Posted at 8:55 AM on November 18, 2010
by Paul Huttner
Filed under: Climate
Our roller coaster temperature ride continues this November.
Get set for more day to day changes as we head into the weekend.
Milder air will begin to pull north into Minnesota tonight. This might be one of those nights where we see steady or rising temps overnight as south winds kick in and push milder air north. We call it "warm advection" in meteorology, and it could lead to sunshine and temps near 40 in southern Minnesota Friday.
A cool front will slide by later Friday, leading to a cooler Saturday before another stronger warm front lifts north Sunday. Sunday could be the warmest day for at least the next week....and maybe for the foreseeable future with temperatures again pushing 40 in some areas!
Coldest Thanksgiving in 5 years?
This may end up being the coldest Thanksgiving Day in Minnesota since 2005, when the high struggled to hit 21 degrees in the metro. The Minnesota Climate Working Group has a great summary of Thanksgiving Day weather here.
A look at Thanksgiving Day temperatures going back to 1989 shows several days with highs in the lower 20s.
Narration from the MN Climate Working Group.
Thanksgiving Day Climatology in the Twin Cities: 1891-2009
Because Thanksgiving Day occurs at the transition period between autumn and winter, Thanksgiving weather can be balmy to brutal. A typical Thanksgiving Day in the Twin Cities has high temperatures in the 30's and at least a bit of filtered sunshine.
Having a mild day in the 50's on Thanksgiving Day is relatively rare, looking at the historical record back to 1891. A maximum of 50 or more has happened only nine times in 116 years, or about once every 13 years or so. The warmest Thanksgiving Day is a tie of 62 degrees set in 1914 and 1922. The mildest recent Thanksgiving Day is 58 degrees on November 26, 1998.
On the other side of the spectrum, it is common to have a high temperature below 32. The average Thanksgiving Day temperature is right around freezing. What about extremely cold Thanksgivings? It is about as likely to have a minimum at or below zero on Thanksgiving Day, as it is to have a maximum of 50 or above. It has occurred eight times in the past 115 years. The coldest Thanksgiving Day temperature is eight degrees below zero. This has happened three times, 1893, 1905 and 1985.
Measurable snow fell on 25 of the past Thanksgivings back to 1891, about every five years or so. The most snow that fell on Thanksgiving was five inches in 1970.
Historically, about one in three Thanksgivings have at least one inch of snow on the ground. The deepest snow pack is a tie with 1921 and 1983, both with 10 inches on the ground by Turkey Day.
It occasionally rains on Thanksgiving Day as well. In 1896, a two-day event in the Twin Cities doused Thanksgiving travelers with nearly three inches of rain.
A shot of arctic air is due to slide right over Minnesota Thanksgiving Day. The exact magnitude of the cold is still to be determined, but it's safe to say highs may be in the teens in northern Minnesota and low 20s south. You'll have no problem keeping the leftovers and beverages chilled on the back porch this year!
China to melt snow for water crisis?
MNDOT may want to watch this one.
The Chinese will collect and melt snow this winter in an effort to ease a brewing water crisis.
According to the Global Times, two vehicles with high-powered heaters capable of processing 3,500 cubic feet of snow and ice an hour will be sent to locations around Tiananmen Square.
Clean snow will also be dumped into dammed sections in three rivers that run through the city to be used for road cleaning, irrigation and to supplement the rivers' water levels.
The Chinese have an active weather modification program, it remains to be seen how successful it is, but it's worth watching.
November is on average our cloudiest month of the year in Minnesota. The Twin Cities averages only about 39% of possible sunshine this month. We got off to a sunny start...but the clouds and November blahs have finally caught up with us. Look for a little more sunshine as we head toward the weekend.
The sooner the better, in the eyes of this weatherman.
"Don't shoot till you see the whites of its eyes."
One of my weather mentors is Denny Trettel. After WW II, Denny and John Murray founded a long time successful Chicago weather forecasting firm Murray & Trettel. Today it's called Weather Command, and led by another one of my excellent weather teachers, Tom Piazza.
Denny ran the operational forecast center at M/T for decades until his retirement. One of the things I love about Denny is that he applied a lot of common sense to the complicated science of meteorology, and to forecasting.
When snow events approach, Denny taught us to use the 48 hour rule. Back in the day, forecast models didn't really lock onto approaching weather systems until you were inside 48 hours. You didn't want to make "the call" on forecast snow totals for a storm until you were inside 48 hours.
Even with all the advances in numerical weather modeling in the past 20 years, that wisdom still holds today. It served us very again well during last weekend's whopper snow storm, when the computers only came into agreement on a pretty accurate scenario about 24 hours before the snow started flying.
That said...the medium range forecast models (specifically the GFS) is hinting at an emerging chance of our next notable snow late Tuesday into Wednesday of next week.
Denny would remind us that it's way too early to talk totals, but suffice to say we could get sideswiped by snow that could be shovelable and plowable, and maybe mess up a rush hour Tuesday evening or Wednesday morning of next week. It does NOT look like anything as heavy as last weekend's 6"-12"+ event right now.
Another rule of forecasting (or maybe just an observation of mine) is that arctic outbreaks like to "pave the way" with at least some snow before the cold air rushes down form Canada. It is very rare to have a big arctic outbreak that is not preceded by at least an inch or so of snow.
In the mean time we will continue our "push-pull" weather pattern and alternate milder and cool days until the big arctic outbreak late next week. Milder Friday, cooler Saturday, milder again Sunday.
One thing that appears nearly certain (there are NO guarantees in weather!) is that arctic air will invade by Thanksgiving Day.
I'll keep an eye out for snow next week...and keep Denny's voice in the back of my mind as we watch the weather maps unfold.