Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 210433

Area Forecast Discussion
National Weather Service Lincoln IL
1133 PM CDT Tue Jun 20 2017

Issued at 910 PM CDT Tue Jun 20 2017

Sufficient elevated instability and wind shear is present to
allow scattered showers and a few storms to linger this evening,
well ahead of an approaching weak cold front. The areas with the
better chances to see rain the rest of the evening look to be east
of Bloomington to Champaign, and south of Shelbyville to Paris.
All precip activity should dissipate by 06z/1am, with skies
becoming mostly clear by morning. Light and variable winds and
decreasing cloud cover the rest of the night will allow for
radiation cooling to put low temps down near or below seasonal
normals (59-66F).

Looking ahead to Wednesday, a weak wave will pass by across N
Illinois, but dry conditions should prevail in central and
southeast IL.

Updates this evening were done mainly to PoPs/Weather, with minor
adjustments down to low temps. Other forecast grids look on track.
Updated info is already available.


.SHORT TERM...(This evening through Wednesday)
ISSUED AT 230 PM CDT Tue Jun 20 2017

Early this evening should be much like 24 hours prior, with
isolated to scattered thunderstorms that fade in coverage and
intensity with loss of diurnal heating. A short wave will track
through the Midwest tonight, providing just enough dynamic support
to produce convection despite relatively dry air and associated
low instability. However, the dry air beneath the cloud bases
will once again support some strong wind gusts on the stronger

Otherwise, the remainder of the period should exhibit quiet
weather as the upper-level flow trends neutral and surface high
pressure builds across the area.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 230 PM CDT Tue Jun 20 2017

The remainder of the forecast period appears to be trending drier
overall. It is looking increasingly like the MCS progged for
Wednesday night into Thursday will stay north of the forecast
area. Then, an upper-level wave tracking across Canada will
slowly drop a cold front across the region Thursday night into
Friday. This period stands the best chance over the next several
days of widespread precipitation across the forecast area. It is
looking increasingly like the front will settle south of the area
by Friday night, with the remainder of the forecast period
trending cooler and drier in its wake. While the Friday night to
Tuesday period will probably not be completely dry, the model
guidance is certainly trending that way. There are varying
solutions of weak disturbances within the developing northwest
upper-level flow that may have rainfall associated with them, but
there is no consensus that warrants going above Slight Chance PoPs
at this time.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1133 PM CDT Tue Jun 20 2017

A few showers lingering near DEC and CMI at 0415z should depart
to the southeast by 06z/1am. Otherwise, a generally weak pressure
pattern across Illinois should help provide quiet weather over
the next 24 hours. Light and variable winds are expected through
sunrise, then winds will be on a steady shift from N to E to SE
during the day on Wednesday. Wind speeds look to prevail below
10kt tomorrow, during the persistent wind shift.

No significant cloud ceilings are expected this TAF period, with
the HRRR suggesting a band of 5-6K FT clouds will develop near the
I-74 corridor around sunrise. Otherwise, SCT150-200 will be the
rule for the majority of the next 24 hours.

A weak shortwave will pass across northern Illinois tomorrow, but
all precipitation looks to remain north of the TAF sites.




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