Sunrise 5:49 AM   Sunset 7:43 PM Moonrise 11:02 PM   Moonset 7:00 AM

  Print   HELP   Reset   Save   Recall

LMZ744 Expires:202404262145;;407839 Fzus53 Klot 261416 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 916 am cdt Fri apr 26 2024
for waters within five nautical miles of shore on lake michigan
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the waves, along with the average height of the highest 10 percent of the waves which will occasionally be encountered.
lmz742>745-262145- northerly island to calumet harbor il- calumet harbor il to gary in-gary to burns harbor in- burns harbor to michigan city in- 916 am cdt Fri apr 26 2024
Rest of today - Southeast winds 15 to 20 kt. Showers likely and slight chance of Thunderstorms in the afternoon. Waves 2 to 4 ft subsiding to 1 to 3 ft. Tonight - Southeast winds 15 to 25 kt becoming south overnight. Showers likely and a chance of Thunderstorms. Waves 1 to 3 ft. Saturday - South winds to 30 kt becoming southwest. Chance of showers and Thunderstorms. Waves 1 to 3 ft. A small craft advisory will likely be needed. Saturday night - South winds 20 to 25 kt becoming southwest 15 to 20 kt. Chance of showers and Thunderstorms. Waves 1 to 3 ft. A small craft advisory will likely be needed.

LMZ700
No data

FXUS63 KLOT 261737 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1237 PM CDT Fri Apr 26 2024

KEY MESSAGES

- Rain moves into the area late this morning and afternoon and continues into tonight. Isolated to scattered thunderstorms may be seen during this time as well, particularly this evening.

- The weekend looks warm and breezy with high temperatures in the upper 70s to lower 80s and overnight lows in the low to mid 60s.

- Multiple rounds of showers and thunderstorms over the weekend through Monday, some of which could be severe late Saturday and again Sunday night.

- After a brief break, shower/storm potential returns toward the middle of next week

DISCUSSION
Issued at 412 AM CDT Fri Apr 26 2024

Through Saturday:

GOES infrared satellite imagery has quite the colorful look to it early this morning across the central Plains with two groups of widespread deep convection evident. One of these is a large conglomerate of thunderstorms over eastern Nebraska and western Iowa, while the other is a newly blossoming swath of isentropically- induced convection over western Missouri. This second thunderstorm cluster is of most relevance to our weather forecast for today as, with time, these storms will propagate towards and eventually into our forecast area later this morning and afternoon.

As this cluster approaches the area, it is likely to outpace the instability reservoir that it currently resides in and, hence, should arrive in a weakened state, with most locales in northern Illinois and northwest likely to just see a plain rain today as a result. The best chances for any lightning in our area through this afternoon will thus likely remain confined to the southwestern half of our CWA The eastern periphery of the main instability plume will eventually creep into the area later tonight and lead to a slightly better chance for thunderstorms area-wide, though exact storm coverage will hinge largely upon how this afternoon and evening's severe thunderstorms in the central/lower Missouri River Valley evolve and whether they manage to survive their northeastward trek across Iowa/Missouri into Illinois. Suppose that there is an outside chance of a strong to marginally severe thunderstorm sneaking into our western counties late this evening -- especially if the cold pools from the upstream convection manage to consolidate and yield a more organized forward-propagating storm cluster. However, in all likelihood, the upstream thunderstorms should weaken below severe limits by the time they reach our forecast area as they encounter an increasingly stabilized boundary layer with eastward extent.

The 992-994 mb surface low passing to our northwest will be culpable for a tight surface pressure gradient across the region that will keep breezy southerly winds in place today through Saturday.
Depending on how deeply we are able to mix Saturday morning, a brief period of 40-45 mph gusts may be observed for a few hours before the overhead low-level jet weakens, resulting in gusts diminishing to closer to 30 mph Saturday afternoon. These winds will also serve to advect in an unseasonably warm and moist air mass with temperatures and dew points likely to be on the rise tonight into Saturday morning. Despite a good deal of cloud cover likely being around on Saturday, warm air advection on its own will push temperatures into mid to upper 70s, and with the expectation that there will still be some sunshine to be seen on Saturday, highs will likely end up near 80 degrees across our forecast area. When paired with dew points climbing into the 60s, Saturday will certainly have a summer-like feel to it.

With this relatively muggy air mass in place on Saturday, there will also be a summer-esque potential for isolated showers and storms to develop in the afternoon. The general thinking is that height rises and subsidence on the backside of the departing upper-level trough, relatively nebulous large scale forcing for ascent, and the presence of a capping inversion should favor most or all of the area remaining dry through most of the daytime hours once any lingering morning showers depart. However, by the late afternoon, forecast soundings show that the cap should have weakened or eroded entirely, and isolated attempts at convection may start to see some success wherever warm air advection and/or confluence in the low-level flow is maximized. Thus, have kept slight chance PoPs going during the afternoon to account for this possibility, with the highest probabilities currently advertised in our southeastern counties, where the convective signal is greatest in the 00Z/06Z CAM suite. With the heart of the aforementioned instability plume expected to be positioned over the area by Saturday afternoon, MLCAPE values may get as high as 2500-3000 J/kg during peak heating, which would be more than enough to support the development of thunderstorms that could grow deep enough to carry some threat of strong to severe downburst winds and/or hail. However, with lingering uncertainties about shear profile quality and the aforementioned dearth of forcing for ascent, whether an isolated threat for severe weather will materialize Saturday afternoon remains in question.

Ogorek

Saturday Night through Thursday:

By Saturday evening the lead short-wave trough and attendant surface low will continue to weaken while lifting northeast into Ontario. Showers and storms may persist along the trailing cold front near and north of the WI/IL stateline into Saturday evening. Meanwhile a secondary and more amplified upper level trough will eject off the Rockies into the PLains with an associated deepening surface low setting the stage for significant severe weather potential near the NE/KS/IA/MO stateline region. This activity is expected to lift northeast toward the area by Saturday evening/overnight. With a warm and moist airmass still in place into the evening (near record warm low temperatures in the low-mid 60s!), a cluster or line of strong to severe storms may manage to persist into portions of the area, currently favoring areas north of a Peru to McHenry, IL line.

The details become less clear heading into Sunday with the evolution of the broader system will be dependent on what transpires Saturday and Saturday night, though there is a signal that much of the area could be dry for much of the daytime hours on Sunday with temperatures warming back into the upper 70s to around 80. Showers and storms are anticipated to develop well to the west across portions of MO/IA which then push east Sunday night across the area. A strong to potentially severe storm cannot be ruled out with this activity though it will likely be on a weakening trend with eastward extent. Showers may linger into Monday as the system lifts out of the region and the trailing cold front gradually moves through.

Southwest flow quickly returns in the wake of the cold frontal passage with highs still in the mid-upper 70s Tuesday and Wednesday. Several mid-level disturbances moves within the broader quasi-zonal upper-jet which could bring additional rounds of showers/storms toward the middle of next week with temperatures turning more seasonable by the end of the week.

Petr

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/
Issued at 1236 PM CDT Fri Apr 26 2024

Key Aviation Impacts for the current TAF period:

- Waves of showers and isolated embedded thunderstorms through the overnight period.

- Stronger wind gusts around 30 knots expected late Saturday morning

As a low pressures system in Eastern Nebraska drifts to the north, waves of showers are expected at area terminals through the day and the overnight period. Lightning has been detected in Western Illinois and is drifting northward. Given the track of the storm, there was enough confidence to add VCTS to the KRFD TAF for the next two hours. But given the more northerly track and the diminishing instability, VCTS was not added in TAFs for the Chicago terminals. While isolated embedded strikes may occasionally occur, it was left out of the TAF but will be monitored very closely. If lightning were to occur over KORD/KMDW, it is expected to happen between 19Z and 21Z.

But that is just the first wave of rain. While there may be breaks in the rain, the next chance for stronger rain showers that would have MVFR cigs/vis associated with them will be after 00Z (closer to 03Z for Chicago terminals). Once again, there will be a risk for embedded thunder with the rain tonight, but the probability is around 30 percent (below the threshold for a TEMPO for thunder). Therefore the PROB30 group was removed from the TAF. There was a TEMPO added for the risk of lower MVFR cigs. There have been isolated obs of IFR level cigs to the west, but confidence was not there to add cigs that low. If thunder would develop over terminals, it would likely be in this window. Showers will gradually diminish into the Saturday morning hours.

Winds are out of the southeast with occasional gusts around and just over 20 knots. Those winds are expected to increase through the afternoon and evening to be more prevailing around 25 knots.
By Saturday morning, the winds will gradually pivot to the southwest and increase as a low level jet increases. There is the potential for gusts up to 35 knots late Saturday morning.
Currently left it through the end of the TAF period, but the duration for the strongest wind gusts will depend on cloud cover tomorrow and the placement and strength of the jet aloft.

DK

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory until 10 PM CDT Saturday for Winthrop Harbor to Northerly Is. IL.

toggle option: (graph/table)

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Chicago, IL,