Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS02 KWNS 220630
SPC AC 220629
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 AM CST Wed Feb 22 2017
Valid 231200Z - 241200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
Isolated thunderstorms are forecast across portions of the Midwest
primarily after sunset Thursday night into early Friday morning. A
few storms are possible along the east coast of Florida.
A strong belt of cyclonically curved mid-level flow located within
the base of a larger western U.S. trough will overspread the central
Great Plains during the day and into the lower MO Valley overnight
Thursday. Models are showing a mid-level vorticity maximum moving
from the central Rockies to the NE/IA vicinity by daybreak Friday.
In the low levels, a surface low is forecast to develop from the
central High Plains northeastward into south-central IA with an
attendant warm frontal zone located east-northeastward from the low
across the southern Great Lakes. A cold front will push
southeastward across KS into OK and western MO.
...northern MO and southern IA into northern portions of IL...
Low-level moisture --characterized by 50s degrees F dewpoints-- over
the lower MS Valley and Mid South regions will stream northward in
response to the developing central U.S. cyclone. A strong cap will
likely limit convective development to the south of the warm front
during the day. An intensifying southwesterly low level jet over
the lower MO Valley will lead to increasing isentropic ascent across
this region, especially beginning by early Thursday evening. Model
guidance suggests isolated storms will develop in the vicinity of
the warm front after dark. Despite steep mid-level lapse rates
yielding 500-1000 J/kg MUCAPE and strong effective shear (50-kt),
confidence in the development/placement of a few potentially strong
updrafts remains nebulous. As a result, will continue to defer the
possible inclusion of low-severe probabilities until greater
confidence can be attained.