Frost in the Forecast; NWS Forecast for O'Hare International Airport Chicago, IL Last Update: 8:57 am CDT Oct 14, 2024

Hazardous Weather Outlook below forecast

Monday Columbus Day: A chance of showers before 1pm, then a chance of showers after 4pm. Partly sunny, with a high near 57. North northwest wind 10 to 15 mph, with gusts as high as 25 mph. Chance of precipitation is 30%.

Monday Night: Showers, mainly after 1am. Low around 41. North northwest wind around 10 mph, with gusts as high as 15 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

Tuesday: Showers likely, mainly before 1pm. Partly sunny, with a high near 51. North wind 10 to 15 mph, with gusts as high as 25 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Tuesday Night: Mostly clear, with a low around 36. North northwest wind 10 to 15 mph, with gusts as high as 20 mph.

Wednesday: Areas of frost before 8am. Otherwise, sunny, with a high near 57. Northwest wind 5 to 10 mph, with gusts as high as 15 mph.

Wednesday Night: Mostly clear, with a low around 37.

Thursday: Areas of frost before 7am. Otherwise, sunny, with a high near 63.

Thursday Night: Clear, with a low around 45.

Friday: Sunny, with a high near 68.

Friday Night: Clear, with a low around 46.

Saturday: Sunny, with a high near 70.

Saturday Night: Partly cloudy, with a low around 51.

Sunday: Mostly sunny, with a high near 72.

Hazardous Weather Outlook

National Weather Service Chicago/Romeoville IL

411 AM CDT Mon Oct 14 2024

Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-

La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-

Northern Cook-Central Cook-Southern Cook-Northern Will-

Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-

411 AM CDT Mon Oct 14 2024 /511 AM EDT Mon Oct 14 2024/

This Hazardous Weather Outlook is for portions of north central

Illinois...northeast Illinois and northwest Indiana.

.DAY ONE...Today and Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk near the lake.

DISCUSSION...

Lake effect showers with isolated embedded thunderstorms are

possible near Lake Michigan.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday...

  Limited Thunderstorm Risk near the lake.

Wednesday and Thursday Mornings...

  Significant Frost Risk.

.SPOTTER INFORMATION STATEMENT...

  Spotter activation will not be necessary through tonight.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the southeast around 30 mph.

Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

631 AM CDT Mon Oct 14 2024

.KEY MESSAGES...

- Strong north winds to 40 mph near the lakeshore through daybreak

- Lake effect showers are expected downwind of Lake Michigan   through Tuesday, including the potential for embedded   thunderstorms and waterspouts.

- Frost and localized freeze conditions are expected Wednesday and   Thursday mornings.

&&

.DISCUSSION... Issued at 329 AM CDT Mon Oct 14 2024

Through Tuesday:

A vigorous mid-upper level shortwave continues to dive across the Great Lakes region early this morning with an associated inverted surface trough axis pivoting across the area. Showers are ongoing along this feature near and over the lake. A pop of winds is also occurring on the north side of this axis with 40+ mph gusts observed near the lakeshore along the IL/WI stateline. This will continue to drift south along the lake over the next few hours.

By daybreak expect a more well-defined north to south oriented lake effect band to develop. This band will then drift mainly into northwest Indiana this afternoon. By this evening another mid- level impulse and associated inverted surface trough axis will pivot around the broader upper level trough/closed low. This will help shift the lake effect band westward into Illinois along with an expansion in shower coverage and intensity, including for inland areas this evening and overnight. Impressive ELs and lake induced instability parameters will support occasional periods of embedded thunderstorms as well as the potential for waterspouts, particularly this afternoon through Tuesday morning. The band will begin to drift back east of the IL/IN stateline Tuesday afternoon, gradually diminishing by late Tuesday night.

High temperatures today will be in the mid-upper 50s with with lows tonight expected to cool into the lower 40s in Chicago and near the lakeshore, with mid to upper 30s expected across the outer metro and rural areas. Frost is not expected due to continued breezy winds and lingering cloud cover/showers across much of the area. Highs on Tuesday will be even cooler in the lower 50s.

Petr

 Tuesday Night through Sunday:

As the upper level trough departs our area to the east on Wednesday morning, an upper level ridge over the Great Plains will track eastward toward Chicago. The result from this setup will be persistent northerly flow driving robust cold air advection with 850 mb temperatures expected to drop below zero. While widespread frost is expected for areas away from the city of Chicago, the main concern is the potential for the first freeze of the season. Morning low temperatures are expected to be down in the upper 20s for areas west of a McHenry to Ford County line (with at or near freezing low temperatures to the east outside of Chicago). There is still some uncertainty on how quickly the clouds clear out and winds come down Tuesday night into the morning. However if trends continue, a Freeze Watch for the western portions of the forecast area is certainly within play.

The previously mentioned ridge will continue to transit toward the region through the end of the week. Surface high pressure will move eastward out ahead of it, centered just east of the area on Thursday. Winds will turn to the south and allow for some modest warm air advection aloft. Despite this, much of the rural areas are still expected to see low temperatures Thursday morning down in the mid to lower 30s. With clearer skies and light winds, there is chance that there could be additional frost development on Thursday morning.

Thursday into Friday is expected to see temperatures gradually increase under the influence of the passing ridge. Models are still suggesting a weak cold front may develop over the upper Plains by the end of the week, but slowly fall apart as it approaches the higher surface pressure around the Great Lakes. Better subsidence and height rises will allow for drier conditions and a slight warming trend into the weekend where afternoon high temperatures could return to the 70s.

DK

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/... Issued at 631 AM CDT Mon Oct 14 2024

Key Aviation Impacts for the current TAF period:

- -SHRA near the lake through the morning, most prolonged at   KGYY.

- Another chance for showers closer to the lake Monday evening   and through the overnight

- Strong northerly wind gusts return Tuesday morning

Winds out of the northwest are still gusting between 20 and 25 knots, but are steadily diminishing. IR satellite has been showing a trend of clearing cloud cover inland, but a north- south oriented band of clouds remains hugging the lake. Lake effect showers associated with these clouds are expected out over the lake moving onshore to NW Indiana through much of the day providing longer periods of showery activity and MVFR conditions over KGYY. Showers may remain close to the city of Chicago in the short term, but are expected to gradually drift east by 15Z.

There is lower confidence in showers arriving at the Chicago terminals prior to 00Z, but there is a non-zero chance depending on if the main lake effect boundary drifts westward earlier. Nevertheless, models have consistently been suggesting another wave moving down the lake after midnight providing higher confidence in a renewed chance for widespread showery activity. There will be a narrow corridor of instability with this wave which could provide a chance for thunder, but for now it was left out of the TAF. Last, there is low confidence in the wind direction in the last line of the TAFs. While north- northwesterly flow is currently favored tomorrow morning, winds have a chance to switch to the northeast depending on where the boundary develops. For now directions west of north remain in the TAF, with a chance for stronger wind gusts over 20 knots to return after 12Z.

DK

&&

.MARINE... Issued at 329 AM CDT Mon Oct 14 2024

Key Messages:

- Northwest gales to 35 kt early this morning

- Lake effect showers with embedded storms and waterspouts through   Tuesday.

- Occasional gale force wind gusts possible again on Tuesday

Northwest gales to 35 kt are expected to persist after daybreak with the Gale Warning now extended through 9 AM CDT.

Conditions remain favorable for several periods of lake effects showers with embedded thunderstorms through Tuesday evening. Conditions will also be conducive for waterspouts out over the lake.

Another period of higher wind gusts to 30 kt and building waves is expected on Tuesday though confidence in an extended period of gales remains low.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...

IL...None.

IN...None.

LM...Gale Warning until 9 AM CDT this morning for the IL and IN

     nearshore waters.

&&

$$