SPC AC 161919
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0119 PM CST Fri Nov 16 2018
Valid 162000Z - 171200Z
...NO THUNDERSTORM AREAS FORECAST...
No thunderstorms are forecast across the U.S. through tonight.
No change has been made to the previous outlook.
.PREV DISCUSSION... /ISSUED 1005 AM CST Fri Nov 16 2018/
Downstream of blocking within the mid-latitude westerlies over the
eastern Pacific, mid/upper flow across much of the U.S., while not
particularly amplified, appears likely to remain broadly confluent
Strongest mid-level height falls, associated with a pair of vigorous
short wave perturbations within this regime, are in the process of
spreading from southeastern Canada and the Northeast toward the
northwestern Atlantic. As this continues, an associated deepening
surface cyclone is forecast to migrate northeast of Cape Cod into
areas near/east of the Canadian Maritimes. A cold front trailing
from this feature has already advanced well south/east of the Gulf
and Atlantic coasts, including the Florida Straits.
In the wake of the front, cold surface ridging remains a prominent
influence across much of the Gulf of Mexico and Gulf Coast region.
While the center of this ridge may shift from the north central Gulf
coast into the vicinity of the central Appalachians by early
Saturday, a significant reinforcing cold intrusion is expected to
nose southeastward to the lee of the northern Rockies.
In response to these developments, generally stable conditions will
prevail across the U.S., with negligible (less than 10 percent) risk
for thunderstorm activity.
...Northern New England coast...
Models do suggest that strong differential thermal advection and
forcing for ascent at mid-levels may contribute to a corridor of
weak destabilization near coastal Downeast Maine early this
afternoon. Forecast soundings indicate that moist parcels
contributing to weak CAPE will be based near/above 700 mb, where
thermal profiles will generally be entirely below freezing, and the
risk for charge separation supportive of lightning appears
...Northern Intermountain region/Rockies...
Beneath strong mid-level cooling, insolation may contribute to weak
boundary layer destabilization across the mountains of central Idaho
and Wyoming through the Black Hills vicinity by late this afternoon.
This may support scattered low-topped convective development, but
forecast soundings suggest that the potential for charge separation
supportive of lightning is negligible.
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