SPC AC 261945
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 PM CDT Wed Jul 26 2017
Valid 262000Z - 271200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
CO TO IL...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE GREAT BASIN...
Isolated strong to severe wind gusts are possible late afternoon
into this evening across parts of the Midwest and Great Basin.
Minor changes to severe probs are warranted for buoyancy starved
regions of KS/MO/IA.
A considerable amount of debris from Monday night convection has
settled into a corridor from south-central KS into northern lower
MI. Surface heating is reduced along this zone which is limiting
buoyancy within an otherwise poor lapse rate environment. Severe
probs have been lowered across portions of this region due to
extensive cloud cover.
.PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Jul 26 2017/
A broad swath of non-severe convection is ongoing from MI southwest
to KS. While most of this convection appears to be steady-state to
decaying, redevelopment persists in the warm-advection regime across
north-central KS. In the downstream warm sector, regional 12Z
soundings sampled weak 700-500 mb lapse rates of 5-6 degree C/km
along with weak tropospheric winds. The net effect of these limiting
factors will be to confine the areal extent and amplitude of
afternoon destabilization, along with restraining the degree of
intensification on the leading edge of broad-scale outflow. Sporadic
wet microbursts appear to be the most likely scenario with a low
chance for an organized MCS.
...South-central High Plains...
Several CAMs are insistent on developing a couple multicell clusters
off the higher terrain this evening. With weak low-level
northeasterlies beneath modest mid/upper-level westerlies, this
scenario may occur. Given relatively warm mid/upper-level
temperatures limiting hail growth, the main hazard should be
isolated strong to severe wind gusts.
The persistent mid-level cyclone over northern CA will shift
northeast into southeast OR by Thursday morning. Scattered storms
will develop again across the Great Basin downstream of this wave,
with the pre-storm environment consisting of well-mixed
thermodynamic profiles given full insolation already underway. With
somewhat larger buoyancy expected compared to previous days amid
25-30 kt effective shear, the setup should yield a risk for
localized severe wind gusts.
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