- Day Three
acus03 kwns 210716
Storm Prediction Center ac 210715
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0215 am CDT Wed Aug 21 2019
Valid 231200z - 241200z
..there is a marginal risk of severe thunderstorms from North
Carolina into southern Virginia...
Isolated severe wind gusts are possible Friday over parts of North
Carolina and southern Virginia.
An upper low will pivot northeast across the Canadian Maritimes,
with a jet streak sweeping across New England and tail end near the
mid Atlantic. At the surface, high pressure will remain over the
Great Lakes, with a cold front moving south toward the Virginia/NC border.
A weak surface low is forecast to develop over eastern Virginia and NC
near the front where 70s f dewpoints and heating will contribute to
To the west, a leading shortwave trough will eject out of the
Dakotas toward western Ontario as a broad upper jet noses into the
northern High Plains Friday night. Dewpoints in the 60s f will exist
over the Dakotas ahead of a dying front related to the leading wave,
and will back westward toward Montana by 12z Saturday.
Elsewhere, a loose east-west boundary will remain roughly from Kentucky/Tennessee
into north TX, with bouts of mainly non-severe thunderstorms through
..NC into southern Virginia...
Strong heating of a moist air mass will occur south of the cold
front approaching the Virginia/NC border late in the day. Forecast
soundings indicate 2000-2500 j/kg MLCAPE developing despite poor
midlevel lapse rates, though low-level lapse rates will become
steep. With no capping present, the front will provide a focus for
scattered storms, which may produce locally severe wind gusts as
they propagate southeastward from Virginia into NC. Models are in good
agreement depicting a relatively concentrated area of storms in this
..northern High Plains...
Elevated thunderstorms may be ongoing Friday morning over central ND
in association with the departing shortwave trough, but will likely
lose strength as lift wanes, and due to dry trajectories out of the
surface high to the east. As cooling aloft arrives from the west,
lapse rates as well as deep shear will increase, conditionally
favoring elevated hail into Saturday morning over eastern Montana. At
this time, storm chances prior to 12z Saturday appear too low to
introduce severe probabilities.