Winter Weather in our part of the Midwest

The winter season represents the coldest part of the year in the northern hemisphere, when daylight hours are at a minimum and darkness lasts all day long in the high latitudes.   Average winter temperatures (as defined as December, January and February) are just below freezing in Kansas City and a few degrees above freezing in St. Louis.  The coldest winter temperatures were recorded in December, 1989 when readings dropped to -23 in Kansas City and -22 in St. Louis. Very warm days can also occur, particularly in late February and 1972 was an example of this when low to mid 80s were recorded.   Winter is also a drier time of year with less moisture available to work with and despite high snowfall totals, liquid equivalent moisture is just around 4″ in Kansas City and 7.5″ in St. Louis.

Winter Stats for Kansas City and St. Louis.

Winter Stats for Kansas City and St. Louis.

Daylight reaches a minimum at the winter (southern) solstice and begins an  increase early in the season, but as with the summer (northern) solstice , temperatures lag the change in daylight.

Winter daylight reaches a minimum at the Winter Solstice and increases by nearly 90 minutes by the last week of February.

Winter daylight reaches a minimum at the Winter Solstice and increases by nearly 90 minutes by the last week of February.

This graphic shows the waxing and waning of daylight during the year from the summer maximum to winter minimum.  A difference of over five and a half hours of daylight exists between the two.

This graphic shows the ebb and flow of the length of daylight during a 13 month period. Five and a half hours difference exist between the summer and winter solstices.

This graphic shows the ebb and flow of the length of daylight during a 13 month period. Five and a half hours difference exist between the summer and winter solstices.

Winter also has a very low sun angle compared to the summer.  The sun rises in the southeast and tracks low in the southern sky and sets in the southwest.  The low sun angle means the light must travel through more atmosphere than in summer and this results in a more reddish and weaker light compared to the bright, harsh, white mid day summer sun. This weaker light is less able to deliver heating to the earth’s surface as the sun’s rays are spread out over a greater area.  It may seem counter-intuitive, but the earth is actually at it’s closest to the sun in January and because of that, the orbit is at it’s fastest.

Light Color and Analemma

St. Louis average monthly winter temperatures.  Only 1 month, January, is below freezing.

The coldest month in Winter in St. Louis is January with an average temperature just below freezing.

The coldest month in Winter in St. Louis is January with an average temperature just below freezing.

Kansas City average monthly winter temperatures.  Two months, December and January, are below freezing.

Average monthly temperatures reach a minimum in January of 28.8" in Kansas City.

Average monthly temperatures reach a minimum in January of 28.8″ in Kansas City.

St. Louis winter precipitation totals show a slow decline through the winter season.

Winter precipitation in St. Louis slowly declines from 2.84" in December to 2.24" in February.

Winter precipitation in St. Louis slowly declines from 2.84″ in December to 2.24″ in February.

Kansas City winter precipitation totals are all less than 2″ and bottom out at just over an inch in January.

Meteorological winter is the driest part of the year in Kansas City with all three months posting averages near or below 1.5".  January is the driest month with just over an inch of liquid equivalent precipitation.

Meteorological winter is the driest part of the year in Kansas City with all three months posting averages near or below 1.5″. January is the driest month with just over an inch of liquid equivalent precipitation.

Kansas City monthly snowfall averages:

Average annual snowfall in St. Louis totals 17.7" spread out over six months.  Peak monthly averages occur in January with 5.6" followed by 4.4" in December and 4.3" in February.

Average annual snowfall in St. Louis totals 17.7″ spread out over six months. Peak monthly averages occur in January with 5.6″ followed by 4.4″ in December and 4.3″ in February.St. Louis monthly snowfall averages:

Kansas City's winter snowfall averages 18.8" and is divided between 7 months of the year.  The peak snowfall average occurs in February with 5.4" followed closely by 4.8" in December and 4.6" in January.

Kansas City’s winter snowfall averages 18.8″ and is divided between 7 months of the year. The peak snowfall average occurs in February with 5.4″ followed closely by 4.8″ in December and 4.6″ in January.

This graphic shows average yearly snowfall accumulation (as measured from July 1 to June 30 of the following year). Average annual snowfall in Missouri ranges from 18-24″ north to just 3 to 6″ in the Bootheel.  Average annual snowfall in Illinois ranges from 36-42″ in the lake effect snow belts around Chicago to 3-6″ in extreme southern Illinois. Kansas City an St. Louis both lie in the 12-18″ belt while SE Missouri and S Illinois lie in the 6-12″ belt.

Average annual snowfall across the region. Snow totals as little as 6" for the Missouri Bootheel and extreme southeastern Illinois, with around 9" from Joplin through West Plains Missouri, Chester and Mt. Vernon, Illinois.  Average annual snowfall of a foot is typical from Springfield, to the Lake of the Ozarks and Hillsboro, Missouri across into Belleville and Vandalia, Illinois. Kansas City, St. Louis and on into central Illinois. Northern Missouri and north central Illinois typically see totals from a foot and a half to two feet with totals steadily increasing to the 2-3 foot range further north,

Average annual snowfall across the region. Snow totals as little as 6″ for the Missouri Bootheel and extreme southeastern Illinois, with around 9″ from Joplin through West Plains Missouri, Chester and Mt. Vernon, Illinois. Average annual snowfall of a foot is typical from Springfield, to the Lake of the Ozarks and Hillsboro, Missouri across into Belleville and Vandalia, Illinois. Kansas City, St. Louis and on into central Illinois. Northern Missouri and north central Illinois typically see totals from a foot and a half to two feet with totals steadily increasing to the 2-3 foot range further north,

Here is a listing of the top 10 snowiest winter seasons in St. Louis and Kansas City. 1911-1912 is the undisputed all time record snowiest winter in both cities.  The snowy winter of 2010-2011 ranks as #6 in St. Louis and #9 in Kansas City, while 2009-2010 ranks as #4 in Kansas City.  The top ten snowiest 24 hour periods are shown for St. Louis and the top 10 biggest snow storms are shown for Kansas City.

The top 10 snowiest seasons (snow falling between July 1 and June 30 of the next year) in St. Louis and Kansas City.

The top 10 snowiest seasons (snow falling between July 1 and June 30 of the next year) in St. Louis and Kansas City.

On the flip side, the top ten least snowiest winter seasons for both cities.  The “non” winter of 2011-2012 ranks as #10 for St. Louis but as the all time least snowiest winter for Kansas City.

The top 10 least snowiest Winter snowfall totals for St. Louis and Kansas City.  The unusually warm and dry winter of 2011-2012 ranked as #1 for least snow in Kansas City and #10 in St. Louis.

The top 10 least snowiest Winter snowfall totals for St. Louis and Kansas City. The unusually warm and dry winter of 2011-2012 ranked as #1 for least snow in Kansas City and #10 in St. Louis.

Snow and Christmas go hand-in-hand in most people’s minds and that may be true, but not so much for our part of the Midwest.  In any year, statistics bear out that there is only 10 to 25% chance for a White Christmas (as defined as having at least 1″ of snow on the ground). In other words in any given decade, 1 to 4 years may see a white Christmas and in any given century 10 to 25 years may have a white Christmas.

The probability of a White Christmas is actually very low at the region's latitude, not reaching 50% or greater until an Omaha-Des Moines-Chicago line and north.

The probability of a White Christmas is actually very low at the region’s latitude, not reaching 50% or greater until an Omaha-Des Moines-Chicago line and north.

Due to the cold temperatures in winter, there are added challenges to deal with.  Summer time rains can be a nuisance, but outside of flash flooding and severe weather, which can be devastating on a local scale, winter storms can and frequently do impact a large part or all of the Midwest.

Winter precipitation is never as straightforward as summer precipitation.  What type of precipitation falls depends upon the temperature of the atmosphere from the cloud layer to the surface and just where these layers are located.  In this winter warm front example, weather conditions range from flurries to rain as the depth of the warm air changes as the warm front approaches.

Winter precipitation is never as straightforward as summer precipitation. What type of precipitation falls depends upon the temperature of the atmosphere from the cloud layer to the surface and just where these layers are located. In this winter warm front example, weather conditions range from flurries to rain as the depth of the warm air changes as the warm front approaches.

Simplified example of how temperature differences aloft impact what kind of precipitation falls.  From right to left: rain, freezing rain, sleet and snow.

Simplified example of how temperature differences aloft impact what kind of precipitation falls. From right to left: rain, freezing rain, sleet and snow.

Winter conditions can depend upon larger scale weather patterns which may last all or part of a season.  The biggest and most well known are El Nino and La Nina.  This winter neither are expected to be a major influence which leaves shorter-term atmospheric patterns to take the lead.  These patterns can work independently of each other or in concert with each other.

The first of these is called the “Pacific-North American” pattern.  It has a positive and negative mode.  The graphics below show generalized weather conditions which can be expected for each mode.

Typical effects of a negative Pacific North American Pattern (-PNA) which tends to place a trough in the west and high pressure in the southeastern U.S. This is an active and stormy pattern for the central and eastern U.S.

Typical effects of a negative Pacific North American Pattern (-PNA) which tends to place a trough in the west and high pressure in the southeastern U.S. This is an active and stormy pattern for the central and eastern U.S.

This is a simplified classic depiction of a Positive Pacific North American (+PNA) weather pattern and some general effects.  This is just a generalized description as each pattern's configuration will be different.

This is a simplified classic depiction of a Positive Pacific North American (+PNA) weather pattern and some general effects. This is just a generalized description as each pattern’s configuration will be different.

The next pattern is the Arctic Oscillation.  Like the Pacific-North American pattern.  It has a positive and negative mode. The graphics below show generalized weather conditions which can be expected for each mode.

Typical effects of a positive Arctic Oscillation include a strong west-to-east (zonal) jet stream and lower pressure near the poles.  Higher pressure at middle latitudes produces mild weather. The pattern can be a dry one for the U.S. when not modulated by other patterns such as the Pacific North American (PNA) El Nino or La Nina.

Typical effects of a positive Arctic Oscillation include a strong west-to-east (zonal) jet stream and lower pressure near the poles. Higher pressure at middle latitudes produces mild weather. The pattern can be a dry one for the U.S. when not modulated by other patterns such as the Pacific North American (PNA) El Nino or La Nina.

"Classic" or typical weather patterns when the Arctic Oscillation is in negative mode. A weaker jet stream and fractured polar vortex allow large north-south swings in the river of air that is the polar jet. Blocking near Greenland is typically established which funnels cold air out of the Arctic into the central and eastern U.S.  The subtropical jet, when active, can interact with the cold for major winter storms.

“Classic” or typical weather patterns when the Arctic Oscillation is in negative mode. A weaker jet stream and fractured polar vortex allow large north-south swings in the river of air that is the polar jet. Blocking near Greenland is typically established which funnels cold air out of the Arctic into the central and eastern U.S. The subtropical jet, when active, can interact with the cold for major winter storms.

A third pattern is the North Atlantic Oscillation.  Like the the previous patterns.  It has a positive and negative mode. The graphics below show generalized weather conditions which can be expected for each mode.

A positive North Atlantic Oscillation (+NAO) typically results in a contained polar vortex with an polar low centered over the Greenland/Iceland area.  Arctic air tends to shift east across Canada rather than dropping southward into the U.S. The subtropical ridge is stronger and further north, with warm and dry weather from the central and eastern U.S. to the coast.  Warm and wet weather is more common in northern Europe with warm and dry weather over the Mediterranean.

A positive North Atlantic Oscillation (+NAO) typically results in a contained polar vortex with an polar low centered over the Greenland/Iceland area. Arctic air tends to shift east across Canada rather than dropping southward into the U.S. The subtropical ridge is stronger and further north, with warm and dry weather from the central and eastern U.S. to the coast. Warm and wet weather is more common in northern Europe with warm and dry weather over the Mediterranean.

A negative North Atlantic Oscillation (-NAO) typically results in blocking over the north Atlantic near Greenland and a stronger polar low near Hudson's Bay.  This can act to funnel Arctic air southward into the central and eastern U.S.  The subtropical high is weak over the Atlantic with cold intrusions more likely into northern Europe and wet weather over the Mediterranean.

A negative North Atlantic Oscillation (-NAO) typically results in blocking over the north Atlantic near Greenland and a stronger polar low near Hudson’s Bay. This can act to funnel Arctic air southward into the central and eastern U.S. The subtropical high is weak over the Atlantic with cold intrusions more likely into northern Europe and wet weather over the Mediterranean.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s