SPC Apr 1, 2017 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0353 AM CDT Sat Apr 01 2017

Valid 041200Z - 091200Z

...DISCUSSION...
Medium-range model output continues to suggest that significant
amplification is possible within the upper flow across North America
during the middle to latter portion of next week, downstream of a
strong mid-latitude Pacific jet which is forecast to begin to shift
inland across the Pacific coast.  Within this regime, increased
phasing of a pair is significant short wave impulses (one turning
east of the southern U.S. Rockies and another digging southeast of
the Canadian Rockies) is expected to lead to large-scale upper
trough amplification over the eastern U.S. by late week.  This
appears likely to be accompanied by significant surface cyclogenesis
from the lee of the southern U.S. Rockies through the Ohio Valley
Tuesday/Wednesday, and to the lee of the central Appalachians into
northern Mid Atlantic Coastal areas Thursday/Friday.

These developments probably will contribute to support for at  least
some severe weather potential over a fairly broad area of the
central and eastern U.S., from the central Plains Tuesday into parts
of the lower Ohio Valley and Southeast Wednesday, and the Atlantic
Seaboard by Friday.  In the wake of a preceding cyclone, uncertain
moisture return tempers severe probabilities at this time from the
Plains into the Ohio Valley.

More substantive moisture return and potential for destabilization
is evident across parts of the southeast Wednesday into to Wednesday
night.  However, greatest confidence in a substantive organized
severe thunderstorm risk appears across the Mid Atlantic region on
Thursday, coinciding with most significant surface cyclone deepening
and strengthening of lower/mid tropospheric wind fields.  This may
include southerly 850 mb flow strengthening to 50-70 kt,
contributing to strong to extreme low-level shear supportive of
considerable thunderstorm wind damage potential, along with a risk
for tornadoes.

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