Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Fri Aug 23 2024
Valid 231200Z - 241200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF MT
INTO THE INTERMOUNTAIN WEST/EASTERN GREAT BASIN...PARTS OF THE
CENTRAL/NORTHERN HIGH PLAINS...AND SOUTHEAST AZ INTO EXTREME
SOUTHWEST NM...
...SUMMARY...
Strong to severe storms with severe gusts and possibly some hail are
possible across Montana, the Intermountain West and central Rockies,
southeast Arizona, and the central and northern High Plains.
...Synopsis...
A seasonably deep mid/upper-level trough will persist over the West
today. A strong embedded shortwave trough and attendant midlevel jet
maximum will move quickly northeastward from the Great Basin into
the interior Northwest/northern Rockies through the day. A surface
low is forecast to deepen across western MT through the day, in
conjunction with the passage of the shortwave trough. A weaker
surface low may move gradually northeastward across the southern
High Plains. Relatively rich low-level moisture will extend from
TX/OK into the central/northern High Plains, while a plume of
monsoonal moisture will persist from the Southwest/southern Rockies
into eastern parts of the Great Basin.
...Parts of UT/western CO into the interior Northwest and
western/central MT...
Stronger ascent related to the ejecting shortwave trough over the
interior Northwest may remain somewhat displaced from better
moisture/instability through the day. However, it will likely aid in
the development of scattered thunderstorms across a broad region
from UT/western CO into parts of the Northwest/northern Rockies. The
combination of relatively high-based convection and increasing
low/midlevel flow will support a threat of at least isolated severe
gusts across a broad region from the eastern Great Basin into parts
of ID/MT. Steep lapse rates and sufficient deep-layer shear could
also support an isolated hail threat, where sufficient
pre-convective buoyancy can be realized.
The Marginal Risk has been expanded across much of western/central
MT, due to increased confidence in sufficiently deep convection to
support a severe-wind threat. Portions of the Marginal Risk may
eventually need greater wind probabilities, if confidence increases
in one or more corridors where a greater coverage of severe gusts
will be possible. Some severe-wind threat could also evolve west of
the current Marginal across parts of OR/WA/western ID, in closer
proximity to the shortwave trough, but confidence is lower at this
time due to very limited forecast buoyancy in this area.
...Parts of the High Plains...
Moderate to locally strong buoyancy is forecast to develop this
afternoon across much of the High Plains, along/east of a wavy
surface trough extending between the surface lows across MT and the
southern High Plains. However, large-scale ascent will likely remain
rather nebulous across this region, and the details of storm
development and coverage remain uncertain. While midlevel flow will
be somewhat weaker compared to areas farther west, it will remain
sufficient to support effective shear of 30+ kt, conditionally
supporting organized convection. Any sustained storms that can
develop and be maintained during the afternoon/evening would pose a
threat of isolated hail and severe gusts.
...Southeast AZ vicinity...
Scattered thunderstorms are again expected across southeast AZ into
adjacent southwest NM. A modest increase in midlevel flow could
support somewhat more organized storms compared to Thursday.
Moderate buoyancy and effective shear increasing into the 20-25 kt
range will support a threat of localized strong/severe gusts and
possibly some hail with the strongest storms.
..Dean.. 08/23/2024
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