Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS01 KWNS 251932
SPC AC 251930
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 PM CDT Tue Apr 25 2017
Valid 252000Z - 261200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
OK INTO SOUTHEAST KS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL OK
INTO WESTERN MO...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL OK
Thunderstorms capable of large hail, damaging winds, and isolated
tornadoes are expected to develop across parts of northeast
Oklahoma, southeast Kansas, northwest Arkansas, and western Missouri
this evening into overnight hours.
...Central and northeast OK...Southeast KS...Southwest MO...
No changes were made to the previous outlook. Storms are expected to
initiate around 23-00Z along the cold front around Ponca City OK and
into southeastern KS, on the surface warm nose where CIN will be
eroded. Dewpoints continue to slowly rise, partly due to
evapotranspiration. Cooling aloft with the shortwave trough will
maintain steep lapse rates aloft, favoring vigorous updrafts and
hail. Hodographs will continue to lengthen, favoring supercells be
evening as the low-level jet backs to more southerly and increases
to around 50 kt by 03Z. Hail, wind and a tornado or two will be
possible. Additional activity is expected along the front by 03Z
extending southwestward into central OK, where large hail and wind
are expected, in addition to a brief tornado for any storms that can
remain along or south of the front.
.PREV DISCUSSION... /ISSUED 1126 AM CDT Tue Apr 25 2017/
The morning surface analysis shows relatively strong southerly
low-level winds over east TX/OK, helping to transport 60s dewpoints
northward today. While 12Z model solutions are likely too moist, it
appears that mid 60s dewpoints will advect/develop into eastern OK,
and lower 60s dewpoints into western MO and southeast KS by 00Z. A
fast-moving shortwave trough now over eastern NM is expected to
begin affecting OK/KS by late this afternoon (21-00Z), resulting in
scattered thunderstorm development along a weak surface boundary.
Forecast soundings around the time of initial development would
support relatively high-based supercells and/or bowing segments
capable of large hail and damaging winds. This activity will likely
spread east-northeastward into western MO this evening with a
continued severe threat.
The continued influx of low-level moisture will help to further
destabilize parts of eastern OK and southeast KS as storms build
slowly southward along the boundary. Most CAM solutions suggest
that an increasing capping inversion will limit how far south storms
can form. However, the southern-most storm/s will be in an area of
large CAPE, strengthening low-level shear profiles, and lower LCL
heights this evening. They could be intense with a risk of very
large hail and isolated tornadoes in the 00-04Z time period.