548 FXUS63 KLOT 160210 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 910 PM CDT Sat Oct 15 2022 .UPDATE... Issued at 910 PM CDT Sat Oct 15 2022 Current forecast remains in good shape for this evening with no major changes made. A quiet and fall-like evening is underway across northeastern Illinois and northwest Indiana with current temperatures sitting in the upper 40s to around 50 degrees. An area of mid-level clouds continues to reside across the area, but the clouds are gradually pushing eastward as a weak frontal boundary continues to move southward across Wisconsin. While this boundary will not bring any precipitation it will allow the cloud cover to persist through much of the overnight hours before skies gradually clear out Sunday morning. The presence of these clouds will help to keep temperatures a tad warmer tonight than last night with lows expected to be in the mid to upper 30s for most of the area with lower 40s for the Chicago metro. Sunday will see similar conditions to what we saw today with mostly sunny skies to start the day becoming partly cloudy by dinner time as an upper-level disturbance moves into the area. Temperatures will once again top out in the mid to upper 50s with breezy northwest winds gusting around 20 to 25 mph during the afternoon. As the aforementioned disturbance moves in guidance is continuing to indicate that a few spotty sprinkles may develop across northern Illinois late Sunday afternoon. However, the shallow moisture forecast to be in place should keep most areas dry. Yack && .SHORT TERM... Issued at 235 PM CDT Sat Oct 15 2022 Through Sunday... A surface high to our west will slip to our south and southeast today, with mostly clear skies and westerly winds becoming southwesterly. Winds will be gusty this afternoon, with gusts up to 25 mph. Cloud cover associated with an approaching front will increase later this afternoon into the evening, but will move off to the east after midnight. No precipitation is expected from this overnight front. Winds will remain a bit gusty this evening, with gusts up to 20 mph possible, but decreasing after midnight. 850 MB temperatures, which started out below 0 C, will climb to around 5 C tonight, which is still below the normal 8 C. This slight increase and slight southerly flow will lead to lows several degrees warmer Sunday morning, ranging from the mid 30s to the north, to around 40 to the south and across Chicago. Temperatures to the north will still be cold enough to create some spotty frost along and north of I-88, and away from Chicago, early Sunday morning. Sunday morning will start with mostly clear skies, but clouds will increase once again midday as a stratocumulus deck develops from a reinforcing shot of cold air Sunday afternoon. Temperatures between 900 and 800 MB will drop below freezing, with a bit of elevated CAPE within the cloud deck, which may lead to a chance for some isolated showers Sunday afternoon, mainly in northeast Illinois. Winds will increase again Sunday afternoon with gusts of 25 to 30 mph. Cold air advection (CAA) at the surface will not start until the later afternoon/early evening, with Sunday high temperatures in the 50s. BKL && .LONG TERM... Issued at 235 PM CDT Sat Oct 15 2022 Sunday night through Saturday... Key messages in the extended forecast period: 1. Blustery conditions expected MON-TUE (Highs in 40s) - Near record cold highs MON - *see climate section below - NNW wind gusts up to 35 mph and sub-freezing wind chills 2. Gradual warming trend expected later in the week 3. Dry for most areas through the period - Flurries possible MON, low chance for snow showers - Lake effect showers MON-TUE into NW IN, some snow may mix in "Cold and blustery" will be the story for the start of the extended forecast period as the upper trough digs into the Great Lakes Region quickly developing into a closed upper low. Heading into Sunday night steady northwest winds will likely persist through the overnight hours. This strong cold air advection will help push overnight temperatures into the upper 20s to lower 30s away from Lake Michigan. Lingering stratus may limit some of the cooling, but the cold advection should make up for any reduction in radiational cooling. Cannot rule out a few flurries or isolated snow showers during the overnight period. The daytime hours on Monday will be notably cold and blustery (for this time of year) with highs struggling to warm out of the lower 40s with low clouds hanging around all day. Strong winds gusting to 30-40 mph will keep wind chill values in the 20s to lower 30s. Time to break out the winter clothing if you haven't already! Given the cold airmass in place and steep low-level lapse rates, the cloud layer will be cold enough to support at least flurries. Given support for lift beneath a strong short-wave rounding the closed low overhead, if we can get a bit deeper cloud layer there could even be a few more robust snow showers across NE IL. There are hints of this into Sunday night toward the end of the 12Z HRRR and supported by the past couple runs of the ECMWF. However, the GFS/NAM suites are leaning less favorable for anything more than flurries at this range. Still something to keep an eye on! Regardless, the signal for lake effect showers remains favorable for portions of northwest Indiana on Monday, especially into northern Porter County. Some snowflakes again could mix in at times in the lake effect showers as well. Tuesday it looks like the lake effect precipitation axis begins to shift a bit further east, but there may be a few remnant showers into Porter County IN through the AM. While strong northwesterly winds will persist through Tuesday, clearing skies should help us warm up a bit more than Monday, with highs in the mid 40s. Wind chills will likely still be in the mid 30s to near 40, however. Even though Lake Michigan water levels are a foot lower than where they were last year, the persistent strong north northwest winds will result in large waves building across southern Lake Michigan and accordingly increases the risk for beach erosion and minor lakeshore flooding along the Indiana shore. Interests along the Indiana shore, especially in areas that have been prone to flooding in the past should monitor the forecast the next couple days. Wednesday will remain unseasonably cool with forecast highs still in the mid to upper 40s. Winds do begin to turn more westerly helping ease the strong cold air advection of the past couple days. Later in the week the upper trough begins to shift east as the western ridge starts to break down. Accordingly, southerly warm advection will return and help highs warm into the 50s Thursday and Friday, with 60s possibly making a return for the start of next weekend. Petr && .CLIMATE... Issued at 235 PM CDT Sat Oct 15 2022 Here are the current records in place for Monday and Tuesday. Most records appear to be safe, with the record cold max for Rockford for Monday 10/17 being the most likely record to be threatened. Though temperatures will not be all that much above the other records... 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 00Z TAFs... Aviation Forecast Concerns: * Marginal weak LLWS possible this evening. * Breezy west-northwest winds Sunday, with gusts near 25 kts especially during the afternoon. Surface low pressure will pass north of the Great Lakes region tonight, with a trailing cold front pushing southeast across the terminals after midnight. Southwest winds ahead of the front have diminished with sunset already, though a brief period of 30-35 kt winds in the 1500-2000 foot AGL layer may make for some marginal LLWS conditions through about midnight. Given sustained surface winds near 10 kts, this is below criteria for including LLWS in the TAFs however. Surface winds turn west-northwest behind the front during the pre-dawn hours, with the cold frontal passage otherwise expected to be uneventful. West-northwest winds (290-310 deg) will become gusty once again late Sunday morning, with gusts around 25 kts persisting through the afternoon and likely in to the evening within a strong cold air advection regime. Will likely see a VFR stratocu deck develop by midday in the 4000 foot AGL range, and this too looks to linger into the evening hours. Can't completely rule out a stray sprinkle from this deck Sunday afternoon/evening, though chances of any meaningful precip appears low. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...nearshore waters until 4 AM Sunday. Gale Watch...LMZ740-LMZ741-LMZ742-LMZ743...10 AM Monday to 10 AM Tuesday. Gale Watch...LMZ744-LMZ745...midnight Monday to 10 AM Tuesday. && $$ 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