Sunday, April18, 2021
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Marine Weather and Tides
Sleepy Hollow, IL

Version 3.4
NOTICE
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 6:05AMSunset 7:39PM Sunday April 18, 2021 3:03 PM CDT (20:03 UTC) Moonrise 10:08AMMoonset 1:12AM Illumination 43% Phase: First Quarter Moon; Moon at 7 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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LMZ740 Winthrop Harbor To Wilmette Harbor- Wilmette Harbor To Northerly Island- Northerly Island To Calumet Harbor- 255 Pm Cdt Sun Apr 18 2021
Tonight..Southeast winds 10 to 15 kt becoming southwest 10 to 15 kt this evening, then increasing to 15 to 20 kt late. Mostly cloudy then becoming party cloudy this evening. Waves 1 ft or less.
Monday..West winds 10 to 20 kt becoming northwest 10 to 15 kt late morning. Chance of rain through the day. Waves 1 ft or less.
Monday night..Northwest winds 10 to 15 kt becoming north after midnight. Chance of rain through the night. Chance of snow after midnight. Waves 1 ft to 3 ft to 2 to 4 ft after midnight.
Tuesday..Northeast winds 10 to 20 kt. Chance of rain and snow. Waves 2 to 4 ft.
LMZ740 Expires:202104190315;;756344 FZUS53 KLOT 181955 NSHLOT NEARSHORE MARINE FORECAST National Weather Service Chicago/Romeoville IL 255 PM CDT Sun Apr 18 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>742-190315-


7 Day Forecast for Marine Location Near Sleepy Hollow, IL
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location: 42.1, -88.29     debug


Area Discussion for - Chicago, IL
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FXUS63 KLOT 181751 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1251 PM CDT Sun Apr 18 2021

SHORT TERM. 346 AM CDT

Through Monday .

Near term forecast features breezy and seasonably mild conditions today, with only limited lake cooling and the potential for some isolated afternoon showers. Modest southwest winds tonight will keep overnight low temps milder in most spots. Cold front pushes across the area Monday, with cooler temps and some additional light rain chances mainly north of the I-80 corridor.

Weak upper level trough lingers across the Midwest today with a couple of minor amplitude short waves rippling through the flow. Impacts will largely be limited to patchy mid-high level cloud cover once again, though a combination of cooler temps aloft and deeper surface-based mixing will result in fairly steep lapse rates by midday/early afternoon which may result in isolated high- based (6000- 7000 feet) showers across the forecast area this afternoon. Roughly north-south axis of slightly higher surface dew points (and weak MLCAPE generally <100 J/kg) over northern IL portion of the forecast area would appear to favor a little better coverage there, with some potential for some gusty winds with any heavier showers given relatively dry low levels below cloud bases. Weak CAPE above the -10C level also suggests the potential for some lightning,especially south of I-80 where positive area is a little deeper. Have added slight chance thunder mention there this afternoon. Many areas may remain dry however. Otherwise, low level wind field looks to be more westerly today, with the deeper mixing supporting some gusts to near 20 mph (again possibly stronger in showers). This should keep the lake breeze mainly close to the Lake Michigan shore (or right along/off the IL shore), and allow seasonably mild temps in the lower 60s for most areas. Any showers/isolated thunderstorms should dissipate quickly with sunset and the loss of diurnal instability. Surface low pressure moving into the northern Great Lakes overnight will maintain modest southwest winds across the forecast area overnight, allowing a little milder low temps from around 40 to the lower 40s.

A cold front trailing the northern Lakes low will push into far northern IL toward morning, and will move southeast across the remainder of the forecast area during the day. Light post-frontal rain (Ana-front precip, driven largely by frontogenesis in the baroclinic thermal gradient behind the surface boundary) is expected mainly north of the I-80 corridor, especially during the morning, with areas south of there being last to cloud over and are expected to remain largely dry through the day. With the later cold fropa south, along with dry conditions and a little more sun, it appears there will be a fairly large spread in high temps for Monday. Highs are expected to range from the lower 50s across far northern IL, to the mid 60s well south of I-80. Breezy west winds will shift northwest behind the front, with southern areas likely seeing gusts of 20+ mph.

Ratzer

LONG TERM. 328 AM CDT

Monday night through Saturday .

The potential for a late snowfall across the region remains in focus early this week. This event has been a moving target with guidance, which further complicates the forecast with the complexities normally associated with snow potential this late in the season. Nonetheless, messaging for this system has not changed much. The main focus continues to be on the potential for slushy snowfall accumulations, even on paved surfaces, late Tuesday afternoon through the evening for areas generally southeast of I-55. Also of potentially high impact across the region is the likelihood of a hard freeze Tuesday night and sub-freezing temps again Wednesday night.

Monday night and Tuesday morning: A strong cold front will have cleared the southern CWA by sunset Monday evening, with colder low- level air expected to gradually filter south across the area through the night. A ribbon of light post-frontal precip primarily driven by low-level dynamics but slightly assisted by the right entrance of a departing upper jet streak will drift south through the night into Tuesday morning. While any potential precip looks to be fairly light, 700-400hPa lapse rates approaching 7C/km late Monday night into Tuesday morning above continuous 50-60kt 700 hPa winds slightly oblique to the frontal boundary may support transient narrow f-gen bands. Thermo profiles support primarily snow mixed with some rain, favoring all snow within any modest banded precip features. It is unlikely precip rates will be strong enough for any appreciable accumulation during this time, but slushy accumulations of a few tenths of an inch on elevated or grassy surfaces north of I-80 and west of the Chicago metro are possible late Monday night into Tuesday morning.

Tuesday afternoon and evening: A loosely coupled upper jet structure dominated by the right entrance of the departing upper jet streak in association with a neutral to slightly negative mid- level trough rotating across the mid-Mississippi Valley on Tuesday will support a strengthening surface low traversing up the Ohio River Valley. An increasingly colder thermo profile across the entire CWA owing to low-level CAA and dynamic cooling will support primarily all snow across in this sector of the system. With the exception of the NAM, the overall 00Z model suite has trended slightly southeast with the associated precip shield during this time. This places the best area of potential snowfall accumulation southeast of I-55. Several inches of accumulation on non-paved surfaces is becoming more likely. Higher snowfall rates up to 1"/hr will be possible, especially with the aforementioned mid- level lapse rates still present. With little to no diurnal solar influence late Tuesday and Tuesday evening, these rates would be sufficient to overcome warm surfaces and result in slushy accumulations on roads and walkways.

As has been noted for a couple days, accumulations with these late season systems normally depends heavily on the ability to generate high enough rates to overcome warmer ground conditions, especially during daytime hours. So while confidence is increasing in accumulations on non-paved surfaces, the impacts to travel conditions remains highly uncertain.

Tuesday night: Even with some cloud cover and precip lingering well into the evening and early overnight hours, temps will likely drop below freezing across nearly the entire forecast area. It is becoming increasingly likely that a hard freeze (28F or lower) will occur for much of northern Illinois and northwest Indiana. Those with agricultural interests should prepare now for potential impacts.

Wednesday through Friday: A secondary wave rotating around the backside of the departing trough may bring additional scattered rain and snow showers Wednesday afternoon. Temps will return to more seasonable levels in the upper 50s to low 60s late this week into the weekend amid more unsettled weather late Friday through Saturday.

Kluber

AVIATION. For the 18Z TAFs .

Primary Forecast Concerns: * Breezy west winds today with spotty showers possible this afternoon * Cold front moves through Monday morning with light rain and MVFR cigs possible behind the front

West to southwest winds today are beginning to gradually pick up after staying rather light and variable through much of the morning hours. Occasionally stronger gusts to 18-20 kt will still be possible through the afternoon before easing toward sunset.

6000-8000ft strato-cu is beginning to expand in coverage early this afternoon with a few spotty showers also trying to develop. The shower coverage is expected to stay low enough to preclude even a formal VCSH mention at this time. A lightning strike or two cannot be entirely ruled out, but the better thunder potential remains well south of the terminals.

A 30-35kt low level jet develops early Monday morning ahead of an approaching cold front which could result in the potential for more gusty southwest winds to mix down to the surface prior to sunrise. The cold front then moves through Monday morning with light rain and MVFR cigs likely behind the front. There remains some variability in timing of the frontal passage and how long the light precipitation lingers over the terminals. For now have opted to maintain a precip mention and MVFR cigs through the end of the TAF period.

Petr

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
WHRI2 - Waukegan Harbor, IL 31 mi63 min S 5.1 G 6 47°F
FSTI2 35 mi123 min 38°F
OKSI2 38 mi123 min ESE 8 G 11 56°F
CHII2 - Chicago, IL 40 mi33 min SE 14 G 15 50°F 39°F
CNII2 40 mi18 min S 1.9 G 9.9 52°F 40°F
KNSW3 - Kenosha, WI 42 mi63 min S 13 G 15 44°F 1011.5 hPa (-1.7)
CMTI2 - 9087044 - Calumet, IL 47 mi45 min ENE 5.1 G 6 1011.4 hPa

Wind History for Calumet Harbor, IL
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Chicago / West Chicago, Dupage Airport, IL12 mi71 minSSW 910.00 miMostly Cloudy61°F33°F35%1011.7 hPa
Chicago / Wheeling, Pal-Waukee Airport, IL21 mi71 minWSW 610.00 miOvercast61°F27°F27%1012.1 hPa
Chicago, Chicago-O'Hare International Airport, IL22 mi72 minSW 10 G 1610.00 miMostly Cloudy60°F26°F27%1011.6 hPa

Link to 5 minute data for KDPA

Wind History from DPA (wind in knots)
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Last 24hrE5E7SE5E10E7NE4NE3CalmCalmSW4S3SW3SW3CalmCalmSE3S3S5SW5SW56W6SW9SW6
1 day agoN8NW8NE8E10E6NE8E6NE4N3N4N4CalmCalmN4N5N6N6N5N5NE5NE4N11
G15
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2 days agoNW13N8N9N9N9NW6NW6NW5W5W3CalmW6NW6NW5NW5N5--Calm4N3N9--6N7

Tide / Current Tables for
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Tide / Current Tables for
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Weather Map
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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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