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ARLINGTON HEIGHTS WEATHER

NWS Forecast for O'Hare International Airport Chicago, IL Last Update: 8:12 am CDT Oct 9, 2024

Wednesday Afternoon: Sunny, with a high near 71. Northeast wind 5 to 10 mph.

Wednesday Night: Clear, with a low around 52. East northeast wind 5 to 10 mph.

Thursday: Sunny, with a high near 73. East wind around 5 mph.

Thursday Night: Mostly clear, with a low around 54. Southeast wind around 5 mph becoming southwest after midnight.

Friday: Mostly sunny, with a high near 83. Southwest wind 5 to 15 mph, with gusts as high as 20 mph.

Friday Night: Mostly cloudy, with a low around 58.

Saturday: A 20 percent chance of showers after 1pm. Mostly sunny, with a high near 69.

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

Sunday: Mostly sunny, with a high near 62. Breezy.

Sunday Night: A chance of showers. Partly cloudy, with a low around 42. Columbus Day: A chance of showers. Mostly sunny, with a high near 56.

Monday Night: A chance of showers. Partly cloudy, with a low around 40.

Tuesday: Mostly sunny, with a high near 54.


Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
609 AM CDT Wed Oct 9 2024

.KEY MESSAGES...

- Continued dry and seasonably warm through Thursday.

- Unseasonably warm and breezy with potential for elevated   brush fire risk Friday afternoon.

- Notable cooldown early next week with the potential for   nightly frost and localized freeze conditions.

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.DISCUSSION... Issued at 301 AM CDT Wed Oct 9 2024

Through Thursday:

Dry, quiet weather and gradually warming temperatures continue through Thursday, though with a little more noticeable lake cooling near Lake Michigan especially today as winds turn east- northeasterly.

The upper level pattern continues to feature a dee Ptrough/closed low across eastern Canada and the Northeast this morning. The trough will gradually move off to the east tonight into Thursday however, as an upper ridge currently stretching from the desert southwest into Manitoba slowly spreads east. Dry, subsident northwest flow will remain in place aloft. At the surface, the weak trough/wind shift which pushed south- southwest across the forecast area last evening has become stationary in a northwest-southeast orientation across our western and southern cwa. Building surface high pressure over the northern Great Lakes will enhance northeast low-level flow north of this boundary today, aided by the influence of a diurnal northeasterly lake breeze. This will help push the stalled trough to the southwest this afternoon and evening, allowing surface winds to become east-northeasterly across the forecast area. The main impact from this will be to supply a little more noticeable lake-cooling across northeast IL and northwest IN this afternoon, with temps expected to range from the upper 60s along the immediate shore to the mid/upper 70s (well-above our mid-60s averages for this time of year) across the western and southern cwa. A few patchy clouds are possible this morning near the lake, but otherwise skies should be sunny/clear for most areas through tonight.

Lows tonight are expected to be a little milder, especially across northern IL where light east winds will persist. Coolest areas will likely be from the IL/IN state line eastward into northwest Indiana, where lower dew points and weaker winds are expected. Min temps are expected to range from around 40 over near KVPZ to the low-mid 40s farther west into IL, while the core of the Chicago metro holds in the low-mid 50s. On Thursday, the upper ridge leans into IA/WI/northern IL, with increasing subsidence and modest warm advection allowing continued moderation in temps. Under sunny skies once again, this will again support above-average afternoon high temperatures from the lower 70s in northwest IN to the upper 70s/near 80 across our western cwa. Lake breeze winds will be lighter and a little more southeasterly Thursday afternoon, limiting lake cooling mainly from the City into the north suburbs.

Ratzer

 Thursday Night through Tuesday:

The area is expected to be beneath the eastern periphery of a broad mid-level ridge sprawled across the central CONUS Thursday night and through the day on Friday. As a result, dry conditions are expected to prevail with mostly sunny skies. These sunny skies in combination with increasing warm advection through the day on Friday should allow high temperatures to become unseasonably warm with readings forecast to be solidly in the low to mid-80s. Furthermore, the warm temperatures should allow for rather deep diurnal mixing to commence Friday afternoon resulting in breezy southwest winds gusting in the 20 to 25 mph range. The winds and deep mixing should also allow dew points to mix down during the afternoon and cause RH values to dip into the 20-30% range which could yield an elevated risk for grass and brush fire spread. Though there is still some uncertainty as to how low dew points (and the resulting RH values) will get on Friday so be sure to check back for updates.

The unseasonably warm weather will be short lived, however; as a pair of shortwave troughs and associated cold fronts are expected to move through this weekend. The first of these waves and fronts is forecast to move through late Friday night into the day on Saturday, but since the trough looks to track more into eastern Lower Michigan front is expected to get hung up in central IL. Thus, a gradient in temperatures seems likely on Saturday with areas north of the front forecast to be in the upper 60s and lower 70s while areas to the south remain in the upper 70s to around 80. Regardless, the lack of sufficient moisture return ahead of this initial front should keep rain chances to virtually zero.

The second and notably stronger shortwave trough and cold front is expected to move through the area early in the day on Sunday which will make for notably cooler conditions with highs in the 60s Sunday afternoon. Additionally, the strong cold advection and tight pressure gradient behind the front will also generate breezy northwest winds Sunday afternoon with gusts likely toping out in the lower 30 mph range. While moisture return ahead of the shortwave continues to look sub-par for widespread rainfall, guidance has trended towards better mid-level moisture returning across northern IL and northwest IN. Therefore, cannot rule out a spotty shower or two developing Sunday afternoon particularly for areas near Lake Michigan where moisture and some lake induced instability look to overlap.

Heading into the early part of next week, the aforementioned shortwave is expected to phase with several other waves as it stalls over the Great Lakes Sunday night into the day on Monday. As a result, lingering chances for afternoon lake effect showers look to persist through at least Tuesday particularly for our northwest IN counties. Otherwise, notably cooler temperatures are expected to move in for the early part of next week with afternoon highs in the 50s and overnight lows in the 30s and 40s. In fact, there is even a decent signal within guidance for frost and some locals to see lows near freezing Monday night and possibly again on Tuesday night. Since there is some uncertainty as to how cloud cover could impact nightly cooling and therefore frost coverage, have decided to cap the frost chances at 20% for now but will continue to assess as we go forward.

Yack

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.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/... Issued at 609 AM CDT Wed Oct 9 2024

High pressure overhead will maintain quiet weather at the terminals through the period. Winds will remain light and variable this morning, but will gradually become northeasterly by early afternoon as a lake enhanced front moves through. While winds will increase slightly behind the front, speeds are expected to remain less than 10 kts through the period. Otherwise, expect clear skies to persist into the day on Thursday.

Yack

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.LOT WATCHES/WARNINGS/ADVISORIES... 
IL...None. 
IN...None. 
LM...None.

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