115 
FXUS63 KILX 140129
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
829 PM CDT SUN SEP 13 2015

.UPDATE...
ISSUED AT 822 PM CDT SUN SEP 13 2015

High pressure continues to move slowly away from central Illinois
this evening bringing a clear sky and light winds to the forecast
area. The light wind flow has allowed temperatures to nose dive
once again early this evening, especially across the east which
is closer to the ridge axis. Later tonight, we are expecting winds
to increase enough out of the south to keep temperatures from
falling too much further. Have adjusted overnight lows across the
east as a few locations were already a few degrees from the
forecast lows. 

Forecast soundings for Monday suggest some rather gusty south
winds to build in by afternoon as the pressure gradient tightens
over the Midwest. This should allow afternoon temperatures to
climb close to 80 degrees. Tweaked the temperatures, including the
overnight lows across the east, and wind gusts for Monday afternoon,
otherwise the rest of the forecast is in good shape. Update out by
845 pm.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 257 PM CDT SUN SEP 13 2015

Ridge axis shifting east across the state early this afternoon. 
Earlier diurnal cumulus that formed across east/northeast parts of 
the forecast area is already fading, although a patch of mid-level 
clouds was approaching from the west. Some of this will eventually 
spread in from the west/southwest later tonight, but mostly clear 
skies will prevail. With southerly winds setting up on the back side 
of the ridge, milder conditions are expected tonight. Temperatures 
in the 40s should be confined to areas along/east of I-57, with 
mainly 50-55 to the west.

.LONG TERM...(Monday THROUGH Sunday)
ISSUED AT 257 PM CDT SUN SEP 13 2015

A pleasant stretch of late summer weather expected through mid week
across IL as upper level high pressure ridge builds across the 
eastern U.S., and surface high pressure over the mid MS river valley 
moves east into the mid Atlantic states Tuesday. Increasing 
southerly winds to gradually return warmth from Mon-Wed with a fair 
amount of sunshine and comfortable humidity levels with dewpoints 
mostly in the 50s. Highs Monday in the upper 70s eastern IL and 
lower 80s western half of IL to climb into the mid 80s by Wed. Lows 
Monday night range from 50-55F southeast of I-70 closer to high 
pressure ridge, and around 60F over the IL river valley. Lows Tue 
night moderate into the mid to upper 50s in eastern IL and lower 60s 
west of I-55. 

12Z medium and extended forecast models show upper level ridge 
over the eastern U.S. gradually breaking down as a series of short 
waves eject ne into the Great Lakes region late this week. So warm 
and dry weather during mid week through Thursday with returning 
chances of showers/thunderstorms from Thu night into Saturday. A 
cold front moving southeast across central IL Friday afternoon and 
Friday night and exiting southeast IL Sat morning will enhance 
chances of convection. Chances of showers and thunderstorms to 
diminish from nw to se behind the cold front during the day Saturday 
as the boundary pushes into the ohio river valley/KY. Warm highs in 
the 80s Tuesday through Friday to cool into the mid to upper 70s 
next weekend which is pretty close to normals for mid September.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z Monday EVENING)
ISSUED AT 605 PM CDT SUN SEP 13 2015

VFR conditions are expected to prevail thru this forecast period.
High pressure will continue to move away from our area tonight
with surface winds backing more into a southerly direction at
all locations. Time height cross sections and forecast soundings
indicate some mid level clouds (7000-1000 feet) will move into
the area during the morning hours mixed in with a little cirrus
as well. Look for southerly winds tonight at 4 to 7 kts early this
evening and 7 to 12 kts after 04z as the gradient start to tighten
up across the forecast area. Some concern for the potential for
LLWS, especially at KSPI and KPIA but enough of an increase in the
surface winds are expected later tonight to keep it out of the
forecast at this time.


&&

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

$$

UPDATE...Smith
SHORT TERM...Geelhart
LONG TERM...07
AVIATION...Smith