SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 PM CDT Thu Aug 18 2022
Valid 182000Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH-CENTRAL
NE TO THE MID-MO VALLEY...
...SUMMARY...
Isolated large hail and localized severe wind gusts are most likely
from south-central Nebraska to the Mid-Missouri Valley through early
evening.
...20z Update...
The Marginal risk area across parts of TX/LA and across FL/GA have
been trimmed a small amount based on the current locations of the
quasi-stationary surface boundary and convective trends. No other
changes have been made to the outlook, and isolated strong to severe
storms are still expected through early evening across parts of the
central Plains into southwest MN. For more details, see previous
outlook discussion below. For information regarding short term
severe potential across MN, reference MCD 1693.
..Leitman.. 08/18/2022
.PREV DISCUSSION... /ISSUED 1051 AM CDT Thu Aug 18 2022/
...KS/NE to southwest MN...
A shortwave trough will gradually amplify as it drifts southeast
across the Upper Midwest through tonight. An initially weak surface
cyclone over the Upper Red River Valley will deepen as it slowly
moves east across northern MN. Trailing cold front to its southwest
will sharpen towards late afternoon across the Mid-MO Valley.
Boundary-layer moisture will be relatively modest by mid-August
standards, but a confined plume of steep mid-level lapse rates
sampled by the 12Z Aberdeen sounding should support a narrow
corridor of moderate buoyancy with MLCAPE of 1000-2000 J/kg.
A belt of enhanced mid-level northwesterlies will overspread much of
the Great Plains to the west and southwest of the shortwave trough.
This will strengthen deep-layer shear, mainly across the central
Great Plains portion of the front, yielding elongation of the
hodograph atop weak low-level SRH. This should support potential for
a few discrete supercells with mid-level rotation centered on the
IA/NE/SD border area southwest into south-central NE. Isolated large
hail and localized severe gusts should be the primary hazards before
convection wanes rapidly after dusk. With northeast extent into MN,
slower-moving storms and more prominent multicell clustering should
serve to marginalize wind/hail intensities.
...Central TX to southern LA and north FL to southeast GA...
While deep-layer shear will be lacking to the south of a
convectively reinforced surface front, very rich boundary-layer
moisture characterized by observed PW values around 2 inches will
support a threat for localized wet microbursts, peaking in the late
afternoon. Extensive pulse to weakly organized multicells are
anticipated before convection decays this evening.
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SWslCd
