SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Sun Sep 11 2022
Valid 121200Z - 131200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC INTO NORTH CAROLINA...AND PORTIONS OF ARIZONA...
...SUMMARY...
Isolated strong to severe thunderstorms may occur across parts of
the Mid-Atlantic into North Carolina on Monday, with occasional
damaging winds the main threat. A few severe thunderstorms also
appear possible across portions of Arizona.
...Mid-Atlantic into North Carolina...
A closed mid/upper-level cyclone will be present over the Midwest
and Great Lakes on Monday. This feature is forecast to advance
slowly eastward across these regions through the period. At the
surface, a weak low initially over southern WI/northern IL should
further occlude as it develops eastward across the Great Lakes and
OH Valley through Monday evening. A cold front should move
east-southeastward across much of the eastern CONUS and Southeast. A
moist low-level airmass is expected to be in place ahead of the
front across much of the Mid-Atlantic and Southeast. Due to occluded
nature of the cyclone, mid-level lapse rates should generally remain
poor across the warm sector. Even so, daytime heating is forecast to
aid in the development of weak to locally moderate instability, with
MLCAPE increasing into the 1000-2000 J/kg range by Monday afternoon.
Thunderstorms should gradually develop through the day both along
the surface cold front and ahead of it along weak low-level
confluence bands. The best potential for robust convection appears
to extend across portions of PA/NJ southward into MD/DE/VA and NC.
This region should have some enhancement to mid-level southwesterly
winds, even with the strongest flow aloft forecast to generally lag
behind the cold front across the OH Valley. It appears that around
25-35 kt of deep-layer shear will be present to support updraft
organization. Multicell clusters capable of producing isolated
strong to damaging winds should be the main severe threat as they
spread eastward through Monday evening. Where the deep-layer shear
is forecast to be strongest (VA/MD/DC vicinity), marginal supercells
may occur and pose a threat for both isolated hail and perhaps a
brief tornado.
...Arizona...
The remnants of a tropical cyclone should spread northward from
southern CA into the Great Basin on Monday. A belt of modestly
enhanced mid-level southerly flow is expected to be in place between
this feature and upper ridging centered over the Four Corners. A
rather moist low-level airmass should be present over the lower
elevations of AZ. Diurnal heating of this airmass and persistent
southerly mid-level flow should aid in the development of scattered
to numerous thunderstorms Monday afternoon and evening across parts
of southeastern into central and northern AZ. Although deep-layer
shear appears marginal for thunderstorm organization, some
clustering may occur. Isolated severe wind gusts appear possible
with any thunderstorms that can develop as low-level lapse rates
steepen. Occasional hail may also occur with the strongest cores.
..Gleason.. 09/11/2022
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