Valid 101630Z – 111200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF ID/MT/WY
AND EASTERN NC…
…SUMMARY…
Scattered severe thunderstorms with large hail and damaging wind
gusts are most likely across parts of Idaho, Montana, Wyoming, and
eastern North Carolina. The severe threat should be greatest during
the late afternoon to early evening.
…Northwest…
A closed mid-level low near the CA/OR coastal border will gradually
evolve into an open wave while ejecting towards the OR/ID border
through tonight, as other subtle speed maxima rotate around the
eastern periphery of the low. A plume of weak to moderate buoyancy
will develop at peak heating, arcing from OR/ID east across the
northern Rockies and High Plains where scattered thunderstorms will
likely form by late afternoon.
Greatest effective shear should be centered across southern MT where
weak low-level easterlies will be present beneath southwesterlies
aloft that strengthen with height. This should yield an elongated,
straight-line hodograph favorable for several splitting supercell
structures. Large hail and severe wind gusts will be the primary
hazards. Relatively high LCLs may limit the overall tornado threat,
but brief ones are possible where 50s surface dew points can be
sustained.
…Eastern NC…
Sea breeze circulations along with a weakly convergent
quasi-stationary front should be the focus for isolated to perhaps
scattered thunderstorm development during the next few hours. Rich
boundary-layer moisture characterized by low to mid 70s surface dew
points exists over coastal southern NC into SC which will result in
a confined corridor of MLCAPE in excess of 2000 J/kg. A few cells
should briefly organize amid 30-40 kt 500-mb west-northwesterlies.
Isolated large hail and damaging winds are anticipated. A marginal
severe threat may persist into tonight amid weak low-level warm
advection.
…Central High Plains to IA vicinity…
A messy/low confidence scenario is anticipated through tonight with
multiple MCVs and lingering cloud debris across the region. Forcing
for ascent will likely persist across the Mid-MO Valley in a zone of
low-level warm advection. Pockets of greater surface heating are
apparent within cloud breaks into IA which combined with low-level
moistening should support weak to moderate MLCAPE. Moderate
enlargement/curvature to the low-level hodograph may foster a
conditional brief tornado/locally damaging wind risk. Relatively
warm profiles aloft and weak mid-level lapse rates will be
unfavorable for large hail.
Otherwise, scattered late afternoon storms should develop off the
southern Rockies across eastern CO. Modest effective shear may be
adequate to support multicell clustering as convection impinges on
substantially greater buoyancy across KS/NE. Low-level warm
advection will also increase across KS tonight in response to a
nocturnal low-level jet, when more widespread convection is expected
in the form of multiple clusters. Given the shear profiles,
convection may be only weakly organized and slow-moving. But a
threat for locally severe wind gusts should exist given heavy
precipitation loading amid PW in excess of 2 inches.
..Grams/Dean.. 08/10/2019
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