860
FXUS63 KILX 290951
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
451 AM CDT Fri May 29 2026

.KEY MESSAGES...

- No major weather systems are expected to affect central and
  southeast Illinois through at least the middle of next week.
  Temperatures will remain above normal, with highs in the low
  to mid 80s into early June.

&&

.DISCUSSION...
Issued at 229 AM CDT Fri May 29 2026

The upper level pattern remains amplified, with an Omega block
expected to be the dominant feature into the middle of next
week. Early Fri morning, IL was situated directly beneath the
upper ridge axis, with a weak, elongated trough present over the
central Plains. Some cirrus clouds continue to stream over
Illinois, but the thicker cloud cover (and precipitation)
associated with this trough extend from the Dakotas to northern
MS/AL. 06z/1am sfc analysis reveals a 1022-mb sfc high remains
positioned over the Great Lakes region, resulting in continued
NE flow and advection of a drier airmass into central IL. Sfc
dewpoints as of this writing range from the low 60s in SE IL to
mid 40s and low 50s north of I-72. Deep layer moisture is also
low, with RAP-analysis depicting a gradient in PWAT values from
SW to NE across the CWA, ranging from 0.4" to 0.7". An axis of
higher moisture content is present ahead of the aforementioned
trough, with values climbing to 1.5-2" over portions of
MO/KS/AR.

The trough over the central Plains will gradually nudge east
today, resulting in increasing cloud cover and mostly cloudy
skies. The NBM high temperature forecast was too cool in
previous days, but given the increasing cloud cover opted not to
adjust temps higher today. The NBM still has temps above normal
today, with highs in the low to mid 80s. There is a low chance
(10-30%) for showers along and southwest of a Rushville to
Lawrenceville line this evening into Saturday morning, but
precip chances remain higher to the south and west of the ILX
CWA.

This weekend, the upper ridge begins to strengthen and a renewed
sfc high pressure pushes south into the Great Lakes. Despite
this, low precip chances linger at times throughout the weekend,
owing to the weakening but persistent shortwave just west of
the area, as well as additional weak waves emanating off the
primary upper low over the Rockies. Still, most locations in our
CWA have less than a 30% chance of seeing rain at any point
this weekend.

The Omega block persists into early next week, but guidance
shows signs of weakening by Tues, followed by a transition to a
more zonal flow regime for the latter half of next week. This
more progressive pattern could offer some better rain chances,
although the zonal flow regime appears short-lived with both GFS
and EC ensembles depicting a return to upper ridging over the
Plains next weekend (around June 7th). CPC 8-14 day outlooks
(valid June 5-11) feature a 50-60% chance of above normal temps.
Normal highs for this time of year are in the low 80s. The NBM
suggests a 15-30% chance for highs to climb into the 90s each
day June 5th-7th. For comparison, despite the forecast calling
for above normal temps today through early next week in response
to this Omega block, the probability of highs climbing above
90F is very low (less than 10% each day).

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 450 AM CDT Fri May 29 2026

VFR conditions will prevail through the period. Cirrus coverage
will increase through the period, while some diurnal cumulus
could develop around 5 kft. There is a low chance, less than
10%, of a shower at KSPI tonight, but precip should stay to the
south and west. Winds will remain light, less than 10 kts,
turning to southeasterly during the day, then backing to
northeasterly overnight.

&&

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

&&

$$

KEY MESSAGES...Erwin
DISCUSSION...Erwin
AVIATION...Erwin