851
FXUS63 KSGF 280829
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
329 AM CDT Sun Apr 28 2024

.KEY MESSAGES...

- Significant and dangerous flooding is ongoing in areas along
  and west of I-49 as training thunderstorms continue to impact
  the area. The flooding threat will slowly shift eastward
  through today and tonight. A Flood Watch is in effect until
  1PM Sunday.

- Severe weather threat continues through this morning as a line
  of storms moves through. Wind gusts up to 70 mph, a couple
  tornadoes, and hail up to the size of half dollars are all
  possible. A Tornado Watch is in effect until 7AM.

- Severe weather is expected again this afternoon into tonight
  as another line of storms develops. The main threat will be
  wind gusts up to 60 mph with secondary marginal threats of
  quarter-size hail and a brief spinup tornado or two.

- The unsettled pattern continues with additional storm chances
  mid to late next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 330 AM CDT Sun Apr 28 2024

Significant and dangerous flooding is ongoing:

A large complex of severe thunderstorms is progressing eastward
across the central/southern Plains. The complex is located on
the east side of a 90-110 kt meridional jet streak associated
with a potent negatively-titled shortwave. This synoptic wave is
very slowly progressing to the NE. That, combined with straight
N-S flow all the way down to the surface is forcing the MCS to
move slowly eastward and train, bringing heavy rain to locations
along the MO/KS border. Latest MRMS QPE estimates put out 5-7
inches of rain in the last 6-12 hours over Bourbon, Vernon, and
Crawford counties, specifically around the Fort Scott, KS area.
This is on top of 4-6 inches that have already fallen the past
couple of days. With all this rain, rivers such as the Little
Osage and Marmaton are approaching major flood stage. Several
considerable flash flood warnings are currently out to address
this threat. Observed PWATs of 1.25" (above 90th percentile) are
allowing for rainrates of 1-2 inches/hr. These will produce an
additional 1-1.5" in this area with localized values greater
than 2-3 inches before the MCS exits the area. Please avoid
traveling in this area if you can! If you cannot, make sure to
turn around, don`t drown. Keep up to date with alerts and have a
plan in place.

As mid-level ascent catches up to the complex and a better cold
pool forms, the thunderstorm complex will pick up its pace and
progress eastward through early this morning. HREF LPMMs suggest
this will produce 1.5-3 inches of rain east of I-49 and along
and west of Hwy 65, including Springfield. Within heavier
training thunderstorms, localized values up to 3-5 inches are
possible (10-30% chance). Once again, this will introduce an
areal, river, and flash flooding threat for the Flood Watch
area.

After the first thunderstorm complex dissipates early this
morning, airmass recovery/destabilization is expected to quickly
occur given any frontal forcing will still be lagging west in
KS/OK and high amounts of moisture will limit the depth and
strength of the cold pool. Even with mild highs in the lower
70s, the appreciable dewpoints in the lower 60s will allow for
enough MLCAPE (300-800 J/kg via RAP model soundings) for new
thunderstorm development Sunday afternoon. All HREF models are
depicting another thunderstorm complex to develop along and west
of I-49 by 3-5PM. This complex should extend through the N-S
extent of our CWA. The mid- and upper-level wave will finally
kick out of the area to the NE this afternoon/evening, so this
MCS will be more progressive than last night`s. However, high
PWATs above the 90th percentile still in the region will allow
for high rainrates in the thunderstorm complex bringing an
additional 0.5-1.5 inches of rain east of I-49 with localized
values up to 2-4 inches suggested by HREF probs (30-40% chance).


Severe weather threat continues through this morning:

A Tornado Watch is in effect for portions of our forecast area
through 7 AM this morning. This threat is mainly for 60-70 mph
wind gusts and brief spin-up circulations within the line of
storms progressing eastward. The threat becomes more marginal
the further east you get, with the severe threat diminishing
east of Hwy 65. A 06Z balloon sounding revealed 90-110 J/kg of
SB/MLCIN with increased low-level and mid-level capping.
Additionally, radar trends are suggesting that the line is
becoming more outflow dominant as cells are beginning to advect
rearward. Both these observations suggest the line will weaken
as it moves eastward. Nevertheless, increased synoptic ascent
and a nocturnal enhanced 45-55 kt low-level jet could make use
of the 700-1000 J/kg of SB/MLCAPE and >400 m2/s2 of SRH to
produce severe wind gusts and perhaps a spinup tornado or two
before 7 AM. The MCS is then expected to dissipate to lingering
stratiform rain as it crosses the Hwy 65 corridor after 7 AM or
so.


Severe weather/flooding expected again this afternoon/evening:

As mentioned above, the morning thunderstorm complex will only
produce modest stabilization in its wake. Lower to mid-60
dewpoints still in place will allow for 300-800 J/kg of MLCAPE
ahead of the upper-level wave (as depicted by the mean HREF
values). 0-6 km bulk shear values will increase to 40-50 kts as
the mid-level jet core overspreads the area. This will set the
stage for a low-CAPE, high-shear severe weather event. Surface
frontal and mid-level jet forcing will enter our CWA Sunday
afternoon and force more storms within the warm/moist sector.
With low-CAPE, high-shear events, these storms will quickly grow
into a line/MCS. Shear vectors strictly parallel to the forcing
adds confidence to this storm mode. The MCS will start just
east of I-49 and progress eastward. This will create mainly a
damaging wind threat with gusts up to 60 mph. An Enhanced (3/5)
risk is in place along and south of I-44 to capture mainly this
wind threat. However, with RAP forecast soundings depicting
200-300 m2/s2 background SRH and mid-level lapse rates nearing 7
C/km, a brief spinup tornado and/or quarter-size hail cannot be
ruled out. The MCS should exit our CWA to the east by the late
evening hours. A cold front following the MCS will drops lows
Monday night into the 50s with cooler temperatures toward the
MO/KS border.


&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 330 AM CDT Sun Apr 28 2024

The upper-level wave will finally exit our area Monday night,
bringing a brief period of drier and warmer weather Tuesday with
highs in the lower 80s.


Additional storm chances mid to late next week:

The dry weather won`t last long, though, as a longwave trough
sets up over the northern CONUS, allowing for multiple
shortwaves to clip through our region. The first of which looks
to lift through NE/IA Tuesday night. The positive vorticity
advection and associated surface front may produce some
showers/thunderstorms that would impact areas NW of I-44 (20-40%
chance). The wave/front should stay NW of the area allowing lows
Tuesday night to stay in the lower 60s.

The next shortwave looks to be deeper, but also slower. This
will allow S`ly low-level flow to persist through Wednesday and
Thursday bringing highs into the mid-80s Wednesday and lows in
the mid-60s Wednesday night. The conceptual model here depicts
an amplified mid-level trough above a warm/moist sector with
strong S`ly flow, and a dryline over central KS/OK. This could
bring a severe threat Wednesday and Thursday, with the greatest
chance Thursday. Details are too far out to give any details,
but the conceptual model is there. CIPS/CSU algorithms are also
hitting this timeframe with 15% contours in our area. This will
continue to be monitored. Nevertheless, chances for
showers/thunderstorms Wednesday are in the 20-50% range and
70-90% range Thursday.

The system that clears through after these storm chances will
bring in cooler air with highs in the lower 70s and lows in the
lower 50s through the weekend.


&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1237 AM CDT Sun Apr 28 2024

VFR conditions will gradually deteriorate through the TAF
period, beginning with JLN. A line of strong to severe
thunderstorms is likely (80-90% chance) to impact all TAF sites,
dropping ceilings to at least MVFR. Rain within these storms may
be heavy at times. The best chance for the line of storms to
move through is between 07-11Z for JLN and 08-13Z for SGF/BBG.
Wind gusts up to 70 mph will be possible with this line of
storms. Hail up to the size of golf balls and a tornado or two
also cannot be ruled out. After the initial line clears out,
there will be some lingering scattered showers before another
line of severe thunderstorms is expected to develop after 22Z.
Wind gusts up to 60 mph will also be possible with these storms.

Besides the heavy rain/thunderstorms, winds will remain
southerly, sometimes gusting up to 25 kts, especially during the
day. A low-level jet will keep wind shear across the TAF sites
until 12Z.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
KS...Flood Watch until 1 PM CDT this afternoon for KSZ073-097-101.
MO...Flood Watch until 1 PM CDT this afternoon for MOZ055-056-
     066>069-077>081-088>096-101>105.

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Price