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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0750 AM CDT Tue Sep 13 2022

Valid 131300Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN NEW
YORK INTO PARTS OF NEW ENGLAND...

...SUMMARY...
Thunderstorms capable of damaging wind gusts, isolated hail and a
brief tornado or two are possible today from eastern New York into
parts of New England, mainly this afternoon into the early evening.

...Synopsis...
In mid/upper levels,a progressive synoptic pattern will continue
over most of the CONUS through the period.  A well-developed cyclone
-- centered initially over southern ON near Lake Erie -- will move
east-northeastward to Lake Ontario by 00Z, while slowly filling. 
meanwhile, the trailing trough will move more slowly eastward,
reaching the southern/central Appalachians.  By 12Z, the cyclone
should devolve to an open-wave trough with primary vorticity max
over northern ME, and 500-mb trough southwestward to northern GA.

Farther west, ridging will progress eastward from its present
position over the Rocky Mountain States across the Plains States
through the period.  Upstream troughing will shift eastward as well,
related mainly to two shortwave perturbations:
1.  A trough now located over NV, the lower Colorado River Valley,
and northern Baja, including the feeble midlevel remnants of former
eastern Pacific tropical cyclone Kay, now over western AZ.  This
trough will eject northeastward to parts of WY and the Four Corners
region by 12z tomorrow.  Large-scale lift and at least marginal
low/middle-level moisture preceding this trough will co*bine with
diurnal heating of higher terrain to support general thunderstorm
potential over a large swath of the Intermountain West.  Though
strong gusts may occur from any cells unloading downbursts into
deep/well-mixed subcloud layers, severe potential appears too
isolated and conditional for outlook areas at this time.
2.  A small cyclone now beco*ing an open shortwave trough over the
Vancouver Island region, southward offshore from WA/OR.  This
perturbation should move slowly inland, reaching eastern WA and
southeastern BC by 12Z.

At the surface, 11Z analysis showed a triple-point low near EWR,
with cold front southwestward across the coastal Delmarva Peninsula,
the eastern Carolinas, and the central/eastern FL Panhandle.  A warm
front extended from that low over coastal southern New England.  The
warm front will move diffusely northward/northeastward through the
afternoon and central/northern New England, while an occluded front
over eastern NY effectively beco*es a cold front moving eastward
through that region, then New England.

...Northeast CONUS...
Multiple episodes of scattered thunderstorms are expected to cross
eastern NY and New England today, offering the potential for
damaging to locally severe gusts, isolated large hail, and marginal
tornado potential.

Ongoing activity, and additional development nearby, may pose a
localized severe threat through midday over coastal areas of
southern New England, south of the warm front.  That portion of this
activity along and south of the warm front will have the earliest
access to a high-theta-e boundary layer characterized by surface
dewpoints near 70 F and minimal CINH, as well as veering flow with
height and somewhat enlarged hodographs in the warm-frontal zone,
supporting sporadic supercell potential.

Additional thunderstorms are expected farther north and northwest
this afternoon, moving eastward to northeastward across the
outlook area as the warm front shifts northward.  Associated low-
level warm/moist advection and muted diurnal heating will
destabilize the boundary layer, beneath the eastern rim of midlevel
DCVA/cooling preceding the approaching mid/upper low/trough.  The
co*bination should result in peak MLCAPE ranging from 300-500 J/kg
in northern areas to around 1500 J/kg in parts of central/southern
New England behind the morning activity.  Strengthening mid/upper-
level winds and deep shear will occur as the low/trough aloft
approach.  Forecast soundings showing magnitudes of 35-45-kt for
effective shear and 70-85 kt cloud-layer shear, as a 90-110-kt
250-mb speed max shifts over southern/eastern New England.  The 15%
wind/"slight" area represents overlap between greatest forecast
convective coverage and a favorable CAPE/shear parameter space for
severe.

..Edwards/Smith.. 09/13/2022