Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 291905
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
105 PM CST Thu Feb 29 2024

.KEY MESSAGES...

- 30-50% chance for rain/snow south of I-72 tomorrow morning into
  early afternoon. Nonzero, but low (10%) chance for freezing
  rain. Any wintry precip accumulations will be minimal.

- Gusty south winds will accompany a weather system Sunday into
  Monday, with gusts upwards of 35 mph expected. Chances for
  hitting Wind Advisory criteria, 45 mph, are generally less than
  30%.

- Widespread showers and perhaps thunderstorms are expected with
  the same system Monday into Tuesday. While uncertainty remains
  high in severe potential, its potential looks low (less than
  15%) at this time.

&&

.DISCUSSION...
Issued at 104 PM CST Thu Feb 29 2024

A return to southerly surface winds marks the beginning of a warming
trend that will bring high temps into the upper 40s this afternoon
amidst clear skies. A mid-level system lifting northeast through the
region will bring a 30-50% chance for some rain and wintry mix
across areas mainly south of I-72 tomorrow morning into early
afternoon, with temps behind it suppressed a bit by lingering cloud
cover. However, the warming trend will return Saturday as southerly
flow increases yet again to bring temps into the 60s.

With the system tomorrow morning, models continue to struggle in
identifying which p-type will be predominant. HREF currently shows a
roughly 20-50% chance for both rain and snow (with snow the more
probable p-type further north), but no members within the ensemble
are depicting any freezing rain. Still, forecast soundings from the
HRW-ARW show a sufficient warm nose aloft that if surface temps drop
to sub-freezing by dynamic cooling during the morning there could be
some freezing rain. Chances for that are estimated at around 10%, so
it`s not expected though it could make for some slick pavement
(especially on sidewalks) if it does occur. LPMM QPF is less than a
tenth of an inch everywhere, while the ensemble max is just over a
tenth, so if that should all come down as snow (and it shouldn`t)
there`d be an inch or less of accumulation on grassy surfaces in the
heaviest band. Winter weather impacts are thus not expected.

The warming trend in temperatures will culminate either Sunday or
Monday, depending on the timing of passage of a cold front which
will slow as it approaches the area. Ahead of that front,
deterministic models bring 850mb temps to the +12-15 degC range,
suggesting surface temps could rise well into the 70s on one or both
of those days. The deterministic models also show decreasing gaps
between north-south oriented isobars, indicating a tightening
pressure gradient favorable for gusty south winds which the ECMWF
ensemble mean suggests will peak around 35-40 mph late Sunday into
Monday. NBM fortunately suggests the chances for hitting advisory
criteria - highest in our northwest - are generally less than 30%.
NBM brings rain (thunder) chances to around 50-70% (20-30%) with
that washed out cold front late Monday into Tuesday, though
instability displaced well south of favorable forcing should limit
severe potential. Beyond Tuesday, ensemble spread in the pattern
increases, leading to uncertainty in temperatures and precip
potential, but CPC advertises a 70% chance for above normal
temperatures throughout days 6-10 (Wednesday, March 6th through
Sunday, the 10th).

Bumgardner

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1127 AM CST Thu Feb 29 2024

VFR conditions will continue through the early overnight period as
high pressure slowly departs to the east and a mid level wave
approaches from the west. The tightening pressure gradient will
lead to increased southerly winds which will gust to around 20 kt
at times through the afternoon. Gusts will diminish and sustained
speeds ease slightly overnight, but by mid morning ceilings and
possibly visibilities drop as scattered rain/snow showers pass
mainly along and south of I-72. The highest chance for a category
dip to MVFR (or lower) will be at SPI, DEC, and CMI, where HREF
guidance suggests a 30-50% (10-20%) chance for such ceilings
(visibilities) after 15z (9am CST).

Bumgardner

&&

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

$$


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