SPC MD 397

MD 0397 CONCERNING TORNADO WATCH 107... FOR SOUTH-CENTRAL AND SOUTHWEST TX

Mesoscale Discussion 0397
NWS Storm Prediction Center Norman OK
0247 AM CDT Sun Apr 02 2017

Areas affected...South-central and southwest TX

Concerning...Tornado Watch 107...

Valid 020747Z - 020915Z

The severe weather threat for Tornado Watch 107 continues.

SUMMARY...Severe storms remain likely across the western half of WW
107 with large hail and damaging winds being the primary threat in
the short term trough 09Z.  Trends with the southern most discrete
storm in northern Coahuila Mexico suggest it could move into
northwest Maverick county TX by 08Z.  Local WFO areal extension may
be needed on the southern part of WW 107.

DISCUSSION...Early overnight trends in mosaic radar imagery
indicated the strongest storms capable of producing severe-weather
(mainly hail and/or damaging winds, at this time) extended from
southern Val Verde county to south of the International border in
northern Coahuila (60 SW to 35 S of DRT).  This activity was located
equatorward of the southern extent of a convectively reinforced cold
front, which at 07Z extended from San Saba County to near KJCT to
northern Val Verde County.  IR satellite imagery indicated the
coldest cloud tops were located along the International border with
Val Verde County, while radar imagery showed new thunderstorm
development occurring along the southwest flank (in northern
Coahuila) of this cluster of thunderstorms.

Forcing for ascent attendant to an apparent midlevel impulse moving
from the TX Big Bend region into the Edwards Plateau and height
falls with the approaching this region from Chihuahua Mexico and Far
West TX are expected to maintain this cluster of storms into the
early morning.  Forecast veering of 40 kt 850-mb and 700-mb jets to
southerly and southwesterly overnight into this morning should
result in an east-northeast advancement of the organizing MCS along
the International border into Val Verde and Kinney Counties.  The
03Z ESRL-HRRR continues to show this evolution in storm mode, given
a persistent influx of rich moisture from the northwest Gulf of
Mexico combined with strong effective bulk shear of 50+ kt.

Farther north across northern Val Verde to Sutton Counties, the
severe-weather threat appears to be diminishing as the air mass has
been convectively overturned.  Thunderstorms should persist
overnight, though the severe risk is likely lower than earlier.

..Peters.. 04/02/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...EWX...SJT...

LAT...LON   28890058 29400094 29800143 30240085 30580008 30779914
            30399872 29509885 29139885 28829969 28740030 28890058 

28890058 29400094 29800143 30240085 30580008 30779914 30399872
            29509885 29139885 28829969 28740030 28890058 

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