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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0748 AM CDT Mon Sep 19 2022

Valid 191300Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE NORTHEAST...AND PORTIONS OF NORTH DAKOTA TO NORTHWESTERN
MINNESOTA...

...SUMMARY...
Isolated severe thunderstorms are possible today over parts of the
Northeast, and portions of North Dakota to northwestern Minnesota.

...Synopsis...
A rather blocky pattern aloft will persist over much of the southern
and western CONUS through the period.  In mid/upper levels, a cut-
off, synoptic-scale cyclone will remain centered off northern CA
through the period, with a wobbly, net southward drift.  Ridging to
its northeast across the northern Rockies will extend northwestward
from a large, early stationary anticyclone centered over central/
north TX.  A subtle shortwave trough -- initially over southern SK
and eastern MT -- will move east-northeastward today over western ND
to southern MB, as heights fall ahead of a stronger, larger,
positively tilted trough digging southeastward across BC/AB.

Downstream, a phased, progressive, split-flow wave feature is
apparent in moisture-channel imagery, with ridging crossing eastern
Hudson Bay toward northern QC on its north side, and south of the
split, a trough now over the Upper Great Lakes.  The trough is
forecast to amplify somewhat as it moves eastward over the Lower
Great Lakes today, reaching southeastern ON, western central NY and
eastern PA by 00Z.  By 12Z, the trough should extend from a weak
500-mb low near the VT/QC line south-southwestward over NJ to the
Delmarva, before moving offshore early day 2.  An embedded,
convectively generated/enhanced vorticity lobe is apparent over
northern OH, and should move eastward over PA today.

The surface analysis at 11Z showed a cold front over southern ON,
northern IN, and central IL, beco*ing quasistationary across
northern MO to a low over extreme east-central CO.  A warm front was
drawn across central NY and coastal southern New England, which will
move diffusely northward across most of eastern NY and western/
central New England through the day, as the cold front approaches
from the west.  A separate low was drawn between 2WX and MLS, with a
short warm front east-southeastward to east-central SD.  This low is
expected to move northeastward across western/northern ND by 00Z, in
step with the warm front that will continue extending to its
southeast.

...Northeast CONUS...
Within a broad swath of prefrontal UVV, thunderstorms are expected
to develop through the remainder of the morning over northern/
western portions of both NY and PA, increasing in coverage mainly in
bands, and moving eastward across the outlook area into the
afternoon.  Occasional damaging downdraft gusts are possible, and
isolated, marginally severe gusts may be noted from the most intense
cells.

Several offsetting factors will exist over this region, keeping the
threat for severe (50+ kt) thunderstorm gusts marginal, despite the
likelihood of scattered convection and strengthening deep-layer
flow.  Abundant mid/high cloud cover will temper diabatic heating
and slow the diurnal increase in boundary-layer lapse rates, though
low-level theta-e advection southwest of the warm front should
offset the lack of stronger insolation enough to support minimally
inhibited, effectively surface-based parcels.  Despite modest
midlevel lapse rates, surface dewpoints generally in the upper 50s
to mod 60s F will support 500-1000 J/kg MLCAPE.

Low-level lift will be subtle, mainly related to prefrontal
trough(s), differential-heating zones and outflows.  As the
mid/upper trough approaches, the area will experience increasing
large-scale ascent, related mainly to both midlevel DCVA and the
divergence acco*panying the left-exit region of a 500-250-mb speed
max.  Mesoscale lift enhancement also may be noted ahead of the
OH/PA embedded perturbation.  Tropospheric wind profiles will be
nearly unidirectional from the southwest, with enough deep speed
shear to support around 30-35-kt effective-shear magnitudes.

...ND/MN...
Ongoing thunderstorms, with intermittent pulses of MESH and dual-pol
hail indicators to near severe levels, are apparent over parts of
southern/central ND.  This activity is occurring in a zone of
low-level WAA and moistening ahead of the MT perturbation, with
modified RAOBs and forecast soundings suggesting inflow in the
700-800-mb layer, MUCAPE in the 500-1000 J/kg range, and 40-50-kt
effective-shear magnitudes in support of some organization. 
Marginally severe hail will continue to be the main concern as this
activity shifts east-northeastward through the remainder of the
morning, with additional development possible to its northwest in
the zone of UVV preceding the mid/upper trough.

A more-uncertain potential exists for thunderstorm development near
the warm front and on the southeastern rim of the shortwave trough's
UVV influence this afternoon.  Despite that, forecast soundings
suggest some increase in EML-related MLCINH that may offset frontal
lift and weak convergence near the low.  Steep low/middle-level
lapse rates and surface dewpoints in the 50s F will support a plume
of 1000-2000 J/kg MLCAPE amidst 40-50-kt effective-shear magnitudes
and well-curved hodographs in the least few km AGL.  This suggests
conditional supercell potential, though coverage likely would be
isolated at best.

..Edwards/Leitman.. 09/19/2022