SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Fri Jul 07 2023
Valid 072000Z - 081200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
OK/NORTHERN TX PANHANDLES INTO FAR NORTHWEST OK...
...SUMMARY...
Scattered severe thunderstorms are expected late this afternoon
through tonight across portions of the central and southern Plains.
Large to very large hail and severe/damaging winds should be the
primary risks, with the greatest potential for significant (75+ mph)
winds across parts of the Oklahoma/Texas Panhandles into western
Oklahoma late this afternoon and evening.
...20Z Update...
The primary change with this outlook is to trim parts of the
Marginal Risk across parts of the northern and central Plains,
generally behind a cold front across parts of ND/MN, and in the wake
of earlier convection across parts of the central Plains. Otherwise,
isolated supercells will be possible this afternoon across eastern
CO into northeast NM, with upscale growth into a severe-wind
producing MCS expected across parts of the TX/OK Panhandles by this
evening.
See MCD 1455 for more information regarding the short-term threat
across the southern High Plains, MCD 1454 for more information
across northern New England, and MCD 1456 for more information
across the northern Plains. Also see the previous discussion below
for more information.
..Dean.. 07/07/2023
.PREV DISCUSSION... /ISSUED 1123 AM CDT Fri Jul 07 2023/
...Southern/Central Plains...Southern/Central High Plains...
Ongoing MCS across central OK is expected to continue weakening over
the next few hours as it moves into the more stable conditions
downstream in the Arklatex vicinity. A large ACCAS field has
developed in the wake of the this MCS across the TX Panhandle,
supported by modest isentropic ascent atop the MCS outflow. A few
elevated storms are possible within this environment this morning,
but warming and drying mid-levels should lead to their dissipation
before this afternoon.
The evolution of this MCS and additional elevated storms this
morning have helped to reinforce a subtle surface boundary extending
across the western TX Panhandle through far northeast NM and into
southeast CO, where it intersects the lee troughing. Additionally, a
cold front is forecast to continue pushing southward/southeastward
across eastern CO and the adjacent central Plains. This front will
likely be through much of eastern CO by the late afternoon, with
post-frontal upslope in place across southeast CO.
Afternoon thunderstorm development is anticipated along the higher
terrain of northeast NM and southern CO, with an initially
supercellular mode possible over southeast CO. Very large hail is
the primary severe risk with these supercells, but the high surface
vorticity environment suggests a tornado or two is possible as well.
Highest storm coverage is anticipated south of the Palmer Divide. An
isolated storm or two capable of hail is possible north of the
divide. These supercells are then expected to move downstream,
interacting with the now modified boundary farther east across the
northern TX/OK Panhandles. Convergence along this boundary will
likely provide a favored corridor for upscale growth. High storm
bases coupled with steep low-level lapse rates will support strong
outflow, with significant severe winds of 75+ mph possible with this
complex as it moves quickly eastward.
Other supercells may form in the strengthening warm advection regime
across south-central KS/northern OK this evening. Steep mid-level
lapse rates and moderate deep-layer shear will support the potential
for very large hail. Some threat for severe/damaging winds may
eventually develop with this convection if it can grow upscale into
one or more small clusters while spreading generally southeastward
tonight.
...Central Plains into the Mid MS Valley...
Decaying MCS continues to push eastward across western IA/northern
MO, with a few thunderstorms ongoing along its southern periphery
across far northwest MO. Redevelopment/restrengthening appears
possible downstream of theses storms over northern and east-central
MO/west-central IL as the air mass destabilizes. This area will be
on the southern periphery of the stronger mid-level flow, supporting
the potential for a few strong to severe storms capable of damaging
gusts. Additional redevelopment is possible farther west over the
southeast NE/northeast KS vicinity as outflow for the IA/MO MCS as
well as outflow from the elevated cluster over central KS moves into
the region. However, ongoing cloud cover may limit destabilization,
precluding this potential redevelopment until later this evening.
...Northeast/Mid-Atlantic...
Daytime heating of a moist low-level airmass should encourage the
development of weak to moderate instability by this afternoon across
parts of the Northeast and Mid-Atlantic. Glancing ascent associated
with a shortwave trough over Quebec and weak low-level convergence
along a surface trough extending from northern NY southward through
central VA will likely foster at least scattered thunderstorm
coverage this afternoon and evening. Deep-layer shear is forecast to
remain fairly modest, generally 25 kt or less, and weakening with
southward extent across the Mid-Atlantic. Still, some loosely
organized thunderstorm clusters capable of producing damaging gusts
are possible, particularly from central NY into northern ME where
shear is strongest.
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