Severe Storm Outlook Narrative (AC)
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ACUS03 KWNS 250744
SWODY3
SPC AC 250743

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0243 AM CDT Thu May 25 2017

Valid 271200Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
OF THE SOUTHERN PLAINS INTO THE MID MISSISSIPPI VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
THE SOUTHERN/CENTRAL PLAINS EAST TO THE MID-ATLANTIC REGION...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED AND SLIGHT RISKS FROM THE CENTRAL HIGH PLAINS TO THE
MID-ATLANTIC COAST...

...SUMMARY...
Widespread severe thunderstorms are expected Saturday and Saturday
night from portions of the central and southern Plains east to the
mid-Atlantic coast.

A widespread and potentially significant severe weather event
appears likely Saturday and Saturday night from the central and
southern Plains east to the mid-Atlantic region.

...Synopsis...
A positive-tilt upper-level trough will extend from a closed low
over Manitoba across the northern Plains and into the Great Basin,
with moderately strong zonal flow and an expansive EML from the
central Rockies east to the mid-Atlantic coast. By late Saturday
afternoon, a surface frontal boundary will extend from the southern
High Plains east across Oklahoma to a surface low over the western
Ohio Valley, with a warm front extending east to the mid-Atlantic
coast. A dryline will extend from central Oklahoma into southwest
Texas. Rich Gulf moisture will be in place along and south of the
front and east of the dryline, contributing to strong to extreme
instability.

...Central/southern Plains east to the middle Mississippi Valley...
An MCS with some severe potential may be ongoing at 12z Saturday in
the Kansas/Nebraska border region, and diurnal intensification of
this complex is possible with a severe threat extending east across
the lower Missouri Valley.

Additional potentially explosive thunderstorm development is
anticipated in the vicinity of the southward sagging cold front from
central/eastern Oklahoma northeast into the western Ohio Valley
Saturday afternoon, and along the dryline from central Oklahoma
southwest into north Texas. More isolated development is possible
farther southwest towards the Edwards Plateau region. GFS and ECMWF
forecast soundings reveal an environment characterized by strong to
extreme surface-based instability and 40-50 kts of deep-layer shear,
and storms should rapidly become severe with all severe hazards
possible, including significant severe hail and wind. Tornado
potential will exist, and likely be influenced by boundary/storm
interactions. Upscale growth into multiple clusters appears probable
late Saturday and Saturday night as a 40-kt southwesterly low-level
jet develops with a continued severe risk.

...Ohio/Tennessee Valley Region east to the mid-Atlantic...
Moderate/pockets of strong instability will exist Saturday
afternoon, and scattered severe thunderstorms are expected to
develop with diurnal heating, potentially aided by ascent with
convectively enhanced low-amplitude impulses within the westerly
mid-level flow. Effective shear ranging from 35-45 kts and steep
mid-level lapse rates will promote a risk for large hail, damaging
winds, and an isolated tornado.  Storms may merge into clusters with
time with a continued severe risk Saturday evening.

..Bunting.. 05/25/2017

$$



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