Springfield, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

979
FXUS63 KILX 241708
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1108 AM CST Sun Nov 24 2024

.KEY MESSAGES...

- A frontal system will slowly push across the region today and
  Monday, resulting in seesawing temperatures and periods of
  drizzle.

- A mix of rain and snow is possible (50-60% chance) during the
  Wednesday-Thursday timeframe. Model guidance continues to
  exhibit high variance with the snowfall potential, particularly
  across central Illinois. This puts us in a low-confidence, high-
  impact situation ahead of the holiday, and will require you to
  monitor the forecast for updates.

- A bona fide cold snap will bring a January-like chill to the
  region by next weekend, with wind chill values cratering into
  the single digits, at least.

&&

.DISCUSSION...
Issued at 1250 AM CST Sun Nov 24 2024

Morning water vapor imagery depicts multiple shortwave impulses,
embedded within broad southwest flow, ejecting out of the Rockies
and into the Plains. Weak surface low pressure will develop
beneath these upper-level impulses and ride along a baroclinic
zone, currently extending from eastern SD to western TX. Model
guidance is in excellent agreement that this baroclinic zone will
sharpen and shift into western IL late tonight as a trough digs
across the Northern Plains. Both warmer temperatures and Gulf
moisture will advect northward into our area today ahead of the
baroclinic zone, with afternoon temperatures reaching into the
upper 50s. With the influx of low-level moisture and isentropic
ascent, we continue to see a signal for light precipitation
this evening and into Monday. Mesoscale soundings reveal stubborn
dry air in the mid- levels and a general lack of cloud-ice
nuclei, suggesting drizzle. This should limit QPF to just a few
hundredths through Monday morning in areas east of the IL River
Valley.

Temperatures will remain mild on Monday as the cold-
front/baroclinic-zone pushes across central IL. Breezy north winds
will then filter into the region late Monday night, advecting in a
drier and much colder airmass. This will result in wind chill
values falling into the teens by Tuesday morning, primarily in
areas north of I-70.

Attention then turns toward the evolution of a midweek frontal
system, which is expected to lift out of the Southern Plains late
Tuesday night and towards the Tennessee Valley by Wednesday. There
remains considerable spread among global deterministic guidance
with respect to storm track and QPE, making this a volatile period
in our forecast. In fact, there has been very little continuity or
run-to-run consistency among the deterministic guidance. Taking
an ensemble approach to the forecast, the ENS remains in a league
of its own with a deeper/more-amplified trough positioned over The
Plains on Wednesday, resulting in a stronger surface low and more
QPF spread further north across our area. This is in contrast to
the GEFS & GEPS, which keeps the upper-level flow pattern a little
more zonal across our area, shunting a weaker surface low with
less QPF to our south. Glancing at the 10-90th goalposts for ensemble
snowfall (10:1) accumulation, the GEFS and GEPS offer between
Tr-2". This is in stark contrast to the 10-90th goalposts from the
ENS, which exhibits much higher variance between Tr-10" across our
area. When comparing the ensemble solutions against the NBM, we
see the NBM more in-line with the GEFS/GEPS solution, which mutes
the snowfall potential by emphasizing a thermo profile (p-type)
that leans more rain than snow during the Wednesday - Thursday
timeframe. That`s kind of the big picture for now, but as always,
the devil will be hidden in the details. Any type of mesoscale
banding that might develop north of the surface low could result
in a narrow band of impactful snowfall. The best thing to do for
now is to not anchor to any one forecast, but instead monitor the
trends into early next week.

Perhaps the greater impact to the region will come next weekend as
an anomalous surface high builds into the northern U.S., expanding
across much of the Midwest and bringing the coldest air so far
this season. Both blended (NBM) and ensemble (LREF) guidance
support overnight lows in the teens by next weekend, with wind
chill values in the single digits.

MJA

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1107 AM CST Sun Nov 24 2024

A cold front will move across central Illinois late tonight into
Monday morning. Well ahead of the front, southerly winds and VFR
conditions will prevail the remainder of today. As the front
approaches this evening, scattered light showers are expected to
overspread central Illinois and ceilings will build down to MVFR
and possibly IFR in the vicinity of the cold front. Confidence in
IFR is greatest at BMI-DEC-CMI. Winds will turn northwesterly
behind the front and any IFR conditions should improve back to
MVFR behind the front while precip chances also taper off.

Deubelbeiss

&&

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

$$