Tornadoes and Flash Flooding in Missouri, May 26 to 28, 2021

Area Forecast Discussion
National Weather Service Springfield MO
1135 PM CDT Wed May 26 2021

.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM CDT Wed May 26 2021

A few isolated showers with some rumbles of thunder over mainly
the eastern CWA into this evening. Good instability with SBCAPE
around 3,000 J/kg, but shear is very weak so no severe weather is
expected. Can't completely rule out a stronger storm or two,
though.

Attention is on Thursday into Thursday night when severe storms
are possible. There are several key small scale features that
need to be resolved before confidence can increase.

An MCS is expected across northern MO, but exact placement is in
question. Models depict an outflow boundary moving south from the
MCS, but vary in how far south to bring it and how much
convective development will occur as a result. Models also differ
in developing convection elsewhere in the morning and in the
extent of that convection if it occurs. All these uncertainties
will play a major role in afternoon and evening convection and
severe weather chances.

It is very challenging to get specific in this scenario. The best
bet at this point is that MCS outflow will make it into at least
the northern CWA in the late morning and early afternoon. Severe
storms will be possible along the boundary with a large hail and
damaging wind threat. Prefer a mostly dry solution elsewhere in
the morning and early afternoon, but it is possible that
convection will develop.

Some isolated to scattered severe convection will be possible in
the mid to late afternoon ahead of a cold front moving in from the
northwest. If morning convection does not occur, instability will
build with SBCAPE of 2,000-3,500 J/kg and deep layer shear of
30-40 kts. If that morning convection does develop and becomes
widespread, then depending on timing and level of instability it
could be severe with large hail and damaging winds or it could
suppress severe convection for the most part. As the front moves
through in the evening and early overnight, expect convection
along the front. Depending on earlier convection and instability,
there could be widespread severe weather with the front or if
instability is limited the threat would be reduced.

Confidence in the wind threat is good, but how widespread that
that is is less certain. Seeing potential for winds in excess of
70 mph in convection along the front or with any upscale growth
that can occur. Aside from that convection, 60 mph winds are
possible with any severe storms.

Confidence in the threat for 1" hail is good with all stronger
convection. However, if enough instability can build and
supercells can develop, very large hail is possible over the
western CWA. The very large hail threat is very dependent on
several other factors so confidence is limited.

Flash flooding will also be a concern where convection trains.
PWATs will be 1.5-1.8" and potentially substantial instability
may allow for very heavy rainfall rates. There is certainly
potential for training convection, but where and how much are
unknown at this time.

The tornado threat is the most conditional and lowest probability
threat for this event. Even if greater instability can develop
and supercells develop ahead of the front, shear profiles with SW
low level winds are not very supportive of tornadoes unless ideal
boundary interactions occur. This is possible, but are a low
probability event. Later in the evening, some isolated QLCS
tornadoes are possible, but shear is borderline for this scenario
and shear vectors are to the east so bowing segments to the east
would be most favored. This threat is uncertain but low overall.

Convection will exit the southeastern CWA by late Thursday night.

.LONG TERM...(Friday through Wednesday)
Issued at 300 PM CDT Wed May 26 2021

Friday through Sunday looks quiet with dry conditions and highs in
the mid 60s to mid 70s. A more active period is possible as early
as Monday, but more likely from Tuesday on. Could see some heavy
rain potential at times next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1129 PM CDT Wed May 26 2021

High cirrus will spread over the region overnight but will have
negligible impacts to aviation. By morning, showers and
thunderstorms will begin to impact the region with the potential
for severe storms bu the afternoon and evening. Where storms occur
MVFR to IFR flight conditions and strong wind shear will occur.
Otherwise, Visibilities will be MVFR in rain.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

SHORT TERM...Titus
LONG TERM...Titus
AVIATION...Hatch

Hazardous Weather Outlook
National Weather Service Springfield MO
1049 PM CDT Wed May 26 2021

KSZ073-097-101-MOZ055>058-066>071-077>083-088>098-101>106-280400-
Bourbon-Crawford-Cherokee-Benton-Morgan-Miller-Maries-Vernon-
St. Clair-Hickory-Camden-Pulaski-Phelps-Barton-Cedar-Polk-Dallas-
Laclede-Texas-Dent-Jasper-Dade-Greene-Webster-Wright-Newton-
Lawrence-Christian-Douglas-Howell-Shannon-McDonald-Barry-Stone-
Taney-Ozark-Oregon-
1049 PM CDT Wed May 26 2021

This Hazardous Weather Outlook is for portions of the Missouri
Ozarks and extreme southeast Kansas.

.DAY ONE...Tonight.

Weather hazards expected...

  Limited lightning risk.

DISCUSSION...

Showers and thunderstorms will begin to spread into southeastern
Kansas and far western Missouri during the overnight.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

An episode of severe thunderstorms is expected on Thursday into
Thursday night. Details remain uncertain due to unknowns with
potential for morning showers and thunderstorms. In general,
damaging wind gusts may be common with some of the most intense
thunderstorms. Large hail will also be possible, especially over
southeast Kansas and western Missouri. With high rainfall rates
expected, there will also be a risk for flash flooding. Check
back
for updates.

.SPOTTER INFORMATION STATEMENT...

  Spotter activation will not be needed through tonight.

&&

More detailed information can be accessed at:
http://www.weather.gov/sgf/sitrep

This product in graphical format...along with other weather...
hydrological and climate information...at
http://www.weather.gov/sgf

Hatch