Valid 171630Z – 181200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NORTHERN HIGH
PLAINS AND PARTS OF THE UPPER MIDWEST…
…SUMMARY…
A few severe storms are possible across the northern High Plains
during the late afternoon and evening, and overnight in parts of the
Upper Midwest.
…Northern High Plains…
A vigorous shortwave trough over southeast ID will eject
northeastward to ND tonight. Surface cyclone near the ND/MT/SK
border area will slowly move east into southern MB. Strong forcing
for ascent will accompany the shortwave trough within the left-exit
region of the mid-upper jet, but lingering convective inhibition and
meager MLCAPE will tend to limit storm coverage/intensity. Still,
there will be enough downdraft and momentum transfer potential to
support isolated severe wind gusts from eastern WY/western SD during
the late afternoon into western ND this evening.
…Upper Midwest…
East of the surface cold front moving across the Dakotas tonight, a
low-level jet will strengthen to 50-60 kt from NE to MN. This will
occur along the low-level moist axis, where moderate buoyancy will
persist well into the overnight hours. One or more pre-frontal
convective clusters are expected to form within the warm conveyor
near the SD/MN/IA/NE border area and spread northeast. Deep-layer
flow will be decreasing with height, suggesting that storms will
struggle to organize and the hail threat should be limited. However,
an enlarged low-level hodograph may compensate for pronounced MLCIN
and support a risk of locally damaging wind.
…Upper TX Coast…
A weak tropical low east of Matagorda Bay will drift northward
towards Houston through early Wednesday. There is some potential for
strengthening with this system prior to moving inland, though wind
fields are not expected to become strong enough to support a threat
for supercells/tornadoes. Otherwise, training convection yielding
very heavy rainfall will be the main concern.
..Grams/Broyles.. 09/17/2019
$$