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000
FXUS63 KILX 241735
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1235 PM CDT Wed Apr 24 2024

.KEY MESSAGES...

- Frost/freeze potential returns tonight when temperatures dip
  down into the 30s to low 40s. There is a 60-90% chance for
  temperatures to fall below 37 degrees near/north of I-74.

- A warmer and more active weather pattern sets up for late in the
  week with temperatures nearing 80 degrees by the weekend.
  Periodic chances for showers and storms exist Friday through
  Monday, which includes the threat of heavy rain and severe
  weather.

&&

.UPDATE...
Issued at 915 AM CDT Wed Apr 24 2024

Cold air-stratocumulus continues to spill southwest across central
Illinois late this morning. Most guidance is not capturing the
cloud cover, though the HRRR has a decent handle so have blended
temps and sky cover with the HRRR. Lower temps several degrees
where cloud cover will be most extensive today, namely portions of
east central Illinois. Cloud cover is somewhat thin so it should
eventually scatter out this afternoon but may linger into the
evening from near Champaign to Effingham and areas east.

Deubelbeiss

&&

.DISCUSSION...
Issued at 412 AM CDT Wed Apr 24 2024

A cold front continues to crawl southeast across the state early
this morning, positioned from roughly Paris to Shelbyville as of 4
am. Dewpoints have fallen behind the front, but are in the 40s out
ahead of it. Patchy dense fog developed ahead of the front late last
night as air temperatures dropped to the dewpoint. Visibilities have
shown a gradual improvement over the last few hours though some
patchy dense spots may continue through daybreak. The overall
trends on satellite imagery show much of the fog exiting our far
southern border.

Further north, stratocumulus stemming off Lake Michigan is marching
southward and will spread into areas north of I-74 through daybreak,
then south of there after. Winds will continue to veer from a
northerly to easterly direction today as surface ridging sinks into
most of the Midwest, cutting off moisture/low clouds from the Great
Lakes. Cooler than normal temperatures will be seen through tonight,
with overnight lows dropping into the 30s to low 40s as winds become
gentle. Aside from some thin cirrus tied to a couple subtle
shortwaves pivoting through northwesterly flow aloft, mostly clear
skies should allow a decent setup for radiational cooling. The NBM
continues to show high probabilities (60-90%+) for temperatures of
37 degrees or less near/north of I-74, which would be favorable for
frost formation. Probabilities for freezing temperatures continue to
be low, with about a 20-40% chance from Minonk to Fisher. Look for
Frost and perhaps Freeze headlines to be issued later today.

An amplifying upper ridge will work into the eastern CONUS by late
this week, setting the stage for an extended period of southwest
flow. This will bring the return of a warm, moist airmass and
periodic chances for showers and storms from Friday through Monday
tied to two upper systems. The first of the two will send a warm
front north through the area Friday morning, bringing likely chances
for showers and storms. The surface low will lift into the northern
Plains Friday evening, with the cold front stretched from western
Iowa southward to eastern Texas. A 50-60 kt LLJ will develop ahead
of an approaching negatively tilted upper shortwave Friday night,
allowing storms to blossom along/ahead of the front where the best
instability will be. Storm activity will spill eastward into parts
of Illinois late Friday night, posing a threat for a few stronger
storms. Instability will generally be weaker here due to lack of
higher dewpoints, but 30-40 kts of effective shear may sustain some
storm organization through the overnight hours.

Better Gulf moisture will advect northward by Saturday with
dewpoints looking to exceed 60 degrees. Moderate instability should
build by Saturday afternoon/evening, but weaker shear and an overall
lack of forcing during the day should keep thunderstorm activity at
bay until the LLJ interacts with a stationary front just west of the
area Saturday night. Some thunderstorm activity could impact western
parts of the CWA Saturday night, posing the threat for a few
stronger storms Saturday night. However, the extent of the severe
threat remains a little uncertain at this time.

A second low will work into the central Plains states by Sunday and
send a cold front through the area later in the day. Depending on
how much storm activity lingers on Sunday morning will determine how
quickly we are able to destabilize ahead of the approaching front.
Sunday could be another day to watch for severe storms with SPC
highlighting a 15% severe threat west of I-57. Rain totals through
the weekend will be generous, with the highest amounts looking to
remain near/west of I-55 where the NBM has a 20-50% chance of
exceeding 2 inches of QPF.

NMA

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1234 PM CDT Wed Apr 24 2024

High pressure will very gradually shift east across the Great
Lakes tonight and Thursday resulting in NE winds slowly veering to
SE across central Illinois. MVFR ceilings across the region will
linger into the afternoon, longest at DEC and CMI, but should
eventually scatter back to VFR. VFR conditions should then prevail
the remainder of the period.

Deubelbeiss

&&

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

$$