Marine Weather and Tide Forecast for Niles, IL

UPDATE
Issued at 933 AM CDT Wed Apr 23 2025

Updated precipitation chances and sky cover primarily with the morning updates. Still expect showers and isolated thunderstorms to diminish south of I-88 generally...with chances lingering around I-88 and north through the afternoon hours.

NWS Lincoln

DISCUSSION
Issued at 403 AM CDT Wed Apr 23 2025


Near Term
(through this afternoon)
A cluster of elevated thunderstorms continues to lift north of the I-80 corridor early this morning in tandem with the nose of a modest 850-mb jet. A quick glance at the IR satellite reveals warming cloud tops as this convective activity begins to outpace the meager instability, and this trend will continue as the cluster lifts further north throughout the morning. Still, we could see some pretty efficient rain rates, with nearby radars depicting rates of 0.5-1"/hr. This lines up reasonably well with recent HRRR 3-hr PMM QPF guidance, which offers 0.1"-0.5" with this activity. One byproduct of these early morning storms is its associated convective debris/outflow which may result in a busted temperature forecast this afternoon. A few of the hi-res guidance, namely the HRRR, continue to hint at this possibility, even offering additional showery activity this afternoon north of I-88 as subtle mid-level shortwave energy interacts with a lingering sfc boundary. Areas south of I-80 should remain dry and easily reach the upper 70s this afternoon, while areas north of I-88 may struggle to breach the upper 60s.

Short Term
(Tonight through Saturday)
A pocket of mid-level dry air will move across the area tonight through Thursday, keeping rain chances at bay. Continued warm advection will push temperatures near 80 degrees in areas south of I-80 Thursday afternoon. The joke will once again be on areas north of I-88, but particularly along the lakefront, as a backdoor front sags into the lower Great Lakes region. The net effect will be sharp temperature gradient across our CWA, with lower 70s north of I-88 and lower 60s smack-up against the lakeshore. A similar trend then continues for Friday as the east- west front stalls in the vicinity of I-80.

Rain chances re-emerge Friday morning or Friday afternoon as mid-level shortwave energy and weak sfc low pressure glide along the stationary front. Overall, the vertical moisture profile with this activity looks fairly paltry with some residual mid-level dry air in place. While this setup doesn't appear like it will deliver much rain, there is an axis of modest MLCAPE (500-1000 J/kg) near and south of the front where convective precip may overachieve our current QPF (< 0.5")
expectations.

Much cooler temperatures will spill across the region Friday night into Saturday as a robust mid-level trough digs across the Upper-Mississippi Valley and helps flush our lingering front well to the south. Temperatures Saturday afternoon will only warm into the lower 60s inland, and lower 50s along the lakefront.

Long Term
(Sunday through Tuesday)
After a seasonably chilly Saturday, temperatures bounce warmer by Sunday as a ridge of high pressure quickly builds across the Plains ahead of a deep western trough. An impressive warm advection regime will push temperatures into the 70s by Sunday and into the lower 80s Monday & Tuesday. Of course, we can't surge into the 80s this time of year without it being accompanied with gusty southerly winds. A quick glance at GEFS/EPS guidance supports mean wind gusts around 30-40 mph during this time as the surface pressure gradient tightens ahead of an impending storm system. At this juncture, widespread thunderstorm activity looks possible late Monday and through Tuesday, and this idea is stoked by multiple machine- learning tools which highlight the Mid- Mississippi Valley and lower Great Lakes regions for severe weather.

NWS Lincoln

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
Issued at 1235 PM CDT Wed Apr 23 2025

The main aviation weather messages are:

- Generally S/SW winds developing this afternoon. Some potential for winds to flip SE/E at the Chicago-area terminals this evening, but chances too low for a mention.

- Main threat for shra/ts shifting north of the Chicago-area sites this afternoon and evening.

- Small potential for TS INVOF RFD this afternoon, but chances are too low/brief for a formal VCTS mention at this time.

- Eventual north/northeast wind shift with a cold front Thursday morning/afternoon. Timing remains a bit uncertain.

Lingering morning convection has largely diminished and shifted east of the terminals. While there remains about a 10-20% chance for an additional shower or storm this afternoon, chances are too low for a precip mention at the Chicago-area sites. At RFD, have prevailed VCSH where additional spotty activity will likely materialize out of a mid-level cloud deck through the afternoon.
Will need to keep an eye on trends, as the TS potential is not zero, but currently is too low to justify a formal VCTS mention.

Wind trends are also a bit uncertain this evening, with some guidance indicating winds will fold over out of the east or southeast with very weak flow in place across the region. For now, have continued with a mention of just light SW winds, but will closely monitor observations and model trends. Regardless, winds will become light this evening and overnight, outside of any convective outflow that gets kicked southward out of afternoon convection across Wisconsin.

A cold front will press south through the region Thursday morning and afternoon. Timing this wind shift remains uncertain, but the inherited mid-late morning timing still seemed appropriate and made minimal changes there. At this time, it appears the threat for low clouds with this front remain pretty minimal, with VFR conditions expected to prevail.

Carlaw

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