Marine Weather and Tide Forecast for Whiting, IN

UPDATE
Issued at 704 AM CDT Tue May 13 2025

Dense fog quickly developed over southern Lake Michigan this morning and oozed in along the Illinois shore. Webcams near and along the shoreline suggest at least patchy dense fog. We went ahead and issued a Special Weather Statement (in effect until 11am) and put out a graphical NowCast for the shore-hugging fog this morning. It's uncertain if/when the fog will improve, so we'll need to monitor observations, webcams, and guidance trends. However the rest of the daytime plays out, expect fog to spread further inland from the lake tonight without the benefit of the strong May sun and recent guidance suggests areas of dense fog will be possible.

Castro/Petr

DISCUSSION
Issued at 337 AM CDT Tue May 13 2025

Through Wednesday:

GOES water vapor imagery shows an expansive closed mid-upper low spinning across the eastern half of the CONUS, currently centered over western Tennessee. This feature will continue to bring isolated to widely scattered (mainly diurnal) shower and storm chances to parts of the area through Wednesday afternoon.
Locations of the greatest coverage will largely be dictated by smaller scale vort lobes that rotate around the low, though a lake shadow (thanks to continued onshore flow) will likely limit coverage across far northeast Illinois today.

Similar to yesterday, any storms that develop will be capable of occasional lightning strikes, locally heavy downpours, and due to their pulse-like nature, gusty winds up to around 30-40 mph will be possible as storms collapse. Cold air funnels were reported in central Illinois yesterday, and given that similar conditions are expected to pivot into the area today, (low- level instability paired with surface vorticity) suspect that they will be possible with any showers/storms that develop today.

The summer-like warmth is expected to continue today with temperatures forecast to warm into the mid 70s to around 80 degrees. The exception to this being near the lakeshore where continued onshore flow will hold highs in the 60s. With warm and moist air lifting across the area, fog development over the lake is likely today through Wednesday. As low-level flow turns more east northeasterly late this evening and overnight, this fog may ooze inland. Accordingly, introduced areas of fog along the immediate lakeshore late this evening through early Wednesday morning and patchy fog further inland across far northeast Illinois.

Wednesday will be similar to today though perhaps slightly warmer for inland areas (low to mid 80s for highs). The mid- upper low will begin to shift further east which should help limit shower coverage overall. However, a surface convergence axis that sets up during the afternoon extending from near Rockford to Rensselaer could could aid in greater shower/storm coverage in those areas.

Petr

Wednesday Night:

The main concern is for fog over the lake to possibly bleed back a bit inland along the immediate Illinois shore given low-level east-southeast flow. If there's still dense fog over the lake during the day on Wednesday, then locally dense fog would be possible along the Illinois shoreline. Aside from this concern, expect a quiet and mild night with lows in the lower to mid 60s except 50s along the Illinois shore and far northeast Illinois.

Thursday-Thursday Evening:

Hot, near record high temps (see forthcoming climate AFD section for more) are the first item of note for Thursday.
Exceptionally warm low- level temps are expected at peak heating. In fact, progged 925 mb temps in the mid to perhaps upper 20s Celsius are above the 90th percentile of DVN and ILX mid May sounding climatology. With these very warm temps aloft (and pushing +20C at 850 mb!), southerly winds gusting to 30-35 mph, and plenty of sunshine should translate to highs in the upper 80s to lower 90s.

These temps paired with dew points in the 60s amidst very steep mid-level lapse rates around 8C/km will likely yield 2-3kg of MLCAPE. In addition to the large instability, strong mid-level shear (effective deep layer shear pushing 50 kt) from seasonably robust southwesterly mid-level flow veering to westerly above 500 mb will set up a conditionally volatile air mass regarding the threat for severe weather. The aforementioned ingredients suggest supercell mode with large to destructive hail being the most notable threat (and a persistent feature on sounding analogs). A cold front/dry-line trailing from the powerhouse 980s mb cyclone over MN will be the source of lower-level convergence.
Meanwhile, the strongest forcing from the deep, negatively tilted mid-upper trough will remain off to our northwest, though modest 500 mb height falls will overspread the mid-upper MS Valley late in the afternoon.

As already alluded to above, this looks to be another conditional severe weather threat scenario (conditional upon storms actually forming). Some of the guidance veers the southerly winds to southwesterly out ahead of the front, which would greatly curtail low-level convergence. Even if a pre-frontal trough or surface wave keeps flow more backed, the large scale forcing is rather meager given the very warm EML base and associated capping from it. Versus the April 28th failed conditional potential, this setup appears much more likely to have strong heating through insolation, helping to erode the capping to an extent. Finally, another competing factor appears to be very dry air at the mid- levels that could provide deleterious dry air entrainment into some updraft attempts.

Given the competing and limiting factors, PoPs in the 30-40% range in the late afternoon and early evening appear sufficient. Even if CI (convective initiation) occurs, coverage may only end up isolated to perhaps widely scattered. Taken in sum, the impressive ingredients for severe weather, but conditional nature support the level 2 of 5 threat for most of the area in SPC's day 3 outlook. In addition to damaging to potentially destructive hail, and strong downburst winds, elevated LCL heights and comparably more modest low-level shear forecast may limit the tornado threat somewhat, if a few supercells do indeed occur.
The threat for thunderstorms and severe weather should end fairly quickly by the mid evening as the dryline/front sweeps across the area.

Friday:

The main forecast concern is the potential for high fire danger due to strong west-southwest winds and very warm temps (well into the 80s) plus dew points in the 40s (or lower) yielding RH in the 20-30% range (or lower). Friday's forecast admittedly is a bit lower confidence due to overall considerable variance among guidance members. With that said, the most consistent suite has been the ECMWF/EPS, which also (unfortunately) happens to feature the most concerning scenario from a fire weather perspective. One of the key items to watch for the forecast will be how fast and how far south the upper trough associated with the strong low pressure to the north closes off, which would act to keep the 980s mb surface low farther south. Should this occur, a very tight pressure gradient will remain in place over our area with dew points mixing out into the 40s or lower. In addition, stronger southwesterly 850 mb flow would be in place to tap into with deep mixing.

Since it's only Tuesday, the main forecast tweak was to nudge up the wind gusts a bit from the NBM initialization into the 35-40 mph range, strongest I-80 and north. Also slightly nudged Td lower. These steps were taken with the good run to run consistency of the ECMWF/EPS in mind. We'll need to closely monitor guidance trends for this period, needless to say.

Later Friday and especially into Friday evening, despite the warm, dry, and windy conditions during the day, an impulse coming up the OH Valley may be able to yield some high based showers and even a storm or two, especially southeast of I-55. Suspect the GEFS/GFS depictions are an outlier for the much wetter scenario on Friday, though low PoPs in the 20-30% range appear sufficient.

Castro

Saturday through Tuesday:

Generally cooler and dry conditions are forecast for the weekend.
While confidence in the details remain low this far out, long-range guidance supports a return to a more active weather period as multiple impulses ejecting off the Rockies next week which could bring additional shower and thunderstorm chances to the region.

Petr

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
Issued at 1239 PM CDT Tue May 13 2025

Key Aviation Messages for the current TAF period:

- IFR/LIFR cigs/vis expected overnight into Tuesday morning

East winds will become light tonight, if not becoming calm altogether overnight. Increasing moisture across the area has created SCT/BKN clouds mainly above 2500 feet across the region.
There is a chance for showers and thunderstorms away from the Chicago Metro this afternoon, but with the probability less than 25 percent, it was kept out of the TAF. Perhaps KGYY has the best chance, but models are keeping it south of the terminal.

The main impact to terminals is the lowering of cigs and vis through the night. There is increasing confidence that after dark, clouds out over the lake will slowly ooze inland and lower cigs and vis through Tuesday morning with a threat of potentially dense fog (vis less than 1/2SM). The greatest threat for fog will be terminals closer to the lake (ORD, MDW, GYY).
There is still some uncertainty on improvement Wednesday morning, though vis is expected to improve after 15Z, with an eventual return to VFR after 18Z.

DK

CLIMATE
Issued at 420 AM CDT Tue May 13 2025

Record high temperatures are possible on Thursday May 15th.

Here are the current record highs for May 15th:

Chicago: 91 in 1962

Rockford: 90 in 1944

Castro

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Dense Fog Advisory until 1 PM CDT Wednesday for the IL and IN nearshore waters.