Saturday, April4, 2020
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Marine Weather and Tides
Chicago, IL

Version 3.4
NOTICE
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 6:25AMSunset 7:21PM Saturday April 4, 2020 7:38 PM CDT (00:38 UTC) Moonrise 3:11PMMoonset 4:49AM Illumination 90% Phase: Waxing Gibbous; Moon at 12 days in cycle
NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.
Marine Forecasts
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LMZ742 Expires:202004050315;;572924 Fzus53 Klot 041959 Nshlot Nearshore Marine Forecast National Weather Service Chicago/romeoville Il 259 Pm Cdt Sat Apr 4 2020 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. Lmz740>743-050315- Winthrop Harbor To Wilmette Harbor- Wilmette Harbor To Northerly Island- Northerly Island To Calumet Harbor-calumet Harbor To Gary- 259 Pm Cdt Sat Apr 4 2020
Tonight..North winds 10 to 15 kt. Partly cloudy. Waves 2 to 4 ft.
Sunday..Northeast winds 10 to 15 kt. Sunny. Waves 1 to 3 ft.
Sunday night..East winds 5 to 10 kt becoming southeast after midnight. Mostly clear in the evening then becoming mostly cloudy. Waves 1 to 3 ft.
Monday..Southeast winds 10 to 15 kt. Chance of showers through the day. Slight chance of Thunderstorms in the afternoon. Waves 1 to 2 ft.
LMZ742


7 Day Forecast for Marine Location Near Chicago, IL
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location: 41.85, -87.6     debug


Area Discussion for - Chicago, IL
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FXUS63 KLOT 042309 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 609 PM CDT Sat Apr 4 2020

SHORT TERM. 239 PM CDT

Through Sunday night .

High pressure has become established across the upper Midwest this afternoon, with increasing surface pressure and dry advection slowly working to erode stratus clouds from the northwest. Areas in the clear have been able to sneak into the 50s, while it remains a slow climb elsewhere. Expect most areas to experience some clearing, though in northwest Indiana it may be a race before sundown.

The surface high will shift over the Great Lakes tonight into Sunday and result in quiet and slightly warmer conditions across the area as more sunshine will be the rule. We will have some mid-level clouds overnight and into early Sunday as a weak vorticity maximum along the Iowa/Missouri border will slide through the local area. Otherwise with more sun than clouds temperatures will rebound to the 50s away from the lakeshore in the onshore flow regime.

KMD

LONG TERM. 320 PM CDT

Monday through Saturday .

The main concern is the occasional threat for thunderstorms Monday PM through Tuesday evening and possibly again Wednesday afternoon and evening. This includes a risk for strong to severe thunderstorms mid to late Tuesday afternoon into Tuesday evening.

A warm front will be located well south of the CWA on Monday morning, across downstate Illinois. Temperatures look to reach the 60s for many areas, except the Illinois shore, which will hold onto onshore flow until late afternoon. On Monday afternoon and evening, low amplitude mid and upper ridging over the Midwest may be topped by a lead short- wave in west- northwest flow aloft. The guidance continues to indicate that a plume of very steep mid- level lapse rates (8+ C/km in 700-500 mb layer) will be advected eastward, which should yield sufficient MUCAPE for a threat for scattered embedded thunderstorms over the region, perhaps in a loosely organized MCS.

On that note, there is variance in the magnitude of MUCAPE realized over the CWA. With the extremely steep mid-level lapse rates but possibly more limited moisture aloft with east/northeastward extent, there may be a sharp MUCAPE gradient across the CWA. Will need to watch for potential that the convection rides this gradient, with best chance for storms in west/southwest CWA and points southwest, roughly as depicted on 12z ECMWF. Given the uncertainty, did carry chance thunder mention across the CWA, and likely PoPs from the NBM. If higher MUCAPE with little/no MUCIN are realized over portions of the CWA, effective deep layer shear could tick up to 30-40 kt, which may support an isolated severe hail risk in strongest storms.

Looking ahead to Tuesday, surface warm front will be lifting north, carrying dew points into the lower 60s for many areas by mid day. Any early morning elevated convection should have exited off to the east and southeast. A very strong EML with mid-level lapse rates at or above 8C/km will still be in place over the area, which would likely present a cap to thunderstorm development for part of the daytime as things stand now. A surface low pressure system will track from the northern Plains to the central Lakes, tied to a mid-level short-wave and speed max. This wave would then potentially approach toward early evening, providing height falls and cooling aloft to erode the cap, with low level convergence from surface cold front. Assuming we are capped and dry out for a portion of the day with some sun, temps will likely warm well into the 70s per 850 mb temps in the mid teens Celsius.

Aforementioned set-up with temps in 70s and around 60/lower 60s dew points could yield moderate instability of 1000-2000 j/kg MLCAPE. This is concerning as strengthening northwest flow aloft with approaching wave later in the day/early evening may support 40-50+ kt of deep layer bulk shear and a strongly veering profile. This period will be one to watch for northwest flow strong to severe thunderstorm risk Tuesday PM. The above described wind profiles would potentially be supportive of supercells with a large to very large hail risk given steep lapse rates and large CAPE in hail growth zone. Steep low level lapse rates may also develop, posing a threat for damaging downburst winds. Looming uncertainty with this threat pertains to the potential for EML capping to hold if there is less insolation and/or forcing and frontal convergence is not enough to erode the MLCINh. ECMWF has been most consistent in favoring convective initiation, with GFS more capped, though ECMWF does have solid ensemble support including from GEFS. Capped PoPs in mid to high chance range due to uncertainty, and did add some 3-hourly temporal detail to PoPs Tuesday afternoon.

Initial cold front will knock temps down only slightly for Wednesday into the 60s to around 70. A secondary cold front Wednesday evening/night will bring a healthier surge of cooler air. The models and ensembles have trended toward a stronger signal for rain showers with this secondary front, so have increased PoPs into chance range. Can't rule out isolated thunderstorms with this activity, but have refrained from mention in the grids. Thursday will have breezy-west northwest winds and temps only in in the upper 40s to around 50, followed by yet another reinforcing shot of cool air for Friday, which may stay in the 40s CWA wide along with continued breezy northwest winds. After a likely unseasonably chilly Friday night, temperatures on Saturday will moderate back to the 50s.

Castro

AVIATION. For the 00Z TAFs .

MVFR cigs continue to push south of the region, but anticipate a quickly-advancing mid-level (VFR) deck will overspread the terminals through the mid to late evening hours. Very dry air in the lowest 10 kft should preclude any precipitation with this incoming disturbance. There are some signs of some patchy BR development late this evening and overnight, but the current thinking is that the expansive deck of mid-level cloud cover will curtail this potential with no formal mention in the TAFs at this time. RFD may clear out a bit quicker late tonight, so we may need keep an eye on visibility trends there.

Otherwise, northeast winds should become a bit more northerly or even north-northwesterly tonight at ORD/MDW, but speeds are expected to remain under 5 kts. Synoptic high pressure building down the lake on Sunday will enhance a lake breeze push through the mid-late morning hours with a reinforcement of northeasterly winds.

Carlaw

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

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Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
CNII2 1 mi24 min NNE 6 G 8 38°F 34°F
OKSI2 4 mi99 min E 4.1 G 5.1 40°F
CHII2 - Chicago, IL 5 mi39 min ENE 5.1 G 6 38°F 37°F
CMTI2 - 9087044 - Calumet, IL 9 mi51 min NE 7 G 8 39°F 1019.9 hPa36°F
MCYI3 - Michigan City, IN 37 mi39 min NNE 13 G 15 38°F 33°F

Wind History for Calumet Harbor, IL
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Chicago, Chicago Midway Airport, IL9 mi46 minE 1010.00 miA Few Clouds42°F35°F76%1021 hPa
Chicago, Chicago-O'Hare International Airport, IL18 mi48 minENE 610.00 miA Few Clouds44°F34°F68%1020.2 hPa
Gary Regional Airport, IN19 mi54 minNE 1210.00 miPartly Cloudy41°F33°F76%1020.7 hPa
Lansing Municipal Airport, IL22 mi64 minNE 510.00 miOvercast39°F34°F83%1020.7 hPa
Chicago / Wheeling, Pal-Waukee Airport, IL24 mi47 minENE 610.00 miFair42°F33°F71%1021.1 hPa

Link to 5 minute data for KMDW

Wind History from MDW (wind in knots)
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Last 24hrE5E5SE4S7W9W10NW9W8NW7NW8NW13NW11N12N11N11NW8N8N7N7NE6NE7NE7NE7E10
1 day ago--E7E4E4E4CalmN3N3E6SW7E3E5SE3SE4S5S6S5S8SW8
G21
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2 days agoNE4E5E5E4SE3E3CalmCalmCalmS3CalmCalmCalmCalmSE6E6SE4--NE8
G16
E9E9--E8--

Tide / Current Tables for
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Tide / Current Tables for
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Weather Map
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wmap_A
GEOS Local Image of Midwest    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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Wind Forecast for Chicago, IL (20,4,5,8)
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Ground Weather Radar Station Chicago, IL
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Disclaimer:
The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerous of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.