Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 180232

Area Forecast Discussion
National Weather Service Lincoln IL
932 PM CDT Tue Apr 17 2018

Issued at 923 PM CDT Tue Apr 17 2018

Updated the forecast into Wednesday based on expected trends.
System developing over the central Plains this evening will track
east-northeast through the night, with the surface low pressure
center approaching western Illinois by daybreak. The local airmass
is quite dry and there should not be a risk of rainfall through
the night. The most notable impact through the night will be a
gradual increase in mid-high level clouds and increasing wind
speeds. The moisture depth on Wednesday is still not impressive
and forecast soundings suggest most of the saturation will occur
within the lowest few thousand feet of the atmosphere. The
moisture/thermal profile through the daytime hours Wednesday is
not supportive of much more than very light rain or drizzle over
most of the area. Left a mention of thunder in the far north, but
not expecting much, if any.

Aside from the more notable PoP adjustments, also lowered
nighttime mins a couple degrees and made a few other adjustments
to hourly trends.


.SHORT TERM...(This evening through Wednesday)
ISSUED AT 306 PM CDT Tue Apr 17 2018

The high pressure ridge axis over Illinois this afternoon will slip
east of the area tonight as low pressure developing to the lee of
the Rockies begins to move rapidly east toward Illinois. Not
quite as cold tonight as clouds and east winds develop with the
approaching low. Lows mid 30s north to low 40s south. Model
consensus has now shifted the track of this low pressure center
southward from previous runs and now is forecast to move across
central Illinois Wednesday afternoon. Therefore, forecast has been
trended toward a bit more precipitation farther south, as well as
colder temperatures in northwestern parts of the forecast
area Wednesday as the warm sector is now only affecting areas from
around I-72 southward briefly. This will also limit some of the wind
associated with the warm sector for central IL, mainly bringing 25-
30 mph winds and gusts around 40 mph to the southeast. With the
colder forecast, now have precipitation type switching to snow as
early as Wednesday afternoon north of Peoria. A few
thunderstorms will also be possible late Wednesday morning in the
north as a few hundred J/kg MUCAPE interacts with lift from this

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 306 PM CDT Tue Apr 17 2018

Low pressure will be northeast of the central IL forecast area by
Wednesday evening with the cold front past the Indiana border. Cold
advection will continue through Wednesday night with any lingering
precipitation associated with the upper level trough changing to
snow across central Illinois by Thursday morning. Fortunately, only
a few hundredths of precipitation are progged Wednesday night
amounting to only a few tenths of snow maximum, and mainly I-74

Central Illinois will be on the cold side of high pressure over the
central U.S. Thursday for highs in the lower 50s.
Thursday night lows should range from near 30 along I-74 to the
low 30s south of I-70. Depending on exact temperatures and
winds, the area along and south of I-70 may need another frost
or freeze headline eventually. High pressure should shift into the
upper Great Lakes Region Friday into the weekend allowing central IL
to warm from highs in the mid to upper 50s Friday to lower 60s by
Sunday and mid to upper 60s by Tuesday. Lows should also trend
upward, starting with mid and upper 30s Friday night to the 40s by
early next work week. During this same time period, a deep cut off
low will develop into the southern Plains and migrate into the Gulf
States. Current model cycle continues to keep this feature too far
south to bring any precipitation into central and southeast IL so
the going forecast continues to be dry Thursday through Tuesday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 657 PM CDT Tue Apr 17 2018

VFR conditions will persist across the central Illinois terminals
through the night, but will quickly fall to MVFR or IFR Wednesday
morning as a storm system tracks through the Midwest. The bulk of
the precipitation with this system will be north of the area, but
at least KPIA and KBMI will get in on showers or drizzle for a
time Wednesday. Gusty winds are also expected with the
approach/passage of this system, with winds picking up later




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