SPC Sep 14, 2018 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0258 PM CDT Fri Sep 14 2018

Valid 142000Z - 151200Z


A risk for a few tornadoes continues this afternoon across parts of
eastern North Carolina, and into tonight, mainly near southeastern
North Carolina coastal areas.

No change was made to the previous outlook.

..Smith.. 09/14/2018

.PREV DISCUSSION... /ISSUED 1115 AM CDT Fri Sep 14 2018/

Much of the nation to the east of the southern Rockies will remain
under the influence of a broad subtropical ridge through this
period.  Models indicate that there will be some amplification of
short wave ridging on its northwestern periphery, across parts of
the northern U.S. Rockies through the central Canadian/U.S. border
area, downstream of a significant short wave impulse digging into
amplified larger-scale troughing across the eastern Pacific/Pacific
coast.  Within the easterlies, to the south of the subtropical ridge
axis, Hurricane Florence is forecast to continue a very slow
southwestward migration across parts of southeastern North Carolina
into northeastern South Carolina.  A much weaker wave is expected to
gradually shift westward inland of the Texas/northeast Mexico Gulf
coast, into the lower Rio Grande Valley.

...Southern Mid Atlantic coast...
Given the motion of Florence with respect to the coast, boundary
layer instability supportive of continuing potential for low-level
mesocyclones with a risk for tornadoes appears likely to remain
confined roughly to its outer northeast quadrant.  This may mostly
continue to be associated with stronger convective bands pivoting
off the Atlantic into the North Carolina coastal plain.  This risk
appears maximized roughly near the periphery of the 40-50+ kt flow
around the 850 mb level, which will gradually shift southwestward
and may begin to shrink.  By late this evening into the overnight
hours, the primary lingering risk area may become more focused near
southeastern North Carolina coastal areas.

...Northern Minnesota and adjacent areas...
On the southernmost fringe of the westerlies (near the northwestern
periphery of the mid/upper ridge), models suggest that modest
destabilization, associated with moisture return above a northward
advancing frontal zone, may become sufficient for scattered vigorous
thunderstorm development tonight.  This appears most likely to
initiate in the 03-06Z time frame, aided by ascent associated with
low-level warm advection accompanying an 850 mb jet strengthening to
30+ kt.  On the northern periphery of warmer and more strongly
capping elevated mixed-layer air, the environment may become
conducive to convection accompanied by a risk for marginally severe
hail, particularly with initial development.

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