SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1143 PM CST Sun Mar 06 2022
Valid 071200Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY FROM PARTS
OF THE LOWER OHIO AND TENNESSEE VALLEYS...INTO THE ALLEGHENY
MOUNTAINS AND NORTHERN MID ATLANTIC COAST...
...SUMMARY...
One or two lines of showers and thunderstorms may spread into and
across the Cumberland Plateau and Allegheny Mountains, into the
northern Mid Atlantic coast region by early this evening,
accompanied by strong to locally damaging wind gusts.
...Synopsis...
While an initially prominent mid-level high over the mid-latitude
eastern Pacific may begin to weaken today through tonight, models
indicate that ridging may continue to build along an axis to its
north, into the Alaskan Arctic latitudes. As this occurs,
downstream mid-level troughing may begin to amplify east of the
Canadian Rockies through the central Canadian/U.S. border area, with
at least a couple of significant embedded short wave impulses.
This regime will be preceded by consolidating troughing digging to
the south and southeast of Hudson Bay, before turning toward the
northern Atlantic coast. It appears likely that this will include a
merger with another significant short wave trough, which has emerged
from the Southwest over the last day or so, and likely will be in
the process of accelerating across and northeast of the middle
Mississippi Valley at 12Z this morning.
The southern impulse is already contributing to surface frontal wave
development across the Ozark Plateau into Ohio Valley, which appears
likely to gradually deepen further while migrating to the east of
the lower Great Lakes, before much stronger secondary surface
cyclogenesis takes place near northern New England coastal areas
into the Canadian Maritimes. A trailing surface cold front likely
will surge offshore of the northern Atlantic coast, and through much
of the Southeast and into the northwestern Gulf of Mexico, where it
is expected to stall near the northern periphery of low-amplitude
subtropical mid-level ridging.
Another significant shortwave perturbation continues to dig within
the remnant mid-level troughing over the Southwest. However, this
impulse is forecast to only slowly turn toward the southern Rockies
today through tonight, lagging well to the northwest of the surface
cold front.
Considerable thunderstorm development is well underway in
association with the surface frontal wave, and substantive further
upscale growth appears probable through 12Z this morning, when
convection focused along the evolving warm and cold frontal zones
may extend through much of the Ohio and lower Mississippi Valleys.
This activity, or its remnants, is expected to spread across much of
the Appalachians and the northern through middle Atlantic Seaboard
by late tonight.
...Southern Appalachians through northern Mid Atlantic coast...
Modest pre-frontal low-level moistening and, perhaps more notably,
relatively warm layers aloft are generally forecast to limit warm
sector boundary-layer destabilization today through tonight.
However, given at least weak conditional instability, mid-level
forcing for ascent along/ahead of the eastward advancing cold front
will probably be sufficient to maintain or support new developing
lines of fairly vigorous convection, particularly across the
Cumberland Plateau and Allegheny Mountains vicinity into the
northern Mid Atlantic coast by this evening. Coinciding with one
belt of 50-70+ kt south-southwesterly flow in the 850-700 mb layer
propagating to the west of the Allegheny Mountains, and another
developing to the lee of the Blue Ridge into the northern Mid
Atlantic coast by this evening, this convection will contribute to
the downward transfer of this momentum toward the surface. It seems
probable that this will contribute to at least scattered, if not
more widespread, damaging wind gusts.
..Kerr/Wendt.. 03/07/2022
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