Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1245 AM CDT Thu Aug 29 2024
Valid 291200Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER/MIDDLE MISSISSIPPI VALLEY...
...SUMMARY...
Severe thunderstorms are expected across the Upper/Middle
Mississippi Valley to the central Plains. A few severe storms also
will be possible over portions of the mid-Atlantic region.
...Upper/Middle Mississippi Valley...
Southern portions of a strong upper trough, currently located over
the northern Rockies, will eject across the Dakotas this afternoon.
As 70-80kt 500mb speed max translates through the base of the trough
across ND, primary upper low will track across southern AB into
northwestern ON during the latter half of the period. Latest model
guidance suggests very strong 12hr mid-level height falls just north
of the international border, with more modest falls into the upper
Mississippi Valley by 29/00z.
Strong low-level warm advection will likely prove instrumental in
one or more thunderstorm clusters over eastern ND/northwestern MN at
the start of the period. LLJ responsible for this activity will
shift into northwestern ON during the day, and this warm-advection
activity should lift north of the border as well. However, strong
boundary-layer heating will occur across eastern NE into extreme
southwest MN by early afternoon. This will aid instability, and CINH
will begin to weaken along the front, as surface temperatures rise
into the mid 80s across central MN. NAM forecast sounding for KLJF
at 22z is thermodynamically impressive with MLCAPE around 5400 J/kg
and 0-6km shear approaching 30kt. 30-35kt deep-layer shear is
expected along the northern extent of the stronger buoyancy. As a
result, supercells are expected to develop along/ahead of the cold
front, supported aloft by the upstream short wave. Large hail,
severe gusts, and a few tornadoes are the expected hazards with
these storms.
Scattered convection, with a more-isolated severe threat, is
forecast along the trailing cold front across the central Plains as
readings breach convective temperatures later in the afternoon. Wind
profiles at lower latitudes are not very strong, so this activity
will be multicellular and less organized. Even so, some risk for
hail/wind can be expected into the evening hours.
...Middle Atlantic Region...
Dominant surface anticyclone over southeastern Canada will shift
across ON/QC, which will allow a synoptic front to drape itself
across the Middle Atlantic during the afternoon. This boundary will
focus scattered thunderstorms as convective temperatures are
breached by mid afternoon. Wind profiles favor mostly disorganized
pulse-multicell updrafts. These storms will move slowly southeast
with an attendant risk for wind and perhaps some hail. Robust
updrafts will be strongly diurnally driven.
..Darrow/Jirak.. 08/29/2024
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