SPC AC 150500
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1200 AM CDT Sun Sep 15 2019
Valid 161200Z - 171200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT
SALT LAKE VICINITY LATE MONDAY NIGHT...
Strong thunderstorms may impact portions of the Great Basin near the
Great Salt Lake late Monday night, perhaps accompanied by at least
some risk for potentially damaging wind gusts.
Within the westerlies, initially amplified mid-level troughing
near/inland of the Pacific coast may already be in the process of
splitting at the outset of the period. Models indicate that this
will continue into early Tuesday, as another significant short wave
trough digs southeast of the Gulf of Alaska, just to the west of the
British Columbia coast, and downstream ridging builds along an axis
from the Upper Midwest into areas as far north as western Hudson
Bay. It appears that one emerging short wave impulse will gradually
accelerate north and northeast of the Canadian Rockies, while
another more vigorous perturbation pivots inland of the Pacific
coast, into northern portions of the Great Basin by 12Z Tuesday.
This latter feature will be preceded by a perturbation emanating
from the lower latitudes, which may accelerate northeast of the
Colorado Rockies, toward the eastern Dakotas Monday through Monday
East of the ridging, large-scale troughing is forecast to continue
digging east-southeast of the Canadian Maritimes and north Atlantic
coast. An associated cold front may advance southward through the
lower Ohio Valley, Mid Atlantic Coast states and adjacent portions
of the western Atlantic. However, it is expected to remain well to
the north of Humberto, which is forecast to reach hurricane strength
well east of the Florida coast, while slowly accelerating eastward
away from the coast.
Although seasonably high (tropical) moisture content appears likely
to remain largely confined to the Gulf of Mexico and western
Atlantic, residual boundary layer moisture, in a corridor along the
remnant western flank of the cold front across the lower/mid
Missouri Valley, into deepening surface troughing across the
northern Plains, may contribute to moderate CAPE with daytime
heating Monday. However, at least some combination of weak forcing
for ascent and mid-level inhibition, associated with a plume of warm
elevated mixed-layer air advecting northeast of the northern
Rockies, and across the international border area, is expected to
limit convective potential. The development of any appreciable risk
for severe weather still seems most probable with strong forcing for
ascent and wind fields/shear associated with the short wave trough
progressing into the Great Basin Monday night.
...Great Salt Lake vicinity...
In the wake of the lead perturbation (of lower latitude origins),
boundary layer moisture across western portions of the Great Basin
may not be supportive of more than very weak CAPE. However, some
northward moisture return appears at least possible to the west of
the Wasatch by late Monday night, ahead of the vigorous approaching
short wave and associated cold front. Coupled with strong forcing
for ascent and mid-level cooling, destabilization may become
sufficient to support scattered thunderstorm development across the
Great Salt Lake vicinity by 17/09-12Z, in the presence of
strengthening (40-70 kt) southwesterly flow in the 700-500 mb layer.
This regime may become conducive to the development of potentially
damaging wind gusts in stronger convection.
...MAXIMUM RISK BY HAZARD...
Tornado: <2% - None
Wind: 5% - Marginal
Hail: <5% - None
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z