NOAA Storm Prediction Center

Convective Outlooks

Convective Outlooks
The convective outlooks serve as guidance to the local NWS forecast offices and are used by emergency managers, private sector meteorologists, media, and other weather customers concerned with public safety. Three separate risk areas (slight, moderate, and high) are used to describe the expected coverage and intensity for the categorical severe weather threat on days 1-3 along with severe weather probabilities for the potential threat.

Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1300Z Outlook
  
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 Forecast Discussion


000
ACUS01 KWNS 191226
SWODY1
SPC AC 191224

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0724 AM CDT Thu May 19 2022

Valid 191300Z - 201200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATER THIS
AFTERNOON INTO EARLY TONIGHT FOR NORTHERN IA...SOUTHEASTERN MN AND
WESTERN WI...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY FROM
SOUTHERN MO TO THE LOWER OH VALLEY AND THE CAROLINAS...

...SUMMARY...
Isolated very large hail, damaging winds, and a couple of tornadoes
will be possible later this afternoon into early tonight across
northern Iowa, southeastern Minnesota and western Wisconsin. 
Occasional large hail, damaging winds, and a couple of tornadoes may
also occur this afternoon from southern Missouri into southern
Illinois, with at least isolated large hail/damaging winds farther
east into the Carolinas.

...IA/MN/WI late this afternoon into tonight...
A deep midlevel trough will move generally eastward along the
international border from MT to MN by the end of the period. 
Downstream from the strengthening midlevel jet, initial lee
cyclogenesis this morning across southwest SD will develop eastward
to southern MN this evening and northwest WI tonight.  East of the
cyclone, a warm front will develop northward across IA/southern
MN/WI through the afternoon/evening.  The more probable area for
initial storm development late this afternoon/evening will be east
of the surface cyclone, along and north of the warm front in the
zone of stronger ascent/warm advection with gradually increasing
low-level moisture.  Other storms will likely form this evening
farther southwest along the trailing cold front.

Uncertainty in this outlook area is related to the remnant MCS and
well-developed MCV moving across northeast OK/southeast KS/southwest
MO, which has intercepted the richer (near 70 F) dewpoints along the
diffuse baroclinic zone straddling the KS/OK and MO/AR borders. 
This leaves residual low-mid 60s dewpoints across eastern KS and
southeastern NE to the north of the MCS, which is below the more
aggressive model forecasts of moisture return.  Thus, the low-level
moisture spreading into IA/MN/WI through the day is likely to be
somewhat marginal for a more substantial tornado threat, when also
considering the effects of afternoon mixing.  Steep lapse rates and
MLCAPE in excess of 2500 J/kg, as well as relatively long hodographs
with low-level clockwise turning, will support supercells capable of
producing very large hail initially.  Storms should tend to evolve
into clusters and line segments with more of a damaging wind threat
by late evening.  As previously discussed, the tornado threat will
depend on the degree of low-level moisture return, which at the
moment appears more supportive of a typical (5%) outlook area.

...Central/southern MO/IL through late evening...
A well-developed MCV from overnight convection is approaching
southwest MO, and will likely persist while continuing
east-northeastward through the day, in response to gradual backing
of midlevel flow related to upstream amplification of the trough
over the northern Rockies.  The MCV will track along a residual
baroclinic zone and corridor of 68-72 F boundary-layer dewpoints
with MLCAPE of 3000-4000 J/kg, which will support the potential for
continued latent heating and maintenance of the MCV through the day.
 Associated convection will likely undergo diurnal intensification
since the richer low-level moisture is already present in advance of
this system.  A couple of tornadoes, large hail, and damaging winds
will all be possible with embedded clusters/supercells coinciding
with MCV-related enhancements to the wind profiles. 

...KY/TN into the Carolinas through late afternoon/evening...
A midlevel shortwave trough is moving over the southern Appalachians
this morning.  As the low levels warm/moisten across the Carolinas
today, at least isolated thunderstorm development is expected in
advance of this trough.  Midlevel lapse rates of 7.5-8 C/km, MLCAPE
at or above 2000 J/kg and straight hodographs with 30-35 kt
effective bulk shear will support a mix of multicell clusters and
supercells capable of producing large hail and damaging winds,
mainly this afternoon/evening.  Farther west, storm development is a
bit less certain to the west of the Appalachians shortwave trough,
and well east of the MO MCV.  Daytime heating/mixing could support
isolated storm development across TN/KY this afternoon, and perhaps
a few storms this evening/early tonight in the warm advection zone
across northern KY/southern IN, east of the weakening MCV.

..Thompson/Leitman.. 05/19/2022

$$