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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1127 AM CDT Mon Jul 18 2022

Valid 181630Z - 191200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHEAST
MONTANA INTO NORTHERN NORTH DAKOTA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MID-ATLANTIC TO NEW ENGLAND REGIONS...

...SUMMARY...
The greatest severe-thunderstorm threat will be for destructive,
severe gusts and hail today into this evening, from northeastern
Montana to northern North Dakota.

...Synopsis...
A Four Corners upper ridge will continue to dominate the upper-level
flow regime for today with broad troughing over the greater Great
Lakes region. A pair of more notable embedded perturbations, one
over the Great Lakes with a second approaching the northern Rockies,
will drive severe weather chances for this afternoon and into
tonight across the northern Great Plains as well as over the
Mid-Atlantic and New England regions.

...Northern Plains...
The eastward progression of a co*pact upper-level perturbation
across the northern Rockies is apparent in mid-morning water vapor
imagery. Ahead of this feature, surface pressure falls are noted
across eastern MT and the Dakotas in recent surface observations,
and the subsequent mass response is bolstering low-level moisture
content with dewpoints increasing into the upper 60s and low 70s.
Consequently, a broad warm frontal zone is beco*ing more apparent
across ND and southern Canada. Lift ahead of the wave coupled with
ascent along an advancing cold front should support thunderstorm
development by late afternoon across eastern MT. Initially discrete
cells will mature in an environment with somewhat marginal
instability, but elongated hodographs and deep, well-mixed boundary
layers that will support organized convection with a severe wind
threat, including the potential for significant gusts. Convection
will likely intensify as it continues eastward into the Dakotas
where boundary-layer moisture will be richer. The best organized
severe threat will likely be found in the vicinity of the triple
point across northeast MT into northwest ND where lift will locally
be maximized. Upscale growth into one or more segments into the late
evening/overnight hours is possible across northern ND along a
diffuse warm frontal zone. 

To the east, a strengthening low-level jet will augment warm
advection over the frontal zone and support thunderstorm development
across northwest to northern MN this evening. Storms will likely
propagate to the east/southeast along the frontal zone and within a
strong northwesterly flow regime. While storm mode is uncertain, a
hail/wind threat appears probable across northern MN into northern
lower MI through the overnight hours.

...Mid-Atlantic and New England...
Latest analysis shows a surface low gradually deepening across Lake
Eerie. This feature will continue to deepen through the day amid
increasing mid and upper-level flow. A trailing surface trough
should act as the impetus of thunderstorm development from New
England into the southern Appalachians as it migrates east through
the day. Mid-morning satellite imagery reveals extensive cloud cover
across much of the New England region. This cloud cover was also
sampled in regional 12 UTC soundings, which featured high column
saturation and poor low and mid-level lapse rates. Despite the
meager thermodynamic profile, boundary-layer moisture across the
region is unseasonably high (surface dewpoints near or above the
90th percentile for mid-July were noted in morning observations).
Because of this, any daytime heating that can occur will likely
yield adequate buoyancy to support thunderstorm development this
afternoon. The degree of destabilization across the New England
region is questionable given the extensive cloud cover; however, the
increasing flow across the region will boost low-level SRH along a
broad warm frontal zone over the region. This will support the
potential for not only damaging winds, but a few weak tornadoes as
well. 

To the south across the Mid-Atlantic, patchy cloud cover is allowing
for temperatures to quickly warm into the low to mid 80s. Regional
VWPs already show winds in the lowest few kilometers increasing to
30 knots, with further strengthening expected through the day.
Thunderstorms developing along the front will support a more robust
severe wind threat co*pared to locations further north where
instability is more questionable. While low-level hodographs may not
feature as much curvature as areas to the north, forecast soundings
feature enough low-level veering to support at least a low-end
tornado concern. 

...Lower Appalachians to Mid-South...
A trailing surface trough/cold front draped across the lower
Appalachians and into the mid-MS River Valley will support
thunderstorm development through the afternoon. While deep-layer
flow is meager (recent effective shear estimates near 20-25 knots
were noted on recent ACARs soundings), favorable buoyancy should
co*pensate for this weakness and support a damaging wind threat
through the afternoon. Latest guidance continues to suggest a
cluster of storms across northern MS may consolidate into a more
cohesive, southward-propagating convective line that could pose a
more widespread damaging wind threat, though confidence this
potential remains low given the weak environment flow.

..Moore/Hart.. 07/18/2022