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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0744 AM CDT Sun May 22 2022

Valid 221300Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN MID-ATLANTIC AND NEW ENGLAND...

...SUMMARY...
Scattered thunderstorms, some with damaging to severe gusts and
large hail, are expected today over parts of the northern
Mid-Atlantic and New England.

...Synopsis...
In mid/upper levels, mean troughing and related large-scale cyclonic
flow will persist from northeastern/Arctic Canada across the
northern Plains, with some eastward shift over the Great Basin to
central Rockies, and across northwestern MX.  Numerous embedded
shortwaves will perturb that broader cyclonic-flow pattern on the
mesoscale.

The most convectively important of those shortwave troughs is
apparent initially in moisture-channel imagery from northeastern MN
across IA.  This feature is expected to stretch northeast/southwest
through the day as the northern portion ejects more rapidly,
reaching southwestern/central QC by 00Z.  As that occurs, height
falls, tightening mid/upper height gradient, and accordingly,
stronger 500-250-mb southwesterlies will overspread much of the
Northeast today on both sides of the front described below. 
Otherwise, a series of convectively induced/enhanced vorticity
maxima will occupy a belt of weaker westerlies and southwesterlies
aloft, from south TX to VA.

At the surface, 11Z analysis showed a cold front from southern ON
across western OH, western KY, southern AR, through a weak frontal-
wave low near SHV, to south-central TX and northern Coahuila.  As
the northern-stream shortwave trough approaches, the front will
accelerate eastward, reaching northern/western New England and near
the I-95 corridor between NYC and northern VA around 00Z.  From
there the front should be positioned across western NC, northern AL,
central MS, southwestern LA, and deep south TX.  By 12Z, the front
will move offshore from the Northeast, and extend across central NC,
beco*ing slow-moving to stationary through a weak frontal wave over
northern AL, southwestward over southern LA and deep south TX.

...Northeastern CONUS...
Scattered thunderstorms are likely in one or more bands, along/ahead
of and largely parallel to the surface front.  Activity may develop
by midday to early afternoon across portions of PA, northern WV and
western NY.  Mainly multicell bands/clusters, with isolated discrete
or embedded supercells over New England, are possible.  This
activity should move eastward to northeastward into a diurnally
destabilizing, favorably moist air mass and intensify while also
growing in coverage.  Damaging to severe gusts and sporadic hail are
possible, and a tornado or two may occur over northeastern portions
of the area.

Low-level and deep shear each should increase with northward extent
under the greater height falls aloft, while moist advection and
pockets of sustained diurnal heating contribute to favorable
destabilization, particularly over the "slight" area.  A corridor of
1000-2000 J/kg MLCAPE may develop ahead of the front across ME and
adjoining parts of northern/central New England, with peak surface
dew points in the 60s F and surface temps into the mid/upper 80s and
90s (elevation-dependent).  Meanwhile, effective-shear magnitudes
around 40-50 kt are possible over northern/western ME, decreasing to
less than 35 kt over southern NY and eastern PA.  While bands or
clusters of thunderstorms may develop farther south, overall
organization and coverage should be less.  Activity should diminish
this evening as it moves into areas from Downeast Maine to southern
New England where the cold/stable marine-layer influence will be
greater.

...Gulf Coast to southern Mid-Atlantic...
Isolated to scattered thunderstorms, sometimes in loosely organized
multicellular clusters, should occur today in a broad, favorably
moist swath from the southern Mid-Atlantic across the Southeast,
ahead of the surface front and along/ahead of an aggregate of
outflow/differential-heating boundaries left by prior convection and
its lingering cloud cover. Additional convection may form along
sea-breeze fronts and serial outflows from successive daytime
activity.  Being well-displaced from substantial midlevel flow and
deep shear, this activity should present a marginal, isolated severe
concern, mainly for damaging gusts.

A convectively active/reinforced midlevel perturbation over the
northern Gulf and southeastern LA may contribute some enhancement to
low/middle-level flow and shear (e.g., via strengthened 850-500-mb
speeds, and some backing of surface winds as well).  This suggests
transient storm-scale rotation may occur with associated cells near
the coast and offshore, particularly this evening into tonight.  As
such, marginal tornado probabilities are maintained across parts of
that region.

..Edwards/Kerr.. 05/22/2022