SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Sat Jul 16 2022
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHEAST
MONTANA...NORTHERN HALF OF NORTH DAKOTA...NORTHWEST MINNESOTA...
...SUMMARY...
Widely scattered severe thunderstorms are possible from northeast
Montana eastward through North Dakota and into northwest Minnesota
on Monday and Monday night.
...Synopsis...
A mid-level anticyclone will remain centered over the
central-southern Rockies, as a potent mid-level low/trough moves
east, cresting the ridge over the northern Rockies into the northern
Great Plains. A surface low initially over MT and downstream of the
mid-level wave, will develop eastward and deepen as it moves into ND
Monday night. A frontal zone will become draped generally from west
to east near the 48th parallel. Farther east, a mid-level trough
will move from the Lower Great Lakes through much of New England. A
surface low will develop northeastward from Lake Erie towards the
mouth of the St. Lawrence River.
...Montana/ND/MN...
The aforementioned strong mid-level disturbance will move into the
northern High Plains during the day. Strong flow with a westerly
component will likely contribute to drying in the immediate lee of
the higher terrain. Nonetheless, model guidance varies somewhat and
isolated thunderstorms may occur across much of central MT during
the afternoon. A more likely scenario entails initial storms
developing near/north of the low within a corridor of low-level
moisture. Steep lapse rates and strengthening mid- to high-level
flow (effective shear increasing to 50 kt by early evening) will
favor storm organization. Supercells capable of mainly a hail risk
may eventually coalesce into a cluster of storms during the evening
with a hail/wind threat accompanying this activity. A strengthening
LLJ during the evening and associated warm-air advection near the
west-east boundary will aid in additional storms perhaps during the
evening and especially into the overnight over ND/MN. The risk for
hail/wind may persist through the end of the day-3 period over
ND/MN.
...Southern New England...
A likely messy/complicated scenario seemingly exists for isolated
severe on Monday across parts of the Northeast.
Showers/thunderstorms will likely increase in coverage during the
day over NY/PA within a relatively moist airmass featuring dewpoints
in the 60s to lower 70s. Planar model guidance implies and forecast
soundings show weak lapse rates which will likely limit buoyancy.
However, greater buoyancy will probably develop over southern New
England (richer moisture) and will be more favorably displaced to
the east from early-day shower/storm activity. However,
strengthening low- to mid-level flow will act to enlarge hodographs.
Although details are nebulous, it is plausible that some storm-scale
rotation potential exists given the moist/sheared environment. This
activity will likely diminish during the evening due to convective
overturning and diurnal heat loss.
..Smith.. 07/16/2022
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