SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0256 PM CDT Tue May 17 2022
Valid 172000Z - 181200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL/EASTERN KANSAS INTO SOUTHEASTERN NEBRASKA...NORTHWESTERN
MISSOURI...AND FAR SOUTHWESTERN IOWA...
...SUMMARY...
Scattered severe thunderstorms are expected across a portion of the
central states through tonight. The area to be most likely impacted,
with potentially multiple rounds of severe weather, is focused on
parts of Nebraska, Kansas, Iowa, and Missouri. A few tornadoes,
significant damaging winds, and very large hail are possible.
...20Z Update...
Primary change with this update was to expand 30% wind probabilities
and the corresponding Enhanced Risk into more of north-central and
central KS. It appears increasingly likely that a substantial
reservoir of buoyancy will become established by early this evening
to the south of ongoing convection across southeastern NE/western IA
and east of a dryline becoming established in western KS. MLCAPE of
3000-4000+ J/kg will likely be in place by this evening across
central/eastern KS as low-level moisture continues to gradually
return northward and rather steep mid-level lapse rates remain
present over the warm sector.
Convection should increase in coverage later this evening from
south-central NE into central KS as a southerly low-level jet
strengthens. A rather quick transition to a mainly linear mode
should occur within a couple of hours of convective initiation.
Severe/damaging winds should become the main threat this evening and
early tonight as thunderstorms spread eastward from central into
eastern KS and southeastern NE. Some of these severe winds could be
75+ mph given the large instability forecast, although the loss of
daytime heating and gradual stabilization of the boundary layer
still lends some uncertainty to the overall magnitude of the severe
wind threat.
For more information on the near-term severe risk from far eastern
NE into southwestern IA and northern MO, see Mesoscale Discussion
800.
..Gleason.. 05/17/2022
.PREV DISCUSSION... /ISSUED 1130 AM CDT Tue May 17 2022/
...Central States...
Low forecast confidence given potential for a variety of convective
scenarios playing out through the period, as illustrated by marked
spread among 12Z guidance. Given this uncertainty, have largely
maintained the cat 3-ENH risk area, which remains more closely
aligned with morning HRRR runs.
A complex, largely zonal flow regime with subtle embedded speed
maxima will affect the central CONUS. Primary feature of initial
interest is a low-amplitude upper trough near the CO/KS/NE border
area expected to move east to the IA/MO border area by early
evening. Elevated convection within a persistent low-level warm
theta-e advection regime has supported scattered storms mainly over
eastern NE. While pronounced insolation is occurring to the south of
this activity, surface dew points remain limited to the mid to upper
50s. Richer moisture characterized surface dew points greater than
65 F remains confined across south-central/southeast KS, given the
impacts of overnight convection and subsequent MCV over the Ozark
Plateau. But moisture recovery through both advection and
evapotranspiration will occur farther north. Some CAMs suggest that
just-in-time moisture return might support an emerging MCS emanating
out of the midday elevated clusters in eastern NE with flanking
southwest convective development near the NE/IA/MO/KS border
vicinity later this afternoon. If this occurs, it would likely
evolve southeast along the warm front.
In the wake of the initial low-amplitude upper trough, weak lee
cyclogenesis is expected over southwest KS with a dryline south, and
a strengthening frontal zone extending north-northeast into central
NE. Isolated to scattered thunderstorms will generally be confined
to the post-frontal upslope regime over the central High Plains and
along the dryline in western KS during the late afternoon. Into
early evening, convection should increase along the frontal zone
into central NE. Largest buoyancy will be most probable across
eastern KS, initially displaced east-southeast of the expected
surface front/dryline development corridors. In addition, most
guidance indicates that belts of enhanced 500-250 mb westerlies will
generally be prominent along the KS/OK border latitude in the
southern stream and the NE/SD border latitude in the northern
stream. This further suggests that convective mode will likely be
quite messy, and within the exit region of a pronounced southern
Great Plains low-level jet, the scenario should foster relatively
quick upscale growth into multiple MCSs tonight. Primary threats
will initially be dominated by large hail and transition to mostly a
severe wind threat that gradually becomes more isolated overnight.
Read more CHECK UPDATE ZOOM GRAPHIC
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