Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 190200
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Sat Mar 18 2017

.UPDATE...
Issued at 900 PM CDT Sat Mar 18 2017

Skies are slowly clearing from west to east across central Illinois
this evening...with 02z/9pm IR satellite imagery indicating the
back edge of the clouds along a Lacon...to Mattoon...to Robinson
line. Based on satellite trends, it appears the clouds will linger
across the far NE KILX CWA around Rantoul and Danville until
shortly after midnight. Overnight lows will mainly be in the lower
30s. Current forecast is right on track, so no major updates are
needed at this time.


&&

.SHORT TERM...(This evening through Sunday)
ISSUED AT 305 PM CDT Sat Mar 18 2017

Western edge of the cloud shield has begun marching eastward this
afternoon, and has made it about as far east as Monmouth and
Springfield as of 2 pm. Temperatures up to around 50 degrees over
west central Illinois in the clear area, but mainly holding in the
lower 40s over the eastern CWA.

High pressure area currently west of the Mississippi River will
continue to edge eastward across the Mississippi Valley tonight.
Eastern areas may take a good portion of the evening to fully clear
out, but mostly clear skies will be the general rule overnight into
early Sunday. Some increase in mid/high clouds can be expected later
on Sunday, but temperatures should still be significantly milder
than today, mainly mid to upper 50s.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 305 PM CDT Sat Mar 18 2017

A surface low will approach western IL Sunday night, as a cold front
pushes toward NW Illinois at the same time. Rain chances will ramp
up to likely after midnight, as the low reaches to near the western
tip of Illinois by 12z/7am Monday. Thunderstorm chances will
increase later Sunday night as well, due to an intensifying low
level jet in combination with mid-level instability MUCAPE values
around 1500 J/kg. SPC has maintained a Marginal Risk (5%) for severe
storms west of I-55 for isolated severe hail reports.

On Monday, the low pressure and cold front will push across
Illinois, with the front stalling our south of the Ohio River Valley
Monday night. Thunder chances will continue with the FROPA south of
I-72, but no severe storms are expected on Monday. Rain chances by
afternoon should be confined to east of I-55, and eventually south
of I-70 Monday night.

A shortwave progressing eastward across Illinois in concert with
some mid-level frontogenesis, will trigger a period of showers
Tuesday afternoon and Tuesday evening. That wave should quickly
depart to the east, with dry conditions expected later Tuesday night
through Wednesday night, under high pressure.

A warm advection wing will advance toward Illinois from the SW Wed
night, possibly producing a rain/snow mix for our SW counties toward
Jacksonville early Thursday morning. Rapid warming at the surface
and aloft will change any snow to rain by mid-morning on Thursday.
It appears a band of rain will advance northeast across the
remainder of central Illinois on Thursday, primarily in the vicinity
of the warm front during its advance. Scattered rain showers could
linger on and off Thursday night and Friday morning in the warm
sector, but precip amounts would be light. Rain and storm chances
will increase dramatically once the cold front finally pushes across
Illinois. However, there are significant timing differences in the
extended models. The GFS shows cold FROPA late Friday afternoon and
evening. The ECMWF doesn`t have a clear FROPA, and actually pushes a
low center across far southern IL instead. The Canadian GEM takes a
surface low up the IL river valley on Saturday, with cold FROPA in
the southern half of the state Saturday afternoon and evening. The
extended blend ramped PoPs up to likely between midnight Friday
night and Noon Saturday, but confidence is low on when likely PoPs
will eventually be necessary.

Friday looks to be the warmest day of the next week, as highs climb
into the upper 60s in most areas.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 638 PM CDT Sat Mar 18 2017

Cloud shield continues to slowly erode and shift northeastward
early this evening...with latest obs showing low VFR/high MVFR
clouds along and east of a KPIA to KDEC line. Based on satellite
trends and latest HRRR forecast, it appears the low clouds will
scatter at all terminals over the next 1-2 hours. Winds will
initially be northwesterly at around 10kt, but will become
light/variable overnight as high pressure moves overhead. As the
high shifts to the east, S/SE winds of around 10kt will develop
from late Sunday morning through the afternoon. Mostly clear skies
will eventually give way to increasing mid-level clouds after 21z:
however, any lower clouds or precip will hold off until after the
00z TAF period.


&&

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

$$

UPDATE...Barnes
SHORT TERM...Geelhart
LONG TERM...Shimon
AVIATION...Barnes



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