SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0233 PM CDT Sun Oct 25 2020

Valid 252000Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not expected through tonight.

...20Z Outlook Update...
Some adjustments were made to the categorical/10 percent probability
of thunderstorms lines,  mostly to account for latest trends
concerning destabilization evident in observational data and a
general consensus of the various latest model output.

Across the Carolinas, a categorical risk for thunderstorms is being
maintained, but probabilities may not be much more than the minimum
10 percent threshold.  Stronger forcing for ascent associated with
low amplitude troughing is in the process of shifting
north-northeast of coastal areas.  General subsidence in its wake
has already overspread much of South Carolina, but insolation within
a residually moist air mass, south of cool air currently nosing
southward to the lee of the southern Appalachians, has supported
weak boundary-layer destabilization.  This is contributing to some
deepening convective development, particularly near Orangeburg SC as
of 1930Z.  It might not be out of the question that this activity
could still briefly intensify into a weak thunderstorm or two late
this afternoon.

..Kerr.. 10/25/2020

.PREV DISCUSSION... /ISSUED 1100 AM CDT Sun Oct 25 2020/

...Synopsis...
A weak midlevel trough will move east-northeastward over the
Carolinas today, and an associated surface cold front will move
southward across the Carolinas in its wake.  There will be a window
of opportunity for isolated thunderstorms today in the zone of
ascent across eastern NC, and where surface heating/destabilization
will be greater along the front into central SC (prior to the onset
of subsidence late today).  Farther south, the threat for occasional
thunderstorms will persist across south FL within a tropical
moisture plume (PW values in excess of 2.3") that extends
north-northeastward from tropical storm Zeta in the western
Caribbean Sea.

Downstream from an amplified northeast Pacific ridge, and midlevel
trough will continue to dig southward over the Great Basin.  A
confluent northern stream will help maintain a large/cold surface
high immediately east of the Rockies, with the consolidated
baroclinic zone on the leading edge of the cold air mass expected to
extend from southwest TX to southeast OK by the end of the period. 
Isolated thunderstorms will be possible later this afternoon into
tonight in the vicinity of the Four Corners in the zone of ascent of
ascent preceding the Great Basin trough, and in advance of an
ejecting southern-stream now just off the southern CA coast. 
Farther east, elevated thunderstorm development is expected the last
3-6 hours of the forecast period in response to strengthening warm
advection and destabilization atop the shallow cold air mass across
northwest TX and OK from 06-12z.

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