Tuesday, October27, 2020
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Marine Weather and Tides
Wilmette, IL

Version 3.4
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8/26/2020 The 7 day forecast is taking about 5 seconds to load but it will eventually load. NOAA is still working on it.
8/18/2020 NOAA continues to have trouble. Wind guest will occasionally be left off graphs. I am working with NOAA to resolve the issue.
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 7:17AMSunset 5:52PM Tuesday October 27, 2020 11:13 AM CDT (16:13 UTC) Moonrise 4:37PMMoonset 3:14AM Illumination 83% Phase: Waxing Gibbous; Moon at 11 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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LMZ741 Expires:202010272130;;920399 Fzus53 Klot 271450 Nshlot Nearshore Marine Forecast National Weather Service Chicago/romeoville Il 950 Am Cdt Tue Oct 27 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>742-272130- Winthrop Harbor To Wilmette Harbor- Wilmette Harbor To Northerly Island- Northerly Island To Calumet Harbor- 950 Am Cdt Tue Oct 27 2020
Rest of today..West winds 10 to 15 kt. Cloudy then becoming partly Sunny mid to late afternoon. Light rain and snow through noon. Waves 1 to 3 ft.
Tonight..Southwest winds 10 to 20 kt. Mostly clear. Waves 1 to 3 ft.
Wednesday..Southwest winds 10 to 20 kt. Sunny. Waves 1 to 3 ft.
Wednesday night..West winds 10 to 15 kt becoming north after midnight. Slight chance of rain after midnight. Waves 2 ft or less.
LMZ741


7 Day Forecast for Marine Location Near Wilmette, IL
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location: 42.08, -87.73     debug


Area Discussion for - Chicago, IL
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FXUS63 KLOT 271550 AAA AFDLOT

Area Forecast Discussion . UPDATED National Weather Service Chicago/Romeoville, IL 1050 AM CDT Tue Oct 27 2020

UPDATE. 1050 AM CDT

Light precipitation continues across roughly the eastern half of the forecast area late this morning, with a transition from a light rain/snow mix to more of a drizzle and intermittent patches of snow grains. This is all within broad lift of a 150 kt upper level and 90 kt mid level jets as sampled on regional 12Z raobs. Low-level isentropic response is not strong nor deep, however the saturated layer is deep, roughly 9,000 ft on the 12Z ILX sounding. Collision and coalescence of droplets within this is helping to support a fairly large area of light to at times moderate drizzle. Cloud top temperatures and recent aircraft sounding data continue to indicate the saturation in the ice nucleation layer is becoming much more marginal, so any snow will likely be brief and "low quality" through the end of the precipitation (~1 pm).

Have lowered highs a smidge today with a later anticipated clearing. With late day/early evening clearing expected and drier dew points likely to inch in, it will allow for a pretty chilly night for this time of year with the mid 20s we have forecast for outlying areas north of I-80 looking on track.

MTF

SHORT TERM. 310 AM CDT

Through Wednesday .

Main near term forecast concern is with additional light precip this morning through midday, likely a mix of rain and wet snow. Little or no accumulation is expected.

Upper air analysis from 00Z continues to depict a large, positive tilt trough from much of east-central Canada southwest to the desert southwest. Early morning water vapor imagery indicates a closed upper low developing in the southwestern base of the upper trough, which is progged to separate from the more progressive northern extent of the upper trough over the upper Midwest. Fast southwest flow remained in place from the southern Rockies through the Great Lakes to the east of the trough axis, with a 135 kt 300 mb jet max observed across the Great Lakes. At the surface, a broad baroclinic zone was evident across the southern Midwest and Ohio Valley region, north of a stationary surface front from the lower Mississippi Valley to the mid-Atlantic states.

Guidance indicates an upper level jet streak will intensify this morning across northern IL and the Great Lakes, in response to a mid- level short wave digging into the northern portion of the aforementioned upper trough. This looks to place the WFO LOT forecast area beneath strengthening upper divergence associated with the right entrance region to this jet streak, atop the mid- level baroclinic zone displaced well to the north/northwest of the surface stationary front. While low-amplitude mid-level ripples may modulate forcing for ascent this morning, the largest contribution to forcing ascent appears to be the strong upper level divergence and resulting mid-level frontogenetic response across the area from early this morning through the midday hours. Comparing 00Z soundings from DVN and ILX last evening, as well as the location of lower cloud bases and current light precip/radar returns, the southeast half of our forecast area appears most likely to see periods of light precip. Indeed, the available suite of guidance highlights the area roughly along and east of the I-55 corridor in northeast IL through midday, while areas farther north/northwest appear to lack sufficient deep saturation for any meaningful precip. Thus am expecting light precip to continue to develop along/east of I-55 this morning, before eventually shifting off to the east of the area early this afternoon as the upper Midwest short wave trough axis moves through.

Forecast soundings depict profiles generally cold enough to produce some snow across the area, though saturation at temperatures cold enough for ice nucleation could be an issue at times. Surface temps in the mid-30s and surface wet-bulbs slightly above freezing would likely support more of a snow/rain mix or just all rain the farther south/southeast one goes. Currently here at WFO LOT a very light wet snow was falling, with a light snow/rain mix at KMDW from some of the light banded radar returns seen in ORD terminal doppler imagery. Thus mainly a mix of rain/snow expected this morning, with little or no accumulation even if precip falls briefly in spots as all snow based on marginal surface thermal conditions. Precip should exit the region to the east/southeast early this afternoon.

Extensive cloud cover across the area has helped to keep temps above freezing overnight in most areas, and will likely hold temps down a bit especially over the southern parts of the forecast area today. Some partial clearing is possible across far northwest/northern IL closer to the WI border this afternoon, with more substantial clearing likely from the north tonight as weak high pressure ridge drifts across the area. From morning lows in the low-mid 30s, temps should recover to only around 40/lower 40s this afternoon. Clearing tonight should allow temps to drop off into the 20s in all but the urban core of Chicago and perhaps the far southern border of our area where clouds will be last to clear.

Southwest flow develops as the surface ridge drops south of the cwa Wednesday. Morning sun and modest warm advection should allow temps to moderate into the low-mid 50s, as 925 mb temps warm above 0C. T High clouds will likely begin to increase somewhat from the south by the afternoon hours as high level moisture associated with Zeta spreads north, though precipitation is expected to hold off until later Wednesday night.

Ratzer

LONG TERM. 254 AM CDT

Wednesday night through Monday .

The evolution of the upper low, now over the Desert Southwest, will be the main feature of interest going into the start of the period Wednesday night and Thursday. This feature promises to produce a large area of moderate to heavy rainfall from the Mid- Mississippi Valley eastward across the Ohio Valley during this period as it interacts with the remnants of Zeta. Our area looks to be along the northern fringe of the precipitation shield, and there is even a possibility that all of northern IL north of I-80 misses out on this rainfall. With this possibility, I have confined the highest chances for rain over my far southern counties, with chances tapering to slight chance for areas north of I-80.

While much of the area does look to miss out on the rainfall, it does appear that surface winds will increase and become gusty out of the north-northeast during the day Thursday as surface low pressure shifts towards the lower Ohio Valley. These gusty winds could in return support some high waves on southern Lake Michigan, and thus increase the threat for at least some minor lakeshore flooding over the northeastern IL and northwestern IN shores. We will have to keep an eye on this potential. Otherwise, expect temperatures to remain cool, with highs only around 50.

Surface high pressure will move overhead on Friday, which will support a day of lighter winds, albeit chilly. Temperatures on Friday look to be a bit cooler than Thursday, with highs likely remaining in the 40s.

Mainly dry weather looks to continue during the weekend. A period of warmer conditions (into the 50s) also looks like a good bet, especially for Saturday as breezy southerly set up over the area ahead of another approaching cold front. This cold front may result in some cooler temperatures to close out the weekend, but there are signs that conditions could warm up again next week.

KJB

AVIATION. For the 12Z TAFs .

The primary forecast element of interest in the TAFs is the MVFR clouds early this morning at KMDW and KGYY, along with some very light snow and rain.

MVFR cloud cover has gotten as far north as KMDW overnight, and it appears unlikely that it will make it into ORD. These MVFR CIGS will hang on for a couple hours early this morning at MDW before the deck of lower clouds gradually sags southeastward later this morning and afternoon. Very light precipitation in the form of snow/flurries and very light rain will also continue for the next couple hours, but it is not expected to have a significant impact on operations.

Expect this light precipitation to scoot eastward by late morning with westerly winds and VFR conditions taking hold through the remainder of the forecast period.

KJB

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
45174 5 mi33 min WNW 7.8 G 9.7 34°F 46°F2 ft1027.6 hPa31°F
FSTI2 8 mi133 min NW 8.9 33°F
OKSI2 13 mi133 min NNW 4.1 G 7 36°F
CNII2 17 mi43 min W 5.1 G 6 35°F 33°F
WHRI2 - Waukegan Harbor, IL 20 mi133 min NNW 8 33°F
CMTI2 - 9087044 - Calumet, IL 26 mi55 min W 2.9 G 6 35°F 1025.9 hPa35°F
45187 29 mi53 min WNW 7.8 G 9.7 35°F 46°F1 ft
KNSW3 - Kenosha, WI 35 mi133 min WNW 4.1 G 5.1 33°F 1026.8 hPa (+0.4)

Wind History for Calumet Harbor, IL
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Chicago / Wheeling, Pal-Waukee Airport, IL9 mi21 minNNW 310.00 miOvercast35°F28°F78%1027.3 hPa
Chicago, Chicago-O'Hare International Airport, IL11 mi22 minN 35.00 miFog/Mist34°F28°F82%1026.9 hPa
Chicago, Chicago Midway Airport, IL20 mi20 minNW 41.50 miLight Snow Fog/Mist34°F30°F89%1027.4 hPa

Link to 5 minute data for KPWK

Wind History from PWK (wind in knots)
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Last 24hrN6NW8NW7NW8NW6NW7NW6N5N6NW4NW4NW4NW4NW3N4NW4NW5NW4N3N3CalmNW4NW4NW3
1 day agoNE10
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2 days agoN7NE5NE5N6NE8E5NE4NE6N4N3N3N4N5N7N5N7N6N7N9N6N6N7NW6NE7

Tide / Current Tables for
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Tide / Current Tables for
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Weather Map
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GEOS Local Image of    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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Ground Weather Radar Station Chicago, IL
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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.