LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1240 AM CDT Sat Apr 01 2023
Valid 011200Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO
VALLEY AND NORTHEAST ALONG WITH THE SOUTHEAST...
...SUMMARY...
Scattered strong-severe thunderstorms are expected across parts of
the Ohio Valley and Northeast and over the Southeastern US. Wind,
hail, and a few tornadoes are possible.
...Ohio Valley/Northeast...
Upper low, currently located over western IA, is forecast to advance
to southern Lake MI by daybreak, then into western NY by early
evening. Strong 12hr height falls, on the order of 210m, will spread
ahead of this feature across the OH Valley into the northern Middle
Atlantic by the end of the period.
Early this morning, several lengthy QLCS features are progressing
across the OH/TN Valley region. This activity should surge into the
central/southern Appalachians by sunrise, then gradually weaken as
it approaches the Atlantic Coast by 18z. While a few strong storms
may be noted with this convection, of more concern will be
convection that develops immediately ahead of the cold front by late
morning over the OH Valley. Latest model guidance suggests strong
surface heating, along with cooling mid-level temperatures, will
result in a fairly buoyant air mass by 16z across eastern OH.
Scattered convection should easily develop ahead of the strongly
forced front where deep-layer shear will support supercells. Very
steep lapse rates will favor hail with this activity and there is
some concern that very strong winds could mix to the surface,
especially if a squall line matures. Wind probabilities currently
reflect a less organized squall line; however, a mature surging
squall line would pose a greater wind threat. Some consideration for
higher wind probabilities may be warranted.
Downstream, in the wake of the early-day convection, air mass will
gradually moisten/destabilize as surface temperatures warm into the
mid-upper 60s across eastern PA/DE/NJ. Forecast soundings suggest
convective temperatures will be breached by 20-21z. Wind profiles
strongly favor supercells and scattered storms should evolve across
this region by early evening, especially as large-scale forcing
overspreads this region. While storms may initially be somewhat
discrete, an upward-evolving squall line will likely mature as it
spreads toward southern New England. All hazards are possible with
this activity across the Middle Atlantic.
...Southeast...
Deep-layer flow will gradually become more westerly with time across
the Gulf States as the strong upper low advances east across the OH
Valley. This evolution will encourage pre-frontal convection that
currently extends from middle TN-northern MS-northern LA to advance
southeast through the period. While the primary large-scale forcing
will spread well north of this region, deep-layer flow will be
strong and organized line segments and clusters are expected.
Additionally, a few supercells may also emerge within an elongated
southeastward-moving cluster of convection. Damaging winds should be
the primary concern, though some risk for a tornado or two can not
be ruled out.
..Darrow/Thornton.. 04/01/2023
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