Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 142330
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
630 PM CDT Sat Apr 14 2018

.SHORT TERM...(This evening through Sunday)
ISSUED AT 219 PM CDT Sat Apr 14 2018

Early afternoon surface map showed low pressure near Springfield,
with a cold front extending south and the oscillating warm front
east to near Champaign. Showers have been ramping up quite a bit
over western Illinois to as far east as Peoria and Springfield.
Eastern CWA is currently dry. SPC mesoanalysis shows surface
instability has been limited so far, despite some thinning of the
clouds that occurred earlier in eastern Illinois. However, RAP
guidance shows potential for 500-1000 J/kg of surface CAPE by
late afternoon in areas east of I-57. Have kept a mention of
isolated/scattered thunder ahead of the low/cold front, which
should be near Champaign by 7 pm.

Widespread showers expected overnight, as the large upper low in
northeast Nebraska moves east, and a new surface low reforms
across the Tennessee Valley. The eastern CWA will be most impacted
by the rain, as the west comes under the influence of the dry slot
currently in western Missouri. However, as the upper low drifts
into western Illinois toward midday Sunday, the showers will be on
the increase again.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 219 PM CDT Sat Apr 14 2018

Looks like the 3rd Sunday in a row with some snow potential across
the CWA, as colder air is drawn in behind the departing upper low.
Rain to snow changeover may begin in the far northwest CWA as
early as late afternoon, but a more rapid changeover is expected
in the evening. Only a minor dusting is currently expected, mainly
north of I-74. Given the first Sunday with snow was on Easter,
here`s hoping the myth of "7 Sundays of rain after an Easter
rain" doesn`t apply to snow as well.

Freeze potential still looks strong for Sunday and Monday nights,
with most of the CWA dropping into the 20s. Right now, the growing
season is considered advanced enough to warrant frost/freeze
headlines south of I-70, though areas to the north likely had some
planting done over the recent warm spell. With the southeast CWA a
bit more uncertain with freezing conditions, will hold off on any
headlines for now.

Not a lot of change in the forecast the remainder of the week. The
midweek storm system still looks to largely track north of us,
though the GFS hints at some light precipitation with the trailing
cold front on Wednesday. Right now, will limit any PoP mention to
the northern CWA closer to the low track. Late in the week,
another strong system will take shape over the central Plains.
The GFS is much quicker with this system, bringing rain into the
area as early as midday Saturday. However, the ECMWF is about
18-24 hours slower. Will keep PoP`s on the lower side (around 30
percent) at this point and will watch things shake out over the
next several runs.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 625 PM CDT Sat Apr 14 2018

Slow moving storm system out to our west will dominate the weather
across the area through this forecast period with mostly MVFR and
IFR conditions. There may be a brief period later this evening
into the overnight hours that we see SPI and DEC break out into
some VFR cigs, but based on forecast soundings, the lower cigs
will return by Sunday morning in all areas. As usual, BMI will
have the lower extremes tonight with periods of rain and drizzle
which will bring cigs and vsbys into the VLIFR range on occasion.
Most areas should see occasional rain with still an outside chance
for a brief TSRA in CMI in the 00z-03z time frame, but that threat
seems to be diminishing.

Lower cigs will hold into Sunday over most of the area with rain
chances increasing again, especially across our northern TAF sites.
Winds tonight will be northeast at 10 to 15 kts across PIA and
BMI with more west to northwest winds at DEC and SPI, while CMI
will start out with south winds at 12 to 17 kts early this
evening, but as the cold front moves thru around 02-03z, winds
should shift into more of a southwest direction at 10 to 15 kts,
which should continue into Sunday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Smith



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