ACUS02 KWNS 150557
SWODY2
SPC AC 150556

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Sun Sep 15 2024

Valid 161200Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE EASTERN
GREAT BASIN TO FOUR CORNERS...THE RED RIVER VALLEY OF THE
NORTH...AND EASTERN NC...

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

...Eastern Great Basin to the Four Corners...
An amplified mid-level low near the Bay Area at 12Z Monday should
initially move east 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 should be ongoing Monday morning immediately
ahead of the mid-level low and separately in the low-level
warm/moist conveyor over the Four Corners region. Greater
boundary-layer heating should occur between these two regimes across
eastern NV into UT, west of the Wasatch Range. Despite meager
MLCAPE, the deepening boundary layer amid a strengthening meridional
wind profile should yield efficient downward mixing. This will be
further augmented by evaporatively cooled downdraft accelerations
and promote a threat for sporadic severe gusts.

Farther southeast, a more southwesterly mid to upper-flow regime
should yield hodograph elongation, supporting a few splitting
supercells. Warmer mid-level temperatures and correspondingly weaker
lapse rates will temper parcel acceleration to an extent, but this
may be offset by somewhat higher PW values. Marginal severe
hail/gusts will be possible.

...Eastern ND to northwest 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 D1
central High Plains convection and gradually progress northeast
towards the Red River Valley. In conjunction with the northern nose
of a strengthening central to northern Great Plains low-level jet, a
focused corridor for regenerative thunderstorm development may occur
during the late afternoon and evening. Some low-level hodograph
enlargement should support a predominantly clustered convective
mode, with transient supercell structures possible. An isolated,
lower-end severe hail/wind threat may develop, and a brief tornado
is also possible.

...Coastal NC...
While guidance consensus increasingly favors offshore cyclogenesis,
the amplitude of this development along with timing of inland
progression remain quite varied for a D2 forecast. The 00Z NAM and
some of the 18Z ECMWF ENS members suggest particularly robust
deepening will occur. The more aggressive scenarios would yield
substantial enlargement of low-level hodographs, likely becoming
coupled with a narrow swath of high theta-e air spreading
west-northwestward from the Gulf Stream. Given the potential range
of scenarios from nil threat to multiple tornadic supercells, a
low-probability tornado highlight appears warranted.

..Grams.. 09/15/2024

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