LIVE MAP (ABOVE) ... Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CDT Thu Mar 30 2023
Valid 021200Z - 071200Z
...DISCUSSION...
A mid/upper shortwave trough located over the southern Rockies Day
4/Sunday morning will weaken as it develops east across OK/TX.
Southerly low-level flow will modestly increase and begin to
transport Gulf moisture northward across east TX toward southeast OK
and the Arklatex vicinity ahead of a dryline. Sufficient vertical
shear will exist for organized convection. However, questions remain
regarding moisture quality/timing and northward extent, and at least
modest midlevel capping. If current model trends continue and/or
indicate better quality moisture, low-end severe probabilities will
likely become necessary in the Day 3 outlook.
A large-scale upper trough will dig across the western states on Day
5/Monday. Stronger height falls spreading east toward the Rockies
will result in lee cyclogenesis and increased southerly low-level
flow across the southern Plains and south-central states. This will
transport Gulf moisture northward through the period, with a broad
warm sector developing ahead of a dryline from central OK/TX
eastward to the Mid/Lower MS Valley by Day 6/Tuesday. While some
stronger southwesterly deep-layer flow will overspread this
developing warm sector on Monday, large-scale ascent will remain
displaced to the west. Furthermore, capping will likely limit
convection in the absence of stronger ascent. Some conditional
severe threat could develop, but confidence is too low to warrant a
15 percent delineation on Monday.
As the western trough ejects on Day 6/Tuesday, potential significant
severe thunderstorms will be possible far eastern OK toward
southeast MO and vicinity. Rich boundary-layer moisture will be in
place amid steep midlevel lapse rates courtesy of an EML advecting
across the region from the Mexican Plateau. This will supply plenty
of instability with stronger vertical shear accompanying the
ejecting trough. There is some uncertainty among medium range
guidance on the northern extent of better moisture return and hence
severe potential. This is mostly driven by differences in surface
low, dryline and warm front positions related to somewhat different
ejection of the upper trough. However, guidance is in very good
agreement with respect to the southern portion of the risk area.
Supercells capable of all severe hazards, some potentially
significant, will be possible.
By Day 7/Wednesday, some severe potential could persist ahead of the
eastward-advancing cold front across portions of the Midwest.
However, the upper low/trough is forecast to quickly lift northeast
into Canada and large-scale ascent will be waning. Still, a
seasonally moist boundary-layer will exist ahead of the front amid
strong vertical shear. Depending on trends, severe probabilities may
become necessary in subsequent outlooks.
Lower-amplitude flow will overspread much of the CONUS east of the
Rockies by day 8/Thursday and a broad area of surface high pressure
will bring mostly dry and stable conditions. The exception may be
across parts of the Mid-Atlantic coast toward the Southeast ahead of
the eastward-advancing cold front. However, nebulous forcing and
modest shear likely will temper severe potential.
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