SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0753 AM CDT Wed Jul 03 2024
Valid 031300Z - 041200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL/NORTHERN HIGH PLAINS...
...SUMMARY...
A threat for all severe hazards is possible this afternoon into
evening over portions of the central/northern High Plains. Damaging
to severe gusts may occur near a separate front, mainly from the
Ozarks to Ohio.
...Synopsis...
In mid/upper levels, broadly cyclonic flow will continue over much
of the northern CONUS from the Pacific Northwest to the Upper Great
Lakes, with numerous embedded vorticity maxima and shortwaves of
varying amplitudes. Of those, the most important for this outlook
will be a shortwave trough now apparent in moisture-channel imagery
over northern Rockies. This feature should dig southeastward to
southwestern ND, southeastern MT, northwestern WY and southeastern
ID by 00Z. By the end of the period (12Z), the trough should extend
diagonal across SD, then to southeastern WY and northwestern CO.
Subtropical ridging will persist over the Gulf Coast States and
portions of southern CA/AZ, with a height weakness in between, over
northwestern MX and NM.
At the surface, 11Z analysis showed a cold front across Lake
Michigan, northwestern IL, central MO, and southeastern KS, becoming
quasistationary across northwestern OK and the TX Panhandle to
northeastern NM. By 00Z, the front should move to Lake Huron,
northwestern OH, southern IN, southern MO, while drifting southward
again to northeastern and west-central OK and the southern
Panhandle/northern South Plains region of TX. By 12Z, the front
should extend over western parts of NY/PA, eastern/southern KY, and
north-central AR, becoming a warm front over north-central/
northwestern OK. Cyclogenesis is forecast late this afternoon
through this evening along a lee trough over east-central CO, with a
cold front developing from the NE Sandhills into northeastern/
central CO by 06Z. By 12Z, the low should migrate to central NE,
with warm front over southern IA, and cold front southwestward
across western KS to northeastern NM.
...Central/northern High Plains and vicinity...
Isolated to scattered thunderstorms are expected to develop this
afternoon -- initially over higher terrain near the Palmer and
Cheyenne Ridges and near lee trough, increasing in coverage while
moving eastward to southeastward over the High Plains. Large hail
(some 2+ inches in diameter) and damaging wind (some gusts over 70
mph) are expected over the north-central High Plains, and a couple
tornadoes also are possible, mainly in and near western NE where
some overlap of favorable moisture and low-level shear is expected.
As the mid/upper trough approaches, expect a favorable strengthening
of large-scale lift, winds aloft, deep shear, and mass response
leading to northward moisture advection/transport, to the north of
the southern frontal zone. Optimal moisture return may be precluded
by effects of ongoing clouds/precip to reinforce the baroclinic zone
over the southern Plains; however, boundary-layer moisture should be
sufficient to support development as heating of higher terrain
preferentially erodes MLCINH. Steep low/middle-level lapse rates
will contribute to development of 1000-2500 J/kg MLCAPE in a
corridor from eastern CO and northwestern KS to southwestern SD,
decreasing from there westward toward the Bighorns and southward
into less-unstable conditions of the Panhandles and northeastern NM.
Veering of winds with height east of the lee trough will contribute
to favorable vertical shear for supercells and organized/upscale-
coalescing multicells, the latter being most commonly progged over
parts of eastern CO and northwestern KS (where wind probabilities
are relatively maximized). Low-level hodographs should be
relatively maximized in size over western NE, and rather elongated
over a broader swath of the central High Plains, supporting large to
significant hail production.
...Lower Ohio Valley region...
Widely scattered to scattered, multicell thunderstorms are expected
to develop this afternoon and focus mainly near the front and
prefrontal outflow/differential-heating boundaries, from northern OK
to the Lower Great Lakes. The greatest concentration of convection
is still expected over the area from the Ozarks to central OH from
late afternoon into early evening. Forecast soundings suggest that
diurnal heating and rich boundary-layer moisture, represented by
upper 60s to lower 70s surface dewpoints, will offset modest
mid/upper-level lapse rates enough to support peak/preconvective
MLCAPE in the 2500-3500 J/kg range over the Ozarks, to 1000-2000
J/kg in OH. Conversely, low-level and deep-layer shear will be
fairly weak overall, and decreasing with southwestward extent.
Damaging to severe gusts will be the main concern. A few short-
lived convective clusters are possible, with locally maximized
potential for severe gusts.
..Edwards/Kerr.. 07/03/2024
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