It's here, right on schedule.
The week's first taste of arctic air has invaded Minnesota as expected today.
Temperatures are colder than -20 in northwest Minnesota this morning, with wind chills in the -30s.
Temps could reach -10 in the metro tomorrow morning, with -20s to -30 north. Friday could bring the season's coldest air mass, with lows pushing -15 to -20 even in the urban core of metro. The GFS is cranking out a respectable -22 for MSP Airport Friday morning!
Coldest week of the year on average:
This is on average the coldest week of the year in Minnesota. The Twin Cities average high of 21 degrees and low of 3 degrees (above zero) sounds really good this week. Instead we're dealing with -21 and colder in parts of Minnesota.
It takes about a month after the winter solstice for temperatures to bottom out in the northern hemisphere. Daylight slowly creeps back into the Arctic Circle in January, but the sun angle and intensity is just too low to start warming arctic air until February.
Our average temperatures start to rise later this week and next week. Increasing daylight and slightly more incoming solar radiation will boost temperatures over the next month.
Our coldest air masses of the year invade from the Arctic Circle this time of year.
Our average temps by February 20th? High of 30 & Low of 14. I know...it's slow progress.
Milder next week: Here's some positive thinking. After this week's cold wave it looks like the cold will mercifully ease next week. In fact, temperatures may approach 30 above zero in the next two weeks.
Brighter days ahead:
Have you noticed how much brighter the days are? We've gained about 30 minutes of daylight in the evening in the past month. We're now gaining about 2 minutes of daylight each day. Sunset is now after 5pm in the metro and the evenings are noticeably brighter on clear evenings.
Hang in there, it's a sign that a seasonal warm up is closer than we might think during our January doldrums!
Stay warm, and be cool.
"So how cold will it get this week Paul?
That's the mantra question from friends and my colleagues at MPR this week.
Plenty cold is the answer....and maybe the coldest in many years by Friday morning. One wonders if you can really feel the difference between -20 and -25 anyway...or if you'd ever want to!
The GFS model is cranking out a temperature of -25 for MSP Airport Friday morning.
If we plunge to -25 in the metro Friday morning, it would be the coldest air in about 15 years. A quick check of records shows that last time temperature plunged to -25 in the Twin Cities was February 2, 1996.
Here are some factors going into the forecast for this week's nose dive, which should bottom out Friday morning around 7 am.
1) Current temperatures in central Canada. Temperatures "upstream" in the arctic air mass have been running between -30 and -45 degrees around Yellowknife and Fort Smith in the Northwest Territories. Temps colder than -30 were as close to Minnesota as Lake Winnipeg Tuesday morning.
Bottom line, the air mass is plenty cold enough to plunge temperatures to -20 to -30 in Minnesota this week.
2) Air mass trajectories: It looks like the coldest core of the arctic air mass will pass through northeast Minnesota and Ontario Friday morning. That should place the coldest temps up north. (can you say Embarrass?) The Twin Cities will be on the edge of the coldest air to the north.
3) High pressure center: The "inner isobar" of arctic high pressure is forecast to pass right over Minnesota and the Twin Cities Friday morning around 6am. That's an ideal time for calm air, clear skies and fresh deep snow cover to generate "maximum radiational cooling."
If no clouds sneak in from the west (due in later Friday), that should allow temperatures to reach the maximum cooling potential of the arctic air mass around 7 am Friday morning. (Oh joy!)
4) Urban Heat Island (UHI) effect: On clear mornings with light northerly winds, there is a very noticeable (pronounced) UHI effect at MSP Airport, which lies just south of downtown Minneapolis. Studies have shown temperatures can be as much as 10 degrees (or more) warmer in UHI's than in the surrounding "countryside."
It could easily be -25 in the suburbs and -15 to -20 at MSP at the same moment.
In reality, it probably doesn't make a huge practical difference whether we reach -17 or -25 Friday...it's going to be really cold either way. But Minnesotans love to know...for bragging rights if nothing else!
Right now I'm leaning toward a low of about -22 at MSP Airport Friday morning, with temps of -25 in the outer suburbs and -30s up north.
Stay tuned as we tweak the forecast temps of the incoming air mass this week.
Twin Cities Almanac for January 18th:
(Data from Weather Underground)
The "Deep Snow" full moon arrives at 3:21pm Wednesday.
NOAA plane over the Pacific boosts data for forecast models:
NOAA aircraft is flying missions to gather data over the North Pacific this winter. The plane gathers real time data, then feeds it into the forecast model initial conditions for the usually "data poor" North Pacific.
Here's the write up from NOAA:
"NOAA has dispatched one of its highly specialized aircraft to collect atmospheric data over the North Pacific Ocean to enhance forecasts of winter storms for the entire North American continent.
NOAA's high-altitude, twin-engine Gulfstream IV-SP jet will be stationed at Yokota Air Force Base in Japan through February before repositioning to Honolulu in March. From these locations, the aircraft will be tasked by the National Centers for Environmental Prediction -- a division of NOAA's National Weather Service -- to collect information such as wind speed and direction, pressure, temperature and humidity. The data will be sent via satellite to global operational weather forecasting centers and fed into sophisticated computer forecast models.
"By expanding our reach to Japan, we are able to gather data upstream of winter storms, thereby gaining more lead time for emergency managers and responders to prepare for the impacts of severe winter weather on lives and property," said meteorologist and flight director Jack Parrish with the NOAA Office of Marine and Aviation Operations."
I've often talked about how the models can't get a good picture and "lock on" to incoming winter storms until they reach the North American surface grid and upper air (weather balloon) network. That often leaves less than 48 hours of good, solid model data before winter storms hit Minnesota. The new data may help improve model forecasts on winter storm before the reach the Pacific coast...and maybe help forecasters in Minnesota.