RSS Mesoscale Discussions from Storm Prediction Center
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1139 PM CST Mon Nov 17 2025
Valid 181200Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
OHIO VALLEY REGION...
...SUMMARY...
A few strong to severe storms are possible across portions of the
Lower Ohio Valley region.
...Lower OH Valley...
Central Plains upper trough is shifting east toward the mid MS
Valley, in line with latest model guidance. As a 60+kt 500mb speed
max translates across MO into southern IL/IN, this feature will
advance into the lower OH Valley by 19/00z, suppressing the height
field as far south as the OH River. Veered, but strong LLJ will
focus across southern MO-southern IL/IN before being nudged
downstream into eastern KY/southern OH by early evening. Net result
will be for a NW-SE oriented corridor of warm advection to shift
east during the day ahead of a weak surface low near the base of the
short-wave trough.
Earlier thoughts regarding the potential for severe continue as
instability will gradually increase along this corridor as midlevel
temperatures cool and lapse rates steepen a bit. In the absence of
strong boundary-layer heating, the majority of convection that
develops across this region will be elevated and aided in large part
by the LLJ. Forecast soundings suggest lifted parcel level will
gradually lower by late afternoon such that near-surface based
parcels could yield modest instability (800-1000 J/kg). Primary
concern today will be hail with elevated supercells, but some
tornado risk is possible with late-day storms, where parcel lift
reflects lower 60s dew points that are expected to return toward the
confluence of the MS/OH Rivers during the afternoon.
...Lower Colorado River Valley/southwest AZ...
Weak midlevel height falls will spread across the lower CO River
Valley today as the upper low off the southern CA Coast eventually
settles toward the international border/northern Baja Peninsula. As
this features digs southeast, a weak LLJ should extend across
southwestern AZ into the early part of the afternoon. Latest
thinking is scattered convection should evolve ahead of the cold
front as it surges across the lower CO River Valley. Forecast
soundings exhibit ample shear for organized rotating updrafts, but
buoyancy is expected to be weak. Given the modest lapse rates, there
is concern updrafts may struggle a bit and hail is expected to
remain below severe levels. Some consideration was given to adding a
2 percent probability for the risk of a brief tornado but will hold
off at this time given the marginality of the situation.
..Darrow/Moore.. 11/18/2025
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SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1213 AM CST Tue Nov 18 2025
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF WEST-CENTRAL TEXAS INTO SOUTH-CENTRAL OKLAHOMA...
...SUMMARY...
Isolated severe storms are possible across parts of the southern
Plains on Wednesday evening into early Thursday.
...Southern Plains...
Southerly low-level flow beneath an upper ridge centered over the
central U.S. will transport Gulf moisture northward across TX and
OK. To the west, an upper low/trough over southern CA and northern
Baja Wednesday morning will develop eastward through the period,
with the system forecast to be over AZ and northwest Mexico by
Thursday morning. Southwesterly deep-layer flow will increase across
the southern Plains as the western upper trough ejects eastward.
However, more substantial height falls are not expected across the
Plains until after 00z, with some guidance maintaining neutral
height tendencies until closer to 06z. Furthermore, warmer midlevel
temperatures around 700 mb may maintain capping for much of the
diurnal period. Forecast soundings across multiple models show quite
a bit of spread with regards to surface-based evolution. While
large-scale ascent will likely remain muted until late in the
period, persistent warm advection and increasing vertical shear may
support isolated to scattered storm development near the stationary
surface boundary from west-central TX toward the Red River during
the evening into the overnight. Modest instability and shear may be
sufficient for isolated strong to severe storms, mainly capable of
producing hail.
...Southeast AZ/southwest NM...
Cooling aloft closer to the upper low/trough will support steep
midlevel lapse rates amid increasing midlevel moisture. This will
result in weak instability amid 40+ kt effective shear magnitudes. A
couple of stronger storms could produce small hail or gusty winds,
but overall severe potential appears limited at this time given a
relatively cool boundary-layer and weak buoyancy.
..Leitman.. 11/18/2025
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SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0158 AM CST Tue Nov 18 2025
Valid 201200Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Scattered thunderstorms are possible across the southern Plains on
Thursday. Severe thunderstorms potential is uncertain, but appears
limited at this time. Isolated thunderstorms may extend into the
Ohio and Tennessee Valleys as well, though this activity is not
expected to be severe.
...Southern Plains...
An upper trough over AZ and northwest Mexico will pivot
east/northeast on Thursday, emerging into the southern Plains. Most
guidance shows some deamplification of this feature with
time/eastward extent. Regardless, increasing ascent and moderate
deep-layer southwesterly flow is expected to overspread TX/OK and
the Ozark Plateau.
Widespread showers/thunderstorms are expected to be ongoing across
portions of the southern Plains Thursday morning. This will likely
limit destabilization and result in weak low-level lapse rates
across much of the warm sector. Some strong storms could be possible
as modest surface cyclogenesis occurs and a Pacific front moves east
across western/central OK and central into eastern TX by Friday
morning. However, with deep-layer flow parallel to the surface
boundary, training/heavy precipitation may be more likely than
organized severe storms. Given uncertainty in degree of
destabilization due to widespread convective contamination of the
warm sector, will hold off delineating any low-end severe
probabilities as confidence is low regarding where any relatively
greater potential may develop.
..Leitman.. 11/18/2025
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