Marine Forecasts

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7 Day Forecast for Marine Location Near Joliet, IL

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Area Discussion for - Chicago, IL

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FXUS63 KLOT 160537 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1137 PM CST Fri Jan 15 2021

UPDATE. 749 PM CST

Mostly clear skies continue to foster patchy shallow dense fog for areas mainly across the southern Chicago metro into the Kankakee River valley early this evening. This is especially true for open areas where bouts of heavy snow occurred during the afternoon. METARs and spotter reports suggest a higher prevalence (albeit still patchy) across western Will County into Kendall and Grundy counties where snow was heavier today (over 2" reported across west Joliet). While pockets of low stratus continue to develop in this area, the lack of any mid to upper-level clouds and several breaks in the low clouds will allow fog formation to continue through most of the evening.

Will continue to message this fog via an SPS (originally issued just prior to 6pm) and graphical forecasts given the patchy and generally shallow nature. However, if the areal extent of development continues to grow, a small targeted dense fog advisory may be needed for the aforementioned counties.

Kluber

SHORT TERM. 315 PM CST

Through Saturday Evening .

Focus shifts from the scattered snow showers this afternoon to a widespread round of light to at times moderate snow late tonight through Saturday morning. There could also be some lingering lake enhanced synoptic snow. Expecting accumulations of up to 1-2", highest probably west of I-355 and I-88 and north.

The snow showers have certainly performed as expected today, with intense cores able to produce sharp visibility reductions and quick localized accumulations up to an inch. Earlier there was even a cloud to ground lightning strike down in Benton County Indiana. As of the 3pm hour, starting to see highest snow shower coverage focus primarily south of I-88. Overall coverage should continue to wane toward and after sunset as instability wanes. Depending on radar and observational trends by 22z, may need to target one more SPS issuance.

Water vapor satellite imagery shows the large upper low circulation over the region, with very cold mid-level temps underneath it. At the surface, the original occluded surface low was north of STL with a secondary low over lower Michigan in the surface trough across the region. An area of snow associated with the deformation axis of the secondary low will pivot south- southeastward from Wisconsin and northeast Iowa this evening to far northern Illinois by about midnight and then spreading across the rest of the CWA. A 700 mb impulse wrapping southward around the departing upper level low gyre will yield an uptick in large scale ascent, in the presence of modest cold advection.

With the modest ascent showing sufficient overlap with the DGZ and cold advection increasing ratios to 11-13:1, up to 0.1 to 0.15 QPF should squeeze out snow totals of up to 1-2", again highest over interior far northern IL. Surface temperatures will range from a few degrees below to slightly above freezing during the light to occasional moderate snow rates, so treated main roads should fair okay. Nonetheless, would expect secondary roads to have some snow/slush on them making for slippery, slowed travel. Despite sub marginal lake effect parameters from a thermodynamics perspective, guidance indicating decent lake induced convergence that could enhance the synoptic snow into Porter County and keep it going a bit longer.

Behind the steadier snow, additional mid-level impulses should provide enough ascent through the lower-mid level saturated layer to wring out occasional flurries or light snow/snow showers into or through Saturday afternoon. Right on the heels of tonight- tomorrow's minor snow producer, our next one will move in on Saturday night. Could see light snow with this into parts of our western and northwestern counties just before midnight. Refer to the Long Term AFD below for full detail on this next round.

Castro

LONG TERM. 206 PM CST

Early Sunday through Friday .

The main focus in the long term portion of the forecast remains on the (increasing) potential for at least some lightly-accumulating snowfall on Sunday, with an additional chance for snow somewhere in the Monday night-Tuesday timeframe.

Full disk GOES-17 moisture channel imagery depicts a region of strong cyclonic shear stretching from Kodiak, Alaska and down into Vancouver and British Columbia with an embedded vort packet spiraling across northern Alberta. These features will eventually drop in tandem southeastward into the northern Great Plains later on Sunday before translating towards our longitude through midday. Coarse-resolution guidance has remained fairly consistent regarding this next feature's track, and we continue to note a good degree of clustering among the deterministic and ensemble output alike today. There's still some degree of uncertainty regarding precipitation start time, as well as the exact track of the upper vort, but confidence is high enough to warrant introducing likely (60-70%) PoPs Sunday morning and into the afternoon for areas roughly south of I-88.

Mid-level DCVA and warm advection look to force a respectable degree of large scale ascent--appearing to maximize at this time along and south of I-80 and through Sunday morning and early afternoon. Moisture will be somewhat limited with this disturbance, although PWATs near 0.3" are actually near or just above climatology for this time of year. While the strongest forcing looks to reside just above the dendritic growth zone, the DGZ depth will grow with time as the column cools, which, taken together, seems to support snow ratios probably near 15-16:1 or so. Liquid amounts should remain fairly modest given the lack of more appreciable moisture, but would not be surprised at all to see some pockets of 2-4" amounts given everything. For this forecast issuance, we've increased snowfall totals for the Saturday overnight through Sunday period towards 2" or so south of I-80, and closer to 1-2" farther north.

With cloud cover probably staying in place through Sunday night, did increase overnight low temperatures a bit above the blended offering. The next fast-moving wave approaches late Monday night and into Tuesday. On a run-to-run basis, deterministic guidance is waffling a bit with this feature's track, but ensemble output continues to indicate a general theme of once again focusing light precipitation across our southern locales. We'll show some low-end chance PoPs for this activity for the time being given model uncertainties. Our more active pattern does look to continue through the end of the week, with the next system within the wave train slated to arrive towards Thursday.

Carlaw

AVIATION. For the 06Z TAFs .

Aviation weather concerns for tonight and Saturday are:

- Shallow patchy fog near MDW through 09Z

- Accumulating snow and IFR visibility spreading over the area prior to daybreak and persisting through mid to possibly late Saturday morning before scattered light snow showers

- Light and variable winds becoming west and then gusty northwest Saturday morning

- More snow spreading over the area late Saturday night into Sunday morning

Areas of dense fog are present over the southern Chicago metro into far northwest Indiana into the overnight. The dense fog and IFR conditions will likely remain south of MDW with medium confidence, with GYY likely seeing occasional dense fog.

Attention then turns to snow moving southeast across the area by daybreak. This has the nature of 1-2SM visibility snow, with any visibility under 1SM looking to be brief. Confidence is somewhat lower on how quickly the snow becomes more off and on (light showery), as it could be as early as 14Z or as late as 17Z. The scattered light snow showers will continue into the afternoon. Total snow accumulation looks to be around one inch at ORD with the composition being near normal snow-to-liquid ratio.

During Saturday afternoon, there is uncertainty in whether the ceilings will remain IFR in the scattered snow shower activity or be more MVFR. Winds Saturday afternoon will be gusty from the northwest.

The next upper level disturbance will move into the region late Saturday night with a broad light to at times moderate snow spreading over the area. This will continue through Sunday morning with additional light accumulation.

MTF

LOT WATCHES/WARNINGS/ADVISORIES. IL . Dense Fog Advisory . ILZ020-ILZ021-ILZ023-ILZ105-ILZ106-ILZ107- ILZ108 until 3 AM Saturday.

IN . Dense Fog Advisory . INZ001 until 3 AM Saturday.

LM . Small Craft Advisory . LMZ740-LMZ741-LMZ742 . 10 AM Saturday to 9 PM Saturday.

Small Craft Advisory . LMZ743-LMZ744-LMZ745 . 10 AM Saturday to 9 AM Sunday.



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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
CMTI2 - 9087044 - Calumet, IL	36 mi	48 min	SSW 7 G 8.9	29°F			1001.2 hPa (-0.4)	29°F
CNII2	37 mi	33 min	WSW 8	31°F				28°F
OKSI2	39 mi	108 min	WNW 2.9 G 5.1	34°F
CHII2 - Chicago, IL	41 mi	28 min	SSW 11 G 12	32°F				32°F
FSTI2	42 mi	108 min		32°F
BHRI3 - Burns Harbor, IN	54 mi	68 min	SSW 5.1 G 5.1	29°F			1002.7 hPa

Wind History for Calumet Harbor, IL

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Joliet Regional Airport, IL	1 mi	73 min	N 0	1.00 mi	Fog/Mist	25°F	24°F	96%	1002.7 hPa
Lewis University Airport, IL	7 mi	73 min	SW 3	0.50 mi	Freezing Fog	25°F	25°F	100%	1002 hPa
Morris Muni-James R Washburn Field Airport, IL	15 mi	53 min	W 3	0.50 mi	Freezing Fog	26°F	25°F	99%	1002.4 hPa
Aurora Municipal Airport, IL	24 mi	56 min	SW 3	9.00 mi	Overcast	26°F	24°F	92%	1002.4 hPa

Link to 5 minute data for KJOT

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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

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