SPC AC 021720
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1220 PM CDT Thu Aug 02 2018
Valid 031200Z - 041200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ...
Isolated severe thunderstorms are possible across parts of the
central and northern Plains in the upper Mississippi Valley. A few
strong storms may also develop across the northern Middle Atlantic
into parts of western New England.
...Central and Northern Plains/Upper Mississippi Valley...
An upper-level trough will move eastward across the northwestern
states on Friday as west to southwest mid-level flow remains over
the central and northern Plains. An upper-level ridge will be in
place across the upper Mississippi Valley. At the surface, a cold
front will move eastward across the northern Plains with a pocket of
maximized low-level moisture in place ahead of the front from
eastern parts of the northern Plains into the upper Mississippi
Valley. Surface dewpoints across this region should be in the mid
60s to lower 70s F by afternoon. As surface temperatures warm during
the day, convection is forecast to develop along the front in
central and southern North Dakota and ahead of the front in central
and eastern South Dakota. Due to warm air aloft and minimal
large-scale ascent, convective coverage should remain isolated. The
NAM forecast sounding at Aberdeen, SD during the late afternoon
shows MLCAPE around 2000 J/kg and 0-6 km shear near 30 kt. This
combined with steep low-level lapse rates would be enough for a
marginal wind damage threat with any storm that can mature in spite
of the warm air aloft. Hail will also be possible. Although the cap
should strengthen during the evening, a gradual increase in
low-level flow may be enough to keep a few marginally severe storms
going into the early evening.
...Mid Atlantic/New England...
An upper-level trough will move eastward across the Great Lakes and
Ohio Valley on Friday as southwest mid-level flow remains over the
Northeast. At the surface, a moist airmass will be in place along
the eastern seaboard with surface dewpoints in the upper 60s and
lower 70s F. As surface temperatures warm during the day and as
large-scale ascent increases ahead of the approaching upper-level
trough, scattered thunderstorms are expected to develop from the
central Appalachians northeastward into New England. The best chance
for a marginal wind damage threat would be from the Mid-Atlantic
into western New England where low-level flow is forecast to be
maximized. Strong wind gusts would be most likely associated with
peak heating late Friday afternoon.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 5% - Marginal
Hail: 5% - Marginal
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z