SPC 0730Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0140 AM CDT Tue Oct 06 2020

Valid 081200Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears negligible across much of the
nation Thursday through Thursday night.

...Discussion...
A strong, zonal mid/upper jet appears likely to continue gradually
propagating across the northern mid-latitude Pacific, with its exit
region perhaps approaching British Columbia/Pacific Northwest
coastal areas toward the end of the period.  Within one belt of
branching downstream flow, broad mid-level ridging is forecast to
gradually shift eastward across the Canadian Prairies and adjacent
international border area, while similar amplitude downstream
troughing progresses across the northern Atlantic coast.

In another branch, a short wave trough and compact embedded
mid-level low may approach northern California coastal areas, with
broad downstream ridging across the Great Basin and Rockies into
Upper Midwest remaining largely in phase with the ridging to the 
north.

In lower latitudes, mid/upper subtropical ridging likely will be
maintained across the western Atlantic into the Gulf of Mexico and
adjacent portions of the Southeast.  While weak troughing may begin
progressing around its northwestern periphery, across the Rio Grande
Valley into Texas, a couple of tropical perturbations will continue
progressing within the lower-level easterlies on its
southern/southwestern periphery.  This will include Hurricane Delta,
which may gradually turn north/northeastward, toward the north
central Gulf coast, ahead of the mid/upper troughing.

At least some model output appears weaker with cold surface ridging
initially encompassing most areas across and east of the Mississippi
Valley, including much of the Gulf Coast states, at the outset of
the period.  However, this feature is forecast to be generally
maintained through the period, though with its center shifting from
the Middle Mississippi Valley vicinity into the Mid Atlantic.

Easterly/northeasterly low-level flow likely will maintain
relatively dry/potentially cool boundary-layer air across much of
the Gulf Coast states.  While there may be a substantive elevated
moisture influx ahead of Delta, accompanied by increasing
precipitation and embedded convection across much of Louisiana,
Mississippi and Alabama Thursday through Thursday night, warm and
moist mid-levels with weak lapse rates are expected to minimize the
risk for lightning.

..Kerr.. 10/06/2020

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