Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1200Z Outlook
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion

ACUS01 KWNS 200543
SPC AC 200541

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1241 AM CDT Sat Oct 20 2018

Valid 201200Z - 211200Z


The risk for severe thunderstorms appears negligible across the U.S.
Saturday through Saturday night.

A vigorous short-wave trough -- embedded in broader cyclonic flow
over the eastern U.S. -- is forecast to dig rapidly southeastward
from the western Upper Great Lakes area initially, across the Lower
Lakes and Midwest/Ohio Valley through the day, and then to the New
England and Mid-Atlantic coasts by period's end.

As this system digs/advances, a strong cold front -- trailing from a
deep low over Quebec, will shift rapidly
eastward/southeastward/southward with time, crossing the Atlantic
and Gulf Coast states before shifting offshore.  

Meanwhile, background ridging will prevail over the West, though a
weak low will linger in the vicinity of the California coast through
the period.

Showers -- and possibly a thunderstorm or two -- may evolve over
portions of southern and western Arizona and into the Colorado River
Valley vicinity.  More numerous showers and a few afternoon
thunderstorms are also expected ahead of the cold front -- mainly
from off the Atlantic Coast west-southwest across the Gulf of Mexico
and Gulf Coastal region.
Finally, low-topped showers and scattered thunderstorms are also
expected to develop diurnally, across the lower Great Lakes and
upper Ohio Valley region.  Cold air aloft near the core of the
digging short-wave trough will provide up to a couple hundred J/kg
CAPE, generally below 500 mb.  Moderately strong west-southwesterly
flow at low-levels may support gusty winds with a few stronger
cells, and very small hail may also occur.  However,  the CAPE/shear
parameter space anticipated during the afternoon does not appear
sufficient at this time to warrant upgrade to even low (5%) severe
probability.  Convection should diminish rapidly in intensity during
the evening.

..Goss/Cook.. 10/20/2018