SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 PM CDT Tue Sep 13 2022
Valid 132000Z - 141200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS UPSTATE NEW
YORK AND 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.
...20z update...
A few severe storms will remain possible through this evening across
upstate New York and southern New England ahead of a well-defined
upper low. While cloud cover and early morning precipitation have
limited severe potential thus far, some clearing has been noted
across southern New England where upper 60s to low 70s F surface
dewpoints are contributing to moderate destabilization. With
effective shear values of 40 kt, a few organized line segments or
supercell structures may evolve with a risk primarily for damaging
wind gusts, hail, and perhaps a weak tornado. Minor adjustments to
the western edge of the thunder area were made. Otherwise the
marginal and Slight Risk areas remain unchanged, see the previous
outlook for additional information.
..Lyons/Jewell.. 09/13/2022
.PREV DISCUSSION... /ISSUED 1109 AM CDT Tue Sep 13 2022/
...Synopsis...
An upper-level low over Lake Erie will gradually shift
east/northeast through the day into the northeastern CONUS. As this
occurs, a weak surface low will undergo some deepening as it moves
northeast across the New England region. A trailing cold front,
analyzed in latest surface observations from central NY southward
along the East Coast, will focus thunderstorm development through
the afternoon and evening hours. Across the western U.S., an
upper-level trough over the Great Basin will phase with a shortwave
disturbance moving into the Pacific Northwest. Ample moisture and
lift ahead of these features will support scattered thunderstorm
development across a broad swath of the inter-mountain West. A few
strong wind gusts and marginally severe hail are possible with this
activity, especially across portions of AZ/NM where deeper
boundary-layer mixing is expected, but marginal wind profiles will
limit the potential for widespread organized convection.
...New England...
Thunderstorm development along the cold front is already underway at
16 UTC across parts of central NY. The 12 UTC ALB sounding sampled
poor low and mid-level lapse rates, but ample moisture throughout
the profile. Extensive cloud cover will likely limit the influence
of daytime heating, but most model solutions suggest that only
modest diurnal warming into the mid 70s is needed to support
surface-based parcels with minimal inhibition and 500-1500 J/kg
SBCAPE. Overall buoyancy magnitudes may be modulated by the poor
mid-level lapse rates, and should generally decrease with
northwestward extent away from the coast and the higher-quality
moisture. The approach of the upper wave through the day will
strengthen mid to upper-level winds and elongate hodographs. Nearly
straight hodographs featuring effective bulk shear values near 35-45
knots will support storm organization, including the potential for
supercell or two. Low-level flow is expected to remain fairly weak
below 2-3 km, but may exhibit sufficient curvature to support
low-level rotation and a brief/weak tornado threat.
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