Thursday, July29, 2021
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Marine Weather and Tides
Chicago, IL

Version 3.4
NOTICE
3/30/2021 -- ANZ330 has been split into ANZ331 and ANZ332. Click EDIT in Marine Forecast and select your new zone.
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.

Sunrise 5:40AMSunset 8:13PM Thursday July 29, 2021 6:04 PM CDT (23:04 UTC) Moonrise 11:28PMMoonset 11:34AM Illumination 70% Phase: Waning Gibbous; Moon at 20 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:202107300315;;658887 Fzus53 Klot 292013 Nshlot Nearshore Marine Forecast National Weather Service Chicago/romeoville Il 313 Pm Cdt Thu Jul 29 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>742-300315- Winthrop Harbor To Wilmette Harbor- Wilmette Harbor To Northerly Island- Northerly Island To Calumet Harbor- 313 Pm Cdt Thu Jul 29 2021
.small craft advisory in effect through Friday evening...
Tonight..North winds 15 to 25 kt increasing to 20 to 25 kt early this evening. Mostly clear. Waves 3 to 5 ft building to 4 to 7 ft occasionally to 9 ft.
Friday..Northeast winds 15 to 25 kt early, diminishing to 10 to 20 kt in the morning. Mostly Sunny. Waves 4 to 7 ft occasionally to 9 ft subsiding to 3 to 6 ft in the afternoon.
Friday night..Northeast winds 10 to 15 kt becoming west 5 to 10 kt after midnight. Partly cloudy. Waves 2 to 4 ft subsiding to 1 to 3 ft after midnight.
Saturday..Southwest winds around 10 kt. Mostly Sunny. Waves 1 ft or less.
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 292000 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 300 PM CDT Thu Jul 29 2021

MESOSCALE DISCUSSION. 300 PM CDT

An east west axis of scattered showers and weak isolated thunderstorms continues mainly south of a Pontiac, IL to Rensselaer, IN line early this afternoon along a remnant outflow boundary from this morning's line of convection.

To the north of this boundary, winds have turned northwesterly and reside under a fairly subsident airmass which has inhibited any additional shower/thunderstorm development today. A lake breeze has attempted to make a strong push inland but has since stalled across northern Cook county. The surface cold front is progressing south through the area, currently near the I-88 corridor based on the latest surface observations.

Expansive and persistent cloud cover from the spotty showers and convection has limited more robust instability in the area, however some clearing north of the outflow boundary could allow for a local corridor of an increasingly unstable airmass south of the same Pontiac to Rensselaer line. An 18Z sounding from Lincoln, IL depicted a capped environment which has likely limited any more robust thunderstorm development so far this afternoon. Deep layer shear of 25-35 kts would be supportive of a strong to potentially isolated severe thunderstorm later this afternoon/early evening although the better potential appears to reside south of the local area. As the cold front pushes further south later this afternoon this could provide some additional support for a few showers/thunderstorms to develop. Will also note that high PWATs of 1.7+" would support locally heavy rain under any thunderstorms.

Petr

SHORT TERM. 300 PM CDT

Tonight through Friday night .

With the departure of the very warm and oppressively humid air mass and associated convective chances behind today's cold front passage, there are no significant forecast concerns on land through Friday night. The main hazard is the dangerous swimming conditions at Lake Michigan beaches through Friday, with no changes to the going Beach Hazards Statement.

A secondary cold front and push of cool air emanating from the lake this evening along with pressure rises will increase already brisk north-northeasterly winds over the lake, with gusts peaking at up to 30-35 mph at times along the immediate shore. Wave heights will maximize at 4-8 feet late this evening and overnight and then only slowly subside through the day on Friday. Strong and dangerous currents spurred by the high wave action will make for life threatening swimming conditions at the beaches, so the message is to stay out of the water. Calmer conditions are in store for Saturday.

Returning to the sensible weather for the rest of the area, the change in air mass will be quite noticeable from the mid to even upper 70s dew points this afternoon to widespread 50s dew points on Friday. Temperatures will be below normal (quite comfortable for late July) on Friday after upper 50s to mid 60s tonight, with low 70s shore and mid to upper 70s inland under partly cloudy skies. Another northwest flow shortwave will touch off convection in the mid-upper MO River Valley tomorrow night, though very dry air through a deep layer under the surface high over the region will keep most locations dry through Friday night, with maybe a few light sprinkles at most for far interior areas late. Otherwise, it will be a quiet and comfortably cool night with lows in the mid 50s to around 60, except low-mid 60s in Chicago.

Castro

LONG TERM. 300 PM CDT

Saturday through Thursday .

Upper pattern features a persistent long-wave trough across the eastern CONUS through the extended portion of the forecast, with cooler and less humid (though still seasonable) conditions expected. North-northwesterly flow across the region will support additional cold frontal passages, with one Saturday night into Sunday and another mid-week most notable in guidance. These fronts will also be the best potential focus for any precip through the period.

An upper level 100 kt jet streak is progged to translate across the Great Lakes region Saturday within a region of northwest flow aloft. Divergence aloft associated with the right entrance to this speed max will be juxtaposed atop a region of low pressure and low level mass/moisture convergence across the mid-Missouri Valley during the morning, driving an area of showers and thunderstorms which should spread east across MO and into west central IL during the day as the jet streak moves east and the low level flow veers more westerly. Precip chances with this disturbance look to be limited to mainly the far west/southwest counties of the forecast area. Farther to our north, a mid-level short wave and associated surface low are progged to dig from Ontario southward across the Great Lakes region Saturday into Sunday. A cold front trailing from the low to our northeast is expected to push south across the forecast area Saturday night into Sunday, and may support some showers and a few isolated thunderstorms across the cwa. Forecast soundings generally indicate a lack of deep moisture however, as well as somewhat weak lapse rates which suggest precip threat may be somewhat limited. Will carry low-chance pops mainly southwest Saturday, and some slights across far northern IL Saturday afternoon closer to the proximity of the approaching northern front. A few showers could linger Saturday night/Sunday across Lake Michigan and into northwest IN as the front slides south-southeast, though increasing mid-level capping is likely by Sunday afternoon as large scale subsidence develops from the north behind the short wave across the Lakes.

Weal surface high pressure ridging develops across the upper Midwest Sunday night, and spreads across the forecast area Monday and Monday night. This should set up a period of quiet weather, with temps slightly cooler than our typical early-August numbers. Highs look to vary from the upper 70s to lower 80s, with daily lake breezes keeping lakeshore areas in the 70s.

With persistent northwest flow aloft within the western periphery of the eastern CONUS upper trough, several short wave ripples will pass through the flow through the period. While some differences exist in these details amongst the medium-range guidance, there is some consensus in another cold front pushing south across the area by mid- week, around Wednesday or so. While this would likely be the next feature which could support the potential for organized precipitation, deep moisture continues to look limited. Blended guidance remains dry Monday-Thursday, and this appears reasonable at this distance. A return of more westerly or southwesterly flow briefly ahead of the mid-week cold front will likely support a bit of a warm-up as well, likely back to more typical early-August levels of low-mid 80's for highs.

Ratzer

AVIATION. For the 18Z TAFs .

Aviation Forecast Concerns:

* Winds shifting northeast for metro terminals early this afternoon, with breezy gusts into the 20-25 kt range at times through this evening.

* MVFR ceilings this afternoon in the 2500-3000 range, eventually lifting to VFR by evening.

Surface cold front was sagging southward along the IL/WI border at midday, with a combination front/lake breeze wind shift was pushing inland toward ORD/MDW. This will result in winds shifting northeast at ORD/MDW around/just prior to the 18Z start of this TAF cycle. Earlier westerly gusts near 30 kts have eased, and will generally be more in the 20-25 kt range from the northeast through this evening and into the early overnight hours. Northeast winds will then persist through the remainder of the forecast period on Friday. It will still be a little breezy as the boundary layer mixes after sunrise, though gust should be under 20 kts. Winds may gradually diminish during the afternoon as surface high pressure builds across the western Great Lakes.

A period of higher-end MVFR ceilings is expected this afternoon, with bases in the 2500-3000 foot range. These should gradually lift and scatter out to VFR this evening. VFR conditions are expected Friday.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES. IL . Beach Hazards Statement . ILZ006-ILZ103-ILZ104 until 7 PM Friday.

IN . Beach Hazards Statement . INZ001-INZ002 until 7 PM Friday.

LM . Small Craft Advisory . nearshore waters until 1 PM Friday.



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Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
CNII2 1 mi19 min N 8 G 8.9 75°F 68°F
OKSI2 4 mi124 min NE 5.1 G 6 76°F
CHII2 - Chicago, IL 5 mi34 min NNE 14 G 16 74°F 70°F
JAKI2 5 mi124 min NE 8 G 13 76°F
CMTI2 - 9087044 - Calumet, IL 9 mi46 min N 6 G 11 1014.1 hPa
45174 20 mi24 min NNE 14 G 19 74°F3 ft1014.1 hPa
BHRI3 - Burns Harbor, IN 28 mi84 min NNE 6 G 7 75°F 1014.2 hPa
45170 34 mi24 min NNE 14 G 19 74°F 2 ft72°F
45186 37 mi24 min 5.8 G 9.7 73°F 72°F2 ft
MCYI3 - Michigan City, IN 37 mi34 min NNE 16 G 18 74°F 1013.5 hPa71°F
WHRI2 - Waukegan Harbor, IL 37 mi64 min NNE 13 G 15 72°F
45187 45 mi24 min 73°F 71°F1 ft

Wind History for Calumet Harbor, IL
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Chicago, Chicago Midway Airport, IL9 mi71 minNNE 12 G 1910.00 miA Few Clouds83°F67°F59%1012.7 hPa
Chicago, Chicago-O'Hare International Airport, IL18 mi73 minNE 1210.00 miA Few Clouds82°F69°F65%1013.5 hPa
Gary Regional Airport, IN19 mi79 minENE 710.00 miFair77°F70°F79%1014.6 hPa
Lansing Municipal Airport, IL22 mi69 minNNE 310.00 miPartly Cloudy81°F70°F70%1013.9 hPa
Chicago / Wheeling, Pal-Waukee Airport, IL24 mi72 minNNE 1310.00 miFair81°F68°F65%1014.3 hPa

Link to 5 minute data for KMDW

Wind History from MDW (wind in knots)
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G25
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1 day agoSW8SW7W5W5W4W3SW6SW5SW5SW4NW5W5S6W6W7W9W96SW9W10SW12SW9SW9SW9
2 days agoSW11SW8SW7S6SW7SW6W4SW4SW6CalmSW3SW3W3N4W4NE106N7SW11SW13SW14
G20
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W12W10

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NOTE: This section has been updated as of 1/26/2021. If the image you are expecting is not showing, please let me know. You may use the EDIT function to update your location.
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