962
FXUS63 KSGF 241040
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
540 AM CDT Tue Sep 24 2024

.KEY MESSAGES...

- Dense Fog Advisory in effect from 4 to 10 AM for areas along
  the Missouri-Kansas border. Visibilities could be reduced to a
  half mile or less this morning.

- 15-30% chances for isolated showers and perhaps a
  thunderstorm or two today and Wednesday. Many locations will
  remain dry.

- Much cooler temperatures will occur this week with highs in
  the 60s and 70s.

- Rainfall chances (50-80%) 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 by Friday and Saturday, as well as breezy
  winds.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 330 AM CDT Tue Sep 24 2024

Current water vapor imagery depicts a deep mid- and upper-level
trough over the central CONUS. Associated with an upstream jet
streak and a downstream jet streak of the trough, two cold
fronts are set up. One that just moved through our area is
draped across TX/AR and across the Ohio River Valley. The other
is in NE and into the eastern Dakotas.

Infrared satellite reveals thick low stratus moving through the
region due to cooler temperatures and lingering moisture behind
the front. These low clouds are starting to clear out of our
western CWA, allowing greater radiational cooling in this area.
Paired with weak winds, fog is developing along the MO/KS
border. Current observations have visibilities around 2-5 miles
and dropping.


Dense Fog Advisory in effect from 4-10 AM along MO/KS border:

Visibilities along the MO/KS border are expected to continue to
drop as dense fog develops after 4 AM. Visibilities could be
reduced to below half a mile at times. The fog should begin
dissipating between the 7-10 AM timeframe as solar heating
mixes out the fog.

Elsewhere, visibilities may be modestly reduced due to drizzle
and/or light fog as low-level RH is >85% and no cloud ice is
present. RAP models suggest several waves of low-level lift, and
with WNW`ly winds providing upslope lift along the Ozark
Plateau, on and off drizzle looks possible through the morning,
especially along the Plateau.


Much cooler temperatures continue with highs in the 70s:

The core of the aforementioned trough will sit over our region
starting today. Along with modest surface high pressure, this
will lock cooler air across our region the entire week. Highs
today and Wednesday will be in the lower to middle 70s with lows
in the lower to middle 50s.


15-30% chances for isolated showers today and Wednesday:

The cold front in the Dakotas will drop to our region over the
course of the day. Weak convergence along this front aided by
synoptic ascent within the left-entrance region of the backside
jet streak could force a few bands of light showers across the
area today. With moisture limited within the core of the trough,
showers will be light and scattered in nature (15-30% chance).

Models depict the core of the upper-level cut-off low sitting
over the Missouri bootheel during the day Wednesday. Some weak
cold-core instability should develop within this region.
Synoptic-scale ascent associated with a strengthening jet streak
over the lower Mississippi River Valley could force some
scattered showers in south-central Missouri Wednesday afternoon (and
perhaps a thunderstorm or two given 500-750 J/kg MLCAPE). Once
again, these will be more scattered in coverage as moisture will
be more limited (15-30% chance).

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 330 AM CDT Tue Sep 24 2024

Much cooler temperatures continue with highs in the 60s & 70s:

As mentioned previously, the cut-off low will hover over our
region with ensembles showing little signs of weakening. This
will keep cooler temperatures in our area throughout the rest of
the forecast period. Highs will consistently be in the lower to
middle 70s with lows consistently in the 50s. Friday and
Saturday look to be the coolest days where highs could only
reach the middle 60s, especially along the Ozark Plateau. This
is largely due to Friday and Saturday having the best chance for
increased deep cloud cover and the potential for prolonged
rainfall.


Potential for widespread and prolonged rainfall late week:

Ensemble members are in better agreement that the tropical
system coming out of the Gulf will be entangled with the upper-
level low in some good ol` Fujiwhara action. The absorption of
a tropical system will certainly bring a boost of moisture to
the upper-level low sitting across our region. Increased
moisture and dynamical lift would force widespread and
prolonged rainfall with high 72-hour rain totals somewhere in
and around Missouri. The main uncertainty now, is how far west
and south the upper-level low gets slingshot by the
entanglement of the tropical system. Both the GEFS and EPS
ensembles take the upper-level low south of our region, while
the CMC ensembles notably have the mean track further east of
our area. The GEFS/EPS scenario would bring higher coverage and
amounts of rain while the CMC scenario would limit higher
rainfall coverage to maybe our eastern counties. Details still
need to be ironed out about the exact track of the system and
subsequent impacts to our region.

Nevertheless, current probabilistic model trends are increasing
chances for widespread and prolonged rainfall somewhere in our
CWA. The Extreme Forecast Index continues to highlight 1-2 shift
of the statistical tail for QPF in the eastern Ozarks for
Friday/Saturday. This is signaling a potentially abnormal
rainfall event. Adding confidence, the WPC has a Day 4 Slight (2
of 4) risk for excessive rainfall along and east of Hwy 65.
Additionally, the NBM is highlighting the eastern Ozarks as an
area with a 1-in-40 year rainfall event should the mean outcome
take place. The mean NBM QPF amounts is 1-4" for Friday through
Sunday with the highest amounts east of Hwy 65. Do not get too
hung up on amounts just yet, though. The mean is merely another
sign of increasing confidence in widespread and prolonged
rainfall across the region. There is still high ensemble
spreads. For example, the 25th percentile has no rain at all
west of Highway 65, while the 75th percentile gives widespread
areas of 3-6". With all that being said, stay tuned to the
forecast with updates to the track of the system, confidence in
rainfall coverage and totals, and any new uncertainties and
scenarios.

Of additional note, given the strong dynamics of the system
(and it being a post-tropical system of course), winds look to
be moderately breezy Friday and Saturday. NBM mean sustained
winds are at 15-20 mph with gusts up to 30 mph. The 75th
percentile (should a stronger system scenario be in play) has
sustained winds at 20-25 mph and wind gusts up to 40 mph.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 540 AM CDT Tue Sep 24 2024

MVFR and IFR conditions will slowly clear away over the first 6
hours of the TAF period. Dense fog is currently struggling to
fully develop at JLN, but there is still the possibility that
visibilities there drop to around a mile before 14Z. After 18Z,
cloud coverage will still be SCT to BKN with mid- and high-
level clouds. Between 20-03Z, a band of light showers could
impact all TAF sites (20-30% chance). While chances are low,
model-to-model and run-to-runs have been consistent on this
feature, so confidence on at least sprinkles impacting the TAF
sites is medium-high.

Otherwise, winds will be 5-10 kts out of the WNW, decreasing to
below 5 kts after 00Z.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
KS...Dense Fog Advisory until 10 AM CDT this morning for KSZ073-097-
     101.
MO...Dense Fog Advisory until 10 AM CDT this morning for MOZ066-077-
     088-093-101.

&&

$$

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