LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1239 AM CDT Mon Jul 03 2023
Valid 031200Z - 041200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE
MIDDLE ATLANTIC AND NORTHERN GREAT PLAINS...
...SUMMARY...
Scattered strong to severe thunderstorms are expected across the Mid
Atlantic Region and portions of the northern Great Plains Monday
into Monday night.
...Middle Atlantic...
Early-morning water-vapor imagery depicts a well-defined upper
trough advancing east across the OH Valley. Strongest 500mb flow has
advanced through the base of the trough and is forecast to translate
across WV into the Delmarva by 18z, then off the Atlantic Coast
during the evening. This scenario will result in strengthening
wind/shear profiles such that any convection that develops later
today has the potential to organize across much of the Middle
Atlantic. Seasonally moist profiles currently reside across this
region with ample low-level moisture (surface dew points in the
lower 70s). As a result, modest buoyancy should develop by mid day
ahead of the aforementioned speed max. Early this morning, several
small clusters of convection continue across the central
Appalachians. This activity is expected to propagate east-northeast
but slowly weaken by the start of the day1 period. Aside from weak
showers/convective debris, boundary-layer heating is expected to aid
instability as temperatures warm to near 90F across the Delmarva.
Forecast soundings suggest convective temperatures will be breached
by 19z and isolated-scattered storms are expected to evolve ahead of
the trough. Soundings suggest some threat for a few supercells,
otherwise organized clusters appear possible. Gusty winds and hail
are the primary threats with these storms.
...Northern Great Plains...
Upper troughing will establish itself over the northern
Rockies/northern Plains later today with weak height falls forecast
as far south as WY into the upper Red River Valley. Lee surface low
should settle into the Black Hills region by 18z, then propagate
into northern NE during the overnight hours as surface pressures
rise across the northern High Plains. Primary corridor of low-level
convergence during the afternoon will focus along the boundary from
the ND/SD border into northern WY where upslope flow will
contribute. Surface temperatures should rise rapidly through the 80s
into the lower 90s over much of SD, south of the boundary. CINH will
weaken considerably by 21z and isolated thunderstorms will likely
evolve. Forecast soundings suggest substantial sub-cloud dry layer
as surface temp-dew point spreads may be on the order of 40F. Ample
PWs will result in modest SBCAPE with steep lapse rates. It also
appears flow will be strong enough for supercells and large hail can
be expected. Additionally, very gusty winds could evolve with this
activity if sufficient clustering occurs and an MCS evolves. Some
consideration was given to increasing severe probabilities across
this region. Two main areas of initiation may occur, one along/near
the front over SD and the other within the upslope region of
northern WY. Multiple clusters could evolve then spread east during
the evening/overnight hours.
..Darrow/Weinman.. 07/03/2023
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