Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
11,719
327,104
Denison, TX...Ada, OK...Durant, OK...
5 %
80,860
13,080,485
San Antonio, TX...Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
9,477
272,403
Ardmore, OK...Ada, OK...
5 %
91,501
13,860,165
San Antonio, TX...Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...
SPC AC 171242
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0642 AM CST Fri Dec 17 2021
Valid 171300Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHEAST OK...
...SUMMARY...
Generally isolated severe thunderstorms are possible beginning this
afternoon across parts of the southern Great Plains.
...Southern Great Plains...
Scattered elevated thunderstorms are ongoing across southeast OK
through north AR in association with low-level warm theta-e
advection to the north of a surface warm front near the Lower Red
River Valley. While this surface boundary will attempt to advance
north, repeated convective development will probably limit its
effective advancement in southeast OK to central AR. Rich
boundary-layer moisture will persist the south of this front and
pockets of modest surface heating should yield a plume of MLCAPE
from 750-1500 J/kg across north TX into southeast OK. An increase in
convective intensity may occur this afternoon with thunderstorms
that can form along the immediate frontal zone. With around 40-kt
effective shear and deep-layer winds nearly parallel to the front, a
few transient supercell structures and weakly organized clusters may
develop, mainly in the late afternoon to early evening. The overall
magnitude of the threat should remain marginal. But a more
concentrated corridor of damaging winds and severe hail might occur
centered on southeast OK.
Increasing convective coverage is expected later in the evening,
with a broad swath of convection persisting overnight. The southward
push of a surface anticyclone over the northern Great Plains will
result in the frontal zone accelerating south. This surging cold
front should ultimately undercut much of the convection and minimize
the severe threat along it. One exception may be towards
south-central TX where some guidance indicates pre-frontal
surface-based development within the warm conveyor during the early
morning. Have extended the cat 1/Marginal Risk south to account for
this possibility.
..Grams/Mosier.. 12/17/2021
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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