December Warmth Continues

December Warmth Continues:

The first half of the month has been dominated by persistent warmer than normal weather. Through the first two weeks of December climate stations are reporting an average temperature that ranges from 8°F to 12°F above normal. On a statewide basis back to 1895 here are the top five warmest first two weeks of December:

1913 and 1939 statewide average temperature 33.1°F
2015 statewide average temperature 32.2°F
1999 statewide average temperature 30.1°F
2023 statewide average temperature 28.4°F
2001 statewide average temperature 28.0°F

It is interesting to note that for these Decembers listed above there was little snow or no snow cover, or only intermittent snow cover present throughout the month. It is also interesting to note that El Nino was in play in only two of these years, 2015 and 2023.

So far this month within the state climate network over 80 high maximum temperature records have been set, and over 40 high daily minimum temperature records have been set. As recently as Thursday, December 14 new record high temperatures were reported from many areas, including:

50°F at Orr, and Park Rapids
52°F at International Falls and Crane Lake
54°F at New Ulm and Fergus Falls
55°F at Hutchinson and Wheaton
56°F at Granite Falls
57°F at Madison

Moderate to Severe Drought area in the state remained fixed at 44 percent heading into the second half of December and is likely to remain unchanged. All of the NOAA CPC outlook models suggest a warmer and drier than normal pattern will prevail throughout the balance of the month.

Nocturnal Character of Winter Storms

Frequencies of hourly precipitation from the Twin Cities climate records show some interesting daily patterns with respect to the onset of winter storms. Patterns in the hourly frequencies of precipitation do vary by month. In the winter months, December through February, the afternoon hours from noon to 4 pm show the lowest relative frequency of measured precipitation. Overnight frequencies of hourly precipitation are relatively higher, especially from 1 am to 6 am. This could be due to the relationship between temperature and the saturation of the air. Low temperatures usually occur during these hours and probably remain closer to the dew point temperature, preserving the structure and continuity of precipitation, whether droplets, sleet or snow crystals. The other feature of winter storm systems to remember is that they are usually large and take some time to move across the area. Precipitation may last for several hours and since most of our 24-hour calendar day is in darkness during the winter, we associate the storminess with the night.

Weekly Weather Potpourri:

The BBC reports this week that globally the year 2023 will be the warmest on record for the measurement period since 1850. They also suggest that the year 2024 may be even hotter and will certainly continue the upward trend in global temperature.

A recent study from University of California Santa Barbara researchers documents the improved thermoregulation of new adaptive materials that can be used for roof tiles. These materials adapt to cool or warm condition to maximize energy efficiency for either heating or cooling buildings. They do so automatically and passively (without the use of electricity). Further study is needed to see how viable the manufacturing of such materials would be economically speaking. You can read more about this in the journal Device.

This week’s AGU-EOS Bulletin features an interesting article about a mobile, cost-effective technology used to measure carbon dioxide flux from soils. Measurement show a strong relationship between carbon dioxide flux and soil temperature and moisture. Soil disturbance by grazing animals also has a measurable impact. The paper presents a case for more widespread use of this measurement system in different environments with variable soils.

MPR listener question:

We understand that there are about 100 years of climate records for Austin, MN. We have recorded only a trace of snowfall so far this month here at Austin. Is this unique in our climate record? If not, how many times have we had a snowless month of December?

Answer:

Yes, over the past 90 years or so, there have been only 4 Decembers without any snowfall or only a trace of snow reported from your community. Those years were 1943, 1962, 1965, and 2006. You are not alone in reporting only a trace of snowfall this month. Many other communities have reported the same. Your long-term average December snowfall is about 9.2 inches.

Twin Cities Almanac for December 15th:

The average MSP high temperature for this date is 29 degrees F (plus or minus 13 degrees F standard deviation), while the average low is 15 degrees F (plus or minus 14 degrees F standard deviation).

MSP Local Records for December 15th:

MSP records for this date: highest daily maximum temperature of 58 degrees F in 2021; lowest daily maximum temperature of -5 degrees F in 1932; lowest daily minimum temperature of -21 degrees F in 1901; highest daily minimum temperature of 39 degrees F in 2021; record precipitation of 0.71 inches in 1902. There was also a record 7.0 inches of snowfall also in 1902.

Average dew point for December 15th is 10°F; the maximum dew point on this date is 49°F in 2014; and the minimum dew point on this date is -22 degrees F in 1963.

All-time state records for December 15th:

The state record high temperature for this date is 63 degrees F at Kinbrae (Nobles County) in 1891. The state record low temperature for this date is -47 degrees F at Pokegam Dam (Itasca County) in 1901. The state record precipitation for this date is 2.25 inches at Grand Rapids (Itasca County) in 1893. The state snowfall record is 14.6 inches at Rockford (Wright County) in 1996.

Past Weather:

In the years prior to statehood (1858) weather records across Minnesota are rather sparse. But we do know from the Ft Snelling readings that December of 1855 was no picnic. Well, actually maybe you could have had a picnic during the first days of the month as temperatures reached the mid 40s F. But following that mild spell a series of arctic fronts descended across the region bringing measurable snowfalls on nine days and an especially heavy snow at mid-month. Friday and Saturday, December 15th and 16th brought snow "with flakes as big as a featherbed" totaling 8 to 12 inches around the St Paul area. Sleighing was said to be excellent as total snowfall amounted to 22 inches for the month. The fresh snow cover and arctic air produced one of the coldest Christmas Eves in Minnesota history with a reading of -33 degrees F at Ft Snelling, -36 degrees F at St Paul, and -38 degrees F elsewhere in southern portions of the state. So after a teasing, mild start what a bitter month it turned out to be.

An Arctic air mass gripped the state on December 15 of 1901 and many low temperature records were set. Morning lows ranged from -20°F to -40°F across the state. The high temperature at Pine River reached only -12°F.

Many communities in the state reported afternoon high temperatures in the 50s F on December 15 of 1998. Some golf courses were open road repair crews were seen working in shirt sleeves. The high at Canby (Yellow Medicine County) reached 60°F.

A slow-moving winter storm brought heavy snowfalls to central and southern Minnesota over December 14-15 of 1996. Many areas reported 12 to 15 inches. Minneota in Lyon County reported 20 inches.

Outlook:

Mild temperatures continue into the weekend with a chance for rain in some areas on Saturday morning, and mixed precipitation (rain/snow) up north. Breezy and cooler on Monday, but then warming up to above normal temperatures again for next Tuesday through Friday, and mostly dry throughout.