SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1230 PM CDT Sun Oct 25 2020

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

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

...Synopsis...
Amplified, large-scale eastern Pacific mid/upper ridging may become
suppressed, as a vigorous short wave impulse progresses around its
crest, from the Gulf of Alaska vicinity through southern Yukon. 
However, models suggest that an embedded high center to the south
will generally maintain strength to the west of the  California
coast through this period.  

In response to these developments, it appears that a significant
short wave trough, initially sharply digging to the lee of the
ridge, will contribute to the evolution of a deepening mid-level
low, near the base of amplifying larger-scale troughing to the
southeast of the high center.  The ECENS and NCEP SREF are in good
agreement that this will take place across southern Arizona,
generally Monday evening through daybreak Tuesday.

Downstream, mid/upper ridging likely will gradually build across
parts of the southern Great Plains and much of the Gulf Coast
through South Atlantic Coast states.

Along the southeastern periphery of this ridging, extending into the
subtropical western Atlantic, Tropical Storm Zeta is forecast to
migrate from the western Caribbean into the southern Gulf of Mexico,
near the northern Yucatan Peninsula vicinity.  As it does, models
indicate that a broad plume of tropical moisture will overspread
much of the Gulf of Mexico, and portions of the southern Florida
Peninsula, to the south of remnant frontal zone advancing away from
the Atlantic Seaboard.

At the same time, seasonably moist air also is expected to continue
advecting in a narrow plume around the northwestern periphery of the
ridging, from the southern Great Plains through the lower Ohio
Valley.  But models indicate that this will occur above a
reinforcing intrusion of cold air overspreading the Upper Midwest,
Great Lakes region and Ohio Valley, while also continuing to dam
southward to the lee of the southern Rockies, toward the Rio Grande
Valley. 

Damming of more modestly cool air, associated with a preceding cold
intrusion, appears likely to proceed to the lee of the southern
Appalachian.  And, aside from the southern Florida Peninsula,
generally stable boundary-layer conditions are likely to prevail
east of the Rockies, as well as across much of the West.

...Florida...
Mid/upper support likely will be negligible/weak, but scattered,
mostly diurnal thunderstorm activity appears possible Monday across
southern into central portions of the Florida Peninsula.

...Southern Great Plains into middle Mississippi Valley...
Weak boundary-layer destabilization may be possible south of the
leading edge of the reinforcing cold front, particularly across the
Texas coastal plain.  However, mid-level inhibition is expected to
confine thunderstorm development to the vicinity of the mid-level
baroclinic zone remaining quasi-stationary to the northwest.

Scattered thunderstorm development may be ongoing early Monday,
aided by frontogenetic forcing, and perhaps forcing in the right
entrance region of a mid/upper jet forecast to shift from the
southern Great Plains Red River Valley vicinity through the Ozark
Plateau during the day Monday.

East of the evolving Southwestern mid-level low, increasing forcing
for ascent may contribute to another round of thunderstorm
development across parts of the Texas South Plains and Big Country
into Red River Valley Monday night.

..Kerr.. 10/25/2020

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