Area Forecast Discussion
Issued by NWS Central Illinois

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717
FXUS63 KILX 250151
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
851 PM CDT Mon Apr 24 2017

.UPDATE...
Issued at 851 PM CDT Mon Apr 24 2017

No significant updates needed this evening. Temperatures at 8 p.m.
had dropped to the low 60s most locations, and winds generally SE
4-8 mph. A slow increase in winds can be expected toward morning,
while temperatures drop to the low 50s.

&&

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 300 PM CDT Mon Apr 24 2017

High pressure will keep conditions tranquil for another night,
under mostly clear skies. The surface ridge axis will depart
farther away to the southeast tonight, allowing SE to S winds at 5
to 10 mph overnight. The south winds will bring warmer air to the
region, along with a warm surge at 850mb. That will keep overnight
lows about 10 degrees warmer than last night, with lows bottoming
out in the lower 50s.

On Tuesday, low pressure advancing eastward across Oklahoma will
be associated with a frontal boundary extending north into the
western Great Lakes region. That would keep Illinois in the warm
sector of that system, where Illinois will experience increasing
mid level warming and increased moisture transport. Clouds will
increase from NW to SE Tuesday afternoon, but no precipitation is
expected before sunset. Despite the increasing clouds, warm air
advection will help to push high temperatures well above normal,
into the upper 70s in most areas, with around 80 toward
Jacksonville.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 300 PM CDT Mon Apr 24 2017

Showers and a few storms will be possible late Tuesday night in
response to low pressure lifting NE from the southern Plains
toward eastern Iowa. Clouds and steady south winds will keep lows
near 60 degrees across the board Tuesday night, well above normal.
The initial low will lift into Wisconsin on Wednesday, as a
secondary low develops in Missouri and lifts toward NW Illinois
late Wed into Wed evening. That second low will bring the
potential for heavy rains and flooding as precipitable water
values climb over 1.5 inches. Instability parameters also look
favorable for some of the stronger storms to produce hail and
damaging winds. The strong storms and heaviest rains look to
arrive Wed evening for areas west of I-55, then advance east of
I-55 to the Indiana border after midnight. Rainfall amounts Wed
and Wed night could reach between 1 to 1.5 inches in some
locations, with locally higher totals where storms train over the
same areas.

A break in the storms is forecast for Thursday afternoon and
Thursday night as cooler air arrives behind the cold front.
Thursday highs will remain mainly in the upper 50s to low 60s. The
cool down will be short lived, as the cold front lifts back north
as a warm front Friday and Saturday. Another strong low pressure
system will progress northeast along the front Saturday night and
cross Illinois from SW to NE roughly along I-55 on Sunday. The
result of the frontal boundary arrival Friday night followed by
the low passage 36-42 hours later will set the stage for an
extended period of rain and storm chances late this week and next
weekend. More heavy rain could occur with that second system, on
top of saturated ground from the mid week system. Several rivers
and creeks could rise above flood stage if we see as much as 3 to
4 inches of rain over the next 7 days. Some flash flooding could
develop during each event if any storm produces very high rainfall
rates for any period of time.

The rain could linger into Monday depending on the speed of the
low pressure movement. The GFS20 and ECMWF both show showers
extending at least into Monday morning, while the Canadian
progressively pushes the low NE of Illinois Sunday night. Another
cool down is projected for Monday under cold air advection, clouds
and possible spotty showers. Highs will drop back down into the
upper 50s to low 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 644 PM CDT Mon Apr 24 2017

VFR conditions expected the next 24 hours as low pressure
developing over the Plains brings increasing high clouds and S-SE
winds. Overnight winds will be generally 6-10 kts, increasing to
SSE 15-20 kts with gusts to around 25 kts during the daytime
Tuesday.

&&

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

&&

$$

UPDATE...37
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...37



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