SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 PM CDT Sat Jun 11 2022
Valid 112000Z - 121200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
QUAD-STATE AREA OF SOUTHEASTERN NEBRASKA/SOUTHWESTERN
IOWA/NORTHEASTERN KANSAS/NORTHWESTERN MISSOURI...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEASTERN
MONTANA EAST-SOUTHEASTWARD INTO CENTRAL SOUTH DAKOTA...
...SUMMARY...
A few clusters of strong to severe thunderstorms are expected to
develop from the northern Rockies into the middle and lower Missouri
Valley this afternoon and tonight. Damaging winds and hail will be
most likely. An isolated tornado is possible over the middle
Missouri Valley and vicinity.
...Discussion...
Few substantive changes are being implemented to the outlook in this
update, as prior reasoning continues to adequately reflect
expectations regarding convective evolution/severe risk this
afternoon and tonight.
The primary adjustment to the areal risk depiction is being made
over the eastern Missouri vicinity, where an eastward expansion in
both SLGT and MRGL risk areas is being included. Continued
heating/destabilization is forecast across this area, which may
support southeastward-moving storms emanating from Iowa to affect
areas as far east as the Mississippi Valley this evening.
Otherwise, the existing outlook remains aligned with current
thinking.
..Goss.. 06/11/2022
.PREV DISCUSSION... /ISSUED 1125 AM CDT Sat Jun 11 2022/
...IA/NE/MO/KS...
Have upgraded portions of the Slight Risk area to Enhanced (Level 3
of 5) Risk with this outlook based on increasing confidence in a
corridor of severe hail (possibly significant) and wind developing
late this afternoon/early evening and moving south tonight.
Daytime heating of a very moist (upper 60s/lower 70s surface dew
points) air mass will contribute to strong instability across the
region by afternoon with MLCAPE values at or above 3000 J/kg from
southeast NE south across eastern KS/western MO. Combined with
strong mid/upper-level northwest flow on the periphery of an
expansive southwest U.S. upper high, a very favorable environment
for supercells should be in place by late afternoon. Expect
initiation by late afternoon or early evening across eastern
NE/western IA in the vicinity of a southward-moving surface
boundary, with storms moving generally south tonight. Forecast
soundings support a risk for very large hail during the first few
hours after initiation, with damaging winds becoming increasingly
likely as storms develop into a cluster/bowing mode with time. Some
tornado risk will exist given forecast curved low-level hodograph
structure, especially across the Enhanced Risk area.
...MT/SD...
Strong westerly flow aloft will reside across the northern Plains as
a weak cold front moves slowly south across MT. Pockets of daytime
heating will result in afternoon temperatures in the 80s from
southern MT into SD, with dewpoints averaging in the upper 40s and
50s. 12z guidance is in agreement that scattered thunderstorms will
form over the mountains of western MT and develop/move eastward
along the front during the afternoon/evening. Forecast soundings
suggest only marginal CAPE will develop, but given the strong winds
aloft and considerable vertical shear, a few supercell storms are
expected capable of large hail and damaging wind gusts. These storms
may be rather isolated, but may persist through much of the evening
and track quickly eastward into western/central SD.
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