090
FXUS63 KILX 120901
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
401 AM CDT Mon May 12 2025

.KEY MESSAGES...

- Scattered afternoon showers and an isolated thunderstorm today
  and Tuesday.

- Near-record warmth by Thursday with a conditional threat for
  severe thunderstorms.

&&

.DISCUSSION...(through next Monday)
Issued at 359 AM CDT Mon May 12 2025

Early morning WV satellite imagery depicts a deepening trough
carving into the western US, with a cut-off low still positioned
over Louisiana.  Model guidance remains in excellent agreement that
the former will help dislodge the latter, with the closed low
expected to open/lift toward the Tennessee Valley by Tuesday.  As
this evolution takes place, an influx of Gulf moisture and synoptic
ascent will overspread Illinois.  The net effect will be diurnally-
driven showers both today and Tuesday, and perhaps an isolated
thunderstorm as instability builds in the vicinity of the cold-core
low.  In addition to the scattered showers, the synoptic pattern
will be quite favorable for cold air funnels, and the normalized NST
parameter continues to flash values > 1 both this afternoon and
Tuesday afternoon, per recent RAP & NAM guidance.  If you happen to
intercept one, please send us a picture, but not while driving.

Precip chances become muted by Wednesday once the upper trough
departs toward the Mid-Atlantic region and subsidence works into
Illinois ahead of an amplified ridge.  Temperatures will become
seasonably hot (mid 80s) on Wednesday beneath the ridge axis, and
hotter still by Thursday (about 90) as a warm front surges north
across the region in tandem with an upstream lifting/pivoting
shortwave trough.  In fact, Thursday`s forecast at Peoria will
threaten a 130-year record (93 degF, 1894).

The severe weather signal for Thursday & Friday remains poorly
resolved by mid-range global guidance (GFS/ECMWF). While the
synoptic pattern supports deep convection across portions of the
Midwest, there are plenty of mitigating factors looming that
continue to apply downward pressure on predictability. Residual
capping across the warm sector, dry air entrainment in both the low-
and mid-levels, and displacement from the main upper forcing
suggests updrafts could struggle to reach the LFC on Thursday,
especially with only modest frontal forcing beneath an otherwise
less favorable right-exit region of the upper jet core.  On the
other hand, a stout EML, very steep mid-level lapse rates,  and an
increasing belt of westerlies ahead of the front will offer
CAPE/Shear profiles that impress professionals and noobs alike. This
all adds up to a conditional severe weather threat for central
Illinois on Thursday.  For what it`s worth, both the 00z GFS & ECMWF
largely mutes CI across SE Iowa and W Illinois, while only about
half of their respective ensemble members indicate CI.  This is in
stark contrast to recent MPAS guidance which convincingly brings
organized, all-hazards convection across central IL Thursday
evening. At this point, it`s a true boom-or-bust scenario and either
narrative is about equally likely.  The best we can do for now is
monitor trends as we eagerly await the hi-res CAMs to begin
resolving the pattern.

Depending on how Thursday evening unfolds, there is another
conditional risk of severe weather Friday evening near and south of
I-70.  In simplistic terms, if convection rips us Thursday evening,
the front and any convective outflows will probably favor
redevelopment just south of our CWA by Friday evening.  By contrast,
if it`s crickets around here Thursday evening, the front may stay a
little further north near I-70, putting our southern counties at
greater risk of severe weather Friday evening.

A ridge of high pressure begins to nose across the Plains by
Saturday, offering a drier and more stable forecast.  Unsettled
weather is then quick to creep back in by early next week, with both
the GEFS & EPS offering some dirty-ridge, nocturnal-MCS action.

MJA

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1208 AM CDT Mon May 12 2025

A large and slow moving upper level low pressure system will drift
north into the area today, and linger through Tuesday. This will
bring scattered showers and a few storms, most numerous during the
afternoon. Ceilings will primarily be VFR, though briefly lower in
showers. Winds will continue to be from the east around 10 kt or
less.

25

&&

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

$$