Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Grand Island, NE...Kearney, NE...North Platte, NE...Norfolk, NE...Hastings, NE...
Omaha, NE...Lincoln, NE...Sioux Falls, SD...Topeka, KS...Sioux City, IA...
SPC AC 200723
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0223 AM CDT Wed Sep 20 2023
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
Scattered strong to severe storms, capable of all severe hazards,
are expected across portions of the central Plains on Friday.
A pronounced mid-level trough will eject into the central and
northern Plains on Friday, supporting surface cyclogenesis across
the central High Plains and modest low-level moisture return across
the central Plains. Cooler mid-level temperatures will overspread
the low-level moisture axis with the ejection of the upper trough,
destabilizing the warm sector and increasing synoptic-scale vertical
ascent in the process. The low-level and mid-level jets are poised
to couple over the central Plains Friday afternoon and evening,
supporting scattered to widespread thunderstorms, with organized
severe potential possible.
By Friday afternoon, northwestward return flow of moisture over the
central Plains will transport at least low to mid 60s F surface
dewpoints up to central NE, where an effective warm front will
become established. As stronger mid-level west-southwesterly winds
begin to overspread the warm sector, 7-8 C/km mid-level lapse rates
should become common, contributing to around 1500 J/kg MLCAPE. Near
the warm front, the aforementioned coupling of the low- and
mid-level jets supports enlarged hodographs with appreciable
curvature and some elongation. Strong deep-layer ascent should
support supercell development during the afternoon, with large hail,
severe gusts, and perhaps a couple of tornadoes possible (especially
with storms that can remain discrete and anchored along the warm
front). It is unclear how far southeast storms will initiate into
KS, with severe potential highly dependent on the track of the
ejecting mid-level trough and accompanying upper support. By
evening, storms could grow upscale into an MCS from southern SD into
NE as low-level convergence is augmented by the terminus of a
low-level jet. Under this scenario, severe gusts would become the
A surface low is expected to meander northward along the Carolina
coastline through Friday, resulting in scattered thunderstorms
moving ashore. At the moment, the northeast quadrant of this cyclone
is expected to remain just offshore (per latest guidance consensus).
However, any westward shift in the track may support the influx of a
higher low-level theta-e airmass, which could coincide with stronger
low-level shear. Should this scenario become more apparent, severe
probabilities may be introduced in future outlooks.
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z