LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1153 AM CDT Mon Jul 17 2023
Valid 171630Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE
CENTRAL/SOUTHERN PLAINS EAST TO THE OHIO VALLEY...AND FROM EASTERN
WYOMING INTO SOUTHWEST SOUTH DAKOTA AND NORTHERN NEBRASKA...
...SUMMARY...
Severe storms producing large hail and damaging wind gusts are
mainly expected from the Black Hills southeastward into Nebraska
tonight, and across portions of the Ozarks and Lower Ohio Valley
today.
...Central/southern Plains east Ozarks and Ohio Valley...
Moderately strong northwest/west mid-level flow will persist from
the central/southern Plains east to the OH Valley through tonight.
Heating of a moist air mass ahead of a nearly stationary front,
combined with a plume of steep mid-level lapse rates will result in
a rather large region of strong to locally extreme instability in
the presence of substantial deep-layer shear supportive of organized
storms.
Ongoing severe storm cluster over southeast KS will likely continue
moving south-southeast into an environment characterized by 40-50
kts of shear and MLCAPE of 3000-4000 J/jg. Damaging winds and
potentially very large hail will be possible with this complex as it
moves across northeast OK. Additional thunderstorm development is
likely across the Ozarks vicinity along remnant outflow boundaries
this afternoon, ultimately resulting in additional clusters or line
segments moving southeast/south through this evening. Damaging
winds will be the primary severe threat, and with large (isolated
very large) hail with the more discrete/intense updrafts.
Across the OH Valley, clusters of thunderstorms are expected to
develop as clearing/heating occurs in the wake of morning storms.
Effective shear of 30-40 kts will support both supercell and
multicell clusters persisting through the late afternoon and early
evening with severe wind/hail potential.
...Eastern Wyoming/Black Hills/Nebraska...
A sharpening lee trough ahead of the northern Rockies upper trough
will result in moist low-level upslope flow into the Black
Hills/eastern Wyoming and southeast Montana vicinity. The
proximity of the upper ridge may somewhat temper the extent of
deeper convection, however at least isolated thunderstorms are
expected to develop by late afternoon/early evening in a moderately
unstable and strongly sheared environment, with storms increasing in
coverage toward/after sunset. Steep lapse rates and long straight
hodographs will support large to locally very large (greater than 2
inch diameter) hail. As the low-level jet strengthens during the
evening, upscale development into a bowing MCS is possible as
convection tracks southeastward across western/southern South Dakota
and Nebraska. Damaging gusts, potentially significant, may accompany
this MCS during the evening and overnight hours, and a Significant
Wind area has been added with this outlook.
...Northern Great Basin and Central/Eastern Montana...
Moderate to strong west-southwest mid/upper-level flow will
overspread the region ahead of the northern Rockies upper trough.
Steep mid-level lapse rates and moistening will support MLCAPE
around 500-1250 J/kg. Well-mixed boundary layers will result in
mostly high-based, low-precipitation convection capable of sporadic
strong dry microburst winds from far northeast Nevada/northern Utah
into central Montana. With eastward extent into parts of eastern
Montana, deeper boundary-layer moisture will result in the potential
for isolated strong gusts as well as hail.
...Southern AZ...
Diurnal heating of a moist environment (PW 1.5 inches) will
contribute to afternoon MLCAPE of 1000-1500 J/kg. Thunderstorm
development is expected this afternoon, and dry mid-levels with
15-20 kts of easterly flow will result in a risk for gusty/damaging
winds as storms move west through evening.
..Bunting/Weinman.. 07/17/2023
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