textproduct: Chicago

KEY MESSAGES

- Generally dry conditions through mid-week with seasonable temperatures inland and cooler conditions near the lake.

- Rain chances return Friday and may linger through the weekend.

DISCUSSION

Issued at 130 AM CDT Tue Jun 2 2026

Sprawling ~1030 mb high pressure will be in control of our weather through Thursday night yielding continued quiet conditions across the region.

Synoptic northeasterly flow today will hold temperatures in the mid 60s lakeside, while highs will warm into the upper 70s and lower 80s inland. Forecast soundings depict a plume of very dry air aloft centered around 750 mb (dewpoints near -30C). Fairly deep PBLs today should allow for some mixing into the base of this dry layer, and surface dewpoints will likely mix out a bit in response to this (away from the immediate lake influence). Have nudged Tds down a bit with this in mind which yields afternoon RH values in the low 20s.

The surface high will wobble eastward on Wednesday and column thicknesses will increase a smidge in response. Highs will jump several degrees as a result, with lingering lake cooling confined particularly to the northeast Illinois shore. Similarly dry conditions to Tuesday may also develop, and it's possible some further reductions to dewpoints/RHs may be needed in future grid updates.

Deeper southwesterly tropospheric flow will establish across the region on Thursday. Attendant offshore flow will commensurately push mid-upper 80 degree temperatures all the way to the lakefront. A modest increase in boundary layer moisture may yield a bit more diurnal cumulus development, as well as some breezier southwesterly winds. At this time, the wind/RH combo doesn't quite look to rise to the level of an elevated fire danger, but given how dry conditions have been, will need to keep an eye on trends for Thursday afternoon.

A transition to an intermittently more showery/stormy period will occur later Friday and through the upcoming weekend and possibly into next week as large scale blocking breaks down. At this time, it looks like the bulk of the day on Friday may remain dry, although chances for showers and some thunderstorms will increase during the afternoon, particularly west of the Fox Valley. Otherwise, warm and breezy conditions are expected.

Given the break down of such a highly-amplified pattern, it's not surprising to see a pretty sizable spread in the handling of the salient synoptic elements over the weekend and into next week. Regardless, there is good agreement in a significant increase in column moisture, particularly Friday night into Saturday/Saturday night with PWATs at times forecast to near 2 inches. With several disturbances or bonafide shortwaves traversing the area, this could yield periodic scattered showers and storms, perhaps with heavier downpours at times.

It's a bit unclear how the large scale pattern will evolve on Sunday and into next week. The GFS and many of its ensembles (and to some degree the CMC/GEPS) continue to suggest the primary frontal zone will push well south of the region leading to a reduction in moisture and precipitation chances, while the ECMWF/EPS hold onto a somewhat stormier/active pattern in the region. For now, the generally low-chance PoPs from the NBM seem appropriate at this range given climatology and the ensemble spread.

Carlaw

AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 1218 AM CDT Tue Jun 2 2026

There are no key concerns for the 06Z TAF period.

Light NE winds through the night will pick up 10 to 12 kt by mid- morning Tuesday before subsiding for the evening. Light winds may go variable late Tuesday night as a center of high pressure nears, but look to favor NE. Expect VFR throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

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