Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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100 FXUS63 KILX 242308 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 508 PM CST Sun Nov 24 2024 .KEY MESSAGES... - Light rain/drizzle (30-40% chance) develops tonight into Monday. Precipitation amounts will be light, less than 0.10". - A frontal system looming on the horizon could bring our next chance for a wintry rain/snow mix (40-60% chance) Wednesday into Thanksgiving morning. Confidence remains low, but probabilities for accumulating snow have decreased. - An arctic blast will bring bitterly cold temperatures late this week into the start of December. In the days following Thanksgiving, air temperatures will struggle to warm above freezing with wind chills in the teens to single digits. && .DISCUSSION... Issued at 239 PM CST Sun Nov 24 2024 Surface ridging has been pushed east into Ohio early this afternoon as southerly flow ramps up ahead of a developing low in the central Plains. Persistent WAA out ahead of the system has filtered warmer air northward, allowing highs to warm into the middle 50s to low 60s as of 2 pm. A warm front is in the process of lifting north through the area, with forecast soundings showing the surface to ~750-800 mb layer saturating by this evening/overnight, introducing light precipitation chances as lift increases ahead of the low. Mid-level air will struggle to moisten even as the surface low lifts through the area on Monday, which should keep any precipitation very light or in the form of drizzle. Some reduced visibility may develop with drizzle, but chances for visibility falling below 1 mile is relatively low. Temperatures drop quite a bit behind a cold front Monday night with overnight lows in the 20s. Temperatures will remain below normal through the midweek period, giving us a taste what`s to come later in the week. The forecast becomes a little more tricky by midweek as a frontal system develops in the southern Plains states and ejects northward toward the Ohio Valley Wednesday into Thanksgiving morning. The last several runs of deterministic guidance have done some flip-flopping, with the ECMWF continuing to show a deeper trough swinging through the middle Mississippi Valley and hence a stronger/deeper surface low. Despite this, ECMWF QPF amounts have come down significantly over central Illinois since yesterday`s 23.12Z run. The GFS and CMC continue to show a shallower trough, which would keep the surface low further south and most of the QPF in southeast IL as rain. Ensemble members show mean snow accumulation from nearly nothing (GEFS and GEPS) to a couple inches of snow (ENS), which is a downward trend from previous runs. The NBM`s probabilities for snow have also decreased with less than a 20% chance of seeing 1 inch north of I-74 where some signal for frontogenetic banding lies ahead of the main wave. This continues to be a relatively low confidence forecast, but the probability of seeing impactful accumulating snow has come down. There is good agreement that arctic air will intrude most of the central and eastern US later this week, sending bitterly cold temperatures southward as a Canadian surface high noses south. Beginning Thanksgiving night, it appears that there will be an extended period where air temperatures do not rise above freezing (32 degrees) for most of our counties. Wind chills late this week could drop into the teens to single digits. Temperatures should break above the freezing mark by the middle of next week, but will remain below normal (60-80% chance) through the first full weekend of December. A quick hitting clipper system could bring light accumulating snow to central Illinois over the weekend, but there remain differences with timing and placement. NMA && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 508 PM CST Sun Nov 24 2024 A cold front will move into the area tonight, spreading scattered showers and MVFR ceilings across the central IL terminals. Models continue to point to ceilings lowering to IFR at KBMI-KDEC-KCMI toward daybreak and continuing through late morning. South winds tonight will veer northwest behind the front Mon morning, becoming gusty at 20-25 kt during the afternoon - while ceilings rise back up to MVFR. 25 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$