Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 260634
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
134 AM CDT Tue Mar 26 2024

.KEY MESSAGES...

- Gusty showers and isolated thunderstorms will develop later this
  morning, with an attendant severe wind risk. Areas east of I-55
  could see convective wind gusts exceeding 45 mph, but confidence
  is low (less than 50% chance). Winds then gradually diminish by
  midday once the cold front departs.

- Sub-freezing temperatures arrive tonight behind the cold front,
  mainly in areas north of a Taylorville-to-Danville line.
  Confidence in areawide sub-freezing temperatures is higher
  Wednesday night (60% chance or greater). Tender, early- season
  vegetation will be susceptible to damage.

- Drier and progressively warmer weather is anticipated mid-to-
  late week, with the next best chance (30-50%) for rain coming
  Friday evening.

&&

.DISCUSSION...
Issued at 133 AM CDT Tue Mar 26 2024

Early morning WV imagery depicts a mid-level low pivoting
northeastward across the Mid-Mississippi Valley as a strong 300-mb
jetcore lifts around the base of the upper trough.
Satellite imagery also reveals the system dry slot working into
western Illinois, with the radar reflection indicating diminishing
rainfall.

Even with widespread rain diminishing overnight, we should begin to
see convective showers developing this morning ahead of the cold
front (currently positioned from Cedar Rapids, Iowa to Little Rock,
Arkansas). These showers will be supported by strong dCVA, 500-mb
height falls, steepening lapse rates, sfc convergence etc.
And, while the latest 00z CAMs do show semblance of an arc of
scattered showers developing west of I-55, instability progs are
underwhelming as these showers move into eastern Illinois. At best,
we see 250-500 J/kg of SBCAPE later in the morning as steepening 0-
3km lapse rates help erode SBCINH in areas east of I-57.

With instability being the limiting factor today, confidence in
severe weather is low. Nevertheless, with robust kinematics in place
ahead of the cold front (e.g. 40 kts of 0-3km shear), we couldn`t
completely dismiss a conditional severe wind risk should any low-
topped convection become organized near the I-57 corridor.

Winds will gradually diminish by evening as the surface pressure
gradient relaxes behind the departing frontal system. Areas of
stratus and patchy drizzle could linger tonight before low-level
moisture gets scoured-out Wednesday morning. Stubborn low clouds may
actually help buoy overnight temperatures above freezing--contrary
to deterministic NBM guidance which has tonight`s lows in the mid-
to-upper 20s in areas west of I-55.  Confidence in sub-freezing
temperatures is higher for Wednesday night as a broad 1024-mb
surface high settles over the Mid- Mississippi Valley. The
probability for areawide sub-freezing temperatures is greater than
60%.

The stretch of dry weather will continue through the remainder of
the work week amid an aggressive warming trend. Daily temperatures
will surge into the 60s to close the week, with low 70s certainly in
play over the holiday weekend.

Mid-range blended and ensemble guidance are both in excellent
agreement in our next chance for rain, which comes Friday evening as
a LLJ impinges upon a east-west frontal zone sagging into central
Illinois. This front then looks to waver over the region for the
remainder of the weekend and into early next week, and its daily
position will have implications on both forecasted temperatures and
rain prospects. Current NBM statistical guidance offers a broad
range for 72-hr QPF between Saturday and Monday; anywhere from 0.05"
- 2.0" across our CWA. That may not be the most helpful forecast,
but there is an 80% chance it verifies. That range will undoubtedly
narrow some in coming days.

MJA

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1024 PM CDT Mon Mar 25 2024

A band of moderate rain will diminish over the next few hours,
leaving MVFR ceilings across the central IL terminals overnight.
While some breaks will occur at times, predominant MVFR ceilings
are forecast for this TAF cycle. After the main area of rain
exits, isolated showers will persist until a cold front pushes
through between 12-17z, and mentioned VCSH for this. Southeast
winds gusting around 25 kt tonight will veer southwest Tuesday
morning, gusting 25-35 kt through afternoon.

25

&&

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

$$


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