LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Tue Jul 25 2023
Valid 251200Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE NORTHERN PLAINS AND THE MID ATLANTIC...
...SUMMARY...
Scattered severe wind/hail-producing thunderstorms are possible
across parts of the Northern Plains and the Northeast this afternoon
and evening. Isolated severe gusts are also possible over portions
of the Interior West.
...Synopsis...
A stationary upper ridge will center over the southern Rockies
today, with multiple mid-level troughs expected to traverse the
periphery of the ridge, supporting regimes favoring strong to severe
storms. Monsoonal moisture trapped near the upper ridge over the
Interior West will support scattered thunderstorm development by
afternoon peak heating. Storms along the periphery of the ridge over
the central/northern Rockies will benefit from stronger upper flow
from a passing mid-level trough, with isolated strong to severe
storms possible. Farther east across the northern Plains, a small
but pronounced mid-level trough will rapidly approach the Upper MS
Valley, supporting the development of severe thunderstorms amid a
buoyant and sheared airmass. Finally, strong to potentially severe
thunderstorms may also develop across portions of the Northeast
ahead of an upper trough.
...Northern Plains...
With afternoon heating, surface temperatures are expected to exceed
90 F amid upper 60s to near 70 F dewpoints. When overspread by 8+
C/km mid-level lapse rates, MLCAPE may exceed 3000 J/kg on a
widespread basis. However, given a somewhat dry surface-700 mb
layer, stronger than -100 J/kg of MLCINH will also be present, with
most of the CAPE (albeit wide) constrained above 700 mb.
Nonetheless, persistent warm-air advection and deep-layer ascent
from the rapidly approaching mid-level trough will support
convective initiation across portions of the central and northern
Plains by afternoon peak heating. Elongated hodographs suggest that
multicellular clusters should be the dominant mode of convection,
though a couple of supercells are also possible. Large hail will be
possible with the initial modes of convection. Low-level shear is
not expected to be overly strong, and storm/cold-pool mergers may
support the development of one or more MCSs by evening. Should this
occur, severe wind gusts will become the primary concern.
...Mid-Atlantic into New England...
A mid-level trough will gradually overspread the East Coast through
the day, with surface lee troughing becoming established east of the
Appalachians by afternoon peak heating, serving as the impetus for
convective initiation. Across the Mid Atlantic, a plume of steeper
(i.e. 7+ C/km) mid-level lapse rates will reside ahead of the
surface lee trough, fostering over 2000 J/kg MLCAPE amid elongated
hodographs. Organized multicells and perhaps supercells should
develop, accompanied by a severe wind/hail threat. Farther northeast
into parts of the Hudson Valley and New England, mid-level lapse
rates should be less steep (i.e. 5.5-6 C/km), supporting tall and
thin CAPE profiles. Nonetheless, the troposphere should be
relatively uncapped in the presence of elongated hodographs.
Multicells will be possible from the Hudson Valley and points
northeast, where a couple of damaging gusts may accompany the
stronger storms by afternoon peak heating.
...Utah to Montana...
Stronger mid-level flow traversing the periphery of the upper ridge
will support elongated hodographs from portions of western Utah into
central Montana by afternoon. Storms developing from the heating of
monsoonal moisture in this regime will have the potential to become
somewhat organized and longer lived compared to storms meandering in
the weaker tropospheric flow farther southeast. A couple of severe
gusts may accompany the stronger, longer-lived storms, warranting
the introduction of Category 1 (Marginal Risk) probabilities.
..Squitieri/Broyles.. 07/25/2023
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SshFz1
