082 FXUS63 KLOT 182001 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 301 PM CDT Fri Mar 18 2022 .SHORT TERM... Issued at 300 PM CDT Fri Mar 18 2022 Through Saturday... The inclement weather will continue through Saturday morning and then conditions will improve gradually Saturday afternoon, especially with north and westward extent. Main items of note: * Threat for additional embedded thunderstorms * Rain possibly mixing with or briefly changing to wet snow Saturday morning across northwest third or so of CWA with no impacts expected * Gusty northerly winds 1000 mb surface low pressure responsible for the "nasty" conditions this afternoon is located between Quincy IL and St. Louis MO as of this writing. Large area of rain showers has essentially become stratiform given more uniform coverage, though still seeing isolated to widely scattered embedded thunderstorms. The threat for additional thunderstorms north of I-80 will be coming to an end by 3-4PM. Farther south, thunder threat will be conditional and tied to encroaching dry slot this evening in poor quality warm sector as surface low scoots northeast. Overall rain coverage this evening will be widespread, though southeastern sections will probably see a trend more toward numerous to even scattered showers in dry slot area. Farther north, looking at categorical type coverage most of the night, eventually trending downward for a time during the late night period as moisture depth decreases. Basically, going from a nearly steady, soaking rain early evening, to waves of showers overnight. Seasonably high PWATs of 0.8 to 1" (200+% of normal) will result in temporary heavy rainfall rates persisting until early evening then easing as coverage of heavier showers diminish. The backside deformation area precip will pivot across the area on Saturday. During Saturday morning, guidance (as depicted in forecast soundings) indicates sufficient cooling aloft and at the surface to introduce potential for very wet snow to mix in or a temporary changeover to wet snow for locations roughly near and west of a Winthrop Harbor to Marseilles line. After gradually dropping to mid to upper 30s later tonight into Saturday morning, temps will only recover to the lower-mid 40s (perhaps upper 40s far W/NW CWA where some late day sunshine is forecast) Saturday afternoon as rain tapers and exits to the southeast. Gusty northeast winds will continue tonight north of the surface low track and shift to northwesterly on Saturday on backside of the system with gusts up to 30 mph. All in all, despite the raw and inclement weather conditions, this is needed rain for the long term drought areas of far northern Illinois. Castro && .LONG TERM... Issued at 158 PM CDT Fri Mar 18 2022 Sunday through Friday... In the wake of the broad upper-level troughing responsible for our recent bout of cold and wet weather, upper-level ridging and an associated surface high pressure system will build into the Great Lakes to close the weekend. Sunday accordingly looks pleasant with mostly sunny skies, light winds, and highs in the lower 60s. It's not all rosy however as the weak winds will provide little to no resistance to an inward-surging lake breeze. In other words, temperatures along the lakeshore will drop some 15 to 20 degrees by early afternoon in the wake of the boundary! So, don't forget a jacket if planning to be out and about along the lakeshore on Sunday. Inland locations will safely remain in the lower 60s. By Sunday night, the aforementioned surface high pressure system will be east of our area leading to broad southwesterly return flow across the Mississippi River Valley. As a result, temperatures Monday will climb into the mid to upper 60s areawide, though at the expense of at least broken cloud cover. Change will once again be in the air as yet another upper-level trough digs and deepens in the Southern Plains Monday night into Tuesday, enabling a surface low pressure system to develop and eject east- northeastward toward our area by Tuesday. Ensemble model guidance remains in good agreement that the low will provide our next opportunity for soaking rain, particularly Tuesday night into Wednesday, though the exact evolution of the low itself is far less certain given a plethora of upper-level waves within the parent trough to provide various phasing opportunities. During the middle of next week, we may have to deal with waves of steady rain, rumbles of thunder, gusty winds, and perhaps even snow showers. For now, will continue to highlight the middle of next week as "wet" and leave room for refinements in later forecast packages. Behind the storm system, ensemble model guidance provides fair confidence in at or below normal temperatures to close the workweek. Borchardt && .AVIATION... For the 18Z TAFs... Aviation weather concerns for the 18Z TAFs * Rain/showers for around the next 24 hours * Chance of lightning for the next few hours * Gusty northeasterly winds throughout the TAF period * Ceilings/visibilities dropping this afternoon to IFR conditions A surface low centered over Missouri is bringing up showers and some thunderstorms from the south, with northeasterly winds gusting into the upper 20s, and occasionally exceeding 30 kt. Greatest threat for lightning is south of I-88 except for western locations, where lightning/storms will continue towards the IL/WI state line. Although the chances are low, occasional lightning cannot be ruled out at all terminals early this afternoon. Steadier rain will move in later this afternoon, with a gradual lowering of ceilings to MVFR initially, and down to IFR late afternoon. Rainfall will occasionally lower visibilities down to 2 to 3 miles. Low CIG/VIS in rain/rain showers will continue throughout Friday night and into Saturday. Winds will remain from the northeast for most of tonight with continued gusts in the mid 20 kt range. As the low shifts to our east early Saturday morning, winds will back to the northwest, with continued 20+ kt gusts. Rain is expected to end Saturday afternoon, with a gradual increase in CIG heights to MVFR towards Saturday evening. BKL && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...IL nearshore waters until 7 PM Saturday. Small Craft Advisory...IN nearshore waters until 10 PM Saturday. && $$ 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