Marine Weather and Tide Forecast for Calumet Park, IL

DISCUSSION
Issued at 328 AM CDT Tue Apr 14 2026

Today through Wednesday Night:

A weakening MCS will continue drifting across northern Illinois through this morning in a weakening phase with a gusty outflow boundary surging out ahead of it. The OFB passage may bring a temporary period of onshore winds and notably cooler conditions to portions of the lakeshore (especially far NE IL) and perhaps patchy fog as well. Towards and after sunrise this morning, a question will be the extent to which widely scattered elevated convection (showers and isolated non-severe storms) may develop with southward extent behind the outflow boundary. Once any convection this morning fades out, expect the rest of the morning and into the early afternoon to be dry as the area once again becomes capped underneath a strong EML (elevated mixed layer) inversion.

A likely key player the rest of this afternoon for the looming PM severe threat will be how far south the outflow boundary from the weakening MCS reaches, before retreating back north as an effective warm front. A farther south remnant outflow boundary could conceivably aid in a bit farther south convective initiation (CI) near the stalled warm front this afternoon than depicted verbatim by most of the CAM guidance. On the other hand, low clouds shifting southward in the wake of the OFB this morning will serve to limit insolation initially, potentially delaying stronger destabilization until the mid afternoon. Conceptually, the area to monitor for explosive CI this afternoon will in closer proximity to the stalled warm front (as previously noted), from northwest Illinois and northeast Iowa into southern Wisconsin. Satellite, observational, and mesoanalysis trends will need to monitored closely for any subtle 700 mb impulses that could help erode the cap as early as 3-5pm. A secondary possible area to watch for isolated storms by the mid to late afternoon will be into portions of central IL as a 500 mb vort lobe translates east-northeast.

Ultimately, the lack of stronger large scale forcing (neutral h5 height tendencies) casts some uncertainty/conditionality to this setup. An ensemble of recent CAM solutions does suggest a realistic play for the daylight hours remaining dry across our CWA counties. With the OFB placement wildcard and possibility that subtle upstream impulses can sufficiently erode the cap, we maintained (30-50%) chance PoPs as early as 3-5 PM over the northwest 1/3 to 1/2 of the CWA, and stair-stepping gradually south from there.

Once clouds scatter enough early this afternoon, several hours of diurnal heating and destabilization of the moist (dew points in the 60s) low-level air mass topped by very steep lapse rates aloft will yield a very favorable thermodynamic environment for severe storms (MLCAPE possibly at or bit upward of 3k J/kg). In the presence of about 40 kt of deep layer bulk shear, this will be a conditionally volatile environment for supercells capable of very large hail (2"+). If CI occurs into the CWA prior to sunset, somewhat weaker low-level flow and storm relative inflow (especially if sfc winds remain veered) would indeed favor damaging to potentially destructive hail as a primary threat initially.
As the low-level jet diurnally intensifies into this evening, a notable tornado threat could also unfold into northeast IA, southern WI, and possibly far northern IL, given enlarged low- level hodographs. Any locally backed surface winds would further enhance SRH.

With the above being said, despite the 3/5 severe threat level (enhanced risk) for locations north of I-80 today-tonight (Tuesday-Tuesday night), our confidence is a bit lower in storms effectively tapping into the volatile environment today within our CWA A later after sunset arrival into far northern Illinois and mid-late evening farther south would give some time for instability to wane. Also, the relatively parallel alignment of the deep layer shear vector to the warm front should lead to a storm mode transition from supercells to upscale growth into forward propagating segments through the evening. Mismatched west-southwesterly 850-300 mb flow vs.
propagation vectors towards the east-southeast may limit how far south and east an appreciable damaging wind (and embedded QLCS type tornado threat can reach). All in all, the area of greatest concern for potential significant severe weather is well outlined by the zone of 10% tornado probs in SPC's day 1 outlook, approximately near and north of a Dixon to Highland Park IL line.

Additional storms should eventually fill in behind the evening activity overnight, favoring our highest official PoPs of the night into the 60-70% range. Hydrology may become an increased concern later tonight, particularly if repeated rounds of storms move over the same area. If this occurs, a notable threat of flash flooding will materialize, perhaps more than implied by a flood threat level of 1/4 (marginal risk) in WPC's excessive rainfall outlook. Exactly how the event will play out through tonight remains quite uncertain.

With so much riding on the effects of prior convection into Wednesday morning, little can be gleaned about Wednesday PM's threat for strong to severe storms with any sort of confidence. It looks quite messy/muddled and we won't be able to sort things out until more is known about the environmental evolution. A 2/5 threat level (slight risk) remains targeted for areas northwest of I-55 in SPC's initial day 2 outlook, with a level 1/5 (marginal risk) I-55 and southeast, including Chicago. At present, independent of where any corridors of severe storms set up, likely veered surface winds, modest low-level flow just off the deck, and mid-level lapse rates not quite as steep, seem to point towards damaging winds as the primary threat after any initial hail threat. Mesoscale evolution may yield a localized enhanced tornado threat, as per the outlook discussion.

Castro/KJB

Thursday through Monday:

There's variance regarding the progression of a cold front across the region, with some of the slower solutions holding onto some potential for storms into Thursday afternoon (particularly southeast ~1/2 of CWA). Thereafter, into Thursday night and at least the start of Friday, ensemble model guidance advertises a brief break in the stormy pattern as shortwave ridging moves through the Great Lakes ahead of a substantial trough digging into the central US. High temperatures look to rebound into the low to even mid 80s by Friday accompanied by another potential threat for strong to severe thunderstorms Friday night into Saturday. Thereafter, there is a reasonably strong signal in ensemble guidance for a cooldown to start next week.

The key aspect for the weekend into early next week cooldown is a recent trend towards a much cooler air mass due to trough amplification over the region. If this comes to pass, parts of the area may flirt with sub-freezing temperatures Saturday night into early Sunday, and again Sunday night into next Monday morning. With the summer-like warmth and rain this week supercharging plant growth and leaf out, the magnitude of the weekend cold shot will be one to watch for agricultural interests.

Castro/Borchardt

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/
Issued at 658 AM CDT Tue Apr 14 2026

Main Concern:

- Timing of next rounds of TS later this afternoon into Wednesday morning, with the highest threat for severe weather through this evening.

- Wind direction trends this morning and in/near TS this afternoon-evening onward.

The clusters of showers and thunderstorms moving across the Chicago area as of this writing will exit east by ~13z (possibly a bit later for GYY). In the wake of this morning convection, currently east and southeast winds should take a couple hours to fully return to breezy southwesterly. It remains highly uncertain if/when additional storms will affect the terminals later today. Overall, it appears RFD has the highest chance to be directly impacted prior to mid evening. With that said, we certainly can't rule out TS as early as mid-late afternoon at any TAF site. Given the uncertainty, maintained PROB30s in the TAFs. Sufficiently early TS impacts would include a threat for large to destructive hail as the main severe threat, with RFD having the overall highest chance (as well as a +FC threat).

There's a bit better signal for showers and embedded TS to fill in later in the evening and especially overnight. Confidence is still on the lower side for this period, and opted for a broad brushed -SHRA VCTS mention with MVFR VSBY. Fairly widespread showers with low (but likely not zero) embedded TS coverage appear likely on Wednesday morning. Withheld any additional PROB30 TS mention in this window, with better chances favored south of the terminals. Lighter southwest winds are likely outside of convective effects tonight. Any direct impacts from TS will likely cause erratic and strong/gusty winds through this evening, with wind direction and speed variability to follow overnight and possibly into Wednesday morning. Finally, some patchy 2-3kft CIGs may develop tonight-Wednesday morning.

Castro

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...None.