207
FXUS63 KILX 110814
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
314 AM CDT Sun Aug 11 2024

.KEY MESSAGES...

- A weak disturbance will bring light showers to parts of central
  Illinois on Monday.

- A stronger system will impact the region later in the week,
  triggering scattered showers and thunderstorms Wednesday night
  through Friday. The potential for severe weather and/or flash
  flooding will remain quite low.

&&

.SHORT TERM...(Today through Monday)
Issued at 314 AM CDT Sun Aug 11 2024

0730z/230am IR satellite imagery shows a large area of mid-level
cloudiness extending from Missouri into south-central Illinois,
mainly along/south of a Quincy...to Lincoln...to Paris line.
Models have handled the cloud cover quite poorly: however, based
on 00z NAM forecast soundings and latest satellite trends, think
the clouds will persist across the southern half of the KILX CWA
through daybreak...then gradually shift further southeast and
dissipate by mid-morning. After that, FEW-SCT diurnal Cu will
develop by peak heating and a few high/thin clouds will stream
overhead as well. End result will be a partly sunny and mild day
with afternoon highs in the upper 70s to around 80 degrees.

A short-wave trough evident on latest water vapor imagery over
Montana will cross the Rockies today, then approach from the NW
late tonight into Monday. Thanks to subsidence from prevailing
high pressure, the atmosphere will initially be quite dry. As a
result, think light showers associated with the wave will remain
along/west of a Galesburg to Springfield line through dawn Monday.

As the wave arrives and the column gradually moistens from the
top-down, scattered showers will spread E/SE across the KILX CWA
later Monday morning. Most of the CAM guidance suggests the
showers will primarily be focused south of the I-74 corridor...with
the 3km NAM keeping the precip entirely S/SW of central Illinois.
Have opted to reject the NAM and follow an HRRR/WRF-ARW/FV3
blend, which places high chance to likely PoPs south of I-74, but
only 30-40 PoPs along/north of I-74. Any rainfall that occurs on
Monday will be light, amounting to 0.25 or less. Thanks to
extensive cloud cover and scattered showers, temperatures will be
held down considerably...with much of the area only reaching the
lower 70s.

Barnes

.LONG TERM...(Tuesday through Saturday)
Issued at 314 AM CDT Sun Aug 11 2024

As has been seen with the past several model runs, it appears the
primary baroclinic zone will remain well S/SW of central Illinois
until the middle/end of the week. As such, think Tuesday will be a
mild and dry day with highs in the upper 70s/lower 80s. As a
stronger short-wave approaches from the Plains, the front will
gradually lift northward by Wednesday. As a result, scattered
showers will develop along/southwest of a Galesburg...to Effingham
line late Tuesday night, then will spread across the remainder of
the area on Wednesday. Despite the uptick in rain chances, think
many locations will remain dry on Wednesday.

As the wave nears and synoptic lift increases, rain chances will
increase markedly Wednesday night through Friday. While it
obviously will not rain the entire time, showers and thunderstorms
will become more prevalent. Instability parameters remain modest,
so the probability of severe weather will be low (less than 5%).
In addition, while GFS precipitable water values increase to
around 2 inches by Wednesday night/Thursday, the soil has dried
out considerably since the previous rainfall...so excessive runoff
is of minimal concern. In addition, the 12z Aug 10 LREF shows
just a 20-25% of exceeding 1 inch of rainfall between 1am Thu and
1am Fri. Am therefore not anticipating any flooding concerns
Wednesday night through Friday. After that, the strongest forcing
and thus greatest rain chances will shift further east into the
Ohio River Valley by Friday night into Saturday.

Barnes

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1109 PM CDT Sat Aug 10 2024

Another VFR set of TAFS as high pressure over MO shifts east
across central IL through Sunday. This will bring calm to light
west to northwest winds and scattered mid to high level clouds.

25

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$