Weekend forecast: Hot and humid; scattered p.m. showers/thunder in the north

I’ll get to the weekend forecast in a bit, but there are several items to mention for this Friday.

First of all, the Minnesota Pollution Control Agency (MPCA) has issued an air quality alert from noon to 9 p.m. this Friday for the Twin Cities metro area plus Isanti and Chisago County:

Here are some details of the air quality alert, from the MPCA:

Air quality is expected to worsen Friday and Air Quality Index values are expected to reach the Orange or Unhealthy for Sensitive Groups category. Sunny skies, hot temperatures, low humidity, and light winds will produce an environment favorable for emissions of nitrogen dioxide (NOx) and volatile organic compounds (VOCs) near the Twin Cities that can quickly form ozone. Ozone concentrations will be the lowest in the morning hours Friday, will gradually rise midday, and peak in the late afternoon. Air quality will improve Friday evening.

People whose health is affected by unhealthy air quality

There are people who are more likely to be affected when ozone pollution reaches an unhealthy level.

• People who have asthma or other breathing conditions like chronic obstructive pulmonary disease (COPD), chronic bronchitis, and emphysema.

• Children and teenagers.

• People of all ages who are doing extended or heavy, physical activity like playing sports or working outdoors.

• Some healthy people who are more sensitive to ozone even though they have none of the risk factors. There may be a genetic base for this increased sensitivity.

The Wisconsin Department of Natural Resources has issued an air quality advisory for three counties in west-central Wisconsin from noon to 9 p.m. this Friday:

Wisconsin Department of Natural Resources Madison WI relayed by National Weather Service Twin Cities/Chanhassen 1116 AM CDT Fri Jun 4 2021 WIZ014-023-024-050200- Polk-St. Croix-Pierce- ...AIR QUALITY ADVISORY ISSUED FOR POLK, ST. CROIX, AND PIERCE COUNTIES... The Wisconsin Department of Natural Resources has issued an Air Quality Advisory for Ozone which will remain in effect from 12:00 PM CDT until 9:00 PM CDT. This advisory affects people living in Polk, St. Croix, and Pierce Counties. The air quality index is expected to reach the UNHEALTHY FOR SENSITIVE GROUPS level. Sensitive groups, including children, elderly people, individuals with respiratory and cardiac problems, and anyone engaged in strenuous outdoor activities for a prolonged period of time, should avoid extended outdoor exposure. For more information on current air quality, please see: https://airquality.wi.gov

Critical fire weather conditions in the north

Much of northern Minnesota is in a red flag warning from noon to 9 p.m. this Friday due to critical fire weather conditions:

Here are details of the red flag warning in northeastern Minnesota:

URGENT - FIRE WEATHER MESSAGE National Weather Service Duluth MN 326 AM CDT Fri Jun 4 2021 ...CRITICAL FIRE WEATHER CONDITIONS TODAY... .Critical fire weather conditions are expected this afternoon and early evening across portions of northeast Minnesota. Temperatures well above normal are forecast, with highs from 90 to 96 degrees. Deep mixing is expected which will allow winds to become gusty in the afternoon. Gusts will likely 20 to 25 MPH with some occasionally higher. Dry air in the low levels is also likely to reduce relative humidities from 20 to 30 percent. The highest wind is expected over far northern Itasca, Koochiching, and far northern St. Louis Counties. MNZ010>012-018-019-025-026-033-034-041730- /O.UPG.KDLH.FW.A.0003.210604T1700Z-210605T0200Z/ /O.NEW.KDLH.FW.W.0006.210604T1700Z-210605T0200Z/ Koochiching-North St. Louis-Northern Cook and Lake-North Itasca- Central St. Louis-North Cass-South Itasca-South Cass-Crow Wing- 326 AM CDT Fri Jun 4 2021 ...RED FLAG WARNING IN EFFECT FROM NOON TODAY TO 9 PM CDT THIS EVENING FOR WIND AND LOW RELATIVE HUMIDITY AND GUSTY WINDS FOR PORTIONS OF NORTHEAST MINNESOTA... The National Weather Service in Duluth has issued a Red Flag Warning for wind and low relative humidity, which is in effect from noon today to 9 PM CDT this evening. The Fire Weather Watch is no longer in effect. * AFFECTED AREA...In Minnesota, Koochiching, North St. Louis, Northern Cook and Lake, North Itasca, Central St. Louis, North Cass, South Itasca, South Cass and Crow Wing. * WINDS...Southwest 10 to 15 mph with gusts up to 25 mph. A few gusts around 30 mph are possible, especially toward Koochiching County. * RELATIVE HUMIDITY...20 to 28 percent. * TEMPERATURES...In the upper 80s to mid 90s. * IMPACTS...These conditions are supportive of rapid fire growth. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Red Flag Warning means that critical fire weather conditions are either occurring now....or will shortly. A combination of strong winds...low relative humidity...and warm temperatures can contribute to extreme fire behavior.

Friday p.m. T-storm chances northwest

Northwestern Minnesota and portions of north-central Minnesota could see scattered thunderstorms at times this Friday evening and overnight.

The NWS Storm Prediction Center shows a slight risk of severe weather in far northwestern Minnesota later today and tonight, with a marginal risk of severe weather elsewhere in northern Minnesota. Here are forecast details from the Grand Forks NWS office:

Slight risk means that scattered severe thunderstorms are possible, marginal risk means that an isolated severe thunderstorm is possible.

You can hear updated weather information for Minnesota and western Wisconsin on the Minnesota Public Radio network, and you can see updated weather info on the MPR News live weather blog.

Weekend highs and dew points

Saturday highs reach the 90s in most of Minnesota and western Wisconsin:

There’ll be some 80s near Lake Superior.

Our Twin Cities record high for June 5 is 92 degrees. I expect that record to fall this Saturday. Our average Twin Cities high is 76 degrees on June 5.

Saturday dew points will be in the sticky 60s in much of eastern Minnesota and western Wisconsin:

Sunday high temps retreat to the 80s in the northern third of Minnesota, with 90s elsewhere:

Sunday afternoon dew points will be in the 60s in many areas:

Rain chances?

The bulk of Saturday looks rain-free in most areas. Parts of far northern Minnesota could see scattered showers and an isolated thunderstorm late Saturday afternoon and Saturday evening.

Scattered showers and a few embedded thunderstorms are possible in northern and central Minnesota and northwestern Wisconsin by late Sunday afternoon and Sunday evening. An isolated thunderstorm could spread into southern Minnesota and west-central Wisconsin after sunset on Sunday.

Programming note

You can hear my live weather updates on MPR News at 7:35 a.m., 9:35 a.m. and 4:39 p.m. each Saturday and Sunday.