SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1241 PM CDT Sun Jul 17 2022
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE MONDAY
AFTERNOON AND EVENING ACROSS PARTS OF NORTHEASTERN MONTANA INTO
NORTHWESTERN NORTH DAKOTA...
CORRECTED FOR A COUPLE TYPOS
...SUMMARY...
Strong to locally severe thunderstorm development is possible near
the Canadian/U.S. border, from the Great Plains into the upper Great
Lakes region, as well as across parts of the northern Mid Atlantic
region, Monday afternoon into Monday night.
...Synopsis...
Models indicate that lower/mid-tropospheric ridging will generally
persist from the subtropical western Atlantic through much of the
southern and central tier of the U.S. through this period. This
will continue to include one prominent embedded mid-level high
centered over the southern Rockies vicinity, and another elongated
along 30N latitude across the western Atlantic, with weak mean
troughing in between, roughly along an axis from the lower
Mississippi Valley into the western slopes of the Appalachians.
It does appear that flow may become a bit more progressive across
the northern tier of the U.S., with a vigorous short wave trough and
embedded low within one belt of westerlies forecast to accelerate
across the northern Rockies into the northern Great Plains by late
Monday night. Downstream, a more modest impulse likely will
accelerate from the lower Great Lakes/upper Ohio Valley vicinity
through northern New England. Both of these perturbations
(preceding significant short wave impulses within a branch to the
north, including one digging near or just south of southern Hudson
Bay and another accelerating inland of the British Columbia coast)
may be accompanied by surface cyclogenesis, with the lead cyclone
probably becoming the more prominent while migrating from the lee of
the lower Great Lakes into the St. Lawrence Valley.
...Northern Mid Atlantic...
Pre-frontal surface troughing, extending from near the migratory low
southward through the Mid Atlantic, likely will become the focus for
the more prominent boundary-layer destabilization during the day
Monday. The boundary-layer probably will become characterized by
seasonably high moisture content, but lower/mid tropospheric lapse
rates are expected to be generally weak, and most guidance suggests
that CAPE may not reach 1000 J/kg. However, a belt of 30-40+ kt
southwesterly flow in the 850-500 mb layer will potentially
contribute to an environment conducive to organized convection given
sufficient destabilization. It is possible that this could include
a couple of supercells with a risk for tornadoes, particularly
across the Poconos and Catskills into Hudson Valley vicinity by late
Monday afternoon.
...Northern Rockies into upper Great Lakes region...
In association with the short wave developments, models indicate
that a lower/mid tropospheric front within an evolving deformation
zone will become focused near the international border area, from
the Great Plains into the upper Great Lakes region. Along and to
the southwest of this front, a plume of warm and capping elevated
mixed-layer air is forecast to advect east of the Rockies. At
mid-levels (around 700 mb) the northeastern periphery of this air
mass may generally extend from north of the international border
across the Great Plains into the western Lake Superior/Upper
Michigan vicinity by early Monday evening. Beneath this regime, in
the presence of moderate west/northwesterly mid-level flow, there
may be sufficient moisture to contribute to mixed-layer CAPE on the
order of 2000+ J/kg, and the environment appears likely to become at
least conditionally supportive of severe storms, potentially
including isolated supercells and organizing storm clusters.
However, forcing to overcome the mid-level inhibition remains
unclear across much of the region.
Most guidance does appear to suggest that a concentrated area of
strong forcing for ascent, just to the east-northeast of the
approaching mid-level low, may overcome inhibition and promote
sustained thunderstorm development across parts of northeastern
Montana by early Monday evening. This may be accompanied by the
risk for severe wind and hail, which probably will spread into
portions of northwestern and north central North Dakota through
Monday night.
..Kerr.. 07/17/2022
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