SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Wed Jul 06 2022
Valid 081200Z - 091200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/PLAINS...
...SUMMARY...
Isolated to scattered severe thunderstorms may occur Friday across
parts of the northern Rockies/Plains.
...Northern Rockies/Plains...
An upper ridge should remain prominent across much of the High
Plains into central Canada on Friday. Strong mid-level southwesterly
flow preceding an upper trough over the West Coast is forecast to
overspread parts of the northern Rockies and adjacent northern
Plains of central/eastern MT through the period. A moist low-level
airmass should also be present along/east of surface trough
extending across the northern High Plains. At least moderate
instability should once again develop across much of MT and vicinity
as daytime heating occurs. Steep mid-level lapse rates should also
be present over the warm sector. Current expectations are for
initially high-based convection that forms over the northern Rockies
Friday afternoon to spread generally northeastward across
central/eastern MT through Friday night. Deep-layer shear appears
strong enough for supercells, with an associated threat for both
large hail and severe wind gusts. Some upscale growth into one or
more small bowing clusters may also occur Friday evening/night with
eastward extent into MT. Overall coverage of thunderstorms becomes
less clear into the Dakotas, but at least an isolated severe threat
should exist owing to a favorable thermodynamic and kinematic
environment.
...Mid Mississippi Valley into the Central/Southern Appalachians and
Southeast...
A weak front should be draped generally west to east across these
regions on Friday. Any appreciable severe threat will likely remain
confined along/south of this boundary through the period. Mid-level
west-northwesterly flow around 15-25 kt should limit deep-layer
shear. But, some modest updraft organization may still occur as
thunderstorms develop along/south of the front Friday afternoon.
With multiple days of preceding convection acting to overturn the
moist low-level airmass across these regions, it remains uncertain
whether the moderate to strong instability forecast by most guidance
will materialize. Have opted to include a fairly broad Marginal Risk
for mainly damaging winds associated with multicell clusters given
this uncertainty and the generally weak deep-layer shear forecast.
Greater severe probabilities may be needed if a more focused
corridor of severe/damaging wind potential becomes clearer.
..Gleason.. 07/06/2022
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