311
FXUS63 KILX 230729
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
229 AM CDT Fri May 23 2025

.KEY MESSAGES...

- Seasonably cool temperatures persist through early next week,
  with highs in the mid 60s to low 70s.

- Severe thunderstorms are unlikely over the next seven days. Rain
  chances return Saturday night into Sunday, mainly south of I-72
  (20-30% chance).

&&

.DISCUSSION...
Issued at 228 AM CDT Fri May 23 2025

Upper level troughing remains in place over the Great Lakes and
interior New England, with a sfc cold front draped east-to-west
across the southern US. As a result, below normal temps persist
throughout the region, with a crisp start to Fri morning as temps
fall into the low/mid 40s. High-res model guidance that arrived
late Thurs evening started to hint at patchy fog across east-
central IL (including the potential for dense fog). As of this
writing (06z/1am), KCMI was varying between 1/4 and 1/2 mi vis and
KBMI had reported 1 1/2 mile vis, but nighttime microphysics
satellite imagery didn`t show any obvious presence of fog outside
of low-lying areas across western IN. MRMS precip estimates
suggests the primary corridor for precip on Thurs was from KBMI to
KMTO and points to the northeast. This would make sense as the
area most likely for fog development, and that is exactly where
the high-res guidance is depicting the fog development. As such,
added a mention of patchy fog to the gridded forecast in these
areas. Have not introduced any text products/headlines for dense
fog at this time, but will continue to monitor trends and issue if
needed.

Into the day today, central IL will find itself situated between
sfc low pressure over the northeast US and pressure falls in the
lee of the Rockies. As that next system develops well to our west,
high clouds will overspread the area from west to east today.
Fcst soundings indicate some diurnal Cu are possible around 5kft,
but the Cu-rule suggests coverage will be fairly sparse. High
temps are still forecast to be near 70/into the low 70s. Such
values are still about 5 deg below normal for this time of year.

Over the weekend, an emerging system will focus precip chances
primarily south of the ILX CWA, with the highest amounts well to
our south across the Ozarks. It seems the NBM is catching up to
the southward trends noted in previous forecasts, with the latest
forecast blend lowering PoPs and QPF across the ILX CWA through
the weekend. Most of the area should be dry through the day on Sat
(10- 15% chnc of rain in the southern fringes of the ILX CWA),
then there is a 20-30% chance of showers Sat night into Sun across
the southern half of the CWA. As that shortwave begins to lift
northeast early next week, it could bring a better chance of rain
(30-40%), though several days of northeasterly sfc flow make me
suspect that dry low- level air could mitigate precip
coverage/intensity somewhat.

By Tues of next week, models indicate a closed upper low over the
northern Plains, but deterministic guidance starts to diverge
considerably in the evolution of this low, with some models
retrograding this low to the west and others merging it into the
jet stream and quickly whisking it off to the east. This model
divergence leads to less confidence in the specifics of the
forecast beyond early next week, but machine-learning products
suggest the svr storm threat is low through at least the upcoming
work week. Additionally, below normal temps will continue for
several days, with high temps in the mid 60s to low 70s favored
through early next week. After that point, the ensemble mean shows
temps on a slow, gradual warming trend.

Erwin

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1212 AM CDT Fri May 23 2025

VFR conditions will generally prevail through the period. Some
concern with the light winds with a little fog formation, with
some of the high-res models lowering visibilities in areas that
had some rain yesterday (mainly the KPIA-KCMI corridor). However,
latest NBM and HREF guidance are only around 15-20% for
visibilities below 5SM, so will hold off a mention until surface
observations start trending in that direction.

Winds pick up from the northwest Friday morning and will be close
to 10 knots, before lightening up again by 00z.

Geelhart

&&

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

$$