We have been waiting for it to happen and it seems that colder and whiter scenes are coming. Below normal temperatures have been showing up in the 11-15 day forecast for about 2 weeks, but when that period moved to the 6-10 day forecast, the trends were much warmer. The weather pattern has supported a cold December, but it has been delayed and it is only a matter of time before it arrives.
We’re seeing signs that it’s finally on its way. Here’s a look at the latest run of the EPS (European Model Ensemble Mean) showing cooler than normal temperatures across much of the US over a 6-10 day period. This image is courtesy of the Tropical Tidbits website:
This holds true for the period December 16-21, where the 5-day temperature is forecast to average cooler than normal. We will likely see a low pressure system bringing a winter mix of freezing rain, sleet and snow to central Michigan on Thursday, December 15, followed by a cold front bringing this cold air. How cold is the cold? Well, so far this month, we have mostly seen highs in the 30s, so at a minimum this should give us more highs in the 20s and lows in the teens. That being said, it also depends on how much snow we can put on the ground. The more snow cover we have, the greater the potential to see even colder air. The arctic air descending from Canada is certainly cold, but the air mass inevitably changes as it travels across different continents. In addition to our ensemble computer models, we are also supported by the East Asian weather pattern that favors cooler than normal temperatures between December 19 and December 23, as shown here:
This cold should help make the environment favorable for lake-effect snow, as the lakes are still relatively warm in early winter. However, this is not all. The cold may return around the 23rd or 24th, just in time for Christmas. We may see a low pressure system move in at this time on Christmas Eve or the day before, which would likely be snow given how cold it will likely be.
A key note here is that there is no way to know the exact path of this storm. It could hit Michigan or stay south of Indiana… we don’t know for sure, but this storm system should exist in this time frame and drag cooler air behind it.
We have agreement from the two major ensemble forecast systems (GEFS and EPS) on temperatures below normal or perhaps well below normal around Christmas. Again, the details on exactly how cold depend on many variables that need to be worked out as we get closer, however I wouldn’t be surprised to see at least a few days with highs in the teens and lows in the single digits. If we have enough snow on the ground and clear the clouds at some point, it wouldn’t be impossible to drop below freezing. The bottom line is that the second half of December looks colder than usual with a better chance of seeing a white Christmas this year than in more recent years.
Winter mix possible from Wednesday to Thursday
We started this week with mostly cloudy skies as the winds shifted to the east due to a high pressure system over Canada. This brings in moisture from Lake Huron, which helps the clouds stay around. Look for highs in the mid 30s. Partly cloudy skies continue through Tuesday with highs again in the mid 30s. Our main concern this week is Wednesday as our next system approaches the area. A low pressure system forms today in the Rocky Mountains, moving toward the Great Lakes and arriving Wednesday. This low brings a complex weather pattern that brings changes of rain, snow, freezing rain and sleet to central Michigan on Wednesday and Thursday.
Forecast model soundings, or graphs that show us what the temperature and humidity in the atmosphere will be like, suggest that the best chance for winter weather will be in areas north of I-96, including Mt. Pleasant, while it should stay more rain further south. Who gets winter weather and who gets rain depends on how much warm air is above the surface and whether surface temperatures are below freezing.
This winter weather could cause travel impacts, but it is not yet known what type of precipitation and how much. Confidence will grow the closer we get to Wednesday, so keep an eye on our page for the latest weather information. The great news is that winter weather could cause problems with travel on Wednesday and Thursday, so students finishing exams should be aware of this.
What is a white Christmas?
We’ve all heard the song and have the nostalgia of looking out the window at Christmas and seeing a blanket of snow on the ground, but what exactly is a white Christmas? A white Christmas means we have at least an inch of snow on the ground on Christmas morning. That means if snow fell at Christmas but melted, it wouldn’t be considered a white Christmas. According to the National Weather Service, we see a white Christmas about 60% of the time in Mt. Pleasant. It’s not as common as the upper part of the peninsula where large amounts of lake effect occur, but it’s more common than not. Will we see one this year? It’s too early to tell, but stay with our team for the Christmas forecast and the other 364 days of the year too.
Mt. Pleasant Almanac for this week:
Almanac information is a way of observing normal temperatures and recording the high and low temperatures for this time of year. Normal temperatures are based on the 30-year average high and low for that date between 1991 and 2020. For example, if you take the high temperature for each December 12 between 1991 and 2020 and average the 30 values, the The result would be 36. Therefore, the normal maximum for today is 36°. Record high and low temperature data dates back to 1895. Sunrise and sunset data are also provided. All information is valid for Mt. Pleasant.
December 12th
Normal High/Low: 36°/23°
Record High: 57° 1899
Record low: 0° 1962
Sunrise: 8:03 a.m.
Sunset: 5:03 p.m.
December 13th
Normal High/Low: 35°/23°
Record High: 57th 1991
Record low: -8° 1986
Sunrise: 8:04 a.m.
Sunset: 5:03 p.m.
December 14th
Normal High/Low: 35°/23°
Record high: 58th 2015
Record low: -13° 1917
Sunrise: 8:03 a.m.
Sunset: 5:02 p.m.
December 15
Normal High/Low: 35°/23°
Record high: 61st 2021
Record low: -5° 1989
Sunrise: 8:06 a.m.
Sunset: 5:03 p.m.
December 16
Normal High/Low: 35°/22°
Record high: 63rd 2021
Record low: -6° 1951
Sunrise: 8:06 a.m.
Sunset: 5:03 p.m.
December 17
Normal High/Low: 34°/22°
Record high: 67th 1984
Record low: -5° 1919
Sunrise: 8:07 AM
Sunset: 5:04 p.m.
December 18 th
Normal High/Low: 34°/22°
Record High: 49° 1939
Record low: -13° 1926
Sunrise: 8:08 a.m.
Sunset: 5:04 p.m.
Mid-Mitten Weather View’s mission is to serve people by providing timely information to help you stay safe and make weather-based decisions. We are passionate about educating both our forecasters and followers about how weather forecasting works and how we can be better prepared when shock weather threatens. Our team is made up of CMU alumni graduate meteorologists and current student forecasters from the University. For daily updates, we invite you to visit our Facebook page! We hope to see you here next week for another weekly 7-day forecast update.
-Weather forecast by CMU student meteorologists Isaac Cleland and Scott Thomas