Valid 171200Z – 181200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE NORTHERN HIGH PLAINS AND THE UPPER MIDWEST…
…SUMMARY…
A few strong/severe storms are expected across the northern high
Plains area afternoon/early evening, and may evolve overnight into
the Upper Midwest. Hail and locally damaging winds will be
possible.
…Northern Plains to the Upper Midwest…
A shortwave impulse over SD early this morning will continue to lift
northeast across MN. Ongoing convection associated with this feature
will spread across MN through midday and should remain elevated.
This activity is not expected to be severe given the elevated nature
of convection.
Further southwest, a compact shortwave trough is forecast to lift
northeast from the Great Basin to the eastern Dakotas/western MN by
Wednesday morning. A surface low near the eastern MT/western ND/SK
border will deepen during the afternoon as height falls begin to
overspread the region. a surface trough/dryline will extend
southward through the northern/central High Plains while a cold
front shifts east across eastern MT by 00z. Deep layer flow will
strengthen considerably as a mid/upper level jet streak overspreads
the central High Plains and steep midlevel lapse rates will aid in
modest destabilization by late afternoon. However,
coverage/intensity of storms remains somewhat uncertain given a
considerable dry slot and capping on the western fringes of the
Midwestern upper ridge. Nevertheless, at least a few storms are
expected near the triple point over eastern MT into northeast WY.
Strong gusts and marginal hail will be possible with the strongest
cells as they shift east/northeast. Additional storms are expected
to develop over eastern SD into MN after 03z ahead of the
eastward-surging cold front. Storms should quickly grow into
clusters or line segments as a 40-50 kt southwesterly low level jet
increases. Strong gusts will be possible with the strongest cells,
though forecast soundings suggest convection may remain elevated.
..Leitman.. 09/17/2019
$$