Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 211841
SPC MCD 211841

Mesoscale Discussion 0280
NWS Storm Prediction Center Norman OK
0141 PM CDT Sat Apr 21 2018

Areas affected...North-central Texas

Concerning...Severe potential...Watch unlikely

Valid 211841Z - 212115Z

Probability of Watch Issuance...20 percent

SUMMARY...A severe threat is expected to develop across parts of
north-central Texas this afternoon. Large hail and damaging wind
gusts will be possible with the strongest of storms. However, the
severe threat should remain isolated and weather watch issuance
appears unlikely.

DISCUSSION...The latest surface analysis shows a 1008 mb low over
the Low Rolling Plains of west Texas. A warm front extends eastward
from the low across north-central Texas. South of this boundary,
surface dewpoints are generally in the upper 50s and lower 60s F.
This is contributing to a narrow corridor of weak instability from
the Texas Hill Country northward into the Low Rolling Plains where
MLCAPE values are estimated in the 250 to 500 J/kg range according
to objective analysis.

Surface-based convection has initiated to the northwest of Abilene,
TX over the last hour. This convection is located just to the west
of the strongest instability and near a pronounced vorticity max
analyzed by the RAP. The Abilene WSR-88D VWP shows strong deep-layer
shear with 0-6 km shear estimated to be from 50 to 55 kts. In
addition, forecast soundings suggest an area of steep mid-level
lapse rates exists near the instability max. These factors should be
supportive of strong updrafts capable of producing hail. Isolated
large hail could occur with any storm that develops persistent
rotation. An isolated wind damage threat may also develop mainly
after convection matures later this afternoon especially if a short
line segment can organize. Isolated storm coverage and the small
affected area make weather watch issuance unlikely.

..Broyles/Hart.. 04/21/2018

...Please see for graphic product...


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