RSS Mesoscale Discussions from Storm Prediction Center
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0630 AM CST Sat Nov 15 2025
Valid 151300Z - 161200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY...
...SUMMARY...
Showers and isolated thunderstorms may be accompanied by strong wind
gusts across parts of the upper Ohio Valley late this afternoon and
evening.
...Ohio Valley...
Large-scale ascent will spread across the OH Valley today ahead of a
mid-level shortwave trough that will dig across the Great Lakes by
this evening. An associated surface low will develop eastward across
southern Ontario, with a cold front extending southward across the
OH Valley/Midwest. This front will serve as the primary focus for
isolated thunderstorms this afternoon and evening. Only modest
daytime heating is forecast ahead of the front, which combined with
limited low-level moisture should temper the amount of surface-based
instability that can develop. Even so, a strongly sheared
environment is expected given the strength of the low/mid-level flow
forecast. Recent high-resolution guidance suggests weak frontal
convection should develop by late afternoon/early evening across
eastern OH/western PA and vicinity. Strong to locally damaging wind
gusts are the primary concern, with convection expected to weaken
with eastward extent into central PA this evening due to meager
instability with the loss of daytime heating.
...Southern California/Southwest...
A strong (60-80 kt) 500 mb speed maximum will translate through the
base of an upper trough and develop towards the northern Baja
Peninsula by midday, with high-level diffluent flow forecast across
southern CA and the Lower CO River Valley. Recent guidance continues
to suggest an associated surface front will move inland later today,
and cooling post-frontal thermal profiles aloft will lead to weak
instability that should favor occasional lightning within deeper
convective updrafts. Pre-frontal convection is expected to be only
weakly buoyant across the Lower CO River Valley due to poor lapse
rates, which should limit updraft strength. While post-frontal
destabilization may lead to more robust updrafts, weaker shear in
this regime does not appear favorable for severe winds, but small
hail could occur.
..Gleason/Broyles.. 11/15/2025
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 AM CST Sat Nov 15 2025
Valid 181200Z - 231200Z
...DISCUSSION...
Upper-level ridging over the Plains on Day 4/Tue will develop
eastward over the eastern third of the CONUS through Day 5/Wed as a
western upper trough slowly ejects over the Rockies and into the
Plains around Day 6/Thu. Gulf moisture will return northward across
the southern Plains and south-central states ahead of the ejecting
upper trough. Isolated strong to severe storms may be possible on
Wednesday across the southern Plains and Ozarks vicinity in a warm
advection regime ahead of the upper trough. By Day 6/Thu, the upper
trough should progress east across the Plains toward the Mississippi
Valley, with a surface cold front sweeping eastward as this occurs,
and some severe potential could accompany widespread thunderstorm
activity ahead of the front.
Confidence in coverage of severe storms Day 5-6/Wed-Thu is
uncertain. Large spread (and poor run-to-run consistency) exists
among forecast guidance. The GFS and ECMWF-AIFS are more similar
compared to the dynamical ECMWF, indicating a slower ejecting trough
and only modest surface cyclogenesis until late Thursday when the
low ejects northeast toward the Mid-MS Valley/Great Lakes.
Furthermore, while strong southwesterly flow will overspread
northward returning Gulf moisture across the Plains and
south-central states, forcing for ascent will be somewhat limited on
Wednesday as the trough ejects more slowly. As the trough ejects on
Thursday and a cold front becomes a focus for storm development,
boundary-parallel deep-layer flow and a northeastward ejecting
cyclone may favor a more anafrontal, training convection/heavy
rainfall scenario. While severe potential certainly is in play for
Days 5-6/Wed-Thu, these uncertainties preclude 15 percent
probabilities at this time.
Beyond Day 6/Thu, model disparity increases substantially and
predictability is low.
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