Latest D3 -
SUMMARY...
An outbreak of severe weather remains likely across portions of the
Upper Midwest, centered on Monday afternoon and evening. Very large
hail, strong tornadoes, and damaging winds are expected.
...Synopsis...
Multiple shortwave impulses embedded within a broader positive-tilt
upper trough will eject into/across the North-Central States during
the period. Primary surface cyclone, over central/eastern SD Monday
morning, will remain nearly steady-state as it tracks east-northeast
across the Upper Great Lakes.
...Upper Midwest...
Elevated convection should be ongoing at 12Z Monday, centered on ND
arcing southeast across the Upper MS Valley. Isolated severe hail
may accompany this morning activity as it progresses eastward along
the leading edge of a stout EML. Regenerative elevated storm
development should persist northeast of the surface cyclone track
across the Red River Valley through northern MN, likely limiting the
northward advancement of the surface warm front during the day.
Guidance differs markedly with the degree of northward
destabilization into northern MN, lowering confidence in the degree
of severe threat here.
South of early-period storms/cloud coverage, pronounced
destabilization will occur beneath the initially stout EML amid
strong low-level moist advection. Cooling mid-level temperatures
during the afternoon will be favorably timed with peak heating to
support thunderstorms across southern MN into northern IA. Greater
coverage is expected with northern extent which may yield more
linear organization, compared to more discrete/isolated coverage
trailing southward. A mix of all hazards is anticipated with an
increasing severe threat into the early/mid evening as the low-level
jet strengthens across the Upper MS Valley to Upper Great Lakes. The
southern portion of this will be the more favored corridor for open
warm sector discrete supercells capable of producing strong
tornadoes. By late evening, linear clusters will likely overtake
much of the discrete convection as the cold front advances rapidly
east-southeast. Damaging wind gusts and embedded tornadoes will
remain possible through the late evening and perhaps into the
overnight hours.
...KS/MO to west TX...
A strongly unstable/sheared warm sector will exist along/east of the
dryline. Forcing for ascent should be much weaker than farther north
with only weak mid-level height falls along the dryline. Most
probable storm signals are after the nocturnal low-level jet
increases during the evening in the southern Great Plains. This
could support isolated supercells into Monday night.
..Grams.. 04/26/2025
