Tuesday, January19, 2021
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Marine Weather and Tides
Chicago, 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 7:11AMSunset 4:51PM Tuesday January 19, 2021 12:55 PM CST (18:55 UTC) Moonrise 11:55AMMoonset 12:00AM Illumination 38% Phase: Waxing Crescent; Moon at 6 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:202101192215;;164584 Fzus53 Klot 191557 Nshlot Nearshore Marine Forecast National Weather Service Chicago/romeoville Il 957 Am Cst Tue Jan 19 2021 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>743-192215- Winthrop Harbor To Wilmette Harbor- Wilmette Harbor To Northerly Island- Northerly Island To Calumet Harbor-calumet Harbor To Gary- 957 Am Cst Tue Jan 19 2021
Rest of today..West winds 15 to 20 kt. Chance of flurries in the morning. Snow likely in the afternoon. Waves 1 to 3 ft.
Tonight..West winds 15 to 25 kt. Snow early in the evening. Waves 2 to 4 ft then 3 to 5 ft after midnight.
Wednesday..West winds 15 to 20 kt becoming southwest to 30 kt in the afternoon. Mostly Sunny. Waves 2 to 4 ft building to 4 to 6 ft occasionally to 8 ft in the afternoon. A small craft advisory will likely be needed.
Wednesday night..Southwest winds to 30 kt becoming west after midnight. Partly cloudy. Waves 4 to 6 ft occasionally to 8 ft subsiding to 2 to 4 ft after midnight.
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 191734 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1134 AM CST Tue Jan 19 2021

UPDATE. 1030 AM CST

Inherited forecast is trending along well this morning. Main updates were to increase PoPs as confidence in a corridor of light snowfall continues to increase, unfortunately centered around the evening commute.

Regional radar mosaics indicating a light area of returns spreading east across northern Illinois. Surface observations indicate cloud bases are all generally above 5 or 6 kft, so much of this activity is likely sublimating before reaching the ground. Did earlier see some PIREPS indicating icing around 5 kft across eastern Iowa which indicates a marginal thermal profile for heterogeneous nucleation. That said, cloud bases are much too high to support a (freezing) drizzle threat. Recent observations indicating light snow (flurries) point to that staying the case as this activity drifts eastward into an increasingly dry low-level airmass.

Latest thinking is that snow will expand in areal extent after 2-4 PM in NW Illinois and then into the Chicago area closer to 4-6 PM. The main window for accumulating snowfall will be short (3-4 hours) before things taper. Upstream visibility observations down to around 1 mile (locally/briefly lower than that) point to bursts or more moderate to even briefly heavier snowfall. As mentioned earlier, this looks to coincide with the heart of the evening commute, with likely minor travel impacts as a result. Otherwise, the going forecast of a general half to one inch of snow looks good, with the potential for a localized corridor of 1-2 inches depending on where any isolated banding sets up. Snow ratios will be high with this event, likely in the 15-20:1 range. Updated products have been sent.

Carlaw

SHORT TERM. 107 AM CST

Through Wednesday .

Two distinct waves in northwest flow, the first over southern MN and the next one across western MN will bring a period of generally light snow today, but with some travel impacts possible.

Snow has spread into southern MN, with these echoes less robust than those closer to the trailing wave to the northwest. Later today the trailing wave may get close to our catch up to the lead one. Expect that we should see snow spread into the Rockford area late this morning and then gradually shift eastward in the afternoon. The snow may be a bit more spotty at first as noted by the more limited visibility reductions currently across SE MN and NE IA, and confined along and north of I-80. There could also be a little gap in between the two waves, with a more significant uptick in snow mid to late afternoon. This does not look to be a big snow as has been the case with most of the wintry systems this January. However, with a fairly cool column and the omega focus in the vicinity of the dendritic growth zone, this could be a bit fluffier snow as it falls. With the wave arriving in the vicinity of the evening commute, expect some travel impacts/slowdowns this evening.

It will turn cool and breezy behind the sharp trough axis this evening and overnight. After the snow and cold advection, many areas will drop into the teens (which is normal for mid-late January). Upper level heights build very quickly on Wednesday, and stout west- southwest winds will result in response to a low pressure system across the upper Midwest. Gusts could reach 30 mph Wednesday afternoon on a day with a good deal of sunshine for the first time quite a while.

KMD

LONG TERM. 122 AM CST

Wednesday night through Monday .

After a snowy and cloudy stretch of weather, Thursday through Saturday looks decidedly quieter with no precipitation and plenty of opportunities to see the sun. Thursday continues to look like the warmest day this week with highs in the mid to upper 30s, with 40s not out of question south of I-80. A dry cold front will pass through Thursday evening, flopping winds west/northwesterly. Highs Friday and Saturday will accordingly be noticeably cooler and in the low to mid 20s. With a surface high pressure system expected to slide overhead in tandem with clearing skies and light winds Friday night, low temperatures Saturday morning may end up the coldest thus far this winter. For example, the 18Z 51-member ECMWF ensemble mean low temperature Saturday morning for Rockford came in at -4 F, with the entire IQR of the distribution below 0 F! As such, we feel confident all areas with a snowpack will drop toward the 0 degree mark Friday night. Away from the snowpack, lows in the single digits are expected. (Note the last time Rockford saw a sub- zero low temperature was February 14 of last year).

Forecast details from Sunday onward become increasingly muddled as both deterministic and ensemble model systems provide an array of scenarios for a low pressure system due to eject out of the southwestern United States. Statistical cluster analysis provided by the Weather Prediction Center (WPC) suggests the greatest source of spread with the forecast early next week relates to whether surface and upper-level features will phase, which we all know can boom or bust a forecast. Instead of chasing individual model runs, we'll continue the message that wintry precipitation is possible from Sunday onward.

Borchardt

AVIATION. For the 18Z TAFs .

The main aviation weather concerns are within the next 9 hours or so and revolve around and incoming clipper system and snow chances.

Patches of flurries will be possible this afternoon as light radar returns across northern Illinois spread eastward. Our primary system is currently spreading snow across southwest Wisconsin and southeast Minnesota, and this activity will continue to track southeastward. Latest best guess on timing has the main batch of steadier light snowfall reaching RFD around 20-21z and then into the Chicago-area terminals about 22-23z. Have continued to advertise the 3 hour TEMPO groups for lower vsbys down to around 1 sm. Wouldn't be too surprised to see vsbys down to 1/2 or 3/4sm but this would likely be on a very brief basis, but will offer up AMDs if this looks to become more of a potential. Any snow of significance will be pulling away from the RFD area by 02z and 04z at ORD/MDW.

Gusty northwesterly winds will then spread across the area in the wake of this system this evening before gradually diminishing through the overnight hours. Cig trends overnight are a little uncertain, with a potential for MVFR cigs to remain in place a bit longer than currently advertised. Even with the anticipated clearing, not expecting much of a BR/FG threat given the lingering breezes, but something we'll keep an eye on.

Southwesterly winds will then start to kick up a bit through the morning and afternoon hours on Wednesday. Currently advertising some 20-25 kt gusts in the extended ORD/MDW TAFs, but there's a good potential for gusts to occasionally tag 25-30 kts at times later in the afternoon. This will be addressed more fully in future TAF issuances.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES. IL . None. IN . None. LM . Small Craft Advisory . LMZ744-LMZ745 . 6 PM Tuesday to 9 AM Wednesday.



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Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
CNII2 1 mi41 min S 6 G 12 27°F 17°F
OKSI2 4 mi116 min W 4.1 G 8.9 29°F
CHII2 - Chicago, IL 5 mi36 min WSW 12 G 14 28°F 19°F
CMTI2 - 9087044 - Calumet, IL 9 mi56 min SSW 6 G 9.9 27°F 1020.7 hPa (-0.7)18°F
FSTI2 9 mi116 min 28°F
BHRI3 - Burns Harbor, IN 28 mi76 min WSW 7 G 8 28°F 1022.4 hPa
MCYI3 - Michigan City, IN 37 mi36 min SW 15 G 16 28°F 19°F
WHRI2 - Waukegan Harbor, IL 37 mi116 min W 11 G 15 26°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 mi63 minSW 810.00 miLight Snow28°F17°F63%1022.9 hPa
Chicago, Chicago-O'Hare International Airport, IL18 mi65 minWSW 910.00 miOvercast26°F17°F69%1021.8 hPa
Gary Regional Airport, IN19 mi71 minWSW 610.00 miOvercast28°F18°F64%1022.3 hPa
Lansing Municipal Airport, IL22 mi61 minWSW 910.00 miOvercast27°F19°F70%1022.3 hPa
Chicago / Wheeling, Pal-Waukee Airport, IL24 mi64 minWSW 910.00 miOvercast29°F17°F61%1022 hPa

Link to 5 minute data for KMDW

Wind History from MDW (wind in knots)
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Last 24hrW11W9W13W13W10W10
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W9W7W6W6W5W7W6W5W6SW6SW6SW8SW11W10SW8
1 day agoW7W8SW7SW7W6W6W6NW7W6W5W7NW8W8W5W5W6W7SW7SW8SW9SW8SW10W10W12
2 days agoNW9NW10NW9NW9NW8NW6W7W6W6W9W6W8W9W7W7W7W6SW8W6W8SW8W8SW6W7

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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