SPC AC 011940
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0240 PM CDT Fri Jul 01 2022
Valid 012000Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHEAST
WY...SOUTHWEST SD...AND NORTHWEST NE...AND ACROSS PARTS OF NORTHERN
VA AND MD...
Scattered severe wind and hail will be possible from about 4 to 10
PM MDT in northeast Wyoming across the Black Hills to the Nebraska
Sandhills. Additional strong to locally damaging wind gusts are
possible across northern Virginia into the northern Chesapeake Bay
vicinity through 7 PM EDT.
A Slight risk has been included across parts of northern VA into the
northern Chesapeake Bay vicinity where WW 417 is in effect. Loosely
organized, pulse-like convection across this area has occasionally
produced tree damage from sub-60 mph gusts, and small hail. This
activity will continue to develop eastward the next 2-3 hours and
may continue to sporadically produce strong/locally damaging gusts.
Otherwise, the previous outlook remains on track and no other
adjustments to severe probabilities have been made with this update.
See discussion below for more details.
.PREV DISCUSSION... /ISSUED 1102 AM CDT Fri Jul 01 2022/
Scattered thunderstorms are expected to develop off the Big Horns to
the Sangre de Cristos and spread east across the adjacent High
Plains later this afternoon within a plume of upper 40s to mid 50s
surface dew points. The greatest potential for organized severe
storms will exist across the northern portion of this region from
eastern WY into western SD and northwest NE. Here, moderate to
strong deep-layer speed shear with height will yield effective bulk
values of 40-50 kt and an elongated straight-line hodograph. A few
high-based outflow-dominated supercells with mid-level rotation
should develop and congeal into a cluster this evening. Initial mix
of severe hail and wind transitioning to predominately wind will be
the primary threats. A lack of appreciable low-level forcing for
ascent this evening in conjunction with a nocturnally stabilizing
boundary layer should result in these threats diminishing towards
late evening. Farther south to the Raton Mesa, slow-moving
thunderstorms may pose a threat for very isolated severe wind gusts
and marginally severe wind hail during the late afternoon and
...Lower Great Lakes to the Lower MO Valley...
A low-amplitude shortwave impulse near the NE/IA border will shift
east along the southern periphery of seasonably moderate to strong
mid-level westerlies across the Great Lakes to northern IL/IN/OH.
Isolated to scattered thunderstorms will be possible along and just
ahead of a cold front sagging southeast across southeast Lower MI
through eastern KS later this afternoon. Abundant cloud coverage and
weak mid-level lapse rates should temper updraft intensity in the
more strongly sheared regime near the Lower Great Lakes.
Nevertheless, a few multicell clusters and transient supercell
structures may develop with a threat for isolated damaging winds and
severe hail through about dusk.
Localized damaging winds and marginally severe hail will be possible
through this afternoon as low-level warm theta-e advection-driven
convection over the central Appalachians spreads east towards the
Mid-Atlantic coast. Poor mid-level lapse rates evident in available
12Z observed soundings and modest deep-layer flow will be limiting
factors to a more robust/organized severe threat. See MCD 1314 for
further short-term discussion. Additional thunderstorms may spread
towards the region tonight from the Lower Great Lakes/Upper OH
Valley, but should largely be in a decaying state.
Pronounced differential diabatic heating and weak low-level
convergence may aid in isolated thunderstorms near the Saint
Lawrence Valley into southeast QC later this afternoon. Morning
guidance suggests a nadir in low-level moisture will be present
across parts of western New England, but adequate moisture may still
hold across northern ME. This may yield a corridor of weak buoyancy
amid poor mid-level lapse rates. The most favorable factor will be
effective bulk shear of 40-50 kts, which would conditionally support
a supercell or two, but confidence is low.
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