013
FXUS63 KILX 031041
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
541 AM CDT Thu Apr 3 2025

.KEY MESSAGES...

- A Flood Watch remains in effect along and southeast of a Paris
  to Shelbyville line through Sunday morning. The latest NBM
  indicates a greater than 50% chance for 4 or more inches of rain
  across this area.

- There is a Slight Risk (level 2 of 5) for severe weather along
  and south of the I-70 corridor for Friday afternoon and evening.
  Hail is the primary severe risk.

- A Hard Freeze is becoming increasingly likely by next Monday
  night...as the NBM now shows a 60-80% chance of low temperatures
  dropping below 28 degrees.

&&

.DISCUSSION...
Issued at 347 AM CDT Thu Apr 3 2025

...Heavy Rainfall Event...

The cold front that brought the severe weather to central Illinois
yesterday afternoon/evening will drop just south of the Ohio
River and become stationary today. While the morning will remain
dry, a short-wave trough tracking along the boundary will trigger
showers across Missouri, which will spill into mainly the southern
half of the KILX CWA this afternoon and evening. Storm total
rainfall with this initial wave will be quite light across much of
the area...but will reach 0.75 to 1 inch south of I-70.

A stronger wave will track out of the Southern Plains on Friday,
causing the boundary to waver northward toward the I-64 corridor
and spreading heavier rains further north into central Illinois.
Have started the day with low chance PoPs, but have increased
those to categorical across the board by Friday afternoon into
Friday night...with locally heavy rainfall likely across the E/SE
CWA where a Flood Watch remains in effect.

Yet another wave will bring additional rainfall for Saturday
before a vigorous short-wave diving southward out of Canada carves
a significant trough over the Great Lakes/Midwest and shoves the
frontal boundary well south of the region by early next week.
Storm total rainfall from today through Saturday night will be
substantial...especially along/south of a Paris to Shelbyville
line where the NBM indicates a greater than 50% chance for 4 or
more inches. The amounts decrease further N/NW, with less than 1
inch expected northwest of the Illinois River.


...Severe Weather Potential on Friday...

As the Ohio River Valley frontal boundary edges northward to near
I-64, showers will overspread all of central and southeast
Illinois by midday Friday. Forecast soundings show little to no
surface-based instability north of the front: however, NAM MUCAPE
values increase into the 1000-2000J/kg range along and south of
the I-70 corridor during the afternoon and evening. Given ample
elevated instability and steep mid-level lapse rates, think hail
will be the primary severe weather risk. Latest SPC Day 2 Outlook
shows a 15-30% chance for quarter-sized hail across this area.


...Hard Freeze Early Next Week...

Once the upper trough becomes established over the Great
Lakes/Midwest, a much cooler and drier airmass will settle
southward into Illinois for Monday and Tuesday. Highs on Monday
will only reach the upper 40s and lower 50s...and as winds
diminish under clear skies, radiational cooling will set up
freezing conditions for Monday night. NBM probabilities show a
60-80% chance for lows dropping below 28 degrees everywhere north
of I-70. These conditions would likely damage any sensitive
outdoor plants.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 540 AM CDT Thu Apr 3 2025

VFR conditions will prevail through the entire 12z TAF period.
Mid/high clouds will gradually increase this morning...with light
showers spreading across the I-72 terminals from the southwest
this afternoon/evening. There is still some question as to exactly
how far north the showers will reach, but given the initially dry
boundary layer in place, have sided with the furthest south
solutions. As such, have kept KPIA dry and have only mentioned
VCSH at KBMI after 23z. Further south, have included predominant
showers and low VFR ceilings after 21z/22z at the other sites.
Winds will be W/SW at 5-10kt today, then will become NE at 5-10kt
tonight.

Barnes

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday morning for ILZ054>057-061>063-
066>068-071>073.

&&

$$