Area Forecast Discussion
Issued by NWS San Angelo, TX

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594
FXUS64 KSJT 201749
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
1249 PM CDT Fri Oct 20 2017

.AVIATION...
/18Z TAFS/

MVFR CIGs have slowly scattered this morning, and most sites are
either SCT at VFR heights, or BKN, but still at VFR heights. With
temperatures warming, expect these low clouds to remain at VFR
heights through the rest of the afternoon. Southerly winds have
increased and will remain gusty through the rest of the afternoon,
before diminishing for southern areas around 00Z this evening.
Winds will likely remain gusty at KABI, and perhaps KSJT through
at least part of the overnight hours. MVFR CIGs are expected to
develop again tonight after 06Z with moist, southerly low level
flow persisting through Saturday morning. These low clouds may
persist through most of the morning hours Saturday. 20

&&

.PREV DISCUSSION... /issued 645 AM CDT Fri Oct 20 2017/

AVIATION...
/12Z TAFS/

MVFR ceilings will affect the terminals this morning, with
ceilings lifting to VFR this afternoon. Widely scattered showers
and isolated thunderstorms will be possible across the area
through early afternoon but due to sporadic coverage will keep
precipitation out of the forecast at this time and monitor trends.
Expect VFR conditions this evening, with MVFR ceilings returning
to the southern terminals towards the end of the forecast period.

PREV DISCUSSION... /issued 419 AM CDT Fri Oct 20 2017/

SHORT TERM...
(Today and Tonight)

An weakening upper level shortwave will move across the area
today, bringing a few showers and thunderstorms to West Central
Texas through this afternoon. Early this morning, scattered
showers and isolated thunderstorms are approaching far western
counties ahead of the aforementioned shortwave. Latest Hi-Res
models weaken this activity as it moves east across West Central
Texas later today. Given the model trends, will maintain slight
POPs areawide today, with precipitation ending by mid to late
afternoon across eastern sections. Cloud cover will be quite
extensive this morning, with a combination of mid/high clouds
advancing east across the area and some low clouds affecting areas
generally south of interstate 20 this morning. Cloud cover will
limit insolation today, resulting in pleasant afternoon highs near
80 degrees. It will be breezy again today, with south winds 10 to
20 mph.

Dry and warm conditions will prevail overnight, with low clouds
developing over southern sections towards daybreak. Lows will be
mainly in the mid 60s.

LONG TERM...
(Saturday and Sunday)

The models are in fairly good agreement in bringing an open upper
trough east into western parts of the Plains states Saturday
afternoon, and across the Plains and western half of Texas
Saturday night. A closed low is progged to develop withing the
southern part of this trough over the ArkLaTex vicinity by Sunday
night. Cold front with this system will push south across the
Texas Panhandle Saturday afternoon and early evening, and across
west central Texas between approximately 11 PM Saturday and 7 AM
Sunday.

With upper support, lift along the cold frontal boundary and a
moist, unstable airmass in place, our area will have increased
chances for showers and thunderstorms mainly on Saturday night. A
few thunderstorms will be possible ahead of the approaching front
across our far northern counties late Saturday afternoon and
evening. Thunderstorms should develop south along the cold front
as it advances south across our area Saturday night. With a
favorable combination of instability and vertical shear, the Day 2
Convective Outlook from the Storm Prediction Center has Slight
Risk for severe storms across a few of our northeastern counties,
with Marginal Risk encompassing roughly the northeastern half of
our area. Large hail and damaging winds will be the primary severe
weather threats Saturday late afternoon and evening, with strong
and possibly damaging wind gusts becoming the main threat Saturday
night. The highest PoPs Saturday night are across approximately
the eastern third of our area, with lower rain chances farther
west where the coverage is expected to be lower. We have a
lingering slight chance PoP across our far southeastern counties
early Sunday morning.

Gusty north winds will follow the cold frontal passage Saturday
night, with breezy conditions continuing through about midday
Sunday. After warm and humid conditions on Saturday, cooler and
much drier conditions are expected on Sunday. North winds will
decrease in the afternoon and diminish in the evening. Good
radiational cooling is expected Sunday night with clear skies, dry
air and light winds as surface high pressure shifts southeast
across our area.

(Monday through Thursday)

Dry conditions are indicated for our area Monday through Thursday
of next week, with mostly clear skies expected. Temperatures are
expected to rebound on Monday after a cool start to the day. A
cold frontal passage is progged late Monday night, associated with
an upper trough deepening over the Midwest. After a cooler day
Tuesday, good radiational cooling is indicated Tuesday night when
surface high pressure is forecast to move southeast across our
area. A warming trend follows Wednesday and Thursday, with the
arrival of another cold front possible by Thursday night. The 00Z
GFS shows a favorable pattern for compressional heating effects
across parts of our area ahead of the front Thursday afternoon.
This would result in well-above normal high temperatures Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  80  66  86  54 /  30  10  20  50
San Angelo  81  65  87  55 /  30  10  10  40
Junction  81  65  85  58 /  20  10  10  60
Brownwood  80  66  85  56 /  20  10  20  70
Sweetwater  80  65  85  53 /  30   5  10  20
Ozona       78  64  84  55 /  30  10   5  30

&&

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

$$



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