Valid 031200Z – 041200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE
NORTHERN HIGH PLAINS…
…SUMMARY…
Isolated strong to severe thunderstorms are possible this afternoon
over the northern High Plains. A few storms producing strong wind
gusts cannot be ruled out from Oklahoma into north Texas.
…Synopsis…
A shortwave trough will move east across the Canadian Prairies, with
a flattening of an upper ridge over MT. Midlevel winds of 30-35 kt
will progress across MT and into the western Dakotas, with 500 mb
temperatures cooling to around -10 C. At the surface, a weak
front/wind shift will approach the MT/ND border during late
afternoon, providing lift of an unstable air mass with dewpoints
near 60 F.
To the south, an upper high will remain centered over the Four
Corners states, with northerly midlevel winds of 25-30 kt from the
central Plains into north TX. Here, a plume of upper 60s to low 70s
F dewpoints will remain, providing sufficient instability for areas
of thunderstorms despite warm temperatures aloft. The primary focus
for daytime storms will be near an inverted surface trough, roughly
from north TX into central OK.
Elsewhere, scattered daytime storms will occur over parts of the
Southeast and Mid Atlantic, well east of the upper high and where
temperatures aloft will be relatively cool.
…Northern High Plains…
Strong heating combined with cooling aloft will result in steep
lapse rates through a deep layer, with an uncapped air mass near a
north-south oriented boundary moving across eastern MT. A band of 35
kt midlevel westerlies, increasing to 50-60 kt near 300 mb, will
provide long hodographs favoring splitting cells as little if any
low-level jet is expected. A few storms will be capable of severe
hail, likely developing around 21Z, from the eastern border of MT
toward the Black Hills. Storms are not expected to get too far east
into the Dakotas due to capping. A few strong wind gusts are also
possible.
…Central OK into north TX…
Areas of showers and thunderstorms are expected to be ongoing early
in the morning over central/east-central OK, and possibly
approaching the Red River and into northeast TX by late morning.
West of this non-severe activity, stronger heating will occur. Only
weak surface convergence will exist over western north TX into
southwest OK, but it will likely support isolated afternoon
redevelopment. Forecast soundings show perhaps 1500 J/kg MLCAPE,
with weakly veering winds with height and little shear. While a few
strong storms producing localized wind gusts cannot be ruled out, at
this time the severe threat appears too low for a risk area.
..Jewell/Nauslar.. 08/03/2019
$$