LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1238 AM CDT Mon Sep 04 2023
Valid 041200Z - 051200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN PLAINS...
...SUMMARY...
Thunderstorms capable of producing isolated to widely scattered
severe wind and hail will be possible Monday afternoon and evening
across parts of the northern Plains.
...Northern Plains...
Strong short-wave trough is currently located over the Great Basin,
progressing inland in line with latest model guidance. This feature
is forecast to advance into WY/western CO by late afternoon as
associated 500mb speed max ejects into the central Rockies and
gradually weakens. This evolution favors a lee surface low forming
over western SD by late afternoon. A synoptic front is expected to
be oriented northeast-southwest across the Dakotas into northern WY
by peak heating.
Boundary layer is expected to warm rapidly across the High Plains
from western NE into the Dakotas south of the aforementioned
synoptic wind shift. While readings will be somewhat cooler across
WY, convective temperatures will be breached by 20z, and scattered
convection should easily develop ahead of the short wave. HREF
guidance depicts a strong signal for high-based convection to
initiate over eastern WY then spread/develop northeast into a much
warmer air mass, with a deeper boundary layer characterized by
temp/dew point spreads around 40F. Forecast soundings exhibit ample
deep-layer flow and shear for organized updrafts. Current thinking
is a few supercells may be noted early in the period, but possibly
transitioning into more clusters/bowing line segments downstream
over the Dakotas. Forecast buoyancy is not that strong, but there is
some concern for significant, organized gusts with these clusters,
especially given the steep lapse rates and large-scale support ahead
of the short wave. There may be a need for higher wind probabilities
across the northern Plains, but will maintain SLGT Risk at this
time. Convection, potentially organized, will spread northeast
across the Dakotas during the evening.
...AR/MO...
Weak upper low over north-central TX should open up and eject
towards the Ozarks later today. Seasonally cool mid-level
temperatures are noted with this feature, and modest 500mb flow will
spread across this region just ahead of the short wave. Forecast
soundings exhibit substantial buoyancy and multicell storms should
evolve as temperatures warm through the upper 80s to near 90F. Local
gusts and perhaps some hail could accompany this diurnally enhanced
convection.
..Darrow/Wendt.. 09/04/2023
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