SPC AC 230055
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0655 PM CST Thu Feb 22 2018
Valid 230100Z - 231200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
A risk for scattered thunderstorm activity continues tonight across
parts of the Ozark Plateau into the southern Plains, and perhaps
northeastward into the lower Ohio Valley.
...01Z Outlook Update...
Subtropical ridging centered off the south Atlantic coast remains
rather strong. Around its northwestern periphery, the large-scale
flow is generally anticyclonic from the Rio Grande Valley through
the Ohio Valley and northern Mid Atlantic region, though there are a
number of embedded smaller-scale short wave perturbations. Another
impulse emanating from the subtropical eastern Pacific may cross the
lower Rio Grande Valley by late tonight.
Otherwise, an initial perturbation emerging from positively tilted
larger-scale troughing over the western U.S. is forecast to migrate
from the north central High Plains toward the Upper Midwest, as a
much stronger upstream short wave trough continues to dig near the
Sierra Nevada into the southern Great Basin/lower Colorado Valley.
Although the track of the lead short wave is well to the west and
north of a sharp surface frontal zone still stalled across parts of
the Cumberland Plateau through the lower Mississippi Valley and
Texas Gulf coast region, a southerly return flow continues to
contribute to moistening off the western Gulf of Mexico, and above
the shallow southern edge of the cold surface-based air mass. This
is being enhanced across the southeastern Plains into the Ozark
Plateau by a 40-50 kt southwesterly 850 mb speed maximum associated
with the upper wave, which is contributing to scattered ongoing
thunderstorm development. As the low-level jet shifts northeastward
overnight, it appears that associated moistening and destabilization
could contribute to scattered thunderstorms spreading across parts
of the middle Mississippi into lower Ohio Valleys.
At the same time, lower/mid tropospheric warm advection is expected
to persist across much of Texas. Models indicate that this may
contribute to additional thunderstorm development along the stalled
leading edge of the deeper cold surge into the southern Plains,
across northern Texas by late tonight. Guidance remains suggestive
that other thunderstorm activity could develop northeast of the
Mexican Plateau into portions of south central Texas. Although the
Texas convection may coincide with some steepening of lower/mid
tropospheric lapse rates, it is still not clear that convective
layer shear and instability will become supportive of the potential
for much more than generally sub-severe hail in strongest storms.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z