140
FXUS63 KILX 210120
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
820 PM CDT Fri Sep 20 2024

.KEY MESSAGES...

- There is a marginal risk (5-15% chance) for severe weather along
  and southeast of a Champaign to Taylorville line through 8pm
  this evening. The primary concerns will be isolated damaging
  wind gusts and large hail.

- Greater rain chances materialize Saturday night through Monday.
  There is a 50-60% chance of 1-2 inches of rain across central
  Illinois during that time period.

&&

.UPDATE...
Issued at 819 PM CDT Fri Sep 20 2024

This evening, a weak cold front is located roughly along a
Taylorville to Danville line. North of the front, dew points have
dropped into the 50s and skies have cleared except for a few
patches of cirrus. South of the front, warm and humid conditions
persist with dew points near 70 degrees. Scattered showers and
storms continue along and south of I-70 but have weakened in
intensity compared to a few hours ago. Storms should continue to
diminish as the boundary layer stabilizes with loss of daytime
heating. The severe threat has ended across this area and expect
the lingering showers and storms to end altogether by 10-11pm this
evening.

Deubelbeiss

&&

.SHORT TERM...(Tonight through Saturday)
Issued at 316 PM CDT Fri Sep 20 2024

19z/2pm surface analysis shows a weak cold front just east of the
I-55 corridor. Convective clouds have been slow to develop
along/ahead of the boundary due to synoptic subsidence in the wake
of the early morning showers: however, clouds have begun to get
organized over the past hour from Danville southwestward to near
Taylorville. This will be the zone to watch for widely scattered
thunderstorm development over the next few hours. The HRRR has
consistently delayed convection until after 22z/5pm, and this
looks reasonable given recent satellite/radar trends. Any storms
that fire will have moderate instability to work with as characterized
by MLCAPEs in excess of 2000J/kg. However, the strongest deep-layer
wind shear remains displaced well to the west and convergence
along the slow-moving boundary is meager. As a result, am only
anticipating widely scattered convection (20-30% chance)
along/southeast of a Champaign to Taylorville line through mid-
evening. A couple of the cells may be capable of damaging wind
gusts and/or large hail, but the overall severe risk will remain
low. After the evening showers/storms fade away, several CAMs are
suggesting fog development along/ahead of the front overnight. The
most consistent signal for widespread low visibilities and
potential dense fog has remained across northern Indiana, but
given high dewpoint air (65F+) think patchy fog is a good bet
across the E/SE KILX CWA after midnight. Will need to keep a
close eye on observations and latest model trends this evening, as
a Dense Fog Advisory may eventually be needed...particularly east
of the I-57 corridor.

Morning fog will quickly dissipate, leading to another partly
sunny and hot day with highs once again reaching the upper 80s and
lower 90s. A few showers may graze the far W/SW CWA during the
morning, with a few showers potentially re-developing west of the
I-55 corridor during the afternoon: however, most locations will
remain dry.

Barnes

.LONG TERM...(Sunday through Next Friday)
Issued at 316 PM CDT Fri Sep 20 2024

A vigorous short-wave trough evident on latest water vapor imagery
over Manitoba/Saskatchewan will dig southeastward into the Great
Lakes, pushing a stronger cold front toward central Illinois late
this weekend. 12z Sep 20 models are all in good agreement that the
front will push into west-central Illinois late Saturday night,
then linger across the region until Monday night when a second
wave across the Plains finally pushes the boundary further east.
Given copious deep-layer moisture from the Gulf of Mexico with NAM
precipitable water values climbing into the 1.75-2.00 inch range
and strong upper dynamics, the stage will be set for beneficial
rainfall across much of central Illinois. The latest projections
suggest widespread amounts of 1.50-2.50...with isolated higher
amounts where stronger storms materialize.

Once the system departs, cooler/drier weather will arrive across
the Midwest for the middle and end of next week. High temperatures
will drop into the lower to middle 70s and overnight lows will dip
into the lower to middle 50s Tuesday through Friday.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 625 PM CDT Fri Sep 20 2024

A weak cold front is settling south of the terminals early this
evening with the threat for showers and thunderstorms also
shifting south of the area. Light north winds will be in place
initially becoming light and variable or calm at times overnight.
Some patchy fog is possible, especially across east central
Illinois. Winds will set up out of the SE Saturday morning and
shift to southerly in the afternoon.

Deubelbeiss

&&

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

$$