SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook RESENT 1
NWS Storm Prediction Center Norman OK
0657 AM CST Wed Jan 19 2022
Valid 191300Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EAST TEXAS TO
SOUTHERN ARKANSAS AND WESTERN MISSISSIPPI...
...SUMMARY...
Damaging thunderstorm winds, isolated large hail, and a tornado or
two may occur from afternoon and evening thunderstorms, mainly from
east Texas to southern Arkansas and western Mississippi.
...Synopsis...
In mid/upper levels, a series of shortwaves will contribute to the
sharpening of a positively tilted mean trough from eastern Canada
across the central Plains and southwestern CONUS to northwestern MX,
by 12Z tomorrow. A downstream perturbation -- apparent in moisture-
channel imagery near the TX/NM line -- will eject east-northeastward
into confluent flow aloft and deamplify through the period. By 00Z,
the feature should be located from the Ozarks to north-central TX.
By 12Z, it should extend from WV southwestward toward MEM.
Surface analysis at 11Z showed a substantial cyclone centered over
ON northeast of Lake Huron -- ahead of a northern-stream, mid/upper-
level shortwave trough. A cold front was drawn across southeastern
Lower MI, western IN, southern IL, southeastern MO, and northwestern
AR, to a weak frontal-wave low over east-central OK that is related
to the approaching southern-stream perturbation. The cold front
extended from there across northwest TX, the TX South Plains, and
east-central/north-central NM. By 00Z, the cold front should extend
across eastern NY, southwestern PA, eastern KY, mid TN, northern
parts of MS/LA, and southeast/south-central TX. By 12Z, the front
should reach the Delmarva Peninsula, western NC, northern GA,
southern parts of MS/LA, and the northwestern Gulf.
...East TX to lower Mississippi Valley region...
Scattered thunderstorms should form this afternoon into tonight
along/ahead of the surface cold front, between the Mid-South region
and southeast TX. Damaging to marginally severe gusts and isolated
large hail are possible, especially over LA/TX portions of the
outlook areas, along with a tornado or two.
Lift should occur both with the front and a prefrontal, warm-sector
convergence zone in a warm-advection plume. Diurnal heating of an
increasingly moist wedge of partially modified return-flow air
(surface dew points of upper 50s to mid 60s F) will weaken MLCINH to
negligible amounts by around 21Z. This will help to offset modest
but adequate mid/upper-level lapse rates and yield MLCAPE ranging
from around 500-800 J/kg over east-central/southeastern AR to 800-
1200 J/kg in east TX and northwestern LA. Initial discrete to
partly linear afternoon development is expected, amidst mean-wind
and deep-shear vectors oriented about 30 deg rightward of convective
lift axes. Forecast soundings reasonably depict around 100 kt
anvil-level winds and similar magnitudes of cloud-layer shear, with
35-45-kt effective-shear magnitudes, supporting both organized
multicells and at least some supercell potential. After the initial
mixed-mode phase, activity should become more linear, with embedded
supercells and LEWPs/mesocirculations possible.
With time this evening and tonight, the front will impinge on the
warm sector and prefrontal ascent zone, faster than the inland
advance of favorable boundary-layer theta-e. This ultimately will
narrow the surface-based warm sector from north to south across the
lower Mississippi Valley region late this evening and tonight. In
addition, the lack of substantial upper support (with the
perturbation's weakening and pulling away to the north) will
contribute to declining overnight severe potential as well.
..Edwards/Broyles.. 01/19/2022
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