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Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1258 AM CDT Wed Jul 27 2022

Valid 281200Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE NORTHEAST...AS WELL AS FROM THE OZARKS EASTWARD ACROSS THE
TENNESSEE AND OHIO VALLEYS...

...SUMMARY...
Isolated severe thunderstorm gusts and hail are possible over
portions of the Northeast, as well as from the Ozarks eastward
across the Tennessee and Ohio Valleys.

...Synopsis...
In mid/upper levels, a slowly progressive synoptic pattern is
evident from now through day 2, featuring broadly cyclonic flow
across the Upper Midwest, Great Lakes and Northeast.  This will be
related to a co*plex cyclone -- its center apparent in moisture-
channel imagery over northeastern MB.  This feature is forecast to
move erratically southeastward then eastward across northwestern and
northern ON through this period.  That will occur as the current low
dissipates and yields to (or merges with) a vorticity lobe -- now
over south-central MB -- that should beco*e the new dominant 500-mb
low.  A series of mostly small-amplitude shortwave troughs --
possibly including convectively induced vorticity maxima entrained
into the flow belt from day-1 High Plains convection -- will
contribute to minor net height falls and gradient tightening over
the Ohio Valley.  Stronger height falls are forecast across the St.
Lawrence Valley, NY and New England, as the main cyclone slowly
progresses across ON. 

At the surface, a wavy, broad frontal zone is evident from the
Tidewater region of the Atlantic Coast westward to the lower
Missouri Valley.  The eastern segment will move diffusely/
erratically northeastward, reaching portions of southern New England
and NY by 28/12Z.  This boundary should reorient meridionally across
central/eastern New England by 29/00Z, then move slowly eastward
overnight.  Meanwhile, the western segment -- reinforced by
convective outflow in the intervening time, should linger over the
Ozarks to Ohio Valley region.  A cold front -- initially extending
from western Lake Superior to the central Plains -- should move
across NY, much of PA and WV by 29/00Z, while merging with the
pre-existing/remnant boundary over the lower Ohio and Missouri
Valleys. 

...Northeast CONUS...
Isolated to scattered thunderstorms are possible from midday through
evening, moving eastward to northeastward across the region. 
Damaging to isolated severe gusts are possible, along with isolated
large hail.  

Moist/warm advection behind the warm front, as well as diurnal
heating, will contribute to favorable destabilization across the
area, with a between-fronts corridor of surface dew points in the
60s over northern areas, to low 70s in southern parts of the
outlook.  Peak/preconvective MLCAPE in the 1000-1500 J/kg range
should result.  Given the counterbalancing factors of weak warm-
sector MLCINH, but also, weak low-level flow and nebulous sources
for lift ahead of the cold front, convective coverage is highly
uncertain at this time.  A prefrontal surface trough is likely to
form, and contribute to convective lift to some extent, along with
the cold front.  Low-level flow will be mostly weak, rendering
hodographs that are small in the boundary layer (with possible
exception of the warm front), and generally near straight in
low/middle levels.  Nonetheless, favorable deep shear is expected
amidst the height falls aloft.  As such, a mix of multicell and at
least short-lived supercell modes may occur before activity weakens
during the evening, upon encountering nocturnally stabilizing
overland air and/or the Atlantic marine layer.

...Ozarks to TN/OH Valleys...
Widely scattered to scattered thunderstorms are expected to form in
and near the blended frontal zone, offering sporadic damaging wind
and a marginal threat of severe gusts. 

Activity should be predominantly diurnally driven, as pockets of
strong diabatic heating away from persistent cloud cover co*bine
with frontal/outflow-boundary lift to erode CINH.  Surface dew
points co*monly in the upper 60s to mid 70s F, in an air mass with
PW co*monly exceeding 2 inches, should contribute to MLCAPE in the
1500-2500 J/kg range (locally higher).  Low-level flow/shear will be
modest, and this area will remain south of the strongest flow aloft.
Still, the southern rim of favorable mid/upper winds will extend
over much of the outlook area, with 500- and 250-mb winds around
25-35 kt and 45-60 kt respectively.  This will contribute to some
potential for organized multicells, perhaps brief supercell
structures, with water-loaded downdrafts being the main source of
strong to marginally severe gusts.  Isolated, marginal hail also may
be noted in the most intense cells.

..Edwards.. 07/27/2022