Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191734

Area Forecast Discussion
National Weather Service Lincoln IL
1234 PM CDT Sun Mar 19 2017

Issued at 940 AM CDT Sun Mar 19 2017

Mainly clear skies across the forecast area this morning courtesy
of the high pressure axis over eastern Illinois, with scattered
mid and high clouds spilling eastward into western Illinois. A
narrow band of convection across Missouri will track eastward with
time today, but the short-range high-res models keep it to our
southwest. Overall, the forecast is in decent shape and only
required some minor edits, mainly to the sky trends over the far
western CWA.


.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CDT Sun Mar 19 2017

High pressure ridge sitting over the CWA early this morning will
move east today and allow the return of southerly winds and warmer
temps. Skies should also be sunny through the day, so temperatures
should reach into the 50s across the whole area this afternoon with
the warmest temps in the upper 50s in the west.

A weather system developing in the northern and central plains today
will slide east and southeast this evening. Precipitation should
develop along and just ahead of the front, across eastern Iowa, and
then slide southeast into the CWA for the overnight hours tonight.
Despite dewpoints only reaching into the 40s this afternoon through
tonight, MUCAPE by 06z should reach to around 1000 j/kg in western
IL and then spread east and southeast through 12z on Monday. Lapse
rates will be greater than 7 C/km in the lower levels and mid levels
along the bulk shear being over 40kts. So instability and shear
looks sufficient for strong thunderstorms in the CWA after midnight.
So have increased chance of thunder overnight to likely over most of
the CWA. Southerly winds will continue into the overnight hours as
well. With southerly winds, clouds and precip, expecting overnight
lows to remain in the mid to upper 40s.

.LONG TERM...(Monday through Saturday)
ISSUED AT 340 AM CDT Sun Mar 19 2017

Even milder temperatures in the 60s expected on Monday, the first
day of spring, with highs ranging from lower 60s along I-74 to the
upper 60s from Springfield and Robinson sw. Areas from Jacksonville
sw will be approaching 70F on Monday, similar to this past
Fridays readings. A cold front will be pushing se across the IL
river valley Monday morning and moving into southeast IL by sunset
Monday. This will likely bring a good chance of showers Monday
with thunderstorms possible se of the IL river Monday morning, and
lingering over eastern/southeast IL Monday afternoon. Isolated
showers could linger south of I-70 Monday night (isolated thunder
south of highway 50 Monday evening) as frontal boundary pushes
southeast to the Ohio river by midnight Monday night, and then
into central KY by dawn Tue. Lows Monday night are in the upper
30s and lower 40s.

A weak short wave tracks ESE over central IL on Tue afternoon and
early Tue evening and returns chances of rain showers especially to
central and southern CWA. Noticed the ECMWF model has trended
further south with qpf over areas south of I-74 Tue afternoon and
south of I-72 Tue evening. So drier trends over northern CWA during
that time. Cooler highs Tue in the low to mid 50s.

Dry conditions expected expected from overnight Tue night through
most of Wed night as 1036 mb high pressure settles se into the Great
Lakes around lower MI by sunset Wed. Wed appears to be the coolest
day this week despite the return of more sunshine, with highs in the
mid to upper 40s with areas from highway 50 south around 50F.

High pressure drifts over the mid Atlantic States Thu and begins
warm air advection pattern over IL with a warming trend Thu/Fri.
Light mixed precipitation possible over western/sw CWA late Wed
night and early Thu morning, then turning to all rain by mid/late
Thu morning as light rain shower chances spread further ne over
CWA by Thu afternoon. Lows Wed night mostly lower 30s, but range
from around 30F from I-74 ne to mid 30s far sw CWA. Highs Thu in
the low to mid 50s, similar to Tue highs.

Milder highs in the upper 60s to near 70F on Friday with continued
chances of showers along with possible thunderstorms by Friday
afternoon. A stronger storm system to eject from eastern CO on Thu
afternoon and track ne into the western Great Lakes by late Friday.
Models still have big timing difference with passage of cold front
late this week, and stayed close to consensus for higher pops
Friday night and early Sat with thunderstorms a risk. Highs Sat
range from mid 50s nw of the IL river, to the lower 60s in
southeast IL.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1234 PM CDT Sun Mar 19 2017

Main forecast challenges come after 06Z, with timing of
convection. Most of the models are in agreement of showers and
storms developing over eastern Iowa late this evening, then
dropping southeast into central Illinois after about 07-08Z. Some
question about southern extent due to model variability, but will
include a mention of at least VCTS at all sites late night into
early Monday morning. Once the rain ends, MVFR conditions expected
to accompany a cold front that will begin arriving around mid
morning, with ceilings down to around 1000-1500 feet.




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