Special Weather Statement, NWS Springfield, MO

Area Forecast Discussion
National Weather Service Springfield MO
411 PM CDT Wed Mar 17 2021

.MESOSCALE DISCUSSION...
Issued at 1131 AM CDT Wed Mar 17 2021

We continue to monitor the potential for severe storms and flooding
from this afternoon into this evening.

Water vapor imagery continues to depict upper level low pressure
churning east across central Oklahoma. At the surface, low pressure
is analyzed between Oklahoma City and Tulsa. A warm front extends
northeast from the low into northwest Arkansas, with this front then
jutting north into south-central Missouri from the Bull Shoals Lake
region to just north of West Plains. This front has become pseudo-
stationary over the past hour.

As we move through the afternoon and early evening, that surface low
will track east-northeast along that front through southern
Missouri. The frontal boundary may make a little more progress to
the north, with the I-44 corridor perhaps being the farthest north
the front makes it. New convective initiation is expected near and
south of the front in the 18-20Z window as strong height falls and
upper level diffluence overspread the warm sector. We then expect
the potential for scattered to numerous storms to persist into this
evening before ending from west to east. Current thinking is that
storms will exit the eastern Missouri Ozarks by around 9 PM.

With low 60s dew points advecting into southern Missouri and the
cooling mid-levels, MLCAPE values of 500 to 1200 J/kg seem
reasonable in the warm sector by later this afternoon and early
evening. Meanwhile, effective bulk shear values of 60-65 knots will
be in place. This will certainly be supportive of supercells,
especially where storm coverage can remain more scattered in nature.
The latest CAM models suggest the potential for arcing, loose bands
of scattered supercells with perhaps some small line-segments also
developing.

All modes of severe storms will remain possible, including the
potential for a few tornadoes. We are confident that the potential
for a tornado outbreak will remain to our southeast down across the
Lower Mississippi Valley. The 700 mb wind fields across southern
Missouri are on the weak side to support a higher tornado threat.
Even 850 mb wind magnitudes are a bit low, but will increase into
the 30 knot range late this afternoon across south-central Missouri.

With that being said, we will be looking at two general areas for
tornado potential later this afternoon and evening. The first will
be with any cells tracking northeast along the warm front. It should
be noted that Bunkers right-moving vectors will tend to be parallel
to the warm front. The second potential area for a few tornadoes
will be across south-central Missouri starting around 22Z as those
850 mb winds nudge upwards. This will result in effective storm
relative helicities in the 150 to 200 m2/s2 range.

Hail potential looks to be the main severe weather mode given the
expected supercellular nature and cooling mid-level temperatures.
Mid-level lapse rates in the 6.5 to 7 C/km range will be present
across western Missouri this afternoon as the cold-core of that
upper level low approaches. This will support a greater threat for
large hail across southwestern Missouri. This is backed well by
SSCRAM guidance with SPC also painting 30% hail probabilities. The
main hail size range would be quarters to half dollars, but we do
suspect that golf ball size hail will certainly be achievable given
the expected supercell storm mode.

The main damaging wind threat would then be with any line segments
that develop. Again, the lack of 700 mb wind magnitudes will not be
supportive of a widespread damaging wind event. However, locally
damaging wind gusts up to 70 mph will be achievable with line
segments containing rear-inflow jet structures or mesovortices.

Given the recent heavy rainfall (including what we saw overnight and
this morning), we continue to be concerned with localized flooding
potential. One piece of good news is that overall storm motions
today will be rather rapid (northeast around 40 knots). Thus, our
main concern for any flooding potential would be for any areas that
see multiple rounds of thunderstorms or brief cell training.

.SHORT TERM...(Tonight through Thursday)
Issued at 350 PM CDT Wed Mar 17 2021

For ongoing severe event, see mesoscale section above.

For tonight, cold air wrapping in behind the system will lead to
precip switching to snow, or perhaps a rain snow mix farther
south and east unto Thursday morning. With a TROWAL setup over
the far NW CWA, greater snowfall intensity is expected across the
northern of our SE Kansas counties which should be able to
overcome relatively warm ground temperatures. Have up to 1-2
inches of snowfall and a Winter Wx Advisory for Bourbon County,
KS. Elsewhere, many locations should see snow or a rain/snow mix,
but do not expect any significant locations, especially on road
surfaces.

As temperatures warm Thursday (only into the upper 30s to low
40s), precip will change to all rain. Precip will gradually
diminish through the day, ending before midnight Thursday night.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 350 PM CDT Wed Mar 17 2021

Thursday night through Saturday will be dry. Lows will be in the
upper 20s to mid 30s Thursday night and Friday night, then in the
mid 30s to low 40s Saturday night. Highs will warm from the low to
mid 50s Friday to the mid 60s Sunday.

A couple of additional systems may impact the region from early to
mid next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1238 PM CDT Wed Mar 17 2021

Expect showers and thunderstorms to develop within the next 1-2
hours. Strong to severe storms will be possible, with risks
primarily for large hail and damaging winds but an isolated
tornado cannot be ruled out. After thunderstorms exit the area
late this evening, a mix of rain and snow snow will move into the
area late tonight into Thursday morning. Relatively warm air and
ground temperatures will prevent accumulations at the TAF sites.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Flash Flood Watch through Thursday morning for MOZ055>058-
     066>071-077>083-088>092-094>098-105-106.

KS...Flash Flood Watch through Thursday morning for KSZ073-097-101.

     Winter Weather Advisory from midnight tonight to noon CDT
     Thursday for KSZ073.

&&

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

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