Valid 050100Z – 051200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TONIGHT ACROSS
PARTS OF THE NORTHERN PLAINS…
…SUMMARY…
Scattered strong storms posing a risk for severe hail and wind may
still develop tonight across parts of the northern Plains,
particularly across parts of central and southern North Dakota into
northern Minnesota.
…01Z Outlook Update…
The lack of more substantive low-level moisture, inhibition
associated with relatively warm mid-levels, and weak to negligible
mid/upper forcing for large-scale ascent have generally suppressed
convective development across much of the northern Plains, aside
from the cluster of storms which developed near the Black Hills
before propagating into northern Nebraska. This convection may have
initiated in response to a subtle short wave impulse migrating
around the northern periphery of the western U.S. subtropical
ridging, but now appears in the process of diminishing.
Stronger mid-level height falls (30 meters at 500 mb), associated
with a vigorous short wave impulse within the mid-latitude
westerlies, are currently spreading across Manitoba into
northwestern Ontario. However, models continue to suggest that a
couple of digging perturbations (currently across parts of southern
Alberta and central Saskatchewan) may still contribute to
suppression of mid-level ridging across the Dakotas and northern
Minnesota late this evening into the overnight hours.
Although this will take place after the onset of nocturnal boundary
layer cooling, a remnant corridor of moderate to strong potential
instability now present across southern/eastern North Dakota into
northern Minnesota, ahead of the cold front, may still provide the
focus and support for at least scattered thunderstorm development.
Coinciding with southeastward progression of 30-50 kt 500 mb flow,
to the south of the central Canadian/U.S. border area, moderate to
strong deep-layer shear could support organized convection capable
of producing severe hail and strong surface gusts.
..Kerr.. 08/05/2019
$$