292
FXUS63 KSGF 211740
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
1240 PM CDT Sat Sep 21 2024

.KEY MESSAGES...

- Hot again for most of the Ozarks today. Heat Index values will
  reach the 95 to 102F range mainly along and west of Highway
  65.

- Multiple rounds of widespread showers and thunderstorms are
  expected through the weekend (40-80% chance). Precipitation
  amounts will be highly variable across the region, but
  generally expect the highest amounts to be north of I-44.

- Marginal (1 of 5) Risk for severe thunderstorms Sunday
  afternoon and evening. Main hazard will be damaging wind gusts
  up to 60 mph.

- A cold front will bring cooler temperatures next week with
  highs in the 70s and limited rain chances.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 400 AM CDT Sat Sep 21 2024

Current water vapor imagery depicts broad clockwise mid-level
flow associated with an amplifying ridge over the Southern
Plains ahead of an approaching potent shortwave trough. Beneath
this pattern aloft, a stationary boundary is currently draped
across central MO and east KS.

Additionally, current radar imagery shows a decaying
thunderstorm complex trekking across our western counties. A
well-defined outflow boundary (thanks to dry, dusty conditions)
can be seen moving through SW Missouri. The cloud cover
associated with the complex is keeping our temperatures rather
mild in the middle to upper 70s. The remnant showers and
associated outflow will then have an impact on shower and
thunderstorm potential later this morning and into the
afternoon/evening.


First couple rounds of showers and thunderstorms today/tonight:

Current thinking is that the current thunderstorm complex will
continue to dissipate through the morning as it moves east.
This decaying precipitation is not expected to make it very far
east of Hwy 65. Simultaneously, the outflow boundary should
clear the east and south CWA borders in the next few hours.

The next round is forecast to occur after 5-8 AM along the
back-end of this complex. Convergence and warm air advection at
the nose of a strengthening nocturnal low-level jet will force
scattered showers and thunderstorms in west-central Missouri
that will dive SSE through our region with latest models
agreeing that much of this precipitation will stay along and
east of Hwy 65, with some storms possibly just clipping
Springfield (30-60% chance). There is question as to the
coverage and longevity of these storms due to outflow from
tonight`s storms. However, given that these storms will initiate
as elevated, the surface outflow will likely not have much of
an impact. These showers and thunderstorms should
clear/dissipate by early to mid-afternoon.

Afternoon and evening thunderstorm redevelopment is another
question largely based on how the first two rounds behave. Surface-
based instability looks to be mostly capped this afternoon due
to remnant cold pools, widespread cloud cover inhibiting solar
heating, and a nose of 21-23 C 850 mb temperatures advecting in.
This means that thunderstorm redevelopment would either have to
be A) elevated initiation along remnant outflow boundaries, or
B) initiated in isolated pockets where solar heating is enough
to erode the cap. With too much uncertainty in exact location of
outflow boundaries and degree of instability, have given 20-30%
PoPs for the whole CWA this afternoon/evening.

The NEXT round then comes late tonight as large-scale ascent
moves into the region from positive vorticity advection
downstream of the potent trough overlapping an approaching
surface cold front. This belt of ascent will force a SW-NE
oriented axis of showers and thunderstorms that will sag into
our NW counties late tonight. As such, the best chances
(30-70%) are north of I-44, with generally <15% south of I-44.

Severe weather is not expected with any of these rounds,
however, PWATs in the 1.75-2.00" range (>97.5th percentile for
this time of year per the ECMWF ESATs), and HREF rainfall rate
probabilities showing 1-2" per hour, some localized areas may
see localized flooding. The WPC has a Marginal (1 of 4 ) risk
for excessive rainfall out for our entire CWA to capture this
threat. See the Long Term discussion for potential rainfall
totals from the rainfall event lasting through Monday.


Hot again for most of the Ozarks today:

We`ll take a brief pause from our regularly scheduled rain
forecast to tell you that once again it will be hot today. Highs
will be in the mid-80s in the eastern Ozarks, to the upper 90s
along the MO/KS border. Joplin will once again become close to
its record high of 99 F, but with cloud debris and thunderstorm
outflows expected, it will be rather difficult to break this
record. Additionally, with dewpoints in the upper 60s, Heat
Index values will range from 95 to 102 F west of Hwy 65. This
will be the last day of the stretch for abnormal heat >95 F
Heat Index values. Continue to practice heat safety today by
staying cool and hydrated! Lows will then again be mild tonight,
hovering within 2 degrees around 70 F.


Marginal (1 of 5) Risk for severe thunderstorms Sunday:

Thunderstorms will likely be ongoing somewhere in Missouri
Sunday morning, most likely north of I-44 (30-70% chance).
However, some of the CAMs depict lulls and clearing of
precipitation Sunday as much of the mid-level and surface
forcing stays north of the CWA. This could allow for at least
500 J/kg MLCAPE across the area, with localized areas up to 1500
J/kg MLCAPE where pockets of solar heating within cloud breaks
occur. Additionally, with a 30-40 kt mid-level jet overspreading
the area as the shortwave lifts through the central Plains,
30-40 kts of 0-6 km bulk shear will overlap the modestly
unstable warm sector. Indeed, the Extreme Forecast Index is at
0.75 with 1 shift of the statistical tail for CAPE/Shear combo
this time of year. Naturally, this will be supportive of
organized thunderstorms, some possibly severe, as the cold front
begins pushing through the area Sunday afternoon and evening.
The main hazard will be damaging wind gusts up to 60 mph within
organized line segments, and brief heavy downpours.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 400 AM CDT Sat Sep 21 2024

Last round of showers and thunderstorms Monday and Monday night:

The cold front will finally push through the region Monday,
bringing the last round of showers and thunderstorms (30-65%,
highest in the eastern Ozarks). Much of the precipitation should
be out of the area by 7 AM Tuesday morning, with only some
lingering very light rain showers possible after that time.

When it`s all said and done, NBM 72-hour precipitation totals
(through 7 PM Monday) are honing in on a tighter range, but
still have a pretty high spread between the 25th and 75th
percentile. As an example, the 25th percentile total for
Springfield is 0.50", while the 75th percentile total is 2.00".
The spreads are quite high due to each round of showers and
thunderstorms working off each other as well as the scattered
nature of most rounds. What is clear, though, is that the better
chances for the highest totals is north of I-44 where the
better forcing aloft and along the warm front is present. Areas
along the Hwy 54 corridor have a 65-85% chance for >1.00" and a
35-55% chance for >2.00" by the end of Monday. Cluster analysis
is in good agreement with this placement, showing an E-W
oriented gradient of QPF through central Missouri. In contrast,
areas south of I-44/Hwy 60 have a 30-40% chance for >1.00" and
a 10-20% chance for >2.00". That being said, most locations will
receive at least some rain (widespread 80-100% chances for
>0.1"). However, it`s not out of the question that localized
areas may miss every single round (5-10% chance along the MO/AR
border). On the flip side, some areas may be impacted by
multiple thunderstorms, leading to localized areas with up to at
least 4-6" by the end of Monday.


Cooler temperatures next week with limited rain chances:

After the front kicks through, a nice temperature drop will
occur with highs Monday ranging from the mid-60s in the northern
counties, to the mid-70s in southern Missouri. Ensembles are in
decent agreement for a deep trough to hang around the
central/eastern CONUS, which will keep high temperatures cool
in the 70s with lows in the 50s all of next week.


Models do begin to diverge with the possibility of an upper-
level low breaking off from the main trough. This could produce
some precipitation late week (15-20% PoPs right now as models
are in disagreement). Trends will have to continue to be
monitored for this scenario.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1237 PM CDT Sat Sep 21 2024

Confidence is high that VFR conditions will persist through most
of the TAF period. There is a 30 percent chance of a
thunderstorm affecting SGF and BBG towards 00z however will not
include at this time. Chances do begin to increase Sunday
morning and especially afternoon as a front approaches. Winds
will remain southeast to south through tonight. A wind shift to
the north will occur by the end of the TAF period.


&&

.CLIMATE...
Issued at 400 AM CDT Fri Sep 18 2024


Record High Temperatures (Joplin):

September 21:
99 (2022) Forecast: 97



Record Highest Minimum Temperatures (Springfield):

September 21:
73 (1931) Forecast: 74

September 22:
70 (2017) Forecast: 70



Record Highest Minimum Temperatures (Joplin):

September 21:
76 (1980) Forecast: 76

&&

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

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Burchfield
CLIMATE...Price