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Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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137 FXUS63 KLOT 211927 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 127 PM CST Fri Feb 21 2025 .KEY MESSAGES... - Milder, above normal temperatures are expected Sunday through Tuesday - Chances for rain/showers Monday night (20-30%) and Wednesday into Wednesday night (40-60%) && .DISCUSSION... Issued at 126 PM CST Fri Feb 21 2025 Through Saturday Night: A large 1040 mb high centered over the Mid-Mississippi Valley will gradually shift eastward towards the mid-Atlantic into Saturday night. The eastward exit of this surface high will continue to set the stage for a warming trend through the weekend as southwesterly low-level flow persists. Dry and primarily clear skies are expected through tonight. While this will aid in temperatures remaining on the cold side again tonight, readings will not be as cold as the last few nights. Overnight lows are slated to generally range from the upper single digits above zero in northwest IL to the low to mid teens elsewhere. Breezy southwest winds will develop during the day on Saturday (afternoon gusts up to 25 mph) as the surface gradient strengthens along the northern periphery of the exiting surface high. These winds will help foster warmer daytime temperatures under mostly sunny skies. Readings look to top the freezing mark in most locations for the first time in about a week. Quiet weather continues Saturday night, albeit with the presence of a few more mid and high level clouds. KJB Sunday through Friday: Southwesterly surface winds will prevail through much of the early part of next week. These winds will help transport a milder air mass northward. While there is still some uncertainty regarding cloud cover and snow pack and their impact on the exact high temperatures, it looks like milder, above normal temperatures are in store. Afternoon temperatures are expected to top out in the 40s, with some potential for reaching into the 50s for areas south of I-80. A low pressure system will pass from west to east through Canada Sunday into Monday, deepening as it traverses Ontario. As the surface trough extends far enough south, it could bring precipitation to southern Wisconsin. For now, models have consistently kept this system to the north of the stateline. While chance for precip in the far northern counties is non- zero, models keep enough low-level dry air around to prevent it from being added to the forecast. In the wake of that system, the upper-level pattern will become predominantly northwesterly with the potential for a number of successive perturbations to pass through during the week. The first being on Monday night and into Tuesday morning. As a short wave trough moves southeast out of Manitoba, the upper-level jet will strengthen as it approaches the Great Lakes supporting vertical ascent. With model sounds showing fairly steepened lapse rates and low-level warm air advection associated with a surge of mid-level moisture, there looks like a decent chance for rain across much of the forecast area Monday night and potentially lingering into the Tuesday morning commute as it exits to the east. Another strong shortwave is projected to move across the northern Plains/Canada Wednesday and into Wednesday night. Models have consistently shown this system to be slightly stronger/deeper; however, they have struggled with the placement and timing of the trough. The system will start out as rain on Wednesday with Illinois being firmly within the warm sector. However, as the surface low moves to the east in the evening/overnight, winds will switch over to the northwest. With better cold air advection, there is a chance for precip to change over to a rain snow mix, if not all snow, overnight into Thursday morning. There is still uncertainty on whether or not it will impact the Thursday morning commute given the lower confidence at this time range. Beyond Thursday, there may be a break on Friday, but an active upper-level pattern looks to continue with additional precip chances in the long range with a trend (at least briefly) back towards below normal temperatures. DK && .AVIATION /18Z TAFS THROUGH 00Z SUNDAY/... Issued at 1121 AM CST Fri Feb 21 2025 There are no significant aviation weather concerns for the 18Z TAF period. WSW winds will continue moving at near or just under 10 kt for the remainder of today. SW winds will gust to around 20 to 25 kt during the day on Saturday. Expect VFR conditions through the period. Doom && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago