow afternoon and evening. Main threat with
these storms will be frequent lightning and a brief, gusty winds.
Temperatures on Thursday will be a little "cooler" than what we have
seen the past couple of days. Forecasted highs for Thursday will be
in the mid 90s.

40

LONG TERM...
(Friday through Wednesday)

The upper trough over the Eastern Pacific will continue to head
eastward through the end of the week into the weekend...bringing
increased mid and upper level moisture and increasing
precipitation chances. Rain chances increase from west to east,
with highest chance of rain for Monday and Tuesday across the
whole area. With abundant moisture, heavy rainfall will be a
possibility mainly Monday and Tuesday. Rain chances should
decrease Wednesday night through the end of the week as the trough
shifts to the east and drier air moves in. With increased cloud
cover, expect temperatures to be several degrees cooler through
next week.

08

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  75  95  71  92 /  20  20  20  10
San Angelo  74  94  71  91 /  20  20  20  10
Junction  73  93  69  90 /  10  20  10  10
Brownwood  73  93  68  90 /  20  20  20  10
Sweetwater  75  93  72  90 /  20  20  20  10
Ozona       73  92  69  89 /  20  20  20  10

&&

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

$$

26/99/99


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