746
ACUS02 KWNS 151727
SWODY2
SPC AC 151725

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1225 PM CDT Sun Sep 15 2024

Valid 161200Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE EASTERN
GREAT BASIN INTO THE FOUR CORNERS REGION...ND INTO NORTHWEST
MN...EASTERN NC AND VICINITY...

...SUMMARY...
On Monday, sporadic severe gusts and hail will be possible during
the afternoon to early evening across parts of the eastern Great
Basin to Four Corners. Isolated severe storms are possible over
eastern North Dakota into northwest Minnesota. Some tornado threat
may develop over eastern North Carolina and vicinity.

...Eastern Great Basin to the Four Corners...
A seasonably strong mid-level low initially near San Francisco Bay
Monday morning should move east during the day, before curling
northeast Monday night towards the NV/UT/ID border area. This will
occur in response to a strong mid-level jet translating through the
basal portion of the large-scale trough across the Desert Southwest
into the eastern Great Basin.

Convection will likely be ongoing at the start of the forecast
period near the midlevel low, and also farther east toward the Four
Corners region, within the warm/moist conveyor. Relatively strong
heating will be possible between these two regimes, from eastern NV
into parts of UT. While buoyancy will likely remain quite weak
within this warmer and more well-mixed regime, high-based convection
will be possible during the afternoon and evening as the midlevel
low approaches the region, with increasing meridional flow and a
deeply mixed boundary layer supporting isolated severe gusts.

Farther southeast into eastern UT and the Four Corners vicinity,
increasing southwesterly flow aloft and strengthening deep-layer
shear will become conditionally supportive of organized convection.
Warmer midlevel temperatures may limit buoyancy to some extent,
though sufficient moisture will support afternoon MLCAPE of 500-1000
J/kg. A few supercells will be possible within this regime, with an
attendant threat of isolated severe gusts and hail.

...Parts of ND into northern MN...
With the primary upper-level trough displaced well to the west,
deep-layer shear will remain weak across much of the Great Plains.
However, most guidance suggests an MCV will emanate out of central
High Plains convection on D1/Sunday and gradually progress northeast
towards the Red River Valley during the day on Monday. In
conjunction with a strengthening low-level jet, this MCV may help to
support relatively vigorous storm redevelopment within a moderately
unstable environment during the afternoon and evening.

Stronger midlevel flow attendant to the MCV could support some storm
organization, and a couple supercells and/or stronger clusters will
be possible, with a threat of isolated hail and damaging wind.
Somewhat favorable low-level shear/SRH could also support a tornado
threat, if a surface-based supercell can be sustained. Uncertainty
remains regarding the strength/timing of any MCV moving across the
region, along with the most favored corridor for diurnal storm
development.

...Eastern NC and vicinity...
Guidance generally suggests that an initially offshore surface low
will move northward or northwestward from later on D1/Sunday into
D2/Monday and D3/Tuesday, and eventually move inland across some
part of the Carolinas. However, uncertainty remains regarding the
timing, track, and intensity of this low, along with the extent to
which it acquires any tropical or subtropical characteristics.

If a deepening low does move onshore, then a higher theta-e airmass
may move inland, accompanied by increasing low-level shear/SRH
along/north of the low track. While the general scenario supports
some potential for low-topped supercells, the magnitude of any
tornado threat will be dependent on the extent of intensification
that occurs with the low (and its attendant wind fields) prior to
landfall. The Marginal Risk has been expanded somewhat across
eastern NC and vicinity, in response to the various uncertainties.

..Dean.. 09/15/2024

$$