SPC 0700Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1230 AM CST Mon Nov 23 2020

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN/CENTRAL PLAINS...OZARKS...MID-SOUTH...AND LOWER
MISSISSIPPI VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms may occur Tuesday into
Tuesday night across portions of the southern/central Plains,
Ozarks, Mid-South, and lower Mississippi Valley. Damaging winds
should be the main threat, but a couple tornadoes and marginally
severe hail also appear possible.

...Southern/Central Plains into the Ozarks, Mid-South, and Lower
Mississippi Valley...
An upper trough/low initially centered over the Four Corners region
will progress eastward across the southern/central Plains by Tuesday
evening, eventually reaching the lower/mid MS Valley by the end of
the period. A 40-50+ kt southerly low-level jet will be present over
much of the southern/central Plains Tuesday morning, with this
feature forecast to likewise shift eastward through the day.
Partially modified Gulf moisture will be transported northward
across the southern/central Plains ahead of a developing surface low
over KS and trailing cold front. A dryline should also mix eastward
through the day across parts of western/central OK and north-central
TX.

Modestly steepened mid-level lapse rates (around 7-7.5 C/km in the
700-500 mb layer) should overspread the warm sector across the
southern/central Plains as the upper trough/low moves eastward.
There remains some model disagreement regarding how quickly and far
north mid/upper 50s to low 60s surface dewpoints will reach by late
Tuesday afternoon. The degree of low-level moisture return will have
a large impact on how much surface-based instability can be realized
ahead of the cold front/dryline across southern KS and
central/eastern OK. Most guidance indicates that only weak
instability (MLCAPE generally less than 1000 J/kg) will develop
across these areas by peak afternoon heating. Still, a strong
(60-70+ kt) southwesterly mid-level jet should overspread the warm
sector through the day, which will support more than enough
deep-layer shear for organized storms.

Convection may initiate by Tuesday afternoon in close proximity to
the upper low and left exit region of the mid-level jet in
southwestern/south-central KS. With cold mid-level temperatures
present, this activity should mainly pose an isolated threat for
marginally severe hail. Modest low-level moisture and instability
will probably limit a greater severe risk with northward extent in
KS. Additional storms may develop by early Tuesday evening
along/east of the dryline in central OK. All severe hazards appear
possible with this convection, but uncertainty regarding how
unstable the airmass across the warm sector will become currently
precludes greater severe probabilities across central/eastern OK and
vicinity.

From Tuesday evening though early Wednesday morning, storms may grow
upscale into a line along or just ahead of the eastward-moving cold
front. Given the strength of the southwesterly low-level flow and
potential for weak surface-based instability ahead of this line,
isolated damaging winds may continue to be a threat through the end
of the period across parts of the Ozarks, Mid-South, and lower MS
Valley. An embedded tornado or two also cannot be ruled out with
very strong 0-1 km SRH forecast. This isolated/marginal severe risk
becomes more uncertain with northward extent into MO and the
Mid-South, where very strong low-level flow will be present, but
instability appears meager at best. Adjustments have been made to
the eastern extent of the Marginal risk area across the Mid-South
and lower MS Valley to account for the probable location of strong
to locally severe storms by the end of the period.

..Gleason.. 11/23/2020

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