10/21/2019 Forecast Update

FORECAST SUMMARY:

Monday, October 21st, 2019 through Monday, October 28th, 2019

Ozone:  8-Hour average Ozone concentrations will be Good through the forecast period.

PM-2.5:  24-hour average Fine Particulate concentrations will also be mostly Good.

FORECAST DISCUSSION

After an extremely pleasant weekend with clear skies and Indian Summer temperatures, a strong October low pressure system will move through the region during Monday and affect our weather for the next two days.

Monday will see continued warmer temperatures but will experience rain showers in advance of a frontal passage Monday night.  Strong winds will accompany this system passage prompting wind advisories, especially in marine areas. This turbulent atmosphere will yield Good Air Quality.  Following winds behind the frontal system will be cooler and clean giving us continued Good Air Quality.

Quieter weather is on tap for the last half of the week although the models indicate a small Wednesday night system with accompanying scattered rain showers. 

Passing weekend high pressure will return winds to the southwest and moderate warming. Air Quality will be mostly Good with scattered Moderate particulate concentrations.  An anticipated Monday front will return northwest winds to the region.

EXTENDED FORECAST:

Air Quality should be mostly Good going into the next work week.

Forecast updated by Jim Haywood: Monday, October 21st, 2019
Next forecast update: Monday, October 28th, 2019

10/14/2019 Forecast Update

FORECAST SUMMARY:

Monday, October 14th, 2019 through Monday, October 21st, 2019

Ozone: 8-hour Ozone concentrations will be Good.

PM-2.5: 24-hour Fine Particulate concentrations will be mostly Good with only a few chances for low Moderates.

FORECAST DISCUSSION:

High pressure slides in Monday ending scattered lake effect showers across the northern portions of the state. Dry conditions will be short-lived, however, as a low-pressure area brings a cold front through late Tuesday/early Wednesday. Moisture lingers as cold air filters in keeping scattered showers in the forecast Wednesday. High pressure moves back in behind this system with dry conditions expected though the end of the workweek.

As for air quality, weather systems every other day will not allow for any extended period of stagnation, therefore, mostly Good air quality levels are expected through Friday. The only exception may be lighter winds early Friday, especially in the southeast, which may cause hourly Moderate fine particulate concentrations during the morning and early afternoon. Readings should improve to Good as winds pick up in speed during the afternoon.

EXTENDED FORECAST:

Extended models show a weak system possibly bringing scattered precipitation Saturday, and a second system with better chances for precipitation coming in late Sunday/Monday. Warmer southerly winds may allow for some low Moderate fine particulate readings this weekend through early next week; however, ozone will be Good.

Next forecast update: Monday, October 21st, 2019

10/07/2019 Forecast Update

FORECAST SUMMARY:

Monday, October 7th, 2019 through Monday, October 14th, 2019

Ozone: 8-Hour average Ozone concentrations will be mostly Good through the forecast period.

PM-2.5: 24-hour average Fine Particulate concentrations will also be mostly Good.

FORECAST DISCUSSION

High pressure will move over the region, during Monday, and will influence our weather through Friday. Calm winds and clear skies will descend, Monday night, causing the coldest night of the week. A small threat of frost is even possible over the northern counties.

As the center of high pressure slowly moves eastward, winds on the back side will be persistently southeasterly. This will give us pleasant weather and seasonable temperatures through Friday. Air Quality should be mostly Good under this weather regime.

Things will drastically change Saturday after the passage of a strong cold front during Friday night. Daytime high temperature drops could be as much as 20 degrees between Friday and Saturday. The northwest winds behind the front will be very clean resulting in Good Air Quality through the weekend.

EXTENDED FORECAST:

Air Quality should be mostly Good going into the next work week.

Forecast updated by Jim Haywood: Monday, October 7th, 2019

Next forecast update: Monday, October 14th, 2019

09/30/2019 Forecast Update

FORECAST SUMMARY:

Monday, September 30th, 2019 through Monday, October 7th, 2019

Ozone:  8-Hour average Ozone concentrations will be mostly Good through the forecast period.

PM-2.5:  24-hour average Fine Particulate concentrations will also be mostly Good.

FORECAST DISCUSSION

The last day of September began as a damp, foggy morning.  But by the time the first day of October arrives, a warm front will have passed through the state and temperatures will push into the low 80’s.  While warm enough to potentially sustain some ozone development, shorter days and mostly cloudy skies will be enough to keep Air Quality in the Good category. 

The cold front associated with this system will pass through Tuesday night and linger in the area through Thursday.  The entire system will be through the region Thursday and will set up the Midwest for below average temperatures through the weekend.  Although cooler than normal, sunny days should make for a nice weekend and Good Air Quality.

EXTENDED FORECAST:

Air Quality should be mostly Good going into the next work week.

Forecast updated by Jim Haywood: Monday, September 30th, 2019
Next forecast update: Monday, October 7th, 2019

09/23/2019 Forecast Update

FORECAST SUMMARY:

Monday, September 23rd, 2019 through Monday, September 30th, 2019

Ozone: 8-hour Ozone concentrations will be mostly Good.

PM-2.5: 24-hour Fine Particulate concentrations will also be mostly Good with only a few chances for low Moderate readings.

FORECAST DISCUSSION:

On and off weather systems this week will bring a couple dry days, followed by chances for precipitation. High pressure sliding in Monday ends precipitation that brought a fair amount of rain to parts of the state late Sunday. Dry, cooler conditions are expected Tuesday, but the next weather system brings precipitation back Wednesday. High pressure then quickly slides in Thursday with the next system bringing showers back in the forecast Friday. Weather systems passing by every couple of days will hamper air pollution from significantly developing. Most locations will be Good for both ozone and fine particulate through Friday.

Precipitation may linger into Saturday with high pressure dominating for Sunday. Weaker winds Saturday and early Sunday could allow for small increases in fine particulate with a few low-end Moderates possible in the south. Otherwise, fine particulate and/or ozone should remain Good through the weekend.

EXTENDED FORECAST:

Extended models show a warm front lifting north Monday bringing another round of precipitation. Increased moisture may allow for a monitor or two of Moderate fine particulate; however, mostly Good pollution levels should prevail.

Next forecast update: Monday, September 30th, 2019

09/16/2019 Forecast Update

FORECAST SUMMARY:

Monday, September 16th, 2019 through Monday, September 23rd, 2019

Ozone:  8-Hour average Ozone concentrations will be mostly Good to Low Moderate through the forecast period.

PM-2.5:  24-hour average Fine Particulate concentrations will be mostly Good.

FORECAST DISCUSSION

The last week of calendar summer looks to be enjoyable with mostly clear skies and warm temperatures.

During Monday, light northeast winds will keep Air Quality numbers in the Good category.  Beginning Tuesday, winds shift to the south-southeast as high pressure sets up over the east coast.  This pattern, with daily high temperatures around 80 degrees and plenty of sun, looks to persist through the week and into the weekend.  With the lateness of the season, there is not much threat of USG readings but very likely that Moderates will be plentiful along the Lake Michigan lakeshore and downwind of Detroit.

This pleasant late summer pattern will persist through Saturday.  An advancing front will swing through the area late Sunday to give us more seasonal temperatures and Good Air Quality.

EXTENDED FORECAST:

Air Quality should be mostly Good going into the next work week.

Forecast updated by Jim Haywood: Monday, September 16th, 2019

Next forecast update: Monday, September 23rd, 2019

09/13/2019 Forecast Update

FORECAST SUMMARY:

Friday, September 13th, 2019 through Monday, September 16th, 2019

Ozone: 8-hour Ozone concentrations will be mostly Good.

PM-2.5: 24-hour Fine Particulate concentrations will range between Good and low Moderate.

FORECAST DISCUSSION:

Showers and storms are in the forecast Friday as a cold front passes west to east across the state. High pressure builds on Saturday, but a weak system Sunday will bring small chances for precipitation. Conditions dry out Monday with highs in the 70s. Forecast models are showing a warm-up as next week progresses.

As for air quality, clouds and precipitation will keep ozone Good Friday. Gusty west winds Saturday behind the front will allow Good ozone to continue. The Good trend for ozone should linger early next week as northerly winds at the surface and upper levels arrive following the Sunday disturbance.

Without a prolonged period of stagnation through early next week fine particulate should remain mostly Good. The only exception would be a few low-Moderates possible in the southeast on Friday, then again Sunday and Monday.

EXTENDED FORECAST:

Extended models show dry conditions through mid-week next week with temperatures increasing as ridging builds over the region. Sunshine and warmer temps could allow for some Moderate pollution to develop.

Next forecast update: Monday, September 16th, 2019

09/09/2019 Forecast Update

FORECAST SUMMARY:

Monday, September 9th, 2019 through Friday, September 13th, 2019

Ozone: 8-hour Ozone concentrations will be mostly Good, but Moderates are a possibility across the south.

PM-2.5: 24-hour Fine Particulate concentrations will range between Good and low Moderate.

FORECAST DISCUSSION:

Cloudy, cool conditions Monday will be replaced with warm summer-like temperatures starting Tuesday, especially in southern and central portions of the state. The weather change occurs as a low tracks west to east just north of Lake Superior pulling warm front north late Monday into Tuesday. This boundary then sinks back south becoming positioned somewhere across lower Michigan through Thursday. A stronger cold front passing Friday will bring back cooler conditions.

As for air quality, temperatures at the surface and upper levels will increase Tuesday through Thursday as winds turn to a more ozone conducive direction, from the southwest/west. However, at least some clouds and chances for precipitation exist each day. Also, considering the lower sun angle this time of year increased ozone is harder to attain. There is enough concern for Moderate levels across the south that  Moderate will be forecasted in those areas. Any Moderate readings will improve to Good Friday as a cold front brings in a cooler, cleaner air mass.

With a boundary positioned nearby, fine particulate may increase over the next few days. Levels are expected to range from upper Good to low Moderate until Friday when readings return to Good statewide.

EXTENDED FORECAST:

Extended models show high pressure moving in for the end of the week and another warm-up looks possible early next week. While the chances for USG ozone are not high, we will evaluate weather conditions Friday to better detail expected air quality levels for the weekend into early next week.

Next forecast update: Friday, September 13th, 2019

09/03/2019 Forecast Update

FORECAST SUMMARY:

Tuesday, September 3rd, 2019 through Monday, September 9th, 2019

Ozone:  8-Hour average Ozone concentrations will be mostly Good to Low Moderate through the forecast period.

PM-2.5:  24-hour average Fine Particulate concentrations will be mostly Good.

FORECAST DISCUSSION

Tuesday through early Wednesday will be a bit unsettled as an active weather system moves through the Midwest.  Air Quality should remain Good with ample clouds and high probability of precipitation.

High pressure follows later Wednesday and will dominate the remainder of Wednesday and into early Thursday.  Northerly wind flow will provide sunny skies, cooler temperatures and Good Air Quality. 

Temperatures should warm a bit late Thursday into Thursday night in advance of a small system which is expected to pass Friday morning.  Light winds and stagnating air could produce some Low Moderates during Thursday afternoon and Friday in southeast Michigan but I expect mostly Good elsewhere.

High pressure returns for the weekend with mostly northerly air flow and Good Air Quality.  Shifting winds to the east-northeast are likely during Monday with little chance of Air Quality issues.

EXTENDED FORECAST:

Air Quality should be mostly Good going into the next work week.

Forecast updated by Jim Haywood: Tuesday, September 3rd, 2019
Next forecast update: Monday, September 9th, 2019

08/30/2019 Forecast Update

FORECAST SUMMARY:

Friday, August 30th, 2019 through Tuesday, September 3rd, 2019

Ozone: 8-hour Ozone concentrations will be mostly Good through the forecast period with Moderates possible Tuesday.

PM-2.5: 24-hour Fine Particulate concentrations will remain mostly Good.

FORECAST DISCUSSION:

Cool, quiet conditions will start the holiday weekend as high pressure settles in and remains in place through Sunday. An upper level systems could bring scattered precipitation late Saturday/early Sunday and again Monday, but these do not look like widespread rain events. Warmer conditions move in Tuesday ahead of a cold front which is expected to pass through later in the day. The big weather story this weekend, however, is hurricane Dorian which is expected to make landfall in Florida early next week.

As for air quality, through Monday a predominant northwesterly flow remains in place. Cooler temperatures and some clouds should keep ozone mostly Good. Warmer surface and upper level temperatures move in Tuesday with southwesterly winds increasing, especially across the southern portion of the state. Weather conditions Tuesday do look a bit conducive for ozone development across the south, but we will be coming off a low background of levels. Also, earlier sunset this time of year and clouds moving in will aid in keeping conditions from reaching higher than Moderate. Weather conditions will be evaluated during the weekend and if needed, the forecast will be updated.

Without much of a stagnant period though early next week, any significant build-up of fine particulate is not anticipated. Readings should remain mostly Good.

EXTENDED FORECAST:

Extended models show high pressure and cooler conditions by midweek next week. Air quality should be Good during this period.

Next forecast update: Tuesday, September 3rd, 2019

08/26/2019 Forecast Update

FORECAST SUMMARY:

Monday, August 26th, 2019 through Friday, August 30th, 2019

Ozone: 8-hour Ozone concentrations will be mostly Good through the forecast period.

PM-2.5: 24-hour Fine Particulate concentrations will also be mostly Good.

FORECAST DISCUSSION:

Rain develops Monday, continuing into Tuesday as a system moves through. A weaker boundary passes later Wednesday, and another on Friday, but the best chance for precipitation will be early in the week. High pressure then builds in for the Holiday weekend.

As for air quality, clouds and precipitation should keep air quality Good Monday and Tuesday. The exception may be the southwest corner of the state on Tuesday. Moderate ozone is a possibility if clouds clear out early in the day. This is shown on some forecast models so the forecast is Moderate in that part of the state to cover the threat. Good ozone is expected Wednesday, but levels could reach Moderate at a few locations on Thursday thanks to plenty of sunshine and seasonable surface temperatures. By Friday, high pressure brings cooler surface and upper level temperatures on a northwesterly flow; this upper level flow remains in place through Sunday keeping ozone mostly Good. Temperatures increase some Monday as high pressure moves east of the state; a few areas may see low Moderates for ozone.

Without much of a stagnant period though the week a significant build-up of fine particulate is not anticipated. Readings should remain mostly Good.

EXTENDED FORECAST:

Extended models show southwest winds and warmer temperatures by Tuesday of next week. It’s too soon to tell if there is a chance for increased pollution, however, this forecast will be updated Friday to detail expected air quality conditions through the Holiday weekend, into next Tuesday.

Next forecast update: Friday, August 30th, 2019
Forecast by: Stephanie M. Hengesbach

08/19/2019 Forecast Update

FORECAST SUMMARY:

Monday, August 19th, 2019 through Monday, August 26th, 2019

Ozone:  8-Hour average Ozone concentrations will be mostly Good to Moderate during Monday and Tuesday, then mostly Good through the remainder of the forecast.

PM-2.5:  24-hour average Fine Particulate concentrations will be mostly Good.

FORECAST DISCUSSION

Monday and Tuesday will be seasonal with temperatures in the mid-to-upper 80’s with increasing humidity.  High pressure builds in during Monday and should persist through Tuesday.  Any chance for some creep in ozone concentrations, during this forecast period, should occur during these two days as light winds become more southwesterly during Tuesday.  Although ozone is expected to begin inching up, there is no compelling evidence that we will get into the USG range during Tuesday although concentrations are expected to get up in the High Moderate range.  However, the shorter days of late summer should work in our favor.

A cold front is projected to pass through the region Tuesday night into Wednesday.  The cooler, dryer air mass that follows the front should keep us solidly in the Good category through the remainder of the work week.  Forecasters are seeing a bit of a warm up during the weekend as winds shift around to the southeast, but nothing is indicating a buildup of ozone to anything worse than Low Moderate. 

EXTENDED FORECAST:

Air Quality should be mostly Good to Low Moderate going into the next work week.

Forecast updated by Jim Haywood: Monday, August 19th, 2019
Next forecast update: Monday, August 26th, 2019

08/16/2019 Forecast Update

FORECAST SUMMARY:

Friday, August 16th, 2019 through Monday, August 19th, 2019

Ozone: 8-hour Ozone concentrations will range from Good to Moderate through the forecast period.

PM-2.5: 24-hour Fine Particulate concentrations will range from Good to low-Moderate.

FORECAST DISCUSSION:

Systems will bring on and off chances for precipitation through the weekend. The first chance will be Friday evening/night; Saturday should be mostly dry; but precipitation chances return Sunday. A stronger front moves through later Monday/Tuesday cooling conditions down by mid-week.

As for air quality, seasonable surface temperatures, coupled with cooler upper level temperatures and at least scattered cloud cover, will keep ozone from reaching higher than Moderate Friday or Saturday. By Sunday, surface and upper level temperatures increase along with dew point readings. Clouds and precipitation associated with a system nearby should again keep ozone from reaching higher than Moderate. Less cloud cover is expected Monday with warmer temperatures continuing; however, the system passing through Sunday should allow for more northerly/westerly winds. Currently, ozone is not expected to get higher than Moderate on Monday.

Significant build-up of fine particulate is not anticipated. Readings should range from middle Good to low Moderate.

EXTENDED FORECAST:

Extended models show cooler conditions by mid-week allowing for Good air quality.

Next forecast update: Monday, August 19th, 2019

08/12/2019 Forecast Update

FORECAST SUMMARY:

Monday, August 12th, 2019 through Friday, August 16th, 2019

Ozone: 8-hour Ozone concentrations will range from Good to Moderate through the forecast period.

PM-2.5: 24-hour Fine Particulate concentrations will range from Good to low-Moderate.

FORECAST DISCUSSION:

A frontal boundary and associated low pressure area will bring precipitation in the forecast later Monday into Tuesday. Then, a second weaker system could trigger scattered precipitation later Wednesday. These systems should keep ozone primarily Good through mid-week. Northerly winds at upper levels then keep cooler temperatures around through Friday. Conditions dry out Thursday and Friday, but lower temperatures will keep ozone from increasing higher than a few Moderates. Moderate fine particulate in the southeast Monday into Tuesday will likely improve to Good by Wednesday, lasting through Friday.

EXTENDED FORECAST:

Extended models are hinting at a warmup for the coming weekend which could make increased ozone a possibility. There is a bit on uncertainty; therefore, this forecast will be updated Friday to detail weekend air quality conditions.

Next forecast update: Friday, August 16th, 2019

08/05/2019 Forecast Update

FORECAST SUMMARY:

Monday, August 5th, 2019 through Monday, August 12th, 2019

Ozone:  8-Hour average Ozone concentrations will be a mostly Good and Low Moderate for the first half of the week then mostly Good through the weekend.

PM-2.5:  24-hour average Fine Particulate concentrations will be mostly Good.

FORECAST DISCUSSION

The first half of the forecast period will feature some active weather patterns followed by cooler, clear weather for the weekend.

As high pressure over the region moves eastward during Monday, it is making way for a trough of low pressure to advance from the west.  There is a chance of a few isolated pop-up storms Monday afternoon ahead of a cold front.  But the better chance of storms will occur Monday night and Tuesday morning as the cold front punches through.  Air Quality should range from Good to Low Moderate on Monday.  Air Quality should be Good on Tuesday.

Another cold front is expected to pass Wednesday night into Thursday morning.  Wednesday’s Air Quality should range between Good and Low Moderate in advance of this frontal passage and Good once it passes/.

The air mass following this front will be cool and dry with sunny daytime high temperatures around 80 and clear nighttime lows around 60.  This should persist through the weekend with Good Air Quality.

EXTENDED FORECAST:

Air Quality should be mostly Good going into the next work week.

Forecast updated by Jim Haywood: Monday, August 5th, 2019
Next forecast update: Monday, August 12th, 2019

08/02/2019 Forecast Update

FORECAST SUMMARY:

Friday, August 2nd, 2019 through Monday, August 5th, 2019

Ozone: 8-hour Ozone concentrations will range from Good to Moderate through the forecast period.

PM-2.5: 24-hour Fine Particulate concentrations will range from Good to low-Moderate.

FORECAST DISCUSSION:

Mainly dry conditions persist this weekend with only small chances for precipitation in association with a weak boundary dropping south Saturday. The next larger chance for precipitation comes into play late Monday/Tuesday as a stronger front passes through. For the most part expect seasonable, dry conditions through Sunday.

As for air quality, upper level northerly winds and cooler temperatures have kept ozone Good. With this flow persisting through the weekend, we don’t expect ozone to reach higher than Moderate. More of a southwesterly surface flow develops Monday ahead of the approaching boundary, but upper level temperatures remain low and northerly even as surface temperatures increase. Higher than Moderate ozone will not likely be seen Monday, but if this changes the forecast will be updated Sunday morning.

Fine particulate has also been Good, and a significant increase isn’t expected over the next few days. Readings should range from middle Good to low Moderate.

EXTENDED FORECAST:

Extended models show a cool down for next week after the Tuesday front passes…air quality will be Good for both ozone and fine particulate.

Next forecast update: Monday, August 5th, 2019

07/29/2019 Forecast Update

FORECAST SUMMARY:

Monday, July 29th, 2019 through Friday, August 2nd, 2019

Ozone: 8-hour Ozone concentrations will be mostly Good through mid-week, then a mix of Good and Moderates are expected.

PM-2.5: 24-hour Fine Particulate concentrations will range from Good to low-Moderate.

FORECAST DISCUSSION:

A cold front passing Monday will bring showers and/or storms. High pressure then moves in Tuesday and forecast models have this high positioned over the Great Lakes region through the end of the week. A small chance for precipitation lingers Tuesday mostly in the east, otherwise, dry conditions, seasonable temperatures, and low humidity’s can be expected.

Clouds and precipitation will keep Ozone Good Monday. Good levels continue Tuesday into Wednesday thanks to northwesterly winds and cooler surface and upper level temperatures. Temperatures will warm at the surface each day past mid-week, but upper level readings remain low through Friday. Ozone could reach Moderate in a few locations, but mostly Good levels should continue.

Fine particulate could also see slow increases starting Thursday, but readings higher than low-Moderate are not anticipated.

EXTENDED FORECAST:

Extended models keep high pressure over the region through early next week. Remaining under the same airmass for a few days could be a set up for increased pollution. At this time readings higher than Moderate are not expected, but this forecast will be updated Friday to better detail air quality conditions through early next week.

Next forecast update: Friday, August 2nd, 2019

Stephanie M. Hengesbach

Meteorologist

Air Quality Division

Michigan Department of Environment, Great Lakes, and Energy

07/22/2019 Forecast Update

FORECAST SUMMARY:

Monday, July 22nd, 2019 through Monday, July 29th, 2019

Ozone:  8-Hour average Ozone concentrations will be a mostly Good for the first half of the week then a mixture of Good and Low Moderate through the weekend.

PM-2.5:  24-hour average Fine Particulate concentrations will be mostly Good.

FORECAST DISCUSSION

After a week of hot and humid weather, we will enjoy a cooling down and Good Air Quality.  We can thank a ridge of high pressure currently located over the Plaines states.  While the center of high pressure remains to the west, we will be under a northerly wind profile.  This will yield cooler and drier air through mid-week with Good Air Quality throughout the state.  The only blemish during the first half of the week will be an upper air disturbance Tuesday afternoon which could produce some showers.

The ridge of high pressure will pass through the state early Thursday.  The wind profile on the back side of the high will become more southwesterly.  With the wind shift will come increasing temperatures and humidity for the weekend.  We will be coming off several days of very clean air and any increase in ozone will be slow in developing.

Right now, the regional forecasters do not have much concern about any elevated ozone for this forecast period.  Should it appear that conditions during the upcoming weekend start looking more threatening, the forecast will be updated.

EXTENDED FORECAST:

Air Quality should be mostly Good to Low Moderate going into the next work week.

Forecast updated by Jim Haywood: Monday, July 22nd, 2019
Next forecast update: Monday, July 29th, 2019

07/19/2019 Forecast Update

FORECAST SUMMARY:

Friday, July 19th, 2019 through Monday, July 22nd, 2019

THE CURRENT ACTION DAY ADVISORY IS EXTENDED THROUGH SATURDAY, JULY 20th IN THE FOLLOWING MICHIGAN COUNTIES...

IN WEST MICHIGAN:

BERRIEN…  ALLEGAN...  KENT...  MUSKEGON...  OTTAWA…  VAN BUREN COUNTIES

Ozone:  8-Hour average Ozone concentrations will be a mixture Moderate and USG during Friday and Saturday.  Air Quality should return to Good and Low Moderate for Sunday and Monday. 

PM-2.5:  24-hour average Fine Particulate concentrations will be mostly Good to Low Moderate. 

FORECAST DISCUSSION

The hot, humid weather will continue through Saturday.  With the current high temperatures and humidity, if we get clear skies then elevated ozone potential is very high. 

The big question is how much cloud cover will we see?  During Thursday, cloud cover was enough to keep ozone production in the Moderate range.  As this forecast is being written Friday morning, cloud cover is present but looks to be thinning.  If that trend continues, we could see ozone numbers reaching the USG levels.

The cloud cover question is also an issue for Saturday.  The various forecast models are very inconsistent with their cloud forecast.  Some of the models have significant cloud cover for Saturday while others keep it mostly clear until late afternoon.  Knowing that clear skies would lead to high ozone concentrations, to err on the side of caution the current Action Day Advisories will be extended through Saturday.  

The threat will end on Sunday following a cold front passage Saturday night.

EXTENDED FORECAST:

Air Quality should be mostly Good to Low Moderate going into the next work week.

Forecast updated by Jim Haywood: Friday, July 19th, 2019
Next forecast update: Monday, July 22nd, 2019

07/18/2019 Forecast Update

FORECAST SUMMARY:

Thursday, July 18th, 2019 through Friday, July 19th, 2019

...AIR QUALITY ACTION DAY ADVISORIES FOR THURSDAY JULY 18TH AND FRIDAY JULY 19TH...

IN WEST MICHIGAN:

ALLEGAN... BERRIEN… CASS… KENT... MUSKEGON... OTTAWA… AND VAN BUREN COUNTIES

Ozone: 8-hour Ozone concentrations will range between Good and Moderate with a threat for USG in the west and southeast.

PM-2.5: 24-hour Fine Particulate concentrations will be in the Good to Moderate range.

FORECAST DISCUSSION:

The easy part of the forecast is the fact that hot, humid conditions can be expected through Saturday with heat indices reaching over 100 degrees in several locations. The difficult part of the forecast is determining when and where storm complexes may develop the next few days.

A storm complex Thursday traveling west to east across southern Lower Michigan was expected to be further north. We currently have Action Days in place across southwest and southeast Michigan since yesterday’s models were showing dryer conditions with plenty of sunshine. The storms may hamper ozone from reaching USG today; but, if the sun breaks out after the system passes ozone may quickly develop in the hot, humid air mass.

We have decided to err on the side of caution for Friday’s air quality forecast and we are continuing the Action Days for both southwest and southeastern parts of the state. Southwesterly winds will prevail under the continued hot, humid air mass. Storm development chances look less for tomorrow and further north. The air quality forecast will be dependent on storm development; however, even just a few hours of afternoon into early evening sunshine could allow for fast increases in ozone. So, Action Days already set in place will be continued.

Fine particulate could also see increases the next few days with readings ranging from upper Good to middle Moderate.

EXTENDED FORECAST:

Extended models show hot conditions lingering through Saturday. Air Quality Division (AQD) forecasters will be holding another call Friday morning to discuss possible Action Days for Saturday. A front passing late Saturday should end the threat for increased pollution early next week.

Next forecast update: Friday, July 19th, 2019
Update by: Stephanie M. Hengesbach, Meteorologist, Air Quality Division Michigan Department of Environment, Great Lakes, and Energy