991
FXUS63 KILX 151726
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1226 PM CDT Wed May 15 2024

.KEY MESSAGES...

- Periods of rainfall are forecast from Thursday through Saturday.
  The chance of greater than one inch of rain at any given
  location during that three day stretch ranges from 10-40%.

- Warmer temperatures are forecast early next week, with the
  probability of high temperatures exceeding 85 F in the 30-60%
  range both Sunday and Monday.

&&

.UPDATE...
Issued at 1007 AM CDT Wed May 15 2024

An upper low was positioned over the Ohio River Valley Wednesday
morning, gradually shifting east. Latest vis satellite imagery
shows mostly cloudy skies to the south of I-72 as well as to the
east of I- 55, while spotty showers continue east of I-57. Made
some edits to sky cover to hold onto the mostly cloudy skies a bit
longer across eastern IL, as NAM-based Cu rule suggests broken to
overcast skies lingering into the afternoon. Also nudged high
temps a bit cooler across eastern IL where those clouds are
expected to persist.

Erwin

&&

.DISCUSSION...
Issued at 310 AM CDT Wed May 15 2024

Early morning mesoanalysis shows a surface low centered near
Louisville KY with steady north/northeasterly flow over Illinois.
A couple hundred J/kg of MUCAPE remains in place south of a line
from about Shelbyville to Paris. However, the north/northeasterly
flow should erode that minimal instability with time as weak
negative theta-E advection continues. Both 925 and 850 mb winds
show a bit of an easterly component to them, which should result
in clouds being a bit slow to erode in eastern Illinois today.
We`ll also keep some low precip chances going near the Indiana
state line through this afternoon.

Relatively quiet weather continues through Thursday morning as a
surface ridge axis moves near central Illinois tonight.
Precipitation sourced from a couple of different areas should be
moving toward the ILX CWA during the day on Thursday...one area of
precipitation associated with a short wave trough crossing the
upper Midwest, and the other being remnants of convective activity
occurring over the southern Plains on Wednesday evening. The
wave denoted by the southern Plains activity will likely have the
most influence on central Illinois, particularly if its arrival
is timed around late morning-early afternoon as shown by several
CAMs. Up to around 1000 J/kg of MUCAPE may be present, but with a
minimal amount of shear across all but the far southern portion
of the ILX CWA severe weather should be limited. A second low
moving out of the southern Plains will continue precip into Friday
over much of central Illinois. It`s most likely we`ll be north of
the warm front with this low, with instability/shear and
therefore severe probabilities again being limited. Some ensemble
members continue precipitation into Saturday, with about 40% of
members depicting a slower/stronger low digging farther south and
the other 60% showing the low moving faster and ending precip
earlier. Overall, the probability of rainfall greater than an inch
at any given location during the entire Thursday-Saturday period
is in the 10-40% range, with any heavy rain adding to runoff.
Heavy rain probabilities are highest south of I-72, particularly
on Friday.

The ensemble mean height forecast shows a mid-level ridge
building into the Midwest early next week, with warming
temperatures forecast as a result. Most likely high temperature
values from Sunday through Tuesday are in the low to mid 80s, with
a 30-60% chance of a high temperature exceeding 85 F at any given
location. In addition to the warming temperatures, moisture
profiles and increasing CAPE/shear threshold probabilities
indicate greater likelihood for the presence of severe weather
ingredients early next week. Exact track and timing of individual
waves will play a part in determining any severe weather
development, and also in determining potential (or not) for
warming temperatures.

AAT

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1226 PM CDT Wed May 15 2024

The eastern sites (DEC/CMI) will be slightly slower to lift ceilings
this afternoon, keeping MVFR ceilings until this evening (~22z).
SPI/PIA/BMI are VFR until late in the period, when ceilings will
start dropping to MVFR again by 16/17z tomorrow morning. All sites
could see brief period of lowered ceilings from the scattered
cumulus field that is lingering this afternoon. No rain or
thunderstorms are expected for this TAF cycle.

Copple

&&

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

$$