Tice, Illinois Weather Forecast Discussion

476
FXUS63 KILX 190821
AFDILX
Area Forecast Discussion
National Weather Service Lincoln IL
321 AM CDT Fri Sep 19 2025
.KEY MESSAGES...
- There is a 40-60% chance of storms tonight, mainly focused in
  areas from the Illinois River Valley to near the I-57 corridor.
  While not everyone will see rain, localized amounts over a half
  inch are possible.
- An unsettled pattern will exist over the next week, with
  frequent chances for isolated to scattered showers and storms.
  Over the next week, there is a slight chance (20-30%) for total
  rainfall amounts over 2".
&&
.DISCUSSION...
Issued at 319 AM CDT Fri Sep 19 2025
*** THROUGH SATURDAY AM ***
Early morning IR satellite imagery shows an upper low located over
the Dakotas with a shortwave/trough axis pivoting cyclonically
through the Midwest. An associated sfc low was present over SE SD,
and while sfc obs are a bit disorganized at the moment, the
expectation is that a weak cold front associated with this sfc low
will be draped across the ILX CWA today. Some convective cells
are still ongoing across west-central IL as of 07z/2am, but
activity was much more robust earlier Thursday evening across
central MO. At 07z, an outflow boundary was evident on the ILX
radar, extending from near Bloomington to Effingham which was well
out ahead of any lingering precip activity. At this point, do not
anticipate any new convective development to the east of
Peoria/Springfield, as MUCAPE (instability) drops sharply east of
there. Short-term PoPs maintain a 15-30% chance of precip in areas
west of Peoria/Springfield through the rest of the pre-dawn
hours.
Another shortwave will pivot around this slow-moving upper low
today, approaching the Midwest tonight. This should result in
plenty of mid/high clouds streaming in from the west today.
Despite this, temps are expected to stay above normal, with highs
ranging from the low/mid 80s west of the IL River to near 90
along/east of I-57. Forecast soundings indicate decent instability
developing by late this afternoon, around 1000-1500 J/kg, and
some convergence is expected along that weak cold front which
could aid precip development during this afternoon. The 19.00z
HREF has just a 15-20% chance for precip through early evening,
mainly near/west of I-55.
As that shortwave reaches the area tonight, there is a consistent
signal among various guidance sources for an uptick in scattered
precip activity, focused primarily on areas from the IL River to
near the I-57 corridor (40-60% chance). Due to the expected
scattered nature of these showers/storms, not everyone will see
rain, but the HREF LPMM suggests that in areas that do see rain
localized amounts of 0.5 to 1" are possible. While instability is
modest, deep layer shear is weak (less than 20 knots), and thus
severe storms are unlikely (though an isolated, locally strong
updraft capable of strong wind gusts can`t be ruled out).
*** SATURDAY INTO NEXT WEEK ***
A gradual weakening of synoptic forcing is expected into the day
on Saturday as this first shortwave lifts off towards the Great
Lakes. While some low PoPs linger through the day (20-30% chance),
it does seem like the daytime hours on Saturday will be a
relative lull in precip activity compared to the rest of the
unsettled forecast. High temps on Saturday appear fairly similar
to Friday, ranging from low 80s in the west to near 90 in the
east. Another shortwave pushes in from the west Saturday evening,
resulting in increasing rain chances Sat night into early Sun
(30-50% areawide).
The upper pattern evolution will be gradual through early next
week, with the primarily upper low slowly shifting by to our
north, allowing additional weak disturbances to trek across the
region. By Tues, an upper pattern shift starts to become evident
in model guidance, with a new closed upper low digging towards the
lee of the central Rockies, and another closed upper low off the
southern Cal. coast, while upper ridging amplifies between them.
As the features evolve towards the latter half of next week,
guidance suggests another Rex block (upper high poleward of upper
low) could develop as the upper low reaches the mid-MS Valley.
This would stall the pattern, but unlike the Rex block that
developed last week, this one (as currently forecast) would leave
central IL on the unsettled side, particularly across the southern
half of the CWA.
All of these various disturbances translate to an unsettled
forecast, with the model blend delivering PoPs of at least 20-40%
through every period of the forecast. There will likely be lulls
in rainfall activity, but slight differences in the model timing
of all these small waves results in the continuous precip mention
throughout the forecast. These rain chances are welcome news given
the worsening/expanding drought across IL (D1/moderate drought
now encompasses almost all of the ILX CWA, with some D2/severe
drought in east-central IL). However, I continue to believe that
the blended model QPF, which suggests 2-3" of total rainfall
across much of the area, is too broad/overdone. Models tend to
overdo the medium range QPF in drought situations, and
probabilistic guidance has just a 20- 30% chance of rainfall over
2" through Thurs morning, so the current forecast of 2-3" is quite
a bit above the median outcome. Still, the fact that there is a
non-zero probability for over 2" of rain is welcome news for the
drought. After Saturday, temps are expected to shift to near
seasonable values, with highs in the upper 70s to low 80s through
next week.
Erwin
&&
.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1207 AM CDT Fri Sep 19 2025
A slow moving upper low will slowly meander east across the mid
Missouri Valley through the period. A decaying line of showers is
pushing across the Mississippi River late this evening with an
outflow boundary turning winds WSW and gusting to around 20 kt.
This will impact SPI in the near term and possibly DEC if it can
persist long enough. Otherwise expect dry weather to prevail
overnight along with light and variable winds outside the
influence of the aforementioned outflow boundary. Another band of
showers and a few storms will be possible across central Illinois
late Friday afternoon into the evening. Low coverage and
confidence of impacts on station preclude more than a prob30
mention at this time.
Deubelbeiss
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$

NWS ILX Office Area Forecast Discussion