Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 181708
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1208 PM CDT Tue Apr 18 2017

.UPDATE...
Issued at 1059 AM CDT Tue Apr 18 2017

Unseasonably warm temps are still expected today. Though some
clouds have begun to develop today and some higher clouds are
advecting into the area from the northwest, should be plenty of
sunshine this afternoon, which will combine with breezy
southeasterly winds to bring warm temps into the area. Mid to
upper 70s by this afternoon still looks like a good forecast.
Southeasterly winds are a little stronger than current forecast so
will be making an adjustment with those. Overall, most of forecast
looks fine, but will be sending an update to reflect slight
stronger winds.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 327 AM CDT Tue Apr 18 2017

Light east-southeast winds early this morning will veer to the south
and increase to 10-15mph by midday...bringing warmer air into the
region today.  Forecast soundings suggest deeper mixing than
yesterday up to about 5500-6000ft, which supports afternoon highs in
the middle to upper 70s.

Low pressure currently over South Dakota will track into eastern
Ontario by 12z Wed, pushing a cold front southward into Illinois
tonight.  As was first seen by the 00z Apr 17 NAM/ECMWF, the latest
GFS now stalls the front further north than previously
forecast...with the boundary hanging up along the I-80 corridor late
tonight into Wednesday morning.  With this more northern solution,
have scaled back PoPs considerably...resulting in rain chances being
confined to locations along/northwest of a Rushville to Minonk line
after midnight.  Overnight lows will remain in the upper 50s to
around 60 degrees.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 327 AM CDT Tue Apr 18 2017

A short-wave trough will cross the Rockies into the Northern Plains
on Wednesday, inducing surface cyclogenesis along the trailing end
of the boundary across Nebraska.  As the surface low tracks
northeastward, it will pull the boundary back northward on
Wednesday...placing central Illinois solidly within the warm sector
of the system.  Will carry low chance PoPs along/north of I-74 in
closer proximity to the retreating front, but think most locations
will remain dry.  With southerly winds and ample sunshine, afternoon
high temperatures will soar into the lower to middle 80s.

The low will track into the Great Lakes Wednesday night, pulling
another cold front toward central Illinois.  Thunderstorms will
develop along the advancing front within the moderately unstable
airmass across Iowa/northern Missouri late Wednesday afternoon and
evening.  Given SBCAPE values of 1500-2000J/kg and modest 0-6km bulk
shear of 30-40kt, a few severe storms with damaging winds and hail
will be possible.  These storms will weaken as they push
northeastward across the Mississippi River into a more stable
airmass over central Illinois Wednesday night...with a few models
suggesting they may totally dissipate before they reach the I-55
corridor.  As a result, have focused highest PoPs in the Illinois
River Valley, with just slight chance PoPs further east to a
Danville to Springfield line.  The cold front will push through the
area on Thursday, triggering a few scattered showers and
thunderstorms...particularly across the E/SE KILX CWA Thursday
afternoon and evening.

The front will then settle southward into the Ohio River Valley
Thursday night, resulting in cooler/drier weather through Friday.
After that, model consistency remains poor for next weekend.
Previous solutions had shown a significant wave developing along
the boundary and lifting it back northward into portions of
central Illinois on Saturday.  00z Apr 18 models are trending
further south with the wave...especially the ECMWF which takes a
more eastward track with the wave and thus keeps the northern CWA
mostly dry into the weekend.  At this point, opted to make very
few changes to the going forecast.  Have gradually introduced
chance PoPs for showers from south to north across the area Friday
night...then have gone with high chance to likely PoPs for
showers Saturday/Saturday night. After that, cool/dry weather will
return by Sunday night and Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1209 PM CDT Tue Apr 18 2017

VFR conditions should prevail at all TAF sites next 24hrs.
Scattered cirrus will spread into the area from the northwest
while scattered CU/AC slowly drifts east across the area.
Expecting the cirrus to thicken and become broken late tonight at
PIA while the other sites should remain scattered to clear with
just cirrus. As the front that is moving toward the Grt Lks region
sags south across northern IL late tonight, broken clouds around
4-5kft will move into the PIA and BMI sites during the morning
hours. Other sites should remain with scattered to broken cirrus
tomorrow morning. Winds will be breezy this afternoon out of the
south-southeast. Tonight, winds should be lighter out of the
south-southwest. Southeast winds will continue tomorrow at around
10kts.


&&

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

$$

UPDATE...Auten
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Auten



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