January Climate Impacts on Agriculture
After a brief lull following the December 28 snow event, an active weather pattern returned to the state the second half of January. The lull in storm activity, coupled with high temperatures primarily in the 30’s and 40’s over the existing snowpack, allowed for the slow infiltration of snow melt into unfrozen soils. The lack of cold air after the snowpack melted meant soils east of the Panhandle remained frost free, or at worst kept the frost depth under 4 inches.
A series of storms moved through the central and southern Plains the second half of the month providing widespread moisture. Without a doubt, the most significant event occurred January 25-26, when a widespread band of 6-15 inches of snow blasted the eastern 2/3 of the state. This wet snowfall resulted in water equivalent moisture of 0.50-1.25 inches. Numerous locations across central, east central, and south central Nebraska received a full season worth of snowfall from December 28-January 25.
The remainder of January was overcast and cool over the existing snowpack allowing for the slow infiltration of snow melt into unfrozen soils. By the end of January, the existing snowpack had shrunk by nearly 50% in areas open to direct sun exposure. High temperatures across western Nebraska that were devoid of a snowpack experienced high temperatures ranging from the middle 40’s to upper 50’s.
With the abundance of snowfall, the eastern 1/3 of the state received 0.90-1.80 inches of moisture during the month of January, while a large portion of the Panhandle received less than 0.10 inches of moisture (Figure 1). Widespread precipitation surpluses of 0.45-1.25 inches were common across the eastern third of the state, while deficits continued to accumulate across western Nebraska (Figure 2).
The importance of the January 25 snow event can be seen in the soil moisture recharge period (October 1 – present) precipitation anomalies (Figure 3). A large area of the i-80 corridor east of Grand Island through portions of northeast Nebraska are running deficits of 0.75 inches to surpluses of 0.75 inches. The precipitation received in January across this region was enough to eliminate the deficits that had accumulated since the beginning of November 2020.
Surplus January moisture was not limited to eastern Nebraska, but extended southward through north central and northeast Texas. Even though western Nebraska missed out on the January moisture, the surplus over the eastern half of the southern and central Plains should translate into more efficient precipitation events moving into the spring months. That is conditional on returning to the active pattern experienced during the second half of January.
The January 25th snowstorm occurred after the Nebraska Agricultural Statistic Service (NASS) released their monthly report of crop conditions through January 24. It is expected that the February release will reflect significant improvements in top soil conditions east of the Panhandle. Even without this storms inclusion into the report, NASS indicated that topsoil moisture improved 4 points from 60% at the end of December to 56% on January 24. Subsoil moisture improved 1 point from 64% to 63% poor to very for the same period.
The lack of precipitation across the Panhandle and southwest Nebraska continues to be a detriment to the condition of the winter wheat crop. NASS reports that 6% is rated very poor, 12% poor, 48% fair, 33% good and 1% excellent as of January 24th. With little or no surface and subsurface moisture, the wheat crop will be vulnerable to winter kill if the predicted Arctic air the first half of February encompasses western Nebraska.
The Arctic air forecast through mid-February will likely put a dent in the anomalously warm conditions experienced during December and January. Figure 4 shows that average temperatures across the eastern half of the state were 4-8 F above normal, while western Nebraska was normal to 4 F above normal. For the winter (Dec-Jan), average temperatures were 8-10 F above normal across northern Nebraska decreasing to 5 F above normal along the Kansas border. These warm winter temperature anomalies will likely be halved over the next two weeks across the northern 1/3 of the state and virtually eliminated along the southern border.
Finally, the January 25 snowstorm created difficult grazing conditions across the eastern 2/3 of the state to end the month. Although the snowpack shrunk significantly, there is still 3-8 inches of dense snowpack left on the ground. With cold Arctic air and additional snowfall expected, grazing conditions will likely deteriorate further. In addition, the upcoming blast of Arctic air will create wind chill values in the -30 F range on occasion. These will be brutal conditions to enter the beginning of calving season.
February Weather Outlook
The Climate Prediction Center (CPC) issued their official February temperature forecast (Figure 5) on January 31 and indicates a strong tendency for below normal temperatures across the northern half of the United States from the west coast through the eastern Great Lakes. The highest odds for these conditions were assigned to the north central United States (MT, ND, MN, SD). The preliminary CPC February temperature outlook issued January 21 had below normal temperature confined to Washington, Idaho, and western Montana.
CPC also altered their final February precipitation outlook with a widespread wet bias (Figure 6). The greatest odds for receiving above normal moisture were assigned to the northwestern High Plains and the lower Ohio River valley. However, the entirety of the northern half of the High Plains eastward to the mid-Atlantic region has odds slightly tilted toward above normal moisture.
The most current run of the GFS model (12z – 2/5) indicates that a large upper air trough will dominate the eastern half of the United States through February 18 before normal to above normal temperatures return to the state. However, it should be cautioned that the GFS model has extended colder temperatures an additional 3 days over the past week. It would not be surprising to see this cold trend extend longer into the month just like we experienced in 2018.
Strong Arctic air will dominate the February 6-13 period, as the eastern U.S. upper air trough allows continuous pushes of cold air to move southward into the High Plains from northern Canada. High temperatures will struggle to break the single digits across eastern Nebraska February 8-10, with mid –teens possible across the western 1/3 of the state. Temperatures will moderate into the teens and 20’s February 9-10, before another Arctic surge arrive February 11-13.
The GFS model indicates that there will be several impulses moving southeastward through the state during this period of Arctic cold. Two waves are projected to move through the state on February 6th and 7th. The first systems has the potential to drop 1-6 inches of dry snow east of the Panhandle, with the area from north central through east central Nebraska having the best opportunity for significant accumulations. The February 7th impulse appears to be much weaker and 1-3 inches of snow may be possible across the eastern half of the state.
The renewed push of Arctic air predicted for February 11th may come at a price. The most current model run indicates an impulse will cross northern Nebraska on the 11th with 1-3 inches of snow possible. A stronger impulse is projected to follow on the 12th with widespread snowfall indicated for areas east of the Panhandle. Currently, the GFS indicates moderate snowfall potential from central through east central Nebraska.
Dry weather is projected by the GFS model February 13-15 with temperatures slowly moderating from the single digits and teens into the middle to upper 20’s as the upper air trough weakens and lifts toward the Great Lakes. This will allow energy entering the Pacific Northwest to push impulses southeastward into the central Rockies. Thus, as it warms up, the potential for storm activity across the northern half of the Rockies will need to be watched closely as it will increase the potential for a snowstorm to develop over the western half of the High Plains (NE, SD, ND, MT).
With the intense Arctic air and impulses moving through the state during the next 10 days, significant ice accumulations are expected to develop on rivers and lakes. Although current models do not depict the intensity of snow experience during February 2018, deep ice formation will still increase the odds of minor to moderate flooding from ice jams once temperatures return to above freezing.
Special Note
The Climate Prediction Center (CPC) will issue their latest El Nino Southern Oscillation (ENSO) update on current La Nina conditions mid-February. An Ag Update will be issued February 22nd to analyze CPC’s predictions, provide a drought update, and take a peek at my thoughts on how the current La Nina event may impact weather trends during the upcoming year.
Al Dutcher, Agricultural Extension Climatologist, Nebraska State Climate Office