866 FXUS63 KDVN 310555 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1155 PM CST Tue Dec 30 2025 ...06z Aviation Update... .KEY MESSAGES... - Light snow and probably patchy freezing drizzle in and near far northwest Illinois this evening, potentially resulting in slippery surfaces. - A clipper system will impact the area Wednesday mainly during the afternoon and early evening. Snow accumulations look to be an inch or less mainly north of I-80. - A slow warming trend will commence late this weekend and into early next week with temperatures trending above normal. && .UPDATE... Issued at 540 PM CST Tue Dec 30 2025 Between the two main clipper systems (the one earlier today and the one on Wednesday) there are a couple other weak upper disturbances traversing the same elevated baroclinic zone from Minnesota through northern Illinois. One such wave is just east of the Twin Cities early this evening and moving southeast, resulting in an enhanced area of low level warm air advection aloft (WAA) / isentropic ascent over southwest Wisconsin. Areas of light snow and patchy freezing drizzle have been observed upstream with this per obs including mPING reports. This forcing and attendant light precipitation will clip far northwest Illinois and likely immediate adjacent areas of eastern Iowa this evening, especially prior to 10 PM. Patchy slick surfaces are the concern and have handled with an SPS for now. Impacts in NWS La Crosse's area thus far have been minor, but keeping a vigilant watch on that and road conditions, and while unlikely it's not impossible that a short-lived Advisory is needed in the WI/IL border region area if impacts ratchet up. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 126 PM CST Tue Dec 30 2025 he first clipper system will exit the area this evening but clouds will be slow to break up overnight. Overall accumulations will be one half inch or less. Return flow developing ahead of the next system will help keep temperatures elevated overnight. Dry conditions are expected through the morning commute on Wednesday. Snow from the next clipper system should begin developing by late morning across the northern half of the area and overspread most areas along/north of I-80 during the afternoon. Snowfall amounts look to be under an inch across northwest Illinois with a dusting as far south and west as a Vinton, IA to Aledo, IL line. Given the timing of the snow on Wednesday, some minor impacts are possible during the evening commute for areas along/north of I-80. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Issued at 126 PM CST Tue Dec 30 2025 Wednesday night Assessment...high (70-80%) confidence on colder than normal temperatures Lingering light snow from the Wednesday clipper system will end in the early evening followed by slowly clearing skies. The clearing skies and fresh snow for the areas that see it will allow temperatures to drop to colder than normal by sunrise Thursday. Thursday through Tuesday Assessment...low to medium (30-50%) confidence on mainly dry conditions. Medium to high (60-80%) confidence on a warming trend. The model consensus continues to show dry conditions with the main storm track north of the area. However, there are at least two weak upper level disturbances progged to move through the area; one Saturday and the other Sunday into Monday (depending upon the model solution). The Saturday disturbance has the better chance at only seeing an increase in clouds given the limited moisture. The Sunday/Monday disturbance is more questionable. Return flow develops on Sunday and continues into Monday. Some deterministic solutions are still hinting at very light precipitation developing while others do not. Most ensemble members continue to be dry which is pushing the model consensus to remain dry. Interestingly, the ECMWF-AIFS develops very light QPF side- swiping the area on Saturday while Sunday into Monday is dry. The AIGFS is the opposite; Saturday is dry with very light QPF Sunday into Monday. As mentioned yesterday, the signal is barely above the background error noise. We will need to observe the trend as the week progresses to see if the signal gets stronger or weakens. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1148 PM CST Tue Dec 30 2025 In-between clipper systems overnight into Wed morning with varying bouts of MVFR CIG categories and west to northwest sfc winds of 10-15 KTs. Most of the spotty flurries and freezing drizzle is exiting off to the southeast of the TAF sites ATTM. Then will await the next banded precip shield/shields streaming in from the northwest by late morning and the Tue afternoon with the next clipper system. Expect mainly MVFR reduced VSBYs with light snow and fog especially clipping the DBQ and MLI sites. The snow may mix with rain or change over to all rain on the southwestern flank of the precip shield because of the mild temperatures drawn up ahead of the clipper system. Thus for now went rain/snow mix at MLI but kept it mainly snow at DBQ. CID and especially BRL may not not see much precip with the system adjusting more northeasterly with it's track. In the heavier precip, there may be bouts of IFR CIGs at DBQ and possibly MLI by this Tue evening. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ UPDATE...Friedlein SHORT TERM...08 LONG TERM...08 AVIATION...12