SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1228 PM CDT Sat Oct 24 2020

Valid 251200Z - 261200Z


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

Mid/upper ridging appears likely to remain highly amplified across
the eastern Pacific through this forecast period.  Models indicate
that there may be some northeastward redevelopment of a prominent
embedded high across the mid-latitudes, and the larger-scale ridging
might take on more of a positive tilt, as a short wave trough is
forced northeastward around its northwestern periphery, ahead of a
mid-level low near the Aleutians.  

As this occurs, a vigorous downstream short wave impulse is forecast
to sharply dig to the lee of the ridging, accompanied by
larger-scale upper trough amplification along a positively tilted
axis across the Intermountain West and Rockies.  This may include
the gradual evolution of an embedded mid-level low across the
southern Great Basin by the end of the period.

At the same time, models indicate that a short wave trough emerging
from the Arctic latitudes will continue digging across and southeast
of Saskatchewan/Manitoba.  Downstream, of the Great Basin low, this
will contribute to an increasing confluent mid-level regime to the
lee of the northern Rockies, beneath which cold surface ridging is
forecast to build and dam southward through much of the high plains
by daybreak Monday.  This will reinforce a cold front which has
already advanced through much of the Great Plains, Mississippi and
Ohio Valleys, and is in the process of advancing across the northern
Atlantic Seaboard.

A relatively moist air mass prevails along and south of the lead
frontal zone across the northwestern Gulf of Mexico and Gulf coast
vicinity, and more so across parts of the Southeast, ahead of weak
mid-level troughing now progressing eastward across the eastern Gulf
States.  Tropically moist conditions are now confined to parts of
the southeastern Gulf of Mexico and the Caribbean, northward into
the Florida Straits vicinity,

The weak mid-level troughing may be in the process of accelerating
northeastward, but generally to the lee of the southern
Appalachians, and progressing across/along south Atlantic coastal
areas by 12Z Sunday.  Although north-northeastward advection of the
tropical moisture will take place well offshore, low/mid-level
moisture near the Carolina coast may contribute to thermodynamic
profiles supportive of weak thunderstorm activity (despite weak
lapse rates), aided by the large-scale forcing for ascent.

...Southern Great Plains...
The leading edge of the low-level cold intrusion likely will
progress well south of the colder air aloft associated with the
evolving mid/upper troughing,  However, moistening on southerly
low-level flow, above the cold front, may support weak CAPE and
scattered thunderstorm activity aided by warm advection, focused
mainly near the mid-level baroclinic zone (where inhibition will
become weaker) by late Sunday night.

...Southern Great Basin/Plateau...
Mid-level cooling and forcing for ascent ahead of the digging short
wave trough may contribute to weak destabilization supportive of
scattered thunderstorm activity Sunday afternoon through Sunday

..Kerr.. 10/24/2020

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