SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1130 PM CST Sat Nov 21 2020

Valid 221200Z - 231200Z


Severe thunderstorms appear unlikely across the U.S. today into

A strong shortwave trough is forecast to move from the
central/northern Plains this morning quickly eastward to the lower
Great Lakes region by 12Z Monday. In conjunction with this feature,
a weak surface low will slowly deepen and move northeastward from
the OH Valley this morning into portions of New England by Monday
morning. Upstream, another mid/upper-level trough will deepen over
the western CONUS through the period. 

Thunderstorm potential is expected to increase this evening into the
overnight hours across the eastern Carolinas, as moisture and
instability gradually increase ahead of an approaching cold front.
Inland storms are expected to remain elevated, though surface-based
convection cannot be entirely ruled out near the Outer Banks. At
this time, the best potential for organized storms is expected to
remain offshore.  

...New England...
Late tonight into early Monday morning, a southerly low-level jet
will advect richer Atlantic low-level moisture into portions of
southern New England. Some convection is likely to develop within a
warm-advection regime, with a few lightning strikes possible in
conjunction with the strongest updrafts. While some stronger gusts
cannot be entirely ruled out, convection is expected to generally
remain disorganized through 12Z Monday, with the cold front not
expected to move through the region until later in the day Monday. 

...Southern Plains into the TN Valley...
Weak convection is likely to be ongoing from southern OK/north TX
eastward into parts of TN/KY at the start of the period. Some
lightning activity will be possible for a few hours this morning
before this convection weakens by afternoon. 

Periodic bouts of weak convection may be capable of a few lightning
strikes across mainly the eastern part of the FL Peninsula today,
though most showers will struggle to deepen due to the presence of
dry air aloft and lack of large-scale ascent across the region. 

...Western CO/Northwest NM...
As the mid/upper-level trough deepens over the West, gradually
increasing moisture and instability may support convection capable
of sporadic lightning activity across portions of northwest
NM/western CO this evening.

..Dean.. 11/22/2020

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