Severe Storm Outlook Narrative (AC)
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949
ACUS48 KWNS 300853
SWOD48
SPC AC 300852

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0352 AM CDT Thu Mar 30 2017

Valid 021200Z - 071200Z

...DISCUSSION...
A series of short wave perturbations emanating from a strong
mid/upper jet over the mid-latitude Pacific have been contributing
to periodic significant surface cyclogenesis, and areas of
strong/severe thunderstorm activity, to the east of the Rockies for
the past week or so.  This general regime may persist at least into
the middle to latter portion of next week, when models suggest that
the jet may begin to nose inland across the Pacific coast.

Interaction/phasing of remnant impulses associated with one of these
perturbations, with a perturbation within the subtropical
westerlies, may contribute to surface cyclogenesis across parts of
the lower Rio Grande Valley through portions of the lower
Mississippi Valley by late this weekend.  This could be accompanied
by considerable warm sector low-level moistening off the Gulf of
Mexico, and associated destabilization supportive of severe weather
potential across parts of the Gulf states and Southeast, Sunday into
Monday.  Given this possibility, and for the sake of consistency, 15
percent severe probabilities will be maintained across parts of
eastern Texas into the lower Mississippi Valley for Sunday/Sunday
night.  The evolution of one or more large convective clusters
appears possible, however guidance may be increasingly suggestive
that the more prominent convection could tend to evolve offshore,
across the northern Gulf of Mexico, and possibly impact convective
potential inland.  This increasing uncertainty carries over into
Monday, and precludes delineating 15 percent severe probabilities
farther east, across the eastern Gulf/South Atlantic coast states.

Thereafter, latest guidance suggests that broad and deep surface
cyclogenesis is possible to the east of the Rockies by the middle of
next week.  The magnitude of this wave appears supportive of at
least some risk for considerable severe weather potential that could
impact portions of the Plains into the Mississippi Valley next
Tuesday/Wednesday, and portions of the Southeast, and perhaps Mid
Atlantic, by 12z Friday April 7th.  However, too many uncertainties
exist, both on the larger and smaller-scale, to allow a forecast of
15 percent probabilities at this time.

..Kerr.. 03/30/2017



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