Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1218 AM CDT Thu Jul 16 2026
Valid 161200Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
WESTERN MONTANA...
...SUMMARY...
Severe thunderstorms will be possible across parts of western
Montana, mainly Thursday afternoon and evening. Locally damaging
winds may also occur across parts of New England, the Upper Midwest,
and the Mid-Atlantic.
...Northern Rockies...
An upper low will skim the Pacific Northwest coast as it lifts
northward through the period. Meanwhile, upper ridging will persist
across much of the Rockies to the Plains. Wedged between the upper
low and the western periphery of the upper ridging, a belt of
enhanced south/southwesterly deep-layer flow will overspread the
northern Rockies. Easterly low-level flow will transport 50s F
dewpoints across region beneath steep midlevel lapse rates. This
will support moderate destabilization (1000-2000 J/kg MLCAPE).
Scattered thunderstorms will develop during the afternoon.
Vertically veering wind profiles and increasing flow aloft will
result in 30+ kt effective shear magnitudes. Organized cells will
pose a risk for strong wind gusts and hail across much of the
region. The greatest risk for 1+ inch hail will be across portions
of western MT.
...New England...
A vigorous upper shortwave trough will move across the region
through evening. Strong west/northwest deep-layer flow is evident in
forecast soundings, with 40+ kt effective shear magnitudes likely.
Boundary layer moisture will be somewhat muted compared to the
previous few days, with dewpoints generally in the 50s F. Stronger
heating is expected to the north of the more prominent smoke plume
across southern New England, aiding in steepening low-level lapse
rates. While instability will remain modest, strong flow and steep
low-level lapse rates may support isolated strong/locally damaging
wind gusts as convection spreads southeast from Quebec and across
portions of northern New England through the afternoon.
...Southern PA/Mid-Atlantic vicinity...
Strong mid/upper-level flow will overspread the region on the
southern periphery of the upper shortwave trough moving across New
England. A surface front is expected to drop southward through the
day, approaching the PA/MD border vicinity by late afternoon. Rich
boundary layer moisture will be in place ahead of the surface front
and beneath steep midlevel lapse rates. This will foster a corridor
of 2000+ J/kg MLCAPE. Furthermore, forecast soundings show 30-40 kt
effective shear magnitudes and steep low-level lapse rates. This
environment generally should support organized cells/line segments.
However, convective coverage is uncertain given stronger forcing for
ascent focused north of the area. Additionally, it is uncertain if
smoke will continue to have a deleterious impact on an otherwise
favorable severe storm environment. Given conditional potential for
at least locally damaging gusts, have included low severe wind
probabilities.
...ND/MN...
A series of convectively enhanced vorticity maxima will migrate
across the Canadian Prairies atop the upper ridge and through
northwesterly flow aloft into parts of ND and northern MN this
afternoon into tonight. At the surface, a weak low and surface front
will move across ND into northern MN during the evening and
overnight hours. South/southeasterly low-level flow will maintain a
moisture-rich boundary layer, supporting a corridor of modest
destabilization. Forecast soundings show supercell wind profiles,
but also increasing capping through the late afternoon/evening.
Nevertheless, most guidance develops convection across southern
Manitoba into northeast ND during the evening, spreading
east/southeast across northern MN during the nighttime hours. Some
risk for strong gusts and marginal hail appears possible,
necessitating low severe probabilities.
...AZ...
Thunderstorms are expected once again to develop over higher terrain
this afternoon/evening and spread westward across portions of
central/southern AZ. Deep layer flow will be weaker compared to
previous days, but modest instability and steep lapse rates amid
strong heating could support sporadic strong gusts.
..Leitman/Lyons.. 07/16/2026
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