SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 PM CDT Sun Jun 11 2023
Valid 121200Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE LOWER MS VALLEY INTO THE CENTRAL GULF COAST...AND ACROSS
NORTHWEST/NORTH-CENTRAL TX...
...SUMMARY...
Severe thunderstorms are expected during the afternoon and evening
across northwest into north-central Texas, with very large hail as
the main risk. Severe thunderstorms are also expected from the Lower
Mississippi Valley into the central Gulf Coast, with damaging gusts
as the primary risk.
...Synopsis...
Upper pattern across the CONUS will feature a pair of cyclones early
Monday morning, one centered over the Upper Great Lakes and the
other one centered over the Great Basin. The Upper Great Lakes
cyclone is forecast to slowly drift eastward towards Lower MI, while
deepening slightly. A pair of shortwave troughs are expected to
rotate through this cyclone, with the lead wave progressing
eastward/northeastward through the Mid-Atlantic and Northeast
states. The following wave will likely move across the OH Valley
Monday afternoon/evening, reaching the Lower Great Lakes vicinity
early Tuesday morning.
The western cyclone is forecast to weaken as it moves into the Four
Corner region, with shortwave troughs expected to move through its
base as well. The lead wave should move through the southern High
Plains and into the central Plains during the period, while the wave
in its wake moves across southern CA and into AZ from Monday
afternoon into early Tuesday morning. Strong mid-level flow will
extend throughout the base of this cyclone, and is expected to
expand into the southern Plains throughout day. Stronger flow is
expected through the base of the Great Lakes cyclone as well, and
the combination of these areas will result in a corridor of enhanced
mid-level flow from northern Baja/northern Mexico across the
southern Plains, Mid-South, and TN Valley, and off the Mid-Atlantic
coast by early Tuesday morning.
The surface pattern on Monday will be dominated by two features,
strong ridging over the northern and central Plains, and a low and
associated front over the eastern CONUS. The surface low will begin
the period over the Lower Great Lakes before drifting northward and
further occluding. The associated cold front is forecast to continue
progressing eastward, interacting with the moist air mass in place
along the Eastern Seaboard. Additionally, the boundary between the
drier continental air mass associated with the ridging and more
moist air mass in place across the southern Plains and Southeast is
expected to sharpen, particularly over TX.
...Northwest into North-Central Texas...
Strong buoyancy (i.e. MLCAPE over 3000 J/kg) is forecast to develop
over the TX Big Country, near a triple point low at the intersection
of the stalled surface front and dryline. Mesoscale ascent
associated will this low is expected to result in isolated
thunderstorm development during the afternoon. Strong vertical shear
is anticipated with hodographs showing supercell wind profiles.
Environmental conditions favor very large hail (i.e. greater than 2"
in diameter) as the primary risk with initial development. Low-level
wind profiles do show veering with height, but flow is generally
weak and the storms should be fairly high based. As such, the
tornado threat is low, but non-zero, particularly if storms interact
with the boundary. Upscale growth is likely, with the resulting line
bringing a severe risk farther into north-central TX. Higher
probabilities may be needed, but uncertainty regarding coverage
limits the confidence to introduce any with this outlook.
...Lower MS Valley into the Southeast...
Moderate to strong buoyancy is expected to develop during the
afternoon, amid the upper 60s/low 70s dewpoints expected to be in
place. Afternoon thunderstorms development appears likely along the
cold front pushing into region. Seasonally strong mid-level flow is
expected across the region as well. All of these factors will result
in a broad area of severe risk. A locally higher severe risk is
anticipated from eastern LA into southern AL and western FL
Panhandle, where guidance suggests a convectively augmented
vorticity maximum will interact with the already favorable
environment. Higher wind probabilities may eventually be needed in
this area, but low predictability of vort max strength and
evolution, and uncertain frontal position currently limit the
forecast confidence.
...Colorado Front Range into the TX Panhandle...
Boundary-layer destabilization will remain confined to a narrow
corridor, along a remnant surface front into the higher terrain, as
a lead short wave impulse emerges from the Great Basin. Still, this
environment may become favorable for a period of isolated to widely
scattered strong/severe thunderstorm development, before convection
tends to advect off and away from the higher terrain.
...Mid-Atlantic through the Carolinas...
Thunderstorms are expected to develop during the afternoon along the
eastward-progressing cold front, with some development possible
along any pre-frontal troughing as well. Lapse rates will generally
be poor, but afternoon dewpoints in the mid to upper 60s should
still support low to moderate buoyancy as the air mass heats up. The
stronger mid-level flow will likely arrive during the evening, after
the peak thunderstorm coverage, but some stronger storms are still
possible, with damaging gusts as the primary risk. Less buoyancy is
anticipated across the northern portions of the region, but stronger
mesoscale ascent and greater shear near the triple point low could
still foster a few severe storms.
..Mosier.. 06/11/2023
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