Severe Thunderstorm Warning 237, NWS San Angelo, TX

Area Forecast Discussion
National Weather Service San Angelo TX
814 PM CDT Sat Oct 21 2017

.UPDATE...

Severe thunderstorm watch number 505 now in effect through 2 AM
Sunday morning, for most of the Big Country and, the norther4n two
Heartland counties, and Runnels county. Just sent a new zone
forecast package to include a watch headline for those counties.

&&

.PREV DISCUSSION... /issued 647 PM CDT Sat Oct 21 2017/

AVIATION...
/00Z TAFS/

Look for VFR conditions to dominate through 00Z tomorrow, with
thunderstorms along and ahead of a cold front this evening and
later tonight. Expect the cold front at the Abilene terminal
around 05Z and at the San Angelo terminal about an hour later.

PREV DISCUSSION... /issued 313 PM CDT Sat Oct 21 2017/

SHORT TERM...
(Tonight and Sunday)

.Severe Storms Possible This evening...

An upper level trough and associated cold front will be the main
focus in the short term, with the potential for some severe storms
later this evening.

At the surface this afternoon, a cold front was moving south and
currently located across the southern Panhandle into northwest
Oklahoma. A diffuse dryline/surface trough extended south across the
eastern Low Rolling Plains and eastern Permain Basin. West Central
Texas was located in the warm sector with good low level southerly
flow. Also, good instability across the area with MLCAPES of
2500 J/KG. At the upper levels, a strong trough was located
across the central and southern Rockies, with large scale ascent
starting to increase across the Southern Plains.

Expect scattered to numerous thunderstorms across mainly northern
and eastern sections of West Central Texas tonight. The Hi Res
models(HRRR, Texas Tech WRF) indicate scattered storms developing
along the cold front and moving east across parts of the Big Country
this evening. More isolated storms are possible further south along
the dryline, mainly west of Sweetwater to San Angelo to Ozona line
for late this afternoon and early evening. The HRRR model is the
most aggressive with this possible development of convection. A few
storms may be severe this evening, mainly across the Big Country, as
vertical shear improves along with the instability. The main hazards
will be large hail, damaging winds and dangerous lightning. After
midnight, a line of storms are likely along the cold front across
the Heartland and Northwest Hill Country. A few strong storms are
still possible. For Sunday, expect a quiet forecast with gusty north
winds for a few hours.  Highs will be in the 70s.

21

LONG TERM...
(Sunday night-Thursday)

Expect a roller coaster of temperature this week as two cold
fronts impact West Central Texas. The second cold front expected
later this week may be the strongest of the season. Mostly dry
weather is expected this week.

Temperatures rebound on Monday into the lower to mid 80s after
chilly morning lows in the 40s Sunday night. Then, a reinforcing
cool front and associated surface high builds into the region
Monday night. This will result in cool afternoon highs in the low
to mid 70s Tuesday with morning lows again in the 40s on
Wednesday. Afternoon highs climb into upper 70s Wednesday, and
into the mid and upper 80s by Thursday.

(Friday-Saturday)

The GFS is more similar to the ECMWF solution with respect to the
upper level and surface features. Both models now show an
amplified ridge building just off the the Pacific Northwest coast by
Friday. Models also prog a deep upper trough developing over the
middle of the country and extending south into Texas. This type of
upper flow should unleash the first Canadian front of this fall
season into Texas.

the two models show this front reaching West Central Texas by
Friday morning. Afternoon high temperatures next Friday and
Saturday may only reach the 60s. Morning lows on Saturday may drop
into the upper 30s to near 40. We'll continue to monitor the
models as they continue to get a better handle on this potential
Canadian Cold frontal surge.

26

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene 	 54  73  47  82 /  50   5   0   0
San Angelo 	 55  76  46  84 /  40   5   0   0
Junction 	 58  77  41  83 /  60   5   0   0
Brownwood 	 56  75  43  83 /  80   5   0   0
Sweetwater 	 53  73  50  81 /  20   5   0   0
Ozona      	 55  75  43  81 /  40   0   0   0

&&

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

Hazardous Weather Outlook
National Weather Service San Angelo TX
245 PM CDT Sat Oct 21 2017

TXZ049-054-064>066-071>073-076>078-098-099-113-114-127-128-139-
140-154-155-168>170-221945-
Fisher-Nolan-Sterling-Coke-Runnels-Irion-Tom Green-Concho-
Crockett-Schleicher-Sutton-Haskell-Throckmorton-Jones-Shackelford-
Taylor-Callahan-Coleman-Brown-McCulloch-San Saba-Menard-Kimble-
Mason-
245 PM CDT Sat Oct 21 2017

This Hazardous Weather Outlook is for portions of west central
Texas.

.DAY ONE...This Afternoon and Tonight

Isolated thunderstorms may develop ahead of a dryline late this
afternoon and early evening generally west of a Sweetwater,
San Angelo to Ozona line. The main hazard will be damaging winds
and large hail.

Strong to severe thunderstorms will be possible this evening and
overnight ahead of a cold front that will move south across the
area. The most favored area for severe storms will be along and
north of Interstate 20 this evening. The primary hazards will be
large hail and damaging winds, although an isolated tornado cannot
be ruled out.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Limited spotter activation may be necessary this evening,
primarily north of Interstate 20.

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