-- Discussion containing changed information from previous version are highlighted. --
536
FXUS63 KSGF 250510
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
1210 AM CDT Sat May 25 2024

.KEY MESSAGES...

- Strong to severe thunderstorms this evening. Hail to 2" in
  diameter and damaging wind gusts to 60 mph are the primary
  severe weather hazards.

- Enhanced to Moderate Risk for severe storms Saturday evening
  and overnight west of U.S. 65. Damaging winds to 75 mph and
  hail to two inches in diameter are the primary potential
  severe weather hazards. There is also a conditional risk for a
  few tornadoes.

- Slight Risk for severe storms again Sunday afternoon and
  evening with damaging winds and large hail the primary
  potential severe weather hazards.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 1234 PM CDT Fri May 24 2024

Synoptic Scale Pattern and Current Conditions:

Water vapor imagery depicts an upper level trough lifting
northeast across the Dakotas with a trough axis extending
southeast into the Corn Belt. Height falls with this feature are
confined to areas near and north of I-80 corridor.

At the surface, low pressure is analyzed across the eastern
Dakotas with a cold front trailing through central Iowa and
into southeastern Kansas and central Oklahoma.

Ahead of the front, the atmosphere has become very unstable with
MLCAPE values of 2500-3500 J/kg. Weak convective inhibition does
remain thanks to the presence of an elevated mixed layer. This
has prevented convective initiation up to this point. Visible
satellite imagery does indicate multiple bands of towering
cumulus in the vicinity of the front.

Deep layer shear is around 30 knots which will be supportive of
multicell clusters and perhaps a few supercells, if we can get
initiation. Low-level shear remains weak with 0-1 km storm
relative helicity values generally below 100 m2/s2.

Late this Afternoon and Tonight:

Forcing along the front will result in scattered thunderstorm
development with some storms expected to become severe. Storms
will initially develop between the I-49 and Highway 65 corridors
around mid-afternoon before gradually shifting southeast into
the remainder of the Ozarks late this afternoon and this evening
with the passing front.

As was mentioned above, we think the primary mode will be
convective clusters as deep layer shear remains around 30
knots. However, 12Z HREF 2-5 km updraft helicity plots do
indicate the presence of a few supercells.

Inspection of the large hail parameter reveals that hail to two
inches in diameter will be possible with any supercells.
Otherwise, hail to the size of half-dollars will be favored with
stronger multicells.

There will also be a damaging wind gust threat with these
storms, especially with storms that can grow upscale into
small line segments. DCAPE values of 1100-1300 J/kg and theta-e
differentials around 30K are supportive of damaging wind gusts
up to 60 mph.

The HREF localized probability-matched mean product indicates a
few pockets of 1.50-2.00" rainfall amounts across south-central
Missouri with max values of 2.00-2.50". Thus, the threat for
any flash flooding is low and very localized.

Late Tonight into Saturday:

This period looks quiet as we see weak height rises from later
tonight into Saturday morning. That cold front will stall out
and begin to lift back north as a warm front. Short term
ensembles have that front already reaching the Highway 54
corridor by 00Z on Sunday.

While there will be a very low-end chance for an afternoon
thunderstorm across southern Missouri (less than 20%), that
elevated mixed layer will become reestablished over the area.
This will likely cap off convective initiation during the day on
Saturday.

Short term ensembles show good agreement that high temperatures
will reach the lower to middle 80s on Saturday. Surface winds
will shift from the east to the southeast as that warm front
lifts north.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 333 PM CDT Fri May 24 2024

Short term ensembles are in good agreement that the warm front
will lift into northern Missouri as surface low pressure
deepens across western Kansas. This low is then forecast to
track across southern Kansas late Saturday night before swinging
northeast to the KC metro by 12Z on Sunday.

An upper level short wave trough will also eject northeast
through the central and southern Plains late Saturday night
with a mid- and upper-level jet streak emerging across Kansas
and Oklahoma. A strong 850 mb jet is forecast to develop and
initially punch into eastern Kansas before veering into western
Missouri by 12Z on Sunday.

Explosive thunderstorm development is expected from late
Saturday afternoon into Saturday evening across central Kansas.
These storms would initially be supercells given extreme
instability and strong deep layer shear. It remains unclear how
far south this initial supercell initiation will develop. There
are a few CAMs, including some MPAS runs, that develop
supercells as far south as the Oklahoma City metro. This will
have implications on convective timing and potential hazards,
especially across southern Missouri.

Convection that initiates across the central and possibly
southern Plains will then tend to grow upscale with time as
cold pools conglomerate. This will lead to a significant
damaging wind threat, especially across southeastern Kansas and
west-central Missouri.

At this time, here are two scenarios that seem most plausible:

Scenario 1 (more likely):

Supercells across central Kansas develop into a squall line
that accelerates eastward into eastern Kansas and west-central
Missouri. Timing is still in question, but the most likely
window looks as if it would be in the 03-12Z time frame. This
scenario is supported by several CAMs.

Widespread and damaging wind gusts up 75 mph will be favored
with this line of storms. Hail to the size of half dollars will
also be possible. The tornado threat will be confined to
portions of the line that are oriented more north to south,
which may tend to be along and north of the Highway 54 corridor.
CAMs indicate the southern extent of the line may fold back to
the southwest south of Highway 54. This would limit the tornado
threat given that this portion of the line would be cold pool
dominant.

Scenario 2 (less likely):

Supercells develop from central Kansas to Oklahoma City. Enough
of a capping inversion exists for these storms to remain semi-
discrete as they track towards the I-49 corridor in the 00-04Z
time frame. All modes of severe weather would be possible with
this scenario, including tornadoes and hail to two inches in
diameter. Eventual upscale growth to a squall line would still
be favored including a threat for damaging straight-line winds
up to 75 mph.

For both scenarios, storm severity will tend to decrease the
farther east you go across the Missouri Ozarks due to
diminishing instability and increasing convective inhibition
throughout the night. This is in line with SPC`s severe weather
risks which taper from a Moderate Risk along and west of I-49 to
a Marginal Risk over the eastern Ozarks.

We will need to monitor the threat for flash flooding late
Saturday night and early Sunday morning if a portion of the
line can become more west to east oriented. This would promote
at least a limited duration of training storms and a localized
risk for flash flooding.

Sunday and Sunday Night:

Short term models indicate another short wave trough progressing
east through the region. This trough will slowly drive a cold
front southeast across the area with most models forecasting the
front to clear south-central Missouri sometime Sunday evening.
Additionally, it is quite possible that an outflow boundary or
two will exist.

The amount of instability present ahead of the front is still
in question for Sunday. Clearing and recovery behind late night
and early morning convection is one component to the uncertainty
as is the location of steeper mid-level lapse rates.
Regardless, most models show at least 2000-3000 J/kg of MLCAPE
being present with little to no convective inhibition during
peak heating.

Deep layer shear on Sunday will be sufficient for a severe
thunderstorm risk if the instability does indeed materialize.
We agree with SPC`s Slight Risk for severe storms across much of
the area with an Enhanced Risk clipping areas around Rolla.

While storm movement on Sunday looks fairly progressive with the
passing front, we will have to watch areas that receive
multiple rounds of heavy rainfall for a flooding risk. At this
time, this still appears as if it would be a localized risk at
most.

Monday through Thursday:

Cluster scenarios show good agreement that a northwesterly flow
aloft will set up over the central U.S. This will lead to much
quieter weather for the Missouri Ozarks and southeast Kansas.

Short wave energy diving southeast across the Great Lakes will
bring the potential for showers to the Corn Belt and northern
Missouri from Monday into Tuesday. Precipitation chances in
central Missouri are less than 20% with the better lift
remaining to the north.

Global ensembles then bring some activity into portions of
southeastern Kansas and far southwestern Missouri from
Wednesday into Thursday. This appears to be tied to MCS activity
pushing southeast across the southern Plains. Oftentimes,
global ensembles can be too far north with QPF in these
scenarios. Thus, we have generally kept PoPs less than 30%.

Temperatures next week will be pleasant with a drier airmass
also in place. NBM statistical guidance is clustered around
highs ranging from the middle 70s to lower 80s. Lows will range
from the lower 50s to lower 60s with the coolest readings in the
valleys across the eastern Ozarks.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
-- Changed Discussion --
Issued at 1207 AM CDT Sat May 25 2024

For the 06z TAFS, was getting some VFR ceilings around 4000-5000
feet developing along the 850mb front at SGF, and even some
convection over Christian county. This has started to weaken
with clouds dissipating at SGF. Drier air should move into the
area behind the front for the remainder of the overnight and
into much of Saturday and Saturday evening. Moisture will start
to return northward during the day in advance of the next
system, however convection is expected to hold off until after
06z at the TAF sites.
-- End Changed Discussion --

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
KS...None.
MO...None.

&&

$$

SHORT TERM...Schaumann
LONG TERM...Schaumann
AVIATION...Lindenberg