Severe Storm Outlook Narrative (AC)
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000
ACUS48 KWNS 250904
SWOD48
SPC AC 250903

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0403 AM CDT Tue Apr 25 2017

Valid 281200Z - 031200Z

...DISCUSSION...
Active severe-weather regime in store for days 4-6 from the southern
Plains into the lower Mississippi and Tennessee Valley regions, with
models trending similar regarding evolution of the upper pattern
during this period.

Friday (day 4)  - A lead shortwave trough will shift northeast
through the OH Valley during the day with upstream height rises from
the southern Plains into the TN Valley. Quasi-stationary front will
reside from the TN valley into northern TX with a dryline evolving
across west central or northwest TX where it will intersect the
front. Limited synoptic forcing for ascent and capping due to
eastward expansion of EML may limit thunderstorm initiation during
the day with best chance being at the intersection of dryline and
front over west-central or northwest TX. Large CAPE and strong
vertical shear would favor a conditional risk for supercells with
very large hail and a few tornadoes should such initiation occur.
Farther east thunderstorms including supercells are more probable
during the day near the warm front from the lower MS Valley into the
TN Valley where the cap should be weaker. Other more numerous storms
including supercells with large hail will occur overnight north of
warm front over OK in association with strengthening LLJ.

Saturday (day 5) - Current indications are the upper trough will
amplify over the southern Rockies and continue east through the
southern Plains accompanied by a strong cold front. Numerous severe
storms are expected to develop along this boundary and progress east
through TX and the lower MS Valley where the atmosphere will be
strongly unstable.

Sunday (Day 6) - As the trough and its associated cold front
progress eastward, the severe-storm threat will spread into the TN
Valley and southeast states where favorable vertical shear will
coexist with a moderately unstable warm sector downstream from an
ongoing MCS.

..Dial.. 04/25/2017


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