Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS01 KWNS 240044
SPC AC 240043
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0743 PM CDT Thu Mar 23 2017
Valid 240100Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
SURROUNDING AREAS OF THE PLAINS...
Thunderstorms may still be accompanied by some risk for severe hail
and wind across parts of the central and southern Plains this
Even with significant lower/mid tropospheric cyclogenesis underway
to the lee of the Colorado Rockies, and forecast to proceed through
the remainder of tonight, dry conditions across much of the central
and southern Plains has and likely will continue to considerably
temper convective potential. The lack of deep low-level moisture
return off the western Gulf of Mexico, and downward mixing of dry
lower/mid tropospheric air, has resulted in rather modest late
afternoon/early evening warm sector surface dew points ranging
mostly in the mid 40s to lower 50s F.
Still, steep mid-level lapse rates associated with warm elevated
mixed-layer air which has advected off the southern Rockies/Mexican
Plateau region has contributed to sufficient instability for
vigorous late afternoon storm development near the surface trough
axis across the high Plains, from the Texas Panhandle into
southwestern Nebraska. In the presence of strong shear near a 50-70
kt southwesterly 500 mb speed maximum nosing across the central high
Plains, strongest storms have produced severe hail and wind. It is
possible that this activity could linger into the 01-03Z time frame,
before weakening as the boundary layer cools and decouples.
Thereafter, it still seems possible that a zone of enhanced warm
advection on the nose of a strengthening southerly low-level jet
(50-70 kt at 850 mb) could maintain ongoing storms and support new
development across parts of north central through northeastern
Nebraska later this evening, with a continuing risk for severe hail.
It is also possible that the leading edge of lower/mid tropospheric
cooling spreading east of the Rockies through portions of the
southern high Plains this evening could become a focus for renewed
convective development accompanied by a continuing risk for strong
surface gusts. As this forcing spreads eastward into the lower
Plains, severe convective wind gust potential probably will diminish
as instability becomes insufficient to maintain vigorous convection.