textproduct: Chicago

KEY MESSAGES

- Cooler and continued dry conditions today and Monday, with shower and storm chances returning on Tuesday.

DISCUSSION

Issued at 158 AM CDT Sun May 10 2026

High pressure will drift across the western Great Lakes through Monday as deep troughing over eastern Canada edges eastward. This will set the stage for a seasonably cool, but dry and mostly clear period for the area. Continued deep diurnal mixing will promote sporadic gusts to 25(20) mph or higher and RH values under 30(35) percent this afternoon (Monday afternoon), resulting in a brief period of elevated brush fire conditions each afternoon.

With high pressure nearing from the northwest and dry conditions noted by PWATs under 0.4 inches, another unseasonably chilly night with some patchy frost for outlying areas of far northern Illinois is possible late. Some mid-level cloud cover associated with a wave/elongated trough currently over southern Manitoba will cross the area tonight and may be keep temps just warm enough to limit coverage of frost. Conditions appear too marginal to issue a Frost Advisory for counties including and north of the I-88 corridor.

A modestly strong trough tracking southeastward over the Boundary Waters early Tuesday will brush the area to the north with WAA-induced showers during the morning, followed by a potential axis of showers and some thunderstorms associated with a cold front Tuesday afternoon into the evening. Will need to monitor for a low-end isolated strong storm risk during this time as a decent kinematic field compensates for marginal mid- level lapse rates and a somewhat dry low-level profile.

High pressure and a return to seasonably cool and dry conditions will return Wednesday and Thursday. The broader flow across North America is then progged to transition into a more active northern stream across the CONUS, with increasing rain/storm chances and potentially a period of seasonably warm conditions beginning as early as Friday and especially late next weekend into the following week.

Kluber

AVIATION /12Z TAFS THROUGH 18Z MONDAY/

Issued at 624 AM CDT Sun May 10 2026

Key Messages:

- Light and variable winds early this morning turn northwesterly later this morning, particularly at interior northern IL terminals (ORD, DPA and RFD).

- Northeast wind shift with lake breeze likely this afternoon at MDW and ORD, potentially as early as 19-20Z at MDW. Confidence on the exact timing remains of low confidence at this time, so further refinement is likely. Wind trends continue to be the only concern at the terminals through the forecast period. Light and variable winds early this morning are expected to trend northwesterly with some afternoon gustiness, particularly at inland terminals (ORD and westward). However, sites closer to the lake may not experience these northwesterly winds. Instead, a developing late morning/early afternoon lake breeze may result in an earlier northeasterly wind shift than previously forecast at MDW, and potentially ORD as well. Accordingly, with the 09Z TAFs we opted to move up the northeasterly wind shift by several hours, and we have held with these timing adjustments for the latest 12Z TAFs. Observational trends will need to monitored closely into early this afternoon, as it remains plausible that the east- northeasterly wind shift occurs an hour or two earlier than the current 22Z advertised time at ORD. Once this wind shift does occur, high pressure building into the western lake regions tonight into Monday will maintain prevailing east-northeasterly onshore winds through Monday.

KJB

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.