Day 3 Convective Outlook  
NWS 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...

...SUMMARY...
Isolated severe wind gusts are possible Friday over parts of North
Carolina and southern Virginia.

...Synopsis...
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 VA/NC border.
A weak surface low is forecast to develop over eastern VA and NC
near the front where 70s F dewpoints and heating will contribute to
moderate destabilization.

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 MT by 12Z Saturday.

Elsewhere, a loose east-west boundary will remain roughly from KY/TN
into north TX, with bouts of mainly non-severe thunderstorms through
the period.

...NC into southern VA...
Strong heating of a moist air mass will occur south of the cold
front approaching the VA/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 VA into NC. Models are in good
agreement depicting a relatively concentrated area of storms in this
area.

...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 MT. At
this time, storm chances prior to 12Z Saturday appear too low to
introduce severe probabilities.

..Jewell.. 08/21/2019

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0316 AM CDT Wed Aug 21 2019

Valid 241200Z - 291200Z

...DISCUSSION...
Strong northwest winds aloft will dive southeastward across the
northern Rockies and into the Plains, with one or more leading waves
affecting the northern Plains on Saturday/D4 and Sunday/D5 before
the larger amplification occurs Tuesday/D7 into Wednesday/D8. These
lead waves will interact with a plume of mid 60s F dewpoints over
the Dakotas and western MN D4 and D5, with at least isolated severe
hail possible. Mitigating severe coverage will be relatively cool
air emanating out of a surface ridge to the east, suggesting storms
may become elevated as they move east away from the deeply mixed air
near the surface trough. That said, models differ on the timing of
these waves, thus predictability is too low to introduce severe
probabilities.

During the D6-D8 time frame, more robust low-level moisture will be
in place from NE toward the Upper Great Lakes, and winds aloft will
increase over the northern Plains, Upper MS Valley and Great Lakes,
suggesting severe potential. Though timing issues exist amongst the
models, the general signal is for the upper winds to become nearly
parallel to the cold front, with areas of damaging wind possible
from the central and northern Plains to the Upper MS Valley and
Midwest.