Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 252306
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
606 PM CDT Mon Mar 25 2024

.KEY MESSAGES...

- Strong south winds will persist in central and eastern Illinois
through tonight with winds gusting up to 45 mph. A Wind Advisory is
in effect through midnight.

- An axis of heavy rainfall will bring 1-2 inches of rain to west-
central Illinois through Tuesday morning.

- Isolated severe thunderstorms will be possible in eastern Illinois
late Tuesday morning into early afternoon.

- Below freezing temperatures are likely both Tuesday and
  Wednesday nights. Early-season vegetation will be susceptible to
  damage.

&&

.DISCUSSION...
Issued at 257 PM CDT Mon Mar 25 2024

Water vapor imagery shows an upper trough starting to lift north
from the southern Plains states with a plume of moisture extending
northward into the Great Lakes Region. At the surface, a 994 mb
surface low is positioned over far northeastern Kansas with strong
southerly winds in place out ahead of it. The highest winds gusts so
far today have ranged from 35-45 mph, but have generally
underperformed. As the low lifts into Iowa this evening, a
strong ~60+ kt LLJ will nose into eastern parts of Illinois and
bring another period where stronger winds can mix down mainly
near/east of I-55, which has been consistently noted on both the
HRRR and NAMNest. The Wind Advisory has been adjusted to remove
counties in far western Illinois where winds have largely
subsided, with it continuing through midnight near and east of
I-55.

Rain showers have become more persistent this afternoon near/west of
the Illinois River. Shower activity will continue to shift eastward
this evening, bringing likely rain chances to the entire area
tonight. A lull in precipitation will be seen early Tuesday morning
before a strong cold front works through the area later in the
morning, bringing another round of scattered showers and even some
thunderstorms. Although instability won`t be overly impressive (a
few hundred J/kg), very strong wind shear could support a couple
organized low-topped storms late Tuesday morning into early
afternoon. Primary hazards with any of these storms would be
damaging wind gusts, though a brief tornado or two may spin up
since LCLs will be rather low. There still remain discrepancies
on where storms will initiate with CAMs split between just west or
just east of the IL/IN state line. The SPC day 2/Tuesday outlook
still highlights a marginal risk for severe storms in eastern
Illinois.

Precipitation totals through Tuesday morning will range from 0.50 to
1.5 inches with the highest amounts near/west of the Illinois River.
The 25.12Z HREF shows some locally higher amounts closer to 2 inches
in this same area due to training. The flooding threat looks pretty
marginal due to recent dry conditions, though some ponding of water
in low lying spots could result. 6 hour flash flood guidance is
between 2.5 and 3 inches areawide, so the threat for flash flooding
will be very low. Ensemble guidance (ENS, GEFS, GEPS) only show a 5-
10% chance of 2.5+ inches of rain near/west of the Illinois River.

Surface ridging settles into the area by the middle of the week as
the upper trough shifts into the eastern CONUS, bringing a period of
cooler temperatures back to the area. Overnight lows Tuesday and
Wednesday nights will fall below freezing and pose a threat to early
season vegetation.

Upper ridging builds over the central CONUS by the end of the week,
with southerly return flow setting up locally. Temperatures will
gradually climb to near normal values on Thursday, and then climb
well above normal for the end of the week into the weekend. Our next
chances for precipitation arrive late Friday night into this weekend
as a few upper shortwaves round the top of the upper ridge.

NMA

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 606 PM CDT Mon Mar 25 2024

A band of moderate rain with MVFR ceilings and visibilities will
spread east across the central IL terminals this evening. Isolated
reductions to IFR are possible in briefly heavier showers but
probabilities were low enough to not include in the TAF. An
isolated TSRA is also possible but again chances too low to
include.  The rain will last about 6 hours then diminish to
isolated showers late tonight. Isolated showers will persist over
eastern IL until a cold front pushes through around 16-18z, and
mentioned VCSH for this. Guidance shows some breaks in the MVFR
ceilings late tonight and Tuesday morning, however kept the
ceilings going through 00z as any breaks should fill in with
diurnal heating. Southeast winds gusting around 25 kt tonight will
veer southwest Tuesday morning, gusting 25-35 kt through
afternoon.

25

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until midnight CDT tonight for ILZ038-042>046-
051>057-061>063-066>068-071>073.

&&

$$


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