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