SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Fri Sep 02 2022
Valid 022000Z - 031200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
ARIZONA AND THE LOWER COLORADO RIVER VALLEY...
...SUMMARY...
Isolated severe thunderstorms are possible late this afternoon and
evening over parts of central/southern Arizona and the Lower
Colorado River Valley, and from the central Great Plains to the
Upper Great Lakes.
...20Z Update...
No changes have been made to the outlook. Convection is beginning to
develop along the Mogollon Rim in Arizona, with storms expected to
grow in coverage and move westward into this evening, with a threat
of strong to locally severe wind gusts eventually spreading into the
lower deserts and Colorado River Valley. Isolated severe storms
capable of hail and damaging wind gusts are still expected to
develop late this afternoon into this evening from the central
Plains into the upper Midwest, though coverage of strong/severe
storms remains uncertain across the region at this time. See the
previous discussion below for more information.
..Dean.. 09/02/2022
.PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Sep 02 2022/
...Arizona/Lower Colorado Valley...
Visible satellite shows relatively cloud-free skies, which will be
conducive for ample insolation/heating coincident with a relatively
moist air mass, with prevalent 60s F surface dewpoints in the lower
elevations of southern Arizona and middle 50s F dewpoints along the
Mogollon Rim as of late morning. An increase in storm coverage as
compared to yesterday seems probable.
Easterly mid-level/steering winds are and will remain notably strong
as the upper high builds to the north over the Great Basin/central
Rockies. Upwards of 25-30 kt mid-level winds are plausible across
the southern half of Arizona, which would be conducive for storm
organization/upscale growth and propagation onto the lower
elevations/desert floor and Lower Colorado River Valley. Initial
discrete development over the higher terrain/near the Rim will pose
a risk for localized severe wind gusts and marginally severe hail.
However, a more organized/substantial wind threat may emerge with
upscale-growing/MCS development by evening.
...Central Plains to Upper Great Lakes...
The primary shortwave trough over northeast Manitoba will shift east
across southern Hudson Bay/far northern Ontario, with the trailing
part of this trough moving across the Upper Great Lakes. A weak
mid-level trough will meander east across the Ozarks. In between
these features, deep-layer shear will be enhanced across the central
Great Plains owing to 25-35 kt mid-level north-northwesterly winds.
Weaker deep-layer shear is anticipated with northeast extent along a
cold front pushing southeastward across the Upper Midwest.
A greater potential for scattered thunderstorms along the front
should exist in the southeast Minnesota/northern Wisconsin/Upper
Michigan vicinity given more pronounced low-level convergence and
trailing influence of the Ontario trough. Multicell clusters mainly
producing isolated damaging winds and perhaps marginally severe hail
will be the primary threats.
A more isolated thunderstorm coverage is anticipated into southeast
Nebraska and northern Kansas, but given the greater vertical shear
and nearly perpendicular orientation of mid-level flow with respect
to the front, a few transient supercells embedded within a cluster
or two may develop. Isolated severe wind and hail will be possible,
with increasing MLCIN after dusk being detrimental for sustaining
severe potential later into the evening.
Read more CHECK UPDATE ZOOM GRAPHIC
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