- Day Three
acus02 kwns 191721
Storm Prediction Center ac 191720
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1220 PM CDT Tue Jun 19 2018
Valid 201200z - 211200z
..there is a marginal risk of severe thunderstorms across parts of
the southern and Central Plains...lower Missouri
Valley...mid-Atlantic and Pacific northwest...
A few severe thunderstorms are possible on Wednesday across parts of
the central and Southern Plains, lower Missouri Valley, mid-Atlantic
and Pacific northwest.
..southern and Central Plains/lower Missouri Valley...
An upper-level low will move southeastward into the northern part of
the Central Plains on Wednesday as an associated shortwave trough,
extending southward from the low, moves eastward across the southern
and Central Plains. At the surface, a cold front is forecast to be
located from northern Oklahoma extending northeastward into eastern
Kansas and northwest Missouri by afternoon. Ahead of the front,
surface dewpoints in the upper 60s to near 70 f should contribute to
the development of moderate instability with thunderstorm
development taking place along the front during the mid to late
afternoon. Several clusters of storms are expected to develop from
Oklahoma northeastward into northwest Missouri and move eastward
across the region during the late afternoon and early evening.
Although deep-layer shear is forecast to generally weak ahead of the
front, steep low-level lapse rates could be enough for a marginal
wind damage threat especially in areas that destabilize the most.
Hail could also occur with the stronger updrafts.
A shortwave trough will move eastward across the central
Appalachians on Wednesday. At the surface, a cold front should be
located across southern Pennsylvania with a low developing across
far northern Virginia during the afternoon. Surface dewpoints near
70 f from near the front and southward will aid destabilization with
the development of a pocket of moderate instability possible by
early afternoon. As low-level convergence increases, thunderstorm
development will likely take place in the vicinity of the front
during the afternoon. Forecast soundings in eastern Virginia
Wednesday afternoon show 0-6 km shear in the 30 to 40 kt range. This
combined with steep low-level lapse rates may be enough for
marginally severe multicells around peak heating. Strong wind gusts
would be the primary threat.
An upper-level ridge will be in place across the western U.S. On
Wednesday as a shortwave trough moves northeastward to near the West
Coast by afternoon. At the surface, a cold front will advance
eastward into the Pacific northwest. Ahead of the front, surface
dewpoints mostly in the 50s f should result in an axis of
instability ahead of the front in western Oregon. Thunderstorms that
develop along the front during the afternoon may have a potential
for marginally severe wind gusts and hail due to the instability,
steep lapse rates and moderate deep-layer shear.
..maximum risk by hazard...
Tornado: 2% - marginal
wind: 5% - marginal
hail: 5% - marginal