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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0746 AM CDT Wed Aug 31 2022

Valid 311300Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE CENTRAL PLAINS...MAINE AND NORTHERN NEW YORK...

...SUMMARY...
Isolated strong to severe thunderstorm gusts may occur over parts of
the central Plains this afternoon and evening.  Isolated hail and
damaging gusts are possible over parts of Maine and northern New
York.

...Synopsis...
In mid/upper levels, mean ridging has beco*e re-established over the
West, with the core anticyclone over the Great Basin.  Troughing
over the Lower Great Lakes and Mid-Atlantic regions is anchored by a
cyclone over the southern Hudson Bay and James Bay.  Height falls
ahead of a series of shortwaves traversing the sharply cyclonic flow
will shift the synoptic trough slowly eastward through the period,
reaching new England by 12Z tomorrow.

In between the larger-scale trough and ridge, a shortwave trough is
apparent in moisture-channel imagery over southeastern WY near the
NE line, extending southwestward over northern CO.  Embedded in
strongly difluent mid/upper flow, this trough should move slowly
southeastward through the period, with its vorticity field augmented
by associated convection over the central High Plains this
afternoon/evening.  Farther south, a broad, weak, cut-off cyclone
over southern NM, Chihuahua and far west TX will contribute to
general thunder potential over a large part of TX and NM.

The 11Z surface analysis showed a cold front from the eastern
Adirondacks/Champlain Valley area south-southwestward over the
Delaware River Valley, to eastern VA, central NC, and northern GA,
beco*ing quasistationary across northern portions of MS/AL, central
AR, southwestern OK, and far west TX.  That portion of this front
east of the Appalachians should move eastward through the period,
reaching Downeast ME and the Hampton Roads area around 00Z, while
offshore in between those locations.  Lee troughing should persist
from central MT to eastern Co, with a secondary surface trough
across western/northern NE by afternoon.

...Central Plains...
Widely scattered to scattered, high-based thunderstorms are forecast
to form this afternoon and move southeastward to eastward, offering
isolated severe-gust potential for a few hours into early evening. 
Activity then should dissipate as a co*bination of spreading outflow
air and ambient/diabatic surface cooling co*bine to stabilize the
boundary layer.

Convection should develop in a zone of weak but sufficient low-level
convergence near the troughs, as surface temperatures heat into the
90s F.  This also times well to the strongest DCVA/cooling aloft
related to the shortwave trough exiting the Rockies.  The result
should be steep low/middle-level lapse rates (8-8.5 deg C/km from
surface to just below 500 mb), inverted-V thermodynamic profiles,
but enough moisture surviving the mixing process to support 300-800
J/kg MLCAPE.  DCAPE values should be about twice that.

...Northeast...
Thunderstorms (and marginal severe potential) should be concentrated
in two primary regimes today, in chronological order:

1.  Eastern ME:  Scattered thunderstorms are expected in two primary
frontal/prefrontal corridors this morning into early afternoon.  The
first is manifest as a broken area of showers and isolated
thunderstorms initially apparent in radar imagery over much of ME,
but with lesser coverage eastward.  This activity is forecast to
move slowly eastward while individual elements move faster
northeastward.  Weak diurnal destabilization is expected through
cloud cover in eastern areas, with a very moist foregoing boundary
layer (surface dewpoints co*monly in the mid 60s to low 70s F). 
This should offset weak midlevel lapse rates enough to support
300-800 J/kg MLCAPE (similar MUCAPE along the coast, over a shallow
marine layer).  Some veering with height in the warm sector, and
strong speed shear in unidirectional south-southeast flow above that
-- will support effective-shear magnitudes of 35-45 kt and effective
SRH around 150 J/kg, in support of some convective organization
within a quasi-linear configuration.  This activity should exit the
area by early afternoon.  A second, more strictly frontal convective
band may cross the outlook area later in the afternoon under even
stronger mid/upper flow.  Associated severe potential appears
marginal and rather uncertain, given the limited time and space for
destabilization behind the earlier activity.

2.  Northern NY to Champlain Valley:  Isolated to widely scattered
thunderstorms should develop across southern QC into northern NY
near the midlevel thermal trough and DCVA max, and close to a
secondary cold front/convergence max in the low levels.  Despite the
cool surface conditions behind the initial front, forecast soundings
suggest that vertical thermal profiles will be cold in midlevels
(-16 to -18 deg C at 500 mb), with enough residual boundary-layer
moisture to render minimally capped, surface-based effective-inflow
parcels and 500-800 J/kg peak MLCAPE.  35-45-kt effective-shear
magnitudes and veering wind with height (with curved low-level
hodographs and 150-250 J/kg effective SRH) suggest some weak
supercells are possible, offering mid/late afternoon potential for
hail and strong/marginally severe gusts.

..Edwards/Goss.. 08/31/2022