Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 210443
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
1043 PM CST Tue Feb 20 2018

.AVIATION...
/06Z TAFS/

An arctic cold front has moved south to I-10 corridor, and will
continue moving south tonight, turning winds to the
north/northeast at 10 to 20 knots with gusts over 20 knots at
times. Behind the front, isolated to scattered showers and
thunderstorms may affect KABI and KJCT at times early this
morning. Also, IFR to MVFR conditions will continue, with
-DZ and BR possible from tonight through most of the day
tomorrow. In addition, temperatures may be cold enough for
freezing precipitation tomorrow, mainly for the KABI terminal. 21

&&

.PREV DISCUSSION... /issued 629 PM CST Tue Feb 20 2018/

AVIATION...
/00Z TAFS/

An arctic cold front has moved through KABI and KSJT early this
evening, and will continue moving south tonight, turning winds to
the north/northeast at 10 to 20 knots with gusts over 20 knots at
times. Ahead of the front, isolated to scattered showers and
thunderstorms may affect KSOA and KJCT at times this evening.
Behind the front, IFR to MVFR conditions will develop, with -DZ
and BR possible from tonight through most of the day tomorrow. In
addition, temperatures may be cold enough for freezing
precipitation tomorrow, mainly for the KABI terminal. 20

PREV DISCUSSION... /issued 255 PM CST Tue Feb 20 2018/

SHORT TERM...
(Tonight and tomorrow)

.Widespread icing event likely...

A strong arctic front will quickly move southward across the region
through the evening. Behind this front, cold air and gusty northeast
winds will filter in quickly following the frontal passage.
Temperatures have already dropped 30 to 35 degrees across the
northern Big Country behind the front. Overnight lows will drop into
the upper 20s across the Big Country and into the low to mid 30s
across the rest of the region.

Freezing rain will be likely across the Concho Valley and Big
Country beginning Wednesday morning

The setup: A shallow arctic airmass will replace a warm and moist
airmass that has been sitting across the region. The arctic airmass
will force this moisture upward and widespread precipitation will
develop across the Concho Valley and spread northward through the
morning. The coldest air looks to settle across the Big Country and
areas along the interstate 20 corridor, this includes the cities of
Abilene and Sweetwater. Across the Concho Valley, temperatures look
to be at or slightly above freezing, but with evaporative cooling
aloft and the atmospheric profile slowly cooling throughout the
day, freezing rain will be possible across San Angelo and
Brownwood Wednesday morning. Both models show the higher QPF
values along the western Big Country. Current forecast has ice
totals around 0.10 to 0.25. Most of the ice accumulation will
occur on elevated surfaces such has trees and power lines.
Locations in these areas could see brief power flickers. Exposed
road surfaces such has bridges and overpasses could be at risk to
see a light glaze of ice develop during the morning commute. With
the above normal temperatures we experienced the past few days,
normal road surfaces should remain warm enough to melt and ice
that falls during the day. This melting ice and the ongoing chance
for precipitation will set the stage for the development of black
ice, as overnight temperatures will drop below freezing. Use
extreme caution during the Wednesday and Thursday morning
commutes.

By Wednesday afternoon, the freezing rain threat will begin to
diminish across the Concho Valley. Isolated showers and thunderstorms
will be possible across these areas by the afternoon bringing the
threat for small hail and brief gusty winds. High temperatures will
be much colder and well below normal for this time of year. Highs
across the interstate 10 corridor will be in the low to mid 40s.
Temperatures will be in the mid 30s across the Concho Valley with
temperatures in the upper 20s to low 30s across the Big Country.

40

LONG TERM...
(Wednesday Night through Tuesday)

Wet forecast continues across West Central Texas with multiple
wave of showers and thunderstorms likely as the individual
shortwaves rotate around the main upper level trough. Still looks
like another round of activity starts Thursday and again on
Friday and Friday Night, with drier conditions working into the
area late Saturday afternoon or evening. The cold mass behind the
arctic front will gradually modify Thursday, with temperatures
rebounding into the 60s by Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  27  32  30  45 /  30  70  20  60
San Angelo  32  35  30  50 /  40  70  20  60
Junction  39  45  34  50 /  80  70  20  70
Brownwood  31  36  31  46 /  60  80  20  70
Sweetwater  26  30  28  46 /  30  60  20  60
Ozona       35  42  31  51 /  50  60  20  50

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST Wednesday for Callahan-
Fisher-Haskell-Jones-Nolan-Shackelford-Taylor-Throckmorton.

Winter Weather Advisory until 6 PM CST Wednesday for Brown-Coke-
Coleman-Concho-Irion-Runnels-Sterling-Tom Green.

&&

$$



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