671 FXUS63 KILX 252055 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 255 PM CST Fri Jan 25 2019 .SHORT TERM...(This evening through Saturday) ISSUED AT 255 PM CST Fri Jan 25 2019 First in a series of low amplitude shortwaves affecting the area this afternoon and evening. Surface low currently entering SE IA is forecast to bisect the CWA from west to east near the I-72 corridor this evening. Most of the snow will fall north of the low path, and current forecast of 1-2" accumulations on track for areas north of a Canton to Bloomington line. Amounts will quickly taper off to the south with less than a half inch expected through the central CWA. Forcing quickly decreases from the west 02-05z, so expect snow to end prior to midnight over the northeast. Cold advection behind this system brings a fresh shot of arctic air overnight, dropping lows below zero again northwest of the IL River and single digits where snowpack remains primarily north of a Taylorville to Paris line. Saturday...another weak clipper slides southeast across MO. With a path favored southwest of the current system, higher snow chances are focused south of I-74. Limited forcing and moisture suggests accumulations less than one inch, mainly 18z-00z. Highs continue well below normal with teens expected north of I-72 to mid 20s farther south. && .LONG TERM...(Saturday night through Friday) ISSUED AT 255 PM CST Fri Jan 25 2019 Third weak clipper embedded in fast northwest flow is forecast to shift southeast across MO early Sunday. Again this system will be moisture starved and focused off to our southwest so only have slight to low chance pops over the SW CWA. A much larger and stronger hybrid clipper/Pacific system will be the main precip maker for late Sunday into early Monday. Still plenty of model disagreement on track and timing, but the trend of the 12z runs has been to shift the low track north, and push the heavier snow threat into northern IL. Thermal profiles to suggest warm advection south of the low will push temperatures above freezing aloft, setting up the potential for another period of freezing rain early Monday morning. After late morning highs which could get above freezing for much of the area, a strong cold front looks to produce falling afternoon temperatures which could be accompanied by snow showers. Brutal cold sets up across the region for Monday night through much of the remainder of the week. A deep upper low is forecast to sink southeast from central Canada into the eastern Great Lakes Tue-Thu. This opens up flow straight from the Arctic into the Midwest. 1000-500mb thickness values fall sub-500 DAM over the area for Tuesday afternoon into Thursday. This is accompanied by 850 mb temps of -25 to -30C on the EC and as low as -35C on the GFS. These are values rarely seen in this area. Magnitude of cold air suggests widespread lows in the teens below zero Wednesday and Thursday mornings over the north half, or where substantial snow cover is present. Winds will be up on Wednesday with strong Arctic high pressure over the northern Plains. This would drop wind chills well into warning criteria, with -20 to -40F values shown north of I-72. If the Arctic high can shift over the area Wednesday night into Thu morning and winds drop off, record lows are likely. Tues/Wed highs in the single digits above and below zero are shown over the north with teens south of I-70. Medium range guidance shows some temp moderation towards the end of the forecast but still well below normal. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1115 AM CST Fri Jan 25 2019 Snow will overspread the terminals this afternoon from the northwest. MVFR ceilings and visibility is expected with the snow, affecting the region primarily 21z-04z. Brief reductions to IFR ceilings possible in brief periods of heavier snow. After the snow diminishes, ceilings will lower near IFR/MVFR threshold for a few hours tonight, before rising into MVFR or VFR later tonight. Winds will be near/under 10 kt, initially from the southwest ahead of the system this afternoon, then switching around to the northwest after the cold frontal passage later this evening. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...25 LONG TERM...25 AVIATION...25