SPC AC 101936
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0136 PM CST Fri Nov 10 2017
Valid 102000Z - 111200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for severe storms appears negligible through tonight.
...20Z Outlook Update...
On the southern periphery of expansive cold surface ridging now
centered over the upper Great Lakes region, an influx of cooler and
drier surface-based air is ongoing across the peninsula. Models
suggest that this may begin to weaken by late tonight, as mid-level
heights slowly rise across much of the Southeast, to the south of
the retreating mid-latitude westerlies. On the stalling leading
edge of the associated broad near surface baroclinic zone, an area
of sustained low-level convergence has maintained convective
development near coastal areas to the north of Palm Beach.
Recently, at least one short-lived intensification of activity has
been strong enough to result in lightning production, but relatively
warm and dry air through a deep mid/upper tropospheric layer
(evident in morning soundings) is tending to suppress convection,
and may continue to do so, given the lack of mid/upper forcing for
ascent, particularly inland of the immediate coast.
As a deamplifying upper trough progresses inland of the Oregon coast
this afternoon, any appreciable potential for thunderstorm activity
seems likely to diminish to the west of the Cascades. While an
isolated/brief thunderstorm may not be completely out of the
question this afternoon and evening, both west of the Cascades and
areas eastward into the intermountain region, given the lack of
activity to this point, lingering uncertainties concerning both
development and coverage seem too large to maintain 10 percent
.PREV DISCUSSION... /ISSUED 0953 AM CST Fri Nov 10 2017/
Offshore convergence appears maximized east of Martin county per
visible satellite imagery. 12Z CAMs are highly consistent in
simulating isolated convection developing to the southwest within
this confluence band. Although mid-level lapse rates will be weak
(around 6 C/km), a brief thunderstorm is possible in the early
evening centered on Palm Beach county.
Shortwave trough off the OR coast will progress east over the
Northwest today. Associated forcing for ascent, steep lapse rates,
and scant buoyancy should yield a risk of very isolated lightning
strikes mainly across southern OR.
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