Valid 271200Z – 281200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
EASTERN KANSAS NORTHEASTWARD INTO EASTERN IOWA AND NORTHERN/WESTERN
ILLINOIS…
…SUMMARY…
Severe storms capable of producing large hail and possibly damaging
winds are expected Friday afternoon and evening from parts of the
central Plains to the mid Mississippi Valley/southern Upper Great
Lakes.
…Synopsis…
Gradual amplification of the upper flow field across the U.S. is
expected to begin over the western states today, as a low shifting
southward across British Columbia at this time continues southward
into the Pacific Northwest through the period. Downstream across
the eastern half of the country, neutral to weakly rising heights
are expected.
At the surface, a cold front is forecast to move eastward across
eastern Canada and the Upper Great Lakes region, while shifting more
slowly southward across the mid Mississippi/lower Missouri Valleys
and central Plains. Elsewhere, high pressure will prevail in the
east, while a low develops over the Great Basin vicinity ahead of
the southward-moving upper system.
…Eastern Kansas northeastward to the southern Upper Great Lakes…
Low-level moistening across the lower Missouri Valley region is
expected today, in the wake of ongoing convection expected to be
moving across eastern portions of the risk area through the morning
hours. The moistening will combine with diurnal heating to result
in moderate destabilization ahead of the southward-moving cold
front. Additionally, with a belt of moderately strong flow aloft
atop the frontal zone, an overall environment that would support
organized storms is expected to evolve across the region through the
afternoon.
However, with a largely capped boundary layer expected south of the
front — as would be expected given neutral to weakly rising
mid-level heights — storm development is expected to occur largely
to the cool side of the surface front. Any storms which could
develop near the front, would be capable of producing gusty/damaging
winds, before being undercut by the boundary. Otherwise, greater
risk is expected to be large hail, with anafrontal convection which
should gradually increase in coverage through the evening.
…The Texas South Plains region…
A mid-level short-wave trough now over the lower Colorado River
Valley/northern Gulf of California vicinity is forecast to move
steadily eastward, just north of the international border today. As
the feature crosses New Mexico overnight, a few storms may develop
as ascent increases over portions of western Texas, where ample
instability atop a weakly stable boundary layer is expected to
reside. As flow aloft increases in conjunction with the approaching
upper feature, a stronger storm or two — capable of producing
severe weather primarily in the form of hail — may evolve during
latter stages of the period.
..Goss/Mosier.. 09/27/2019
$$