SPC 0600Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1142 PM CDT Tue Oct 06 2020

Valid 081200Z - 091200Z


Aside from low probabilities for thunderstorms inland of the
northwestern Gulf coast, the risk for thunderstorms appears
negligible across much of the rest of the nation Thursday through
Thursday night.

Downstream of a strong, zonal jet propagating across the northern
mid-latitude Pacific, a low-amplitude short wave trough may progress
across the Canadian Prairies during this period, within the main
belt of branching flow.  Otherwise, it appears that this regime will
remain broadly anticyclonic and confluent across much of southern
Canada and the northern tier of the U.S., into large-scale
negatively tilted troughing gradually shifting east of the north
Atlantic coast.

In a separate stream to the south, broad troughing may begin to
progress inland of the California coast, but an embedded closed low
probably will remain well offshore.  As this occurs, weak troughing
evolving in somewhat lower latitudes, across the southern Great
Plains/lower Rio Grande Valley, may begin progressing slowly

At the same time, at least a couple of tropical perturbations will
continue to slowly migrate within the low/mid-level easterlies, on
the southern and southwestern periphery of lingering mid-level
ridging across the subtropical western Atlantic into parts of the
Southeast.  This will include Hurricane Delta, which is forecast to
migrate northwestward, then northward, into the northwestern Gulf of
Mexico Thursday through Thursday night.

Preceding Delta's approach of the northwestern Gulf coast, beneath
the confluent mid-level flow in the wake of the negatively tilted
trough in the westerlies, the center of a fairly expansive area of
cold surface ridging is forecast to shift from the Upper Midwest
into the Mid Atlantic Coast region.  It appears that this probably
will reinforce a relatively dry/potentially cold boundary-layer air
mass as far south as the Gulf Coastal plain by 12Z Thursday.  There
may be little modification through Thursday night, except perhaps
across parts of the northwestern Gulf coast into parts of the
southern Great Plains, where at least a weak southerly return flow
may commence.

...Gulf States...
It still appears that moisture return will initially occur above a
stable boundary layer.  However, this may contribute to weak/modest
CAPE in lower to mid-levels.  In the presence of large-scale ascent,
aided by forcing in the right entrance region of an anticyclonic
high-level jet, this is expected to support increasing precipitation
and embedded convection.  With mid/upper levels moistening,
relatively warm and characterized by weak lapse rates, it remains
unclear whether thermodynamic profiles will become conducive to
convection capable of producing lightning.  However, it may not be
out of the question.

...Upper Great Lakes region...
Models indicate a zone of steepening lower/mid tropospheric lapse
rates and strengthening lift associated with warm advection, with
perhaps sufficient elevated moistening to support weak thunderstorm
activity late Thursday night across the western upper Michigan/Lake
Superior vicinity.

..Kerr.. 10/07/2020

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