Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1245 AM CDT Fri Jul 18 2025
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF VA/NC
AND NE/SD/MN/IA...
...SUMMARY...
Scattered severe thunderstorms with large hail, damaging winds, and
a few tornadoes are possible across parts of the Corn Belt in Iowa,
Minnesota, Nebraska, and South Dakota this evening into tonight.
Scattered damaging winds are possible across parts of Virginia and
northern North Carolina this afternoon.
...SD/MN/IA/NE...
A low-amplitude shortwave impulse along the international border
over the northern Great Plains will progress across the Upper
Midwest/Great Lakes and ON. A belt of seasonably strong mid-level
westerlies should be centered this afternoon from central MN to Lake
Huron. Elevated convection is expected to be ongoing at 12Z across
parts of the eastern Dakotas into northern MN ahead of the mid-level
impulse, amid a low-level warm theta-e advection regime. As this
overspreads a preceding cool/dry surface airmass over the Upper
Midwest, pronounced differential diabatic surface heating will
strengthen a baroclinic zone across southeast SD bisecting IA to the
southeast by late afternoon. Thunderstorm development in this time
frame should be confined to along/northeast of the surface warm
front across far eastern SD and southern MN. Large-scale ascent
appears nebulous, but a strengthening low-level jet should aid in
convection flanking to the southwest across the Mid-MO Valley during
the evening. This may merge with high-based convection shifting east
from western NE.
Deep-layer shear will be sufficient for initial supercells that will
probably grow upscale into multiple clusters and/or an MCS tonight.
The latter may accelerate east-southeast for a time in the western
IA vicinity before weakening during the early morning. A mix of all
severe hazards are possible in this setup with hail being favored
early and wind later. Moderately enlarged low-level hodographs
should also support a tornado threat with any sustained supercell to
QLCS evolution.
...VA/NC...
00Z HREF guidance supports scattered to numerous thunderstorms this
afternoon with transient organizational structures that should be
sufficient for a scattered damaging wind threat. This appears to be
largely in response to the eastward progression of an MCV currently
near the IN/OH/KY border. A compact belt of enhanced mid-level
westerlies should overspread the northern periphery of ample MLCAPE
emanating from the South Atlantic Coastal Plain. Multicell clusters
that can progress towards a warmer/deeper boundary layer across the
Piedmont and Coastal Plain should produce strong to sporadic severe
gusts through early evening.
..Grams/Wendt.. 07/18/2025
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