Foggy & Smoggy
It’s called a “temperature inversion.”
A warmer layer of air about 4,000 feet above our heads trapped pollutants near the ground, and caused the MPCA Air Quality Index (AQI) to spike early Tuesday.
In this edition of Updraft we look at how the inversion helped our foggy & smoggy starts this week, the prospects for breathing easier. We also track “Rocky” as it dumps on Iowa & Chicago…and talk about our prospects for more snow by next Monday.
Is it March yet?
Metro AQI “Spike:” Blame the inversion
“Buoyancy” is a concept we learn in metrology 101.
It’s basic physics. Warm air rises. Basically air parcels rise until they encounter air that is warmer above. When that happens, we call that a “stable” situation.
Since temperatures usually cool with height above ground, warmer air aloft is called a “temperature inversion.”
The trapping effect causes fog & smog to hang near ground level, and not “mix out” higher into the atmosphere as it does when no inversion is present.
Tuesday’s inversion had multiple levels, but the main bubble of warm air is suspended abouyt 4,000 feet above our heads. Temps were in the 20s & 30s where we live, but it was a nicer day about 4k up with temps in the 40s.
Breathing easier later this week?
We’ve been breathing some quality arctic air this month in Minnesota. With a cold northwest flow most of this month you can see how the AQI has been excellent many days this month. There are very few pollutant sources between here and the Arctic Circle, and a cold northwest wind is not favorable for stagnant air and trapping effect.
Data from MPCA
The good news in the forecast this week is that our northerly wind flow will return, and that should shove some of our “particulate matter” south and bring in some fresh puffs of air from Canada.
Look for AQI numbers to fall to more healthy levels as the week wears on.
Rocky punches away:
After pounding the Texas Panhandle with an historic blizzard, Winter Storm “Rocky” is still punching away in Chicago.
Here’s a nice radar overview of the storm courtesy of WSI.
Image: WSI Corp
Here are some early snow totals from Iowa, where snow crept as far north as Des Moines and Waterloo.
In Chicago, the storm has delivered it’s worst punch in the west & northwest suburbs, McHenry County and Boone Counties are getting hit hard, with reports of 5″+ snow totals in 3 hours and high winds producing blizzard conditions.
Image: Stephanie Price
NWS local storm reports confirm the ferocity of the storm slamming Chicago.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
421 PM CST TUE FEB 26 2013
0406 PM SNOW CRYSTAL LAKE, IL M5.0 INCH
TRAINED SPOTTER. STORM TOTAL 5.0 INCHES. SEVERAL VEHICLES IN DITCHES.
0220 PM HEAVY SNOW POPLAR GROVE, IL M1.5 INCH BOONE TRAINED SPOTTER
STORM TOTAL AS OF 200PM. GROUND BLIZZARD IN OPEN AREAS. EAST WEST ORIENTED ROADS…PARTICULARLY RT 173 ARE DRIFTING OVER AND PRACTICALLY IMPASSABLE. ALSO VERY ICY ROAD SURFACE LEADING NUMEROUS ACCIDENTS. VISIBILITY AT TIME OF REPORT 1/4 TO 1/2 MILE.
Storm totals of 5″ to 10″ of wind whipped snow will blast Chicago’s north & west suburbs creating near blizzard conditions overnight.
Scanning the forecast maps: Snow possible next Monday?
Our weather looks quiet in Minnesota for the next few days.
Looking ahead to next week, there appears to be some chance of snow next Monday, according to the GFS model and more recently supported by the Euro.
Snow chance next Monday?
Image: NOAA GFS
The system appears ot be coming from the northwest…so it may not be a major storm, but there is a chance we could see a dusting to a few inches next Monday.