SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1155 PM CST Sun Mar 03 2024
Valid 041200Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
SOUTHERN PLAINS INTO THE LOWER/MID MS VALLEY AND MIDWEST...
...SUMMARY...
Isolated strong to severe thunderstorms will be possible this
afternoon into tonight from parts of central Texas into the lower
Mississippi Valley, as well as from the Ozarks into the Midwest.
Large hail is expected to be the main threat, but strong/gusty winds
and a tornado or two may also occur.
...Synopsis...
A large-scale mid/upper-level trough will cover much of the
central/western CONUS through the day. Within the broader trough,
multiple belts of stronger flow will impinge upon portions of the
southern Plains, lower/mid MS Valley, and Midwest. A strong
northern-stream shortwave trough will move quickly northeastward
away from the upper Great Lakes during the morning, with multiple
lower-amplitude vorticity maxima following in its wake. Meanwhile, a
southern-stream mid/upper-level shortwave trough will move from
northern Mexico into Texas by afternoon, and towards the lower MS
Valley by late evening. A surface cyclone is forecast to move along
a frontal boundary from the south-central Plains northeastward
toward the mid MS Valley by evening.
...Parts of IL/MO into eastern IA and southern WI...
A surface boundary is forecast to move northward as a warm front
into parts of eastern IA, northern IL, and perhaps southern WI
during the day, before stalling and then moving southeastward as a
cold front during the evening. Across the warm sector, modest
low-level moisture (dewpoints generally in the mid/upper 50s F)
beneath relatively cold temperatures aloft will support MLCAPE
increasing into the 1000-1500 J/kg range this afternoon. Some
weakening of mid/upper-level flow is expected through the day in the
wake of the departing shortwave, but will remain sufficient to
support effective shear of 35-45 kt, which is conditionally
favorable for organized convection.
While a strong elevated storm or two will be possible across WI
during the morning, the primary concern is for storm development in
the vicinity of the surface front by late afternoon or early
evening. Guidance varies regarding the timing of initiation and
placement of the surface features, but in general, scattered
thunderstorm development is expected from northeast MO/eastern IA
into northern IL and southern WI. An initial supercell or two will
be possible, though there may be a tendency toward more of a complex
or linear mode with time as the front begins to push southeastward.
Hail appears to be the most likely hazard at this time, though there
will also be some potential for isolated strong/damaging gusts. Some
tornado potential could also evolve if a surface-based supercell or
two can be sustained. Uncertainties regarding placement/timing of
the surface front and longevity of any supercell potential preclude
higher probabilities across the region at this time.
...Parts of TX/eastern OK into the Ozarks and lower MS Valley...
Relatively rich low-level moisture (with dewpoints increasing
through the 60s F) will stream northward through the day across
parts of TX, eastern OK, AR, and LA. Thunderstorm development will
be possible by late morning into the afternoon along the northern
periphery of the deeper returning moisture across parts of LA and
perhaps into adjacent portions of southwest MS and southeast TX.
Steep midlevel lapse rates atop the deepening moisture will support
preconvective MLCAPE of 1500-2000 J/kg, with sufficient deep-layer
shear for organized convection. A few strong multicells and perhaps
a supercell or two will be possible, with an attendant threat of
hail and locally damaging gusts.
Farther west into TX, the diurnal severe threat is more conditional,
with large-scale ascent expected to remain rather weak and
relatively limited convergence along the dryline. However, a very
isolated supercell or two cannot be ruled out during the late
afternoon and evening, which would pose a large-hail threat.
Overnight, most guidance suggests renewed storm development near the
ArkLaTex region, likely in response to the southern-stream shortwave
trough approaching the region. Storms within this late-night regime
would likely be slightly elevated, but moderate buoyancy and
favorable deep-layer shear may support an isolated hail and/or
damaging-gust threat into early Tuesday morning.
..Dean/Weinman.. 03/04/2024
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