Here’s what’s ahead this final full weekend of September and over the coming two weeks;
First a warmer than normal weekend is ahead—and a weekend which should average 6-deg warmer than last weekend. And as indicated yesterday, modeling indicates we’re in an EXTENDED PERIOD OF ABOVE NORMAL TEMPS with each day over the coming 2 weeks predicted to average ABOVE NORMAL. This week will finish 3-deg above normal; next week should come in 6-deg above normal and the week after is to come in 9-deg above normal if current forecast trends continue.
As also indicated yesterday, an ATMOSPHERIC BLOCKING PATTERN IS COMING TOGETHER ACROSS EASTERN & CENTRAL NORTH AMERICA. What’s known as a REX BLOCK is developing aloft. This is where an expanded dome of warm air develops at the same time low pressure develops to the south. When that happens, the jet stream splits around the block and a good deal of weather movement between the two streams slows down.
This will have the effect of locking the above normal autumn season temps in place over the next 1-2 weeks while deflecting MAJOR PRECIP SYSTEM AWAY FROM US. Thus, BELOW NORMAL PRECIP IS ANTICIPATED.
HIGH PRESSURE DEVELOPING ACROSS SOUTHERN CANADA AND EXTENDING SOUTHWARD INTO THE LOWER 48 will keep an easterly wind flow going in the Chicago area through the coming week. That means that while the air mass as a whole will be warmer than normal, the easterly flow off the average 68-deg southern Lake Michigan waters will lead to some cooling on area beaches and in lakeshore areas each of the coming 7 days.
There will be several disturbances that make a move on our area. This will occur primarily in the Monday night through Wednesday time frame and could produce some spotty showers and more clouds than we’ll see in coming days. But huge amounts of rain are unlikely.
Skies won’t be completely without clouds this weekend. Clouds will fill in tonight; break up to allow mixed sunshine Saturday then fill in a bit later tomorrow night and Sunday—though cloud breaks should allow some mixed sun Sunday.
Fires are still burning in Canada. Smoke models bring some of that smoke into Chicago’s airspace from the east around the southern flank of the Canadian high I’ve mentioned. So there will be a bit of haziness to weekend skies as a result.
The astronomical start to Fall, 2023 commences overnight with the arrival of the AUTUMNAL EQUINOX at 1:50am CDT Saturday morning.
There are two equinoxes each year—the first marking the start of spring (the VERNAL EQUINOX); the second the AUTUMNAL EQUINOX. The notion eggs stand on end on the equinox is mythology. Any egg you can get to stand on end will do so ANY DAY of the year. But WHAT IS TRUE ABOUT EQUINOXES is they mark the moment the sun’s most direct rays fall on the equator. They also mark one of the two days a year the length of days and nights are approximately equal in both the northern and southern hemisphere.
In addition, the SO-CALLED “CHICAGOHENGE” phenomenon occurs on and near equinoxes. That’s where you will be able to see the rising and setting sun looking down east-west roads and thoroughfares.
Daylight here in Chicago has dropped off just over 3 hours since our longest day back on June 21st—and another 80+ minutes of daylight disappears over the coming month—thus the OVERALL trend toward cooling temps in the fall season.
Full forecast details and more at the WGN Weather Center blog
FALL COLORS are on the way too. We reach the peak of fall colors here in mid-October—another 3 weeks or so from now, give or take a week. A given year’s weather can effect by how much the arrival of peak fall colors varies each year. FALL COLORS are already showing up across the North Woods areas of the Upper Midwest—and there are some hints fall colors are beginning in parts of our area as well. These colors will increase in coming weeks.
ONE OTHER NOTE: The National Hurricane Center has christening TROPICAL STORM OPHELIA OFF THE NORTH CAROLINA COAST. This northbound storm is being fueled by the warm waters of the Gulf Stream and is to bring wind, a pounding surf, heavy rains and a storm surge (i.e. higher than normal tides with coastal flooding) to an area from North Carolina north to New Jersey and to a lesser extent parts of southeast New York over the weekend. HERE’S A LINK TO THE LATEST NHC ADVISORY: https://www.nhc.noaa.gov/text/refresh/MIATCPAT1+shtml/221751.shtml?
TONIGHT: Partly cloudy, mild for the season. Low 66.
SATURDAY: Clouds decrease allowing skies to become mostly sunny. Warm for late September with easterly lake winds cooling the shoreline and area beaches. High 78—but low 70s lakeshore.
SATURDAY NIGHT: Turning partly cloudy, still mild. Low 61.
SUNDAY: Cloudier than Saturday but with cloud breaks still allowing some mixed sun. Mild with east winds off Lake Michigan. High 74—but in the upper 60s beaches. (Normal high is 72).
MONDAY: Partly cloudy. Another day of easterly winds. High 73—but 60s lakeshore.
TUESDAY, WEDNESDAY and THURSDAY: Cloudy at times—,temps continue at levels similar to those of recent days, coming in modestly above normal. But continuing easterly winds will cool lakeshore areas a bit. Slight chance of several light showers or some sprinkles. High Tuesday 73; Wednesday’s high 72—with mid to upper 60s along Lake Michigan.
FRIDAY: Increased sunshine, warmer. High 78—but low 70s lakeshore.