163 FXUS63 KLOT 162019 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 319 PM CDT Sun Oct 16 2022 .SHORT TERM... Issued at 315 PM CDT Sun Oct 16 2022 Through Tuesday... Key messages up front: 1. Dynamic weather system moves into the region bringing cold and windy (and possibly snowy!) conditions 2. Chance of scattered flurries/snow showers MON afternoon - visibility reductions possible during PM commute 3. Near record cold highs MON with winds gusting to 30-40 mph - sub-freezing wind chills all day 4. Lake effect showers MON-TUE into NW IN, some snow may mix in 5. Building waves into IN with a minor lakeshore flooding risk The focus in the short term is on a deepening closed upper low descending over the Great Lake Region and the associated weather impacts during the start of the work week. For the rest of the afternoon through tonight there is a low chance for a few spotty light showers or sprinkles across far northeast Illinois otherwise dry conditions are expected. Winds will remain breezy through the overnight hours as cold air continues to advect into the area. As far as low temperatures go for tonight, there remains questions with how much cloud cover will linger overhead. If we are slow to clear out, forecast low temperatures are likely a bit too low. For this reason, have opted to hold off on any Freeze Warning headlines for counties west of the Chicago metro. Will let the evening shift get another look at things. Heading into Monday a vigorous upper level vort will round the western periphery of the closed upper low. As it moves overhead, steep low and mid-level lapse rates will set the stage for the potential for flurries and even snow showers by early afternoon across northeast Illinois placing the cloud layer right in the middle of the dendritic growth layer and model sounding wet-bulb temperatures remain mainly below freezing. This suggests that the favored precipitation type will be snow in spite of surface temperatures in the upper 30s to around 40! Can't rule out some rain or even graupel at times though. There is the concern that if more robust snow showers can develop that there could be notable visibility reductions, which could impact travel during the afternoon commute. Winds during the day will steadily increase out of the northwest during the day, gusting at times to 30-40+ mph making for a blustery day with wind chill values struggling to get above freezing the entire day. Locally higher gusts are possible, especially along the northwest Indiana shore areas which could be brushing up against wind advisory criteria. An impressive lake effect set-up Monday into Tuesday will be in place into Michigan and northwest Indiana as well, particularly just east of our area. Expect lake effect showers into northwest Indiana Monday through Tuesday. A few rumbles of thunder can't be ruled out especially nearest to the lake. Some snow could also mix in at times as well, especially further inland where some minor accumulation on grassy surfaces are possible. The persistent winds over Lake Michigan through Tuesday will also build large waves into the Indiana shore. Due to the increased risk of minor flooding along the shoreline have opted to issue a Lakeshore Flood Advisory for Porter County, IN for Monday afternoon through Tuesday afternoon. While not as cool as Monday, Tuesday will still be rather blustery with highs in the mid 40s and gusty north winds continuing. Conditions gradually improve through the day, however, with much warmer weather expected later in the week - more details on that below! Petr && .LONG TERM... Issued at 234 PM CDT Sun Oct 16 2022 Tuesday Night through Sunday... The long term forecast message is continued anomalously cold Wednesday before moderation through next weekend, with highs next weekend quite possibly 30 degrees warmer than Monday (tomorrow). Chances for precipitation are few and far between at this time. The anomalously deep upper longwave trough across eastern North America is forecast to still have a center magnitude of 200 to 250m below normal over the eastern Great Lakes on Tuesday night, with anomalies of 150 to 200m below extending westward over the forecast area. The low-level cyclonic flow will be gradually easing Tuesday night and there is uncertainty on how much stratocumulus there will be left. At present it looks like for away from the lake shadow (far northwest Indiana), it very well could be mainly clear and more than supportive of a night well down into the 20s for many locations. The upper trough will slowly weaken Wednesday and then pull northeast on Thursday. Any backside mid-level disturbances look to track to our northeast at this time, and even if they are further west, may be moisture-starved in the low-levels for any flurries or sprinkles. Temperature moderation will gradually ensue on Thursday into Friday. Though high pressure is not forecast to directly move over the area, the pressure gradient is not forecast to rapidly increase. So Thursday and Friday, which will still have low dew points, do not look windy at this time for a notable fire weather concern. By the weekend though, winds could be stronger as deep low pressure has been shown on recent global solution over either the Northern Plains or southern Canada. Not surprisingly, there are vast differences on location and track of such a feature this far out. This general regime though does support temperatures stepping back up to near or over 70F. In fact, this morning's National Blend of Models (NBM) has 75 percent of its membership forecasting 71-75F for Chicago a week from today. Things can change at this distance, but does seem like next weekend we flip to the other side of normal, which by that time is highs a little above 60F. MTF && .CLIMATE... Last updated at 315 PM CDT Sun Oct 16 2022 Here are the current records in place for Monday and Tuesday. October 17 October 18 Record Cold Record Low Record Cold Record Low Maximum Maximum Chicago 40 (1880) 26 (1948) 38 (1930) 20 (1948) Rockford 44 (2002) 24 (1992) 41 (1972) 19 (1952) Petr/Izzi && .AVIATION... For the 18Z TAFs... 18Z TAF weather concerns: * Gusty northwesterly winds with gusts of 25 kt increasing to 30 kt Monday afternoon. * Chance for snow flurries or light snow showers Monday afternoon. We'll continue to see west to northwesterly winds behind the front, with winds gusts up to 25 kt today into overnight. A broken 4500 ft cloud deck will move in and out of the terminals this afternoon, becoming more predominant late afternoon and overnight. There may be some brief moments of MVFR ceilings of around 2500 ft overnight, but confidence in the timing and location of this occurring is not high, so are presently not included in the TAFs. Northwesterly winds will continue Monday, with gusts increasing to around 30 kt Monday midday. There is a chance for some type of snow to occur at the terminals near Lake Michigan Monday afternoon, with increasing chances of snow as you go further east. Again, we are presently not confident in the form this snow will take, as it could be just flurries, or it could be snow showers with restricted visibilities. Therefore we have not included this possibility in the 18Z TAFs, and will continue to monitor and assess. BKL && .MARINE... Issued at 315 PM CDT Sun Oct 16 2022 Northwest gales are expected to develop late tonight and especially Monday afternoon into Tuesday morning. The strongest gales to 40 knots are expected Monday evening as a secondary trough shifts across Lake Michigan. A brief period of gales to 45 knots is possible in the Indiana nearshore during this time. Winds will only slowly diminish through the day Tuesday, with some gale gusts to 35 knots remaining possible into Tuesday evening. Kluber/Petr && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...Lakeshore Flood Advisory...INZ002...1 PM Monday to 7 PM Tuesday. LM...Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743...1 PM Monday to 10 AM Tuesday. Small Craft Advisory...Winthrop Harbor to Gary IN until 1 PM Monday. Gale Warning...LMZ744-LMZ745...4 AM Monday to 10 AM Tuesday. Small Craft Advisory...Gary to Michigan City IN until 4 AM Monday. && $$ Visit us at weather.gov/chicago Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSChicago www.twitter.com/NWSChicago www.youtube.com/NWSChicago