RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0237 PM CDT Fri Mar 20 2026
Valid 202000Z - 211200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE UPPER OH
VALLEY AND CENTRAL APPALACHIANS...
...SUMMARY...
Strong to locally severe thunderstorms are possible across parts of
the Upper Ohio Valley and central Appalachians this evening.
...20Z Update...
No changes needed to the level 1-MRGL risk. Ongoing rain swath with
very isolated thunder coverage should continue shifting
southeastward from the northern/central Appalachians. Severe
potential should be confined to its wake as the northern extent of a
modest boundary-layer moisture plume reaches the Upper OH Valley by
early evening. Despite latitudinal differences in guidance since 12Z
with placement of redevelopment this evening, the southern envelope
appears more probable given the degree of rain-cooled air to the
northeast. Convection should struggle to readily deepen/intensify
with such meager buoyancy. But hodograph elongation amid
northwesterly speed shear within the cloud-bearing layer will favor
a threat for isolated, marginal severe storms before convection
wanes overnight.
..Grams.. 03/20/2026
.PREV DISCUSSION... /ISSUED 1115 AM CDT Fri Mar 20 2026/
...Upper Ohio Valley into the Central Appalachians...
Midday water-vapor imagery indicates a mid-level shortwave trough
over Lower Michigan as a belt of strong west-northwesterly flow is
maintained across the north-central U.S. eastward to the
Mid-Atlantic and New England coastal vicinity. This disturbance is
forecast to quickly move to the Delmarva/NJ by midnight.
The northern extent of a moisture plume, and an airmass still
undergoing modification over the Gulf Basin, will protrude northeast
into the upper OH Valley by late afternoon. Forecast guidance shows
surface dewpoints perhaps reaching near 50 deg F near the OH-WV-PA
border region towards 00z. Cold 500-mb temperatures and diurnal
heating will act to partially compensate for modest moisture and
contribute to weak buoyancy. Isolated to widely scattered
low-topped thunderstorms will probably develop along a
southeastward-moving cold front during the evening. Elongated
hodographs support updraft organization but the overall limited
moisture will act to constrain otherwise greater storm coverage.
Marginally severe hail and perhaps a couple of damaging gusts are
the primary hazards with the stronger storms.
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