LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1239 AM CDT Tue Aug 01 2023
Valid 011200Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHERN PLAINS...
...SUMMARY...
Severe thunderstorms capable of producing large hail and damaging
winds are expected Tuesday across parts of North Dakota into
northern Minnesota. A few strong/severe storms are also expected
across the central High Plains into the mid Missouri Valley.
Thunderstorms capable of producing occasional damaging winds may
also occur over parts of the coastal Southeast.
...Northern Plains...
Water-vapor imagery depicts a ridge-topping short-wave trough
ejecting east across AB/SK region early this morning. This feature
is forecast to dig southeast and should progress into northwest
ON/Arrowhead of MN by the end of the period. While appreciable
height changes are not expected south of the international border,
it appears this short wave will encourage deep convection
downstream. Latest model guidance suggests low-level warm advection
ahead of the short wave/surface front will spread south across MB
into northern MN by 18z. This activity could evolve into an MCS as
it propagates south along a corridor of warm advection.
Additionally, strong boundary-layer heating will occur across the
northern Plains, extending across ND into eastern MT. This will
ensure CINH weakens by late afternoon along the southward-moving
surface front that should extend from southern MB-northern
ND-northeast MT by late afternoon. This boundary will focus
additional thunderstorm development as temperatures warm through the
lower 90s. Forecast soundings exhibit modest 500mb flow, but
low-level shear should remain weak. While some early-day weak
convection may drift across the SK border into the US, surface
heating is expected to be the primary mechanism for renewed
convective development by 21-23z along the boundary. Large hail and
gusty winds are the expected threats.
...Central Plains/Mid MO Valley...
Early-day MCS will likely be ongoing at the start of the period over
the lower MO Valley. This activity will be supported by low-level
warm advection as 850mb west-southwesterly flow is forecast across
eastern KS into northwestern MO at daybreak. LLJ is expected to
weaken during the day, and high-res models subsequently allow this
activity to weaken. It's not entirely clear how soon convection will
weaken but convective debris and showers will likely linger across
much of MO through the period. However, strong surface heating
across much of KS will allow surface temperatures to warm to near
100F. Convective temperatures will be breached with these readings,
and isolated thunderstorms may redevelop along the old convectively
reinforced boundary that will be draped from southwest MO-northern
KS-eastern CO. Scattered storms will also evolve over CO which will
spread downstream into an air mass seemingly favorable for
supporting at least gusty winds and some threat for hail.
...Southeast...
Low-level convergence corridor will likely extend from northeast FL
to the Carolina Coast. Scattered convection should develop early in
the period then spread south within strengthening northwesterly
mid-level flow in the wake of the east-coast trough. Modest lapse
rates and high PW values suggest gusty winds are the primary
concern.
..Darrow/Bentley.. 08/01/2023
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