798
FXUS63 KILX 291535
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1035 AM CDT Wed May 29 2024

.KEY MESSAGES...

- Dry and fair weather through Friday, with high temperatures in
  the 70s.

- Rain chances return late Friday night into Saturday. Severe
  storms are not expected, but there is a 40-50% chance for
  rainfall amounts exceeding 0.25".

&&

.UPDATE...
Issued at 1027 AM CDT Wed May 29 2024

Have opted to lower dewpoints and increase temperatures by a
degree or two this afternoon. This is mainly a speculative hedge
due to a very dry boundary layer, perhaps permitting deeper mixing
than what model soundings indicate. Otherwise, no changes were
made to the near-term forecast.

MJA

&&

.DISCUSSION...
Issued at 207 AM CDT Wed May 29 2024

An amplified upper level ridge axis extends from the western
Plains to the central Canadian Prairie early Wed AM, with an
associated 1024-mb sfc high pressure centered over northern MN.
Closer to home, a weak shortwave lingered over southern Lake
Michigan, resulting in decaying rain showers and a cloud deck over
northeastern IL. This cloud deck is expected to pivot across
areas northeast of a Bloomington-Champaign line over the next few
hours and remain in place into the day.

The aforementioned sfc high pressure will be the dominant feature
over the next two days, resulting in fantastic weather across the
local area. Today continues to look cloudier than Thurs, with the
NAM Cu-rule suggesting scattered to broken diurnal Cu around
4-5kft today. This evening, a backdoor cold front drops into the
area, ushering in drier, lower dewpoint air. Forecast soundings
show a shallow unstable layer above the cloud deck, so can`t
completely rule out a few sprinkles this evening, particularly if
that front pushes into the area before sfc heating is completely
lost. That being said, the potential for sprinkles seemed too low
to introduce in the grids. With mostly clear skies Wed night, lows
could drop into the upper 40s across the northern half of the
area, which is about 10 degrees below normal. Thursday should be
quite pleasant, with mostly sunny skies, low humidity, and
temperatures in the upper 70s.

Into the weekend the ridge axis will start to shift east, opening
the door for renewed precip chances, but latest guidance has
slowed the onset a bit such that the daytime hours on Fri look dry
area- wide. A shortwave moves through the Ohio Valley on
Saturday, with central IL on the north side of the system where
instability progs are quite low. PWAT values have been trending
upward, with the ens mean for Sat increasing from around 1.1" to
closer to 1.5" in more recent cycles, and accordingly the QPF
probs have ticket upward as well. Through Sun AM, the NBM now
shows a 40-50% chance of exceeding 0.25" of rain across the area
(as opposed to the previous forecast which had 25-40% chance).

The pattern becomes more zonal into early next week, resulting in
additional precip chances, but there should be a least some dry
time between the Saturday system and the subsequent precip
chances. An early look at Monday suggests a disturbance will pass
well to the north, across Canada, and based on that alone the
forcing would be pretty weak for precip locally. There are small
perturbations in the upper flow closer to home that could aid
precip development early next week, but we`ll have to see if these
are correctly timed by the models or not. The NBM populated with
30-50% precip chances during the Mon-Wed time frame, which will
likely need some refinement but there was too much temporal
uncertainty to make meaningful adjustments at this range.

Temperatures are generally expected to warm after Wednesday,
although the increased confidence in cloud cover and rain on
Saturday has knocked the forecast highs down a bit (into the mid
70s). By next week, highs should be back in the 80s.

Erwin

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 547 AM CDT Wed May 29 2024

VFR conditions should prevail through the period, but there is an
MVFR cloud deck that could clip KCMI during the first few hours of
the period. Otherwise, light northwesterly winds will turn
northerly today, then eventually shift to northeasterly late this
evening. Scattered to widespread diurnal Cu are expected during
the afternoon, around 4-5 kft.

Erwin

&&

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

$$