840 FXUS63 KILX 042053 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 253 PM CST Thu Jan 4 2018 .SHORT TERM...(This evening through Friday) ISSUED AT 253 PM CST Thu Jan 4 2018 The eastern CONUS continues to be locked in a very cold northwesterly flow pattern. A weak short-wave trough embedded within the flow will track southeastward out of the Dakotas tonight...bringing clouds and a period of light snow to portions of central Illinois. All 12z model guidance has shifted the snow axis slightly further northeast into mainly the W/SW KILX CWA. As a result, have increased PoPs accordingly to go with high chance along/southwest of a Rushville to Jacksonville line where a couple tenths of an inch will likely accumulate. Further northeast, conditions are expected to remain cold and dry. Low temperatures will remain in the single digits above zero where clouds and very light precip will occur, but will once again fall into the single digits below zero across the N/NE where partly to mostly clear skies will prevail. Given the bitterly cold temperatures and expected overnight wind-chills of 10 below to 20 below zero, have issued a Wind Chill Advisory for all locations along and northeast of a Galesburg...to Clinton...to Paris line. After the short-wave tracks by to the south overnight, the very light snow and flurries will come to an end and skies will become sunny across the board by midday Friday. Despite the abundant sunshine, high temperatures will remain in the single digits and teens. && .LONG TERM...(Friday night through Thursday) ISSUED AT 253 PM CST Thu Jan 4 2018 Clear skies and light winds will allow for excellent radiational cooling conditions Friday night...with overnight lows dropping below zero across the entire CWA. With temperatures that bitterly cold, even the light N/NW winds of around 5mph that are expected will create wind-chill readings from 15 below to 25 below zero in some spots. Another Wind-Chill Advisory will likely be needed at that time. After a cold/dry day on Saturday, the next storm system of interest will come into the picture by Sunday. 12z Jan 4 models have come into reasonably good agreement concerning the track and timing of this system, with all solutions showing a potent short- wave trough tracking from the Pacific Northwest on Saturday...across the Southern Rockies on Sunday...then into the Deep South by Monday. The corresponding surface low remains weak and well to the south of Illinois: therefore, lighter QPF and a colder thermal profile are anticipated. There are still some minor discrepancies as to when precip will begin...with the GFS being the fastest to develop precip Sunday morning and the ECMWF showing a mostly dry Sunday morning...but the overall trend is becoming clear. Given colder soundings, precip will begin as light snow across all of central and southeast Illinois Sunday morning. Then as a 1-3C warm layer develops aloft, the precip will mix with sleet and freezing rain during the afternoon and evening. Surface temperatures will warm into the lower to middle 30s, perhaps warm enough to transition to mainly rain south of I-70 where no snow cover currently exists. As the system moves further east and begins to depart the region, soundings suggest a gradual loss of ice crystals within the profile...leading to a period of light freezing rain/drizzle Sunday night. Snowfall looks to be on the light side with this system, with amounts of 1-2 inches possible across the CWA. However, the distinct potential for mixed precipitation will likely create hazardous driving conditions...especially Sunday afternoon through early Monday morning. Once the wave passes to the south, warmer weather will be on tap next week. With the predominant upper trough across the eastern CONUS finally losing its grip, heights will rise substantially and temperatures will climb back to normal or even a few degrees above normal. In fact, highs could reach the lower to middle 40s by next Wednesday and Thursday. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1128 AM CST Thu Jan 4 2018 VFR conditions will prevail through the entire 18z TAF period. A weak disturbance will pass W/SW of Illinois tonight and will bring mid-level clouds and perhaps a few snow flurries to KSPI from late evening through the overnight hours. Based on current upstream satellite/radar trends and NAM forecast soundings, have taken ceilings down to 5000ft at KSPI between 05z and 15z. Further northeast at KBMI/KCMI, skies will remain mostly clear with only FEW-SCT mid clouds. Once the system passes, skies will become mostly clear at all terminals after 15z. Winds will be NW at 5-10kt this afternoon, then will become N/NW by Friday morning. && .ILX WATCHES/WARNINGS/ADVISORIES... Wind Chill Advisory from midnight tonight to 10 AM CST Friday for ILZ027>031-037-038-043>046-055-057. && $$ SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Barnes