The probably of precipitation has been adjusted down slightly for the next 2 to 3 hours by NWS Chicago. Many areas will have periods of drier conditions through
the early afternoon; however, localized pop-up showers are possible. The outlook is consistent with dissipating images on radar.
The risk of scattered strong-severe storms remains late Thursday afternoon and into the evening, with a chance of continued storms until about 4:00 p.m. Friday.
After the thunderstorm risk ends Friday afternoon, the possibility of an active pattern of showers and thunderstorms returns early next week.
Weather Radarat 1:30 p.m. Thursday, August 1, 2024 shows no precipitation targeting the northwest suburbs of Chicago. Some precipitation is developed as far west as Hoffman Estates, and intensified at lakefront, and moving out over Lake Michigan.
See also Arlingtoncardinal.com/clouds
Scattered showers and storms are expected to develop later this afternoon and evening. A few of the storm may even become strong to severe with a threat for locally damaging winds and hail. Uncertainty remains in storm coverage so stay updated on the forecast. #ILwx #INwx pic.twitter.com/aiOVteKSaa
— NWS Chicago (@NWSChicago) August 1, 2024
O’HARE FORECAST …
Thursday Afternoon: A 30 percent chance of showers and thunderstorms, mainly after 4pm. Partly sunny, with a high near 86. Southwest wind 5 to 10 mph.
Thursday Night: Showers and thunderstorms likely, mainly between 7pm and 10pm. Mostly cloudy, with a low around 71. West southwest wind 5 to 10 mph becoming north northwest after midnight. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.
Friday: Showers likely and possibly a thunderstorm before 1pm, then a chance of showers and thunderstorms between 1pm and 4pm. Cloudy, then gradually becoming mostly sunny, with a high near 82. North wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Friday Night: Mostly clear, with a low around 69. North northwest wind 5 to 10 mph.
Saturday: Sunny, with a high near 88. North northeast wind 5 to 10 mph.
Saturday Night: Mostly clear, with a low around 69.
Sunday: Mostly sunny, with a high near 89.
Sunday Night: Mostly cloudy, with a low around 69.
Monday: Mostly cloudy, with a high near 83.
Monday Night: A chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 69.
Tuesday: A chance of showers and thunderstorms. Mostly sunny, with a high near 82.
Tuesday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 66.
Wednesday: Partly sunny, with a high near 79.
LAKE TEMPS …
SOUTHERN LAKE MICHIGAN WATER TEMPERATURES
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
931 AM CDT Thu Aug 1 2024
LAKE MICHIGAN WATER TEMPERATURES…
CHICAGO SHORE………..75.
CHICAGO CRIB…………67.
CHICAGO BUOY…………75.
WILMETTE BUOY………..76.
WAUKEGAN BUOY………..75.
WINTHROP HARBOR BUOY….75.
MICHIGAN CITY………..62.
MICHIGAN CITY BUOY……75.
SOUTH MID LAKE BUOY…..75.
CENTRAL MID LAKE BUOY…73.
NORTH MID LAKE BUOY…..73.
&&
THE MICHIGAN CITY WATER TEMPERATURE SENSOR IS LOCATED AT A WATER INTAKE ONE MILE OFFSHORE AND 60 FEET BELOW THE WATER SURFACE. IT IS READ EVERY DAY OF THE YEAR.
august.chicagoweatherstation.com
Chicago Weather Forecast for your MAC/PC/TABLET includes surrounding suburbs.
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Area Forecast Discussion
National Weather Service
Chicago/Romeoville, IL
1246 PM CDT Thu Aug 1 2024
.KEY MESSAGES…
– Scattered strong-severe storms possible late this afternoon and into the evening.
– Possible active pattern returns early next week with shower/thunderstorm chances returning.
&&
.UPDATE… Issued at 1015 AM CDT Thu Aug 1 2024
The heaviest rain has slowly dissipated and moved south and east of the forecast area. With coverage continuing to diminish to scattered and even isolated showers with no recent lightning activity, PoPs were adjusted down slightly for the next 2 to 3 hours. Many areas will have periods of drier conditions through the early afternoon though localized pop-up showers are possible.
As an upper level low moves southeastward from Minnesota over the forecast area today, chances increase for the return of scattered showers and thunderstorms with coverage potentially increasing just before sunset. With modeled deep layer wind shear at or less than 20 knots and mid level lapse rates around 6C/km, the severe set up seems a bit more marginal – which makes it no surprise that the the Storm Prediction Center has downgraded the Slight Risk for severe weather (level 2 out of 5) to a Marginal Risk (level 1 out of 5). However, with 2000+ J/kg of CAPE, around 1000 J/kg of DCAPE and steeper low level rates, it would not be surprising if some of the storms were strong enough to produce some gusty winds tonight. Lastly, storm motions will likely be fairly slow tonight. And with precipitable water amounts well over 1.5 inches and soils that are already soggy, there is the potential for localized ponding and even flooding of poor drainage areas for the strongest cells.
The severe threat is expected to gradually wane overnight as the instability drops off. However, showers will likely continue through Friday morning as the low tracks southeast. For more information on the extended forecast, see the discussion below.
— DK/NWS Chicago
&&
.DISCUSSION… Issued at 203 AM CDT Thu Aug 1 2024
Through Friday:
A remnant outflow boundary from a previously intense MCS is moving east of the Mississippi River at press time. Latest objective analysis reveals limited mid and upper-level flow, leading to paltry deep layer shear. Additionally, a notable moisture gradient/discontinuity exists with eastward extent, likely leftover from yesterday`s convective episodes. The resulting profiles look like typical “onion” soundings, with a moist 600-400 mb layer, near dry adiabatic dry layer underneath, and lingering shallow inverted layer near the surface. These thermodynamic setups are not overly favorable for vigorous convection in the absence of a mature/severe MCS. As such, outflow is expected to remain along and ahead of any new convective cores, with activity preferentially building more south and eastward through early this morning into the 925-850 mb theta-e axis. Have confined the highest PoPs through mid-morning south of about a Dixon to Rensselaer line as a result. Generally expect this leading activity to slowly diminish in intensity.
Farther to the west across central Iowa, an expansive outflow boundary with notable undular bore characteristics–exhausted from earlier robust MCS activity across southern Minnesota–is just now meandering south of I-80. Across southern Iowa, a modest westerly low-level jet of 35 knots is developing and as this impinges on the outflow, suspect renewed convective clusters will try to pop in a W-E axis within a locally enhanced 925-850 mb moist layer. Unsure just how expansive this activity will become, but conceptually soundings look supportive of scattered to even numerous showers and storms materializing across southern Iowa and then tracking eastward. Once again, any activity would preferentially track east to southeastward, with the greatest coverage again south of about a Dixon to Rensselaer or DeMotte line. *IF* this activity can sustain, suppose there might be a modestly higher chance for some gustier winds as the 700 mb flow is forecast to increase a smidge. This would all be after sunrise into the mid-morning hours and relegated to our far far southern locales.
With fairly extensive debris cloud cover and showers around, continued to cut high temperatures for today. If we clear out more than expected, temperatures would certainly need a boost. An additional round of scattered showers and thunderstorms is then expected late this afternoon into the evening as a cold front approaches ahead of a well-defined upper low/vort packet. Dee Player shear won`t be particularly high, less than 30 knots based on most guidance suggesting that pulse/multicell clusters will be the dominant storm mode. A strong to perhaps localized damaging wind gust and marginally-severe hail threat will be supported in this environment, with a somewhat later show mostly after 4 pm given the morning cloud cover. Low-level shear is also forecast to remain suppressed today, although does look to locally increase a bit well south of I-80 early this evening. With a very moist boundary layer in place, low LCLs, and what look to be plentiful near-surface confluence axes in place, some funnel clouds (upper low “funny business” as we`ve said in the past) can`t be ruled out.
The short-wave trough will become a closed low by early Friday over the interior central or eastern CWA. Thunderstorm coverage should steadily diminish in the late evening and overnight tonight as instability quickly wanes, though with enough large scale support for scattered showers “festering” into the overnight. Variable cell motions under 10 mph could lead to a highly localized heavy rainfall threat from any more developed cores, but this would not be on a widespread basis. Friday will likely be showery, especially in the morning into the early afternoon, due to the proximity of the upper low, with embedded thunder most favored in far interior sections, especially I-80 and south. There continues to be a signal for a localized corridor of heavier/steadier rainfall rates setting up in the vicinity of the lakefront as enhanced surface convergence develops with the upper low essentially right overhead. Jet level winds are not forecast to be high, but subtly increased upper divergence may foster slow-moving heavier showers and embedded storms that we`ll have to keep an eye on through the morning hours, including over downtown Chicago.
Shower activity will probably wind down/scour out in the afternoon from north-northeast to south-southwest with cooler and slightly drier air working its way inland from the lake. Thus, for interests in downtown Chicago, the afternoon forecast appears to be trending more favorably. Temperatures will top out in the lower 80s inland, and upper 70s near the lake due to onshore flow.
— Carlaw/NWS Chicago
Friday Night through Wednesday:
There may be a few lingering showers across northwest IN Friday evening, but overall, the weekend is looking dry and warm with highs in the mid/upper 80s both days, but cooler near the lake with onshore winds. By Sunday afternoon/evening, there will be a slight chance of a shower/thunderstorm across far northern IL as a frontal boundary sags south across the western Great Lakes. This frontal boundary will likely be in or just south of the area through the middle of next week allowing for another possible unsettled pattern with chances for showers and thunderstorms. The blended pops have increased with some amount of low chance pops from Sunday evening through Wednesday night and this seems reasonable given the pattern. Temperatures will be tricky, likely upper 70s/lower 80s north of the front, possibly 90ish south of the front. cms
&&
.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/… Issued at 1228 PM CDT Thu Aug 1 2024
Aviation Forecast Concerns:
– Spotty showers increase in coverage late this afternoon/evening, with isolated to scattered thunderstorms likely.
– Period of MVFR and patchy IFR ceilings late tonight/early Friday morning, with an additional period of rain/showers.
– Light SSW winds become more WSW by evening, and eventually NNW later tonight. NNE winds likely Wednesday, especially Chicago area terminals.
Weak surface low pressure was across the forecast area at midday, with a few spotty light showers lingering in association with the remnant circulation of a now-decayed thunderstorm complex from early this morning. Some patchy MVFR ceilings have developed across parts of north central IL (including KRFD), though these should remain patchy or lift to low-VFR this afternoon. Surface winds generally less than 10 kts will gradually veer from south to west-southwest into early evening as the surface low drifts slowly east. Surface winds will eventually turn north-northwest later tonight, and north- northeast on Friday.
Upstream to our northwest, a seasonably strong mid-level disturbance was evident in satellite imagery across the upper Mississippi Valley, and is expected to drift slowly southeast across northern IL/northwest IN through tonight. A combination of diurnal low-level destabilization and mid-level cooling/ascent with the approaching disturbance is expected to result in the development and expansion of isolated to scattered showers and thunderstorms from northwest to southeast late this afternoon into this evening. Have continued to highlight a 2-3 hour TEMPO for TSRA within a broader period of VCSH for this into mid-evening. Another period of perhaps moderate rain/showers is expected after midnight tonight as the core of the upper disturbance moves across the area. Can`t rule out a few showers lingering into Wednesday morning, though a decrease in coverage is expected. A period of MVFR and patchy IFR ceilings is likely late tonight into early Friday morning, with gradual improvement to VFR by midday.
— Ratzer/NWS Chicago
&&
.LOT WATCHES/WARNINGS/ADVISORIES… IL…None. IN…None. LM…None.