Valid 082000Z – 091200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN CO…FAR SOUTHEASTERN WY…AND THE NE PANHANDLE…
…SUMMARY…
Severe thunderstorms with strong/gusty winds and hail remain
possible across parts of the central Rockies and adjacent High
Plains this afternoon and evening. Other strong storms may affect
parts of southeast Virginia and northeast North Carolina.
…20Z Update…
Storms have begun to increase in coverage across the higher terrain
of central CO ahead of a northeastward-moving upper trough over the
Great Basin. As this activity spreads eastward and encounters
greater low-level moisture across northeastern CO and vicinity later
this afternoon and evening, isolated severe thunderstorms may occur.
Damaging winds still appear to be the main threat as storms will
likely grow upscale into a small cluster this evening, but
marginally severe hail may also occur early in the convective life
cycle. Ongoing forecast still appears on track, and no changes have
been made to the Marginal/Slight risk areas across this region.
..Gleason.. 09/08/2019
.PREV DISCUSSION… /ISSUED 1130 AM CDT Sun Sep 08 2019/
…Central Rockies into High Plains…
Morning water vapor loop shows a strong and progressive upper trough
moving across parts of NV/UT. This feature will track into WY/CO
later today, with an associated zone of enhanced forcing for ascent
overspreading the region. Strong daytime heating is occurring over
much of the mountains and foothills of CO, where steep low-level
lapse rates will develop and scattered thunderstorms are expected.
As these storms move off the higher terrain late this afternoon and
early evening, continued easterly low-level winds will help to
establish an axis of sufficient CAPE for a few robust
updrafts/downdrafts capable of damaging winds and some hail.
Vertical shear profiles are sufficient for supercell/bowing
structures. This activity will spread northeastward across the SLGT
risk area during the evening.
…VA/NC…
The southern fringe of stronger westerly flow aloft has sagged into
southeast VA/northeast NC today, where a very moist and potentially
unstable air mass is present. Dewpoints in the mid 70s and strong
heating will lead to moderate CAPE values and the development of a
few afternoon thunderstorms. Low-level winds are weak, suggesting
that storms will be rather disorganized. However, sufficient
midlevel winds and favorable thermodynamic parameters indicate a low
risk of gusty winds in the stronger cells.
$$