556
FXUS63 KSGF 230846
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
346 AM CDT Mon Sep 23 2024

.KEY MESSAGES...

- Marginal (1 of 5) Risk for severe thunderstorms today in
  across the eastern Ozarks. Main hazards will be damaging wind
  gusts up to 60 mph, small hail with isolated instances up to
  a quarter inch, and brief heavy downpours.

- Multiple rounds of widespread showers and thunderstorms are
  expected through tonight (60-85% chance). Most locations will
  see an additional 0.25 to 1.5 inches of rainfall through
  tonight, with localized amounts up to 3 to 5 inches.

- Much cooler temperatures will occur this week with highs in
  the 70s.

- Rainfall chances (50-70%) continue to increase for late in the
  week as confidence increases on track of the next system.
  There is the potential for widespread and prolonged rainfall
  with this system.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 345 AM CDT Mon Sep 23 2024

Current water vapor imagery depicts the positively-tilted
shortwave trough still situated over the central Plains. Height
falls and associated positive vorticity advection over the last
few hours have provided enough ascent for scattered showers and
thunderstorms to develop across the area. These are expected to
increase in coverage through the morning as the trough
progresses eastward.

Noted on SPC Mesoanalysis, a 60-80 kt upper-level jet over
KS/MO is synoptically forcing weak surface cyclogenesis in NW AR
along a cold front currently analyzed from Michigan, down into
SE MO, and through NW AR, SE OK, and central TX. This will
create a high temperature gradient across our CWA. Highs will be
in the mid-60s NW of I-44 and in the mid-70s SE of I-44. This
front and surface low and their exact positions during the day
will be the focus for additional thunderstorm development this
afternoon, some potentially being strong to severe.


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

As noted in our 00Z observed sounding, deep cloud cover is
keeping environmental lapse rates rather meager in the 5.5-6.5
C/km range. The clouds are not expected to go anywhere today,
which will continue to keep shallow lapse rates across the
region. However, surface low cyclogenesis along the AR/MO border
will reorient the cold front to more SSW-NNE, and should
provide just enough moisture advection ahead of that front to
generate 500-1500 J/kg of MLCAPE characterized by skinny
instability profiles. As heights fall with the approaching
shortwave, thunderstorm development should occur along the front
in an area bounded by east of Hwy 65 and south of I-44. This
could occur as early as 12 PM today. Ahead of the shortwave, 0-6
km shear will increase to 25-35 kts, characterized by
unidirectional hodographs. With this overlapping the marginal
instability, some of these thunderstorms this afternoon in the
eastern Ozarks could become severe (5% chance). Wind gusts up to
60 mph and hail up to the size of quarters will be the main
hazards.

Coverage of these storms will be determined by the degree of
instability. If enough cloud breaks occur in areas across the
eastern Ozarks (increasing low-level lapse rates), and colder
air in the mid-levels advects in with the height falls
(increasing mid-level lapse rates), it seems plausible that
higher coverage of robust updrafts could develop across the
eastern Ozarks. Interacting with the higher range of bulk shear
(30-35 kts), some multicells could cluster into lines,
otherwise, downbursts would be the main wind threats. These
storms would all still have wind gusts up to 60 mph and hail up
to the size of quarters as the main threats.


0.25 to 1.5 inches of additional rainfall through tonight:

A northern-stream shortwave trough digging into the Northern
Plains will modestly amplify the shortwave across our region and
prompt it to slowly progress eastward. With a large zone of
increasing synoptic-scale ascent spread across our area, several
rounds of showers and thunderstorms are expected to continue to
develop and move through our area (60-85% chance). Since the
shortwave will slowly progress eastward, some areas, especially
in the eastern Ozarks, could see multiple thunderstorms. As
such, many areas will see an additional 0.25-1.5" with HREF
LPMMs highlighting some localized areas receiving up to 3-5".
This will introduce a minor and localized flooding threat across
the eastern Ozarks where there`s a better chance of multiple
thunderstorms moving over the same area and there are less dry
conditions.


Lingering rain chances into Tuesday:

The front will finally kick through the rest of the region
Monday night and lows will drop into the upper 50s and lower 60s.
With the surface low lifting through east MO and into Illinois,
backside light showers could impact areas toward central MO
(20-40% chance).

Additionally, the aforementioned northern-stream shortwave will
dig into the central Plains through Tuesday. A strong N-S
oriented 100-120 kt upper-level jet will drop through NE and KS.
Left-entrance region synoptic ascent will overspread a small
corridor of weak elevated instability associated with the cold-
core system. This could bring some elevated showers and
thunderstorms into the MO/KS border vicinity Tuesday afternoon
and evening (15-20% chance).

Then, lows Tuesday night will be slightly cooler in the lower to
middle 50s.


&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 345 AM CDT Mon Sep 23 2024

Much cooler temperatures this week with highs in the 60s and 70s:

The deep shortwave will settle over the eastern CONUS through
mid-week, bringing high pressure in behind the cold front. This
will bring cooler temperatures with highs in the lower to middle
70s Wednesday and Thursday. Ensemble cluster analysis shows
members starting to come into good agreement with the shortwave
cutting off from the main flow aloft, and sitting somewhere
over the southern/central CONUS. The cold core of the upper-
level low would decrease highs into the upper 60s and lower 70s
Friday through Sunday. However, if the cut-off low does not
develop, or stays out of our region, highs could be closer to
the middle 70s. Lows during this whole time period will
consistently be in the 50s.


Rainfall chances (50-70%) continue to increase for late week:

As previously mentioned, models are coming into better agreement
on the scenario discussed in the last two forecast packages
about an upper-level cut-off low squatting somewhere around our
region late this week. Ensemble cluster analysis reveals that
85% of members are now favoring this scenario since the GEFS has
caught onto it (though exact location and intensity of the
upper-level low is still uncertain). Additionally, GFS/ECMWF/CMC
ensemble spaghetti plots of Invest-97L in the Gulf all have the
mean track wrapping into the upper-level low, which would
provide a boost in deep moisture. This scenario could produce
widespread and prolonged rainfall somewhere in the east/central
CONUS late this week, including potentially our CWA (50-70%
chances Thursday through Sunday). The Extreme Forecast Index is
already hitting on our CWA this far out with a value of 0.59 and
1-2 shifts of the statistical tail for QPF, signaling a
potential abnormal precipitation event. Adding confidence, the
WPC has a Slight (2 of 5) Risk for excessive rainfall in our SE
counties for Day 5 (Friday). NBM mean 72-hour precipitation
ending Saturday night has amounts in the 2-5" range.

Everything mentioned above is adding confidence to this
scenario. That being said, any small shift in track and/or
intensity will change rainfall chances and amounts across our
region. For example, a more northward and/or eastward shift
could leave us with less than half an inch of rain (~25th NBM
percentile). Whereas a more westward and/or southward shift
could bring more than 5 inches to portions of the region (~75th
NBM percentile). Trends will continue to be monitored in the
coming days, but consider this a heads-up for a potentially
widespread and prolonged rainfall event late this week.



&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1245 AM CDT Mon Sep 23 2024

Medium-high confidence that conditions will oscillate between
MVFR and IFR throughout the TAF period at all TAF sites as there
is a 60-80% chance of ceilings staying below 1 kft through the
period. There is a slight chance (20-30%) that TAF sites fall
into LIFR at times, especially during periods of precipitation.
Indeed, BBG is currently oscillating between IFR and LIFR.

Additionally, there is a 60-80% chance that showers and/or
thunderstorms will impact the TAF sites at some point during
the period. Confidence on timing is still low, but expect at
least two rounds of storms to move through the vicinities of the
TAF sites. The first round will be between 10-15Z and the
second round later this afternoon in the 18-03Z timeframe.
Generally, showers and thunderstorms will be in southwest
Missouri the whole TAF period, but those marked in the TAFs are
the higher confidence timeframes for higher coverage around the
sites.

Otherwise, winds will remain relatively calm at 3-8 kts out of
the north.

&&

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

&&

$$

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