Perspectives Snow and Winterkill of Alfalfa

Perspectives Snow and Winterkill of Alfalfa:

The weather since December 1st has been up and down with respect to temperature. Most places in Minnesota reported a colder than normal month of December, with abundant snowfall, well above normal in many areas. January so far has tracked warmer than normal and maintained the trend this winter for above normal snowfall. Snow cover across the landscape has been consistently above 6 inches in many areas of the state since the third week of December. One exception to this snow cover description is southeastern Minnesota, where recent warm temperatures and unusual January rainfall have eroded the snow cover to less than 2 inches in many counties. However, the winter storm on Thursday of this week deposited a fresh coating of 4 to 6 inches of snowfall there.

Snow cover is an asset for an alfalfa crop in winter as it serves as a blanket to insulate the crop from wide swings in temperature and helps prevent extremely low soil temperatures that might damage or kill the crop. Soil temperatures so far this winter have been greatly modified by the snow cover. Winter injury to alfalfa becomes more probable when soil temperatures at the 4 inch depth fall below 15°F, and very likely when soil temperatures fall into the single digits. Looking at reports from around the state most average 4” soil temperatures have remained in the upper 20s to low 30s F even during the cold snaps that have produced subzero air temperature readings this winter.

About the only negative factor with respect to winter injury potential to forage crops this winter has been the recent freezing drizzle and freezing rain which has put a sheet of ice over much of the landscape, especially in southeastern Minnesota where snow cover was sparse. This prevents the normal exchange of gases between the soil and the atmosphere and can cause substantial winter injury to grasses and forage crops such as alfalfa. For both drought recovery and for reducing the risk of winterkill to forage crops, more snowfall in January and February would be welcome by most farmers.

On the other hand, foresters in northern Minnesota would not mind seeing a break from the snow, as Dan Kraker from MPR radio has reported the severe damage done by earlier snowstorms that were so heavy and laden with moisture they caused many trees (especially Aspen) to bend and break. The winter so far has produced a number of snowstorms that have delivered very high quantities of moisture.

There is an excellent article on this topic by Dr. Craig Sheaffer who is a University of Minnesota Extension forage agronomist in a recent Crop News blog.

Weather Potpourri:

This week BBC meteorologist Ben Rich offers an explanation for how winter weather patterns are changing across the United Kingdom due to climate change. Among other changes the number of frosts, as well as the number of days with snow cover are shrinking.

There is a very good article this week by Jonathan Erdman of the Weather Underground about how the National Weather Service performs storm surveys and tornado damage analysis to determine all the characteristics of the storm. Lots of work goes into documenting this surveys which are use to learn more about tornadoes and helps in severe weather forecasting.

A study published in the journal Nature documents a 1000 year old ice core from Central Greenland that showed the rapid level of warming which has occurred there in recent decades. Temperature reconstruction from the ice core shows that the decadal temperature average for 2001-2011 was a striking anomaly from anything in the historical record.

MPR listener question:

After the extraordinary windy year in 2022, and very windy January of last year, it seems like we are off to a much less windy year so far in 2023. Is that true?

Answer:

Yes, for Minnesota climate stations this month has seen far less very windy days than observed last January. In the list below, I compare the number of days with wind gusts of 30 mph or stronger observed last January vs this January (through the 19th) for three locations in Minnesota.
MSP Airport, January of 2022 14 days, January of 2023 2 days
Rochester, January 2022 16 days, January of 2023 3 days
Redwood Falls, January 2022 18 days, January 2023 3 day

Twin Cities Almanac for January 20th:

The average MSP high temperature for this date is 23 degrees F (plus or minus 15 degrees F standard deviation), while the average low is 8 degrees F (plus or minus 15 degrees F standard deviation).

MSP Local Records for January 20th:

MSP records for this date: highest daily maximum temperature of 52 degrees F in 1908; lowest daily maximum temperature of -17 degrees F in 1888; lowest daily minimum temperature of -32 degrees F in 1888; highest daily minimum temperature of 35 degrees F in 1921; record precipitation of 0.80 inches in 1982. Record snowfall is 17.2 inches in 1982.

Average dew point for January 20th is 4°F; the maximum dew point on this date is 36°F in 1921; and the minimum dew point on this date is -38 degrees F in 1985.

All-time state records for January 20th:

The state record high temperature for this date is 61 degrees F at Madison (Lac Qui Parle County) in 1944. The state record low temperature for this date is -57 degrees F at Embarrass and Tower (St Louis County) in 1996. The state record precipitation for this date is 1.76 inches at Preston (Fillmore County) in 1988. Record snowfall is 17.1 inches also at MSP Airport (Hennepin County) in 1982.

Past Weather:

One of the coldest Cold Waves of the 19th Century gripped Minnesota during the week of January 14-21 in 1888. The average temperature in the Twin Cities for the 8 days was -17°F and the same average for Morris was -24°F which was also the daily high temperature on January 20th after a morning low of -35°F.

The warmest January 20 in state history was in 1944 when most areas of the state saw daytime high temperatures reach the 40s and 50s F. Temperatures of 60°F were observed in much of southwestern Minnesota. Redwood Falls started out in the morning with 15°F but saw the temperature climb to 60°F by afternoon.

January 20 to 26 of 1982 was one of the snowiest weeks in Minnesota history for many climate stations. A series closely spaced winter storms dumped enormous amounts of snowfall. Several climate stations reported over 25 inches that week. Jordan reported over 40 inches, while the Twin Cities reported 39.7 inches. Snowplow operators were busy almost everyday of the week working 16-hour shifts.

Outlook:

Dry over the weekend with warmer than normal temperatures. Increasing cloudiness on Monday with a slight chance for snow flurries and snow showers in far northern areas. Drier the rest of next week with colder than normal temperatures.