Marine Weather and Tide Forecast for Joliet, IL

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 /12Z TAFS THROUGH 18Z THURSDAY/
Issued at 625 AM CDT Wed Apr 23 2025

Forecast concerns for the terminals...

- Scattered showers remain a possibility (40% chance) through about 15z/10am this morning.

- Generally light surface winds (5-10 kts) will oscillate between southwest and southeast through this evening.

Showers and thunderstorms will continue to exit the regional terminals this morning, leaving behind erratic surface winds.
Short-term model guidance is in reasonable agreement that winds will oscillate between southwest and southeast this afternoon, becoming variable for a time tonight before adopting an easterly component by Thursday morning. Otherwise, clearing skies later this morning will result in VFR conditions through the remainder of the TAF period.

NWS Lincoln

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